Does anything actually solve the oil pressure drop in corners?

There are a few different baffle designs and a few different sump cover designs, but a lot of what I read suggests the problem persists. Does any of these actually make a material difference to the oil pressure in corners, except for the 2qt extension since that cuts too much ground clearance?

My wrench suggested the one sold by Mantis Racing.

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Nope, buddy had one. Even with fresh motor, pressure drops everywhere

Nothing fixes it, other than going slower. I have found the LN one makes it better, but it is not perfect.

An accusump is probably the only real answer on this, but it isn't a fix. It's more like a capacitor in an electrical circuit. When oil pressure drops, it feeds in oil from it's own pressurized reservoir. If I were racing an M96 or M97 engine or even doing time trials on slicks, I'd probably install an accusump as added insurance.

I think that the kit LN makes/made to add a scavenge pump to the LH bank would be the real fix. Maybe in conjunction with a higher capacity sump.

In 2011 when I bought a '99 to use primarily as a DE car, I was asking all these questions too. Not happy with the answers I got on this forum, I went to the Racing and DE forum. 996 drivers there had been fighting oil starvation for a long time. A lot of knowledge had been gained since the intro of the car. It was the prevailing theory at that time that on the track, oil starvation would occur on long left hand sweepers when running true racing slicks. They did not think that street / track tires like RA1 or NT01's could generate enough g's to cause this to happen. I ran my car for 4+ years with an X51 oil pan and Bridgestone RE-11 tires. Over that time I got maybe a flicker or 2 from the oil pressure light or saw the needle drop to 10. Since then, I have seen two things of interest on this topic. First, the original X51 package over came oil starvation by adding a second scavenging pump to the passenger side cylinder bank. The driver's side aready had a pump and is why you should not get an starvation on right hand sweepers. I am adding a diagram of the X51 oil circuit and a picture of the actual pump below. If you have the full X51 package, which the 40th Anniversary cars do not have, you would see the pump and return oil lines easily when looking under the car. The second point of interest is that I read that if you are running tires with more grip than "N" spec, then you may be able to generate the g's to pool the oil in the right bank. I think that was from Adrian Streather's 996 Essential Companion. So the bottom line as I see it is that for "spirited runs around town" an oversized sump should keep you very safe. If you are going to the track, then an ACCUSUMP is the ticket.

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Do you know if those highlighted X51 parts were offered as a retrofit? Are they plug-and-play into M96 or are the X51 casings somehow different? Is the extra pump the same unit (maybe rotated 180 degrees) as the driver's side? I wonder why LN and other aftermarket vendors do not offer this type of solution. Edit: Yikes!! https://www.ecstuning.com/b-genuine-...p/99610798001/ = $ 3315.58

Definitely not bolt on. My understanding is they almost unobtainable even for X51 package cars. And when available from Porsche, they we pricey. The last price I saw was around $3100.00, I think. Best shot would be Gert ay Carnewal.

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Just saw your edit. I think there is an issue getting both sides. They are mirror images of each other and not just a 180 degree turn to fit the opposite side. Can you find a complete X51 package anywhere?

from what i remember, LN/flat six tested these additional scavenge pumps but found little difference in pressure as a result

So in the present day is the consensus that if I'm tired of the oil pressure going below 2 bar in turns I should put in the EBS Racing baffle at my next oil change, or save my money?

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Remind us what the situation is when you drop to 2 bar?

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High speed hard turns, to the right or the left but I think moreso to the right.

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Are you on the track or AX?

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Niether, but I would say most comparable to AX. There are areas of the country that might as well be a track, but yeah not lap after lap after lap like a track.

With all the oil starvation issues and issues related to crankcase ventilation it is too bad there is not money to be made by developing a true dry sump system. If it were $3k or under, I would buy it. I have been happy with my pressure stability on track running 2QT deep sump, XP9 oil and street tires, PS4S and have only noticed drops below 3 bar under heavy cornering when the oil is hot. Like late 2nd or 3rd track session. That said, the switch to track specific tires is coming and I know this issue will never get better then it is right now. So again, I would certainly go dry sump for a number of reasons, even addition to the pressure stabilization of it were available.

Yes, a dry sump is the ultimate solution and I'm amazed that there is not one offered for the M96/M97 engine. You can get dry sump solutions for everything from 2.0 Pinto engines to LS's for Pete's sake! I suspect that the cost would be high and not too many systems would be sold, integration would be difficult, and so on. What do Spec 996 and Spec Boxsters use, Accumsump?

I have the same issue and I'm working on the solution since this drives me crazy. Don't take my word for it at all, I'm in the middle of the process and this is where I am right now. The two main things I found is that the return swirl pots are too restrictive and too high oil pressure is causing aeration, both at high RPMs. These issues should be exaggerated when running thicker oils. Solution: get the 997 return pipes, updated pressure relief valve (its stronger and doesn't open as easy including the smoothed edges which helps for aeration) and don't run too thick oil. As long as oil return to the sump quick enough the original design should easily be able to sustain a 1g turn(check oil level according to the manual, hot and level). It should be able to do 1.4g very briefly if filled full, <2 seconds. I see no benefit from different baffles right now. Deeper sump have several benefits as long as flow is not restricted to the pick up, but maybe not needed. I'm in the process with these modifications, as said, this is very preliminary.

Let me go back and restate my post #7. The left hand cylinder bank has a scavenger pump. When you go through a right hand sweeper the oil that goes to the cylinder head is pumped back to the sump by the scavenger pump. The factory did not add a scavenger pump to the right hand cylinder bank. So, again, if you go through a left hand sweeper with enough g-force, the oil will continue to build in the right hand cylinder head as there is no scavenger pump to push it down to the pump. In other words, the right hand cylinder bank relies on gravity to return the oil. The only thing I can think of is you have a bad component in the oil pressure reporting circuit. No idea where. Need to get it tested and certified as accurate to know if you do, in fact, have a pressure issue.

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I wonder if modern tire technology (improvements in grip) could be partially responsible for an increase in pressure losses in the turns for street tires over the last 10 years or so? I was able to get pressure loss in turn 9-10 (Carousel) at Road America with just Michelin All Seasons (AS3+)!

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Just to be clear, please correct me if I�m wrong: The 996 original engine has one scavenging pump per cylinder bank, but another 1 or 2 pumps have been added over time (one on the X51 like you say) and then 2 more on the 9A1 engine, is that correct?

Mike, in my first full DE season, my instructor took me out in my car with all season tires in the PCA Red group. The car was a bone stock 911SC. The instructor was one of the better PCA racers. We were passing just about everything on the track expect dedicated track cars or stock GT3’s. This was 2008 and the 2006 tires didn’t squeal once. My point is car balance is a major factor in going fast. If you are not smooth, you probably aren’t going fast for long.

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There is scavenge pumps in both heads, it's standard. What you might be thinking about is the dual scavenge pump on the X51 which I believe was a one head only fitment?

No idea what the 9A1 has for oil management. I am quoting info from the UK 911 site and the topic is the X51 package. They are calling the cylinder head pumps “scavenger “ pumps. And according to that site the X51 would not suffer from oil starvation as a result of oil pooling in the right hand cylinder head. For my 2 years of ownership of my 40th Anniversary car, I have been looking for definitive info on this and this is as close as I can find. Would love to be corrected and pointed to more definitive info and sources.

I'm not really buying the idea that oil pools in the heads. There is oil residing in the head but if you measure oil level according to the manual(hot), this is canceled out. The heads are symmetrical(more or less comes from the same cast) and the scavenge pumps sits on opposite ends. What this means is if one head was pooling, the other would be in a off-pooling state....so flow to the sump would still be even. My theory (just a theory!) is that oil pools inside of the swirl pots and the cavity above at high RPM. Oil is pumped to the top of the pot but then it needs gravity to go down and out thru a small exit at the bottom. In a turn at high RPM oil would probably fill it, gush out the top and in to the cavity above instead of going in to the sump. No de-aeration and lower level in the sump as a result.

You are leaving out the factor that we are talking pooling happening under high g-force that is stronger than gravity to drain the oil back down. Plus we are talking about happening on a long sweeper, not a quick turn with plenty of oil in the sump to continue pumping.

It does exist, and has around here for a long time. That said, the main driving factor I've seen behind the oil control issues is oil temperature. If the oil is kept cool, the oil pressure fluctuations are limited, and very controllable. Couple this to an oil with a proper viscosity index, formulated to operate in a proper temperature window, while maintaining viscosity. We learned this building these engines for Grand Am and etc back in the day. We could run a whole race, with perfect reliability, and never use a single bolt on additional sump, extra scavenge pumps, or etc. The other key is internal specifications. In factory form these engines are too tight, and the induces shear, which leads to even higher oil temperatures, and reduced oil life. Loose is fast. Loose lives.

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This makes a lot of sense. Who manufactures the referenced dry sump system and is it currently available ?

Well, I must be mixed up. I understand standard 996 engines have a scavenge pump for each cylinder head. Because of the symmetry, one of these pumps is in the front of the head and the other is in the rear. I thought the front pump was in the driver side / LH head and was the reason fast (high G load) uphill right hand turns starved the engine of oil. The oil accumulates in that head where the scavenge pump can't reach it to return it to the sump. I think I have the situation correct, but perhaps I am wrong about which head has the pump in the front (of the car).

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No, you're right, if you look you will see there is plenty of reports that the right turns are the bigger problem.

Either way, some folks have had pressure drops on right sweepers, and others have had it on left sweepers. Deficient oiling system either way.

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Its a system I developed. Its an option on all Stage 3 and Stage 4 engines built here at Flat 6. Again, the key is to keep oil temps in check, and use a proper oil. Right oil, right place, right time, and in the right pressure are the basic fundamentals of lubrication. The shape and size of the stock sump area is another problem with oil control.

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I have been thinking about adding a large external cooler. Do you (would you) sell dry sump discrete ? You can feel free to PM me detail. I currently run SPOFA, 1042, 2QT LN and XP9 oil.

No, I do not sell any parts of my engines. The only commodity that we have is a complete engine. This focus is what separates us from all the folks out there that try to sell anything they can get their hands on.

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OK, then we’re back to there is not currently a dry sump available as yours are are only available for those purchasing one of your motors.

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Not deep sump, dry sump. Which makes it existing, and available. A few people have built their own systems using other commercially available pumps, and tanks/ etc. Most of them learned a huge lesson on their first try, and so did I. Lots of the internal oil system has to change if you add a dry sump. These are internal mods to passageways, and that iOS why I believe the engine has to be manipulated during the build process to fit a dry sump that will be effective. Packaging of the system is the biggest challenge.

Sure, I will be more deliberate in my wording. Unless you purchase as a component on a FSI engine, there are no dry sump kits available for our motors and that is too bad for those of us that would be interested in purchasing. If I am ever in your que, I’d be interested in discussing with you your setup.

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Even if a "kit" were available, you'd not be able to optimize the oil system for proper dry sump oiling without full engine disassembly. This is the reason why a kit of components to make this work would be less than effective.

@zbomb your experience mirrors mine. On the 3rd or 4th heat on track days is when I start to notice oil pressure drops and more sloshing of oil with the potential of overwhelming the aos. My car almost always ends up with a little smoke from the tailpipe on the last start up before I go home as some oil gets into the intake. My plan was to go with the Mantis 1.2 deep sump as the larger one eats up too much ground clearance next year and live with it. I now will not push the car for too many consecutive laps without a cool down lap in between as well as a proper cool down in the parking area after a track session. I also leave the car idling for 2-3 min for the aos to cycle a bit before shutting it off. I think the reality is that it is too cost prohibitive to "bulletproof" a M96 motor for heavy track use and you either drive around it or live with the wear and tear (or spend $30k on a FSI motor in which case you have more options in porsche ownership IMO).

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Chris Cervelli at Cervelli Technical Service designed a dry sump kit. I believe he's only run it on boxsters but could potentially be used on a 911. I would reach out to him. Be forewarned, the cost will likely be 6k+, plus install, which is not trivial Do your external oil cooler (keep the lines short) and run xp9 or xp6. Then keep the revs below redline. And pray.

Packaging is a lot easier in the Boxster.. You have a lot more real estate to work with due to the trunk area, and etc. Yes- 6K+ is a real figure for a system like this. At that, there's hardly any margin in it for the person who designs/ builds the setup.

I have an oil pick up that is modified. It is based on the principle of the oil pick up in an airplane. There they use it for flying upside down. So a dual pickup in a vertical orientation as for the plane. Becomes a horizontal configuration in the sump of the car. The pick up is T-shaped with baffles on each distal end left and right in the sump. The baffles slide back and forth under centrifugal force in a curve to open the pick up at the side where the oil is moving due to centrifugal force. Works like a charm. Whatever oil is available piles up on one side of the sump where the pick up is open. You can even see the oil pressure going up at certain point as the oil column at the inlet at the outside side of the curve becomes much higher in the curve as all the oil is there. The extra pressure at the inlet due to the extra height of the oil level compared to normal helps the oil pump. Unfortunately I have no picture of it. Kind of a secret of my mechanic.

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I saw my first one of these in the mid 1980s in a dirt track car. Some have been made to float in the pool of oil, others pivot to follow the pool of oil as the inertia moves it in the sump. These were first employed on moonshine cars that would later form NASCAR.

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Do you mind sharing who your mechanic is? Ive drawn up plans for something similar but if its already been done id rather not reinvent wheel.

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Hmmm. This is intriguing. I wonder how well an aircraft style flop tube would work in these engines? A flop tube is a flexible oil pickup that is weighted at the free end. This gives the tube momentum to follow the oil in turns.

All rigid! like a T shaped flute. nothing moves except the flaps sliding left and right opening/closing the pick up openings at the distal ends of the T.

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Are the baffles still in place or does the tube ends extend all(almost) the way to the sump wall?

The red line here shows where the oil level is when doing a steady 1g turn with 10cm oil level in the sump. 10cm is 1cm lower than minimum(the dot) on the dip stick. So, i doubt that the oil pressure drops we are seeing is due to oil moving left/right in the sump and causing the pick up going dry. I suspect the baffled chamber goes dry because the flow in-to it is too slow...or fills with aerated oil due to the inlets is skimming the aerated top surface of the oil. I haven't found an exact number but the flow is roughly 1qt of oil per second close to redline, that is a lot of oil flow. Jake, maybe you have a more exact oil flow number I can use?

If the oil pickup positions are altered to the sides as shown (purple zones) the oil level at these positions places a significant role. Can somebody indicate more or less at what level the oil pump is. just wondering how big the difference in hydrostatic pressure of the oil column is and how it would affect the oil being supplied to the pump compared to the original or deeper sump kits. I am not aware of the absolute effects of these oil level differences and how sensible a gear type pump is to supply pressures. The lower the pick-up and the oil level is with respect to the oil pump the more it needs to suck the oil. Maybe it is minor to no effect. Anyone?

The problem I see with locating the two oil pickup tubes to the outer side of the sump is in a hard left/right sweeper, yes, one pickup tube would be sucking up the oil that sloshes to that side, but the other one would be sucking air, and thus probably creating a lot of aeration. Only a thought...

From the lowest part of the pick-up to the pump gear center, it's around 95mm...give or take a few mm. The oil level is higher than this if the car is on level ground. The pump is very capable. This type of pump delivers a constant flow depending of RPM and can deliver enormous pressure. To protect the engine from over pressure there is a bypass pressure relief and ultimately the driveshaft to the pump is designed to break before you damage something serious.

Yeah, it's not like shearing the oil pump drive would ever cause something else "serious", right? It makes a ton of sense... "Let's design the oil pump to stop delivering primary oil supply completely, in case we have too much pressure", It takes a real engineer to design something like this.. One that has no practical application experience, or common sense. The very first M9X engine failure I experienced with my program was due to the factory oil pump hex drive shearing in half. If you want to see a total, and instant loss of everything within the engine, try this failure on for size. Nothing was salvageable. It was at that instant that I stopped building engines completely, until we could develop the billet oil pump hex drive that has been sold by LN Engineering since 2007. 100% of my engines have received them since this period, and I won't build an engine without it. I love the inventive discussion in this thread. The thing that each of you need to realize is to get this sort of thing "right" you'll need a sacrificial engine. You are almost guaranteed not to get it right on the first try. I popped 3 engines before I figured it out. At the end of the day, you are reinventing the wheel for no real reason. 95% of the people on this forum can't create a scenario where the stock oil system is put over the edge, as long as oil temperatures are kept in check. Keep the oil cool, and that's all you need to do. I have several hundred examples that prove this, some in service since 2008, like the engine that @ltusler has had in his 996 since late 2008, which has only seen the track. Just keep the oil cool, then the rest works. You are much more likely to become a zero, by trying to be the hero who solves the problems with this oil system, that you'll likely never experience if you just keep the oil cool. The enemy of excess oil temperatures lies in the factory engine oil/ coolant "heat exchanger"... You notice that I didn't refer to it as an "oil cooler". I blow things up for fun. Next week I plan to sacrifice an M97 engine in the name of fun, and entertainment. We learn something with everything that we kill on purpose.

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As an owner of a FSI 4.0 Stage III Track Performer, I have no trouble with the pressure dropping. Yes it dips a bit on long right handers, but I have had no issues. Jake built the engine for the intended use. Its been in service since 2014 and has seen 3250 track miles, through DE and 3 seasons of PCA Club Racing running in the GT-3 group. I run Hoosier R7's. My home track is BIR so that accounts for 2/3rds of the miles and Road America is the other 1/3rd. LN Sump plate 3rd Radiator Motorsports AOS Custom Bearing Clearances Billet Crank All the improvements FSI had in 2014 Amsoil Dominator 15-50

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True.. I was adding up the first generation period too; before the AOS popped.. But at least I called it, and the UOA told me that things were imminent!

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No, no problem. It is designed with a system that closes/opens the right side of the pick-up due to the g-forces applied. That is the whole clue. Jake, it has been tested. On track. In the particular problematic turns the oil pressure goes up instead down. Surprisingly to see. As a hypothesis I cannot find any other explanation then that the oil is pressure fed better to the pump due to the much higher hydrostatic (or we have to say oiliostatic &#128521 pressure at the outer parts of the sump in a turn. Or just less air in the oil at such relative deeper levels. But I am not an expert to judge such theory.

Jake, if you broke the drive you did something that you where not supposed to do. Or maybe you already compromised the part at assembly? Apart from you I haven't read/heard one single person experience it. If you know one which is documented, please link.

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I break every rule. This engine ran 14:1 CR, among other things. It revved like a motorcycle. It's my job to break things before anyone else does, and to experience the things that others never get the opportunity to. The engine that I used as a "core" for this 4.0 that failed due to the drive snapping was a brand new, Porsche factory crate engine with zero miles on it. Back when these engines were cheap, and cores were not plentiful, I used to buy brand new ones, and take them apart, to make them my way.. That said, I've had two people in my hands- on classes experience this, and have assisted at least 2-3 other people who have had this occur. The other engines were stock, where mine was insanely modified. I'll find the pics of the failed drive over the weekend. They are stored online in an archive, and they are pretty deep in there. Also, you never answered my questions about your direct experience with building these engines. I guess I'll keep waiting for that.

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As a data point, the 996's were used at the Porsche Sport Driving School in that period when they were new at Barber Motorsport park. I was lead Porsche Technician at the Porsche Birmingham Dealership 5 miles away and was in charge of repairs to the fleet of 996's at that time (later changed out for 997's, 991's ect as new models were released.) These cars were tracked daily 7 days week by Instructors and Students of the Driving School and none had oil pressure drops on turns using Mobil 1 0w-40 and running on "N" spec tires of Pirelli, Michelin, Continental. That said, some of these cars definitely experience pressure drops on turns after they have some age on them. That is not a good thing, but some survive a long time with no terminal failures.There are over 50 critical clearances in the M96 engine. 7 main bearings, 6 rod bearings, 16 cam bearings, 32 lifters, 3 chain tensioners, 2 vario-cam Actuators.ect. Like Jake said Porsche built these engines a bit on the tight side (as far as racing engines are concerned) but if only one thousandths of wear in over 50 places will cause a significant increase in oil flow. The oil pump is large enough to handle the extra flow without any pressure loss, but the extra flow causes more aeration of the oil, and there is some oil drain back passages that are too small ( about .250) IMO, these needs to be enlarged so the more oil flow can get back to the sump quicker.Like Jake said, keeping the oil cooler will keep it thicker and keep the flow less.Extra oil capacity helps in both cooler and thicker oil/less flow,( deep sump).. This is actually a very good concept !! It will give the effect of 2-3 quarts of extra oil capacity, and with a 2 qt deep sump, will give the effect of 4-5 extra qts. 9qts is plenty of oil for our engines if controlled properly. This design concept will definitely keep the oil pump pickup in the desired place on turns/high g-force if the hardware construction/switching device is solid..

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Share the secret!

I also notice bigger pressure drops, and issues with 3 chain engines. This is due to the difference in the cam adjuster on the 5 chain, and the vane cell adjuster on the 3 chain engine. Others have yet to connect those dots. I did when working with Lake at Driven Racing Oil on the development of oil for the Ford Coyote engines. The primary oil system didn't change enough between the 5 and 3 chain engines, despite a huge difference in the way the engine uses volumes of oil, and pressure to actuate VV and Variocam+. Adding a 25% larger oil pump will open your eyes, if you know what to look for.

Yes Jake I think you probably compromised that part in the assembly process because you haven't got a scooby Doo what your doing have you lol

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That is interesting, thanks for sharing. Do you remember if you followed the Porsche standard 15,000mil on oil changes or did you have an internal oil change interval? My look in to the pressure drop issues so far points very much to the use of too thick oils. You wrote That's not correct. The pump(positive displacement pump, google) has a fixed flow directly in proportion to RPM. If there was any increase of clearances/leak this would show up as a pressure drop. I had a discussion with my wife over lunch today, she is an hydraulic engineers. Completely un-interested in engines until I brought up baffling in a tank, hydraulic stuff. She told me the main reason for using baffles is to lower the highest level in the tank....that would mean in our case they are there to prevent oil pushing up in to the crank/cylinder area. After looking at the dimensions on the X51 baffles inlet ports, it is most likely design for this purpose. It's not design for keeping more oil at the pick up, it's just a short lived side effect (1-2 seconds). I'm waiting for your answer of your direct experience with rolling bearing elements...or engineering for that matter....guess we will wait forever on each other.

As Jake pointed out �keep the oil cool�. This makes sense to me and seems to be supported by anecdotal evidence: I never loose oil pressure in turns (on ramps as an example) when the oil is cooler. Once it gets up to operating temp, I see drops. I am going to install an oil temp gage to document at what temps I notice this. If oil temps are high, then I can investigate as to why.

Written by an MIT student, interesting read(p12-25): https://dspace.mit.edu/bitstream/han...=2&isAllowed=y

I tried to explain the correlation of oil temp and lubrication problems to Nick in a different thread. I was a miserable failure on that objective. Now the real experts have weighed in, but there�s still disagreement. Sometimes when everyone else is wrong, it means that you are either: 1.) Jesus 2.) Wrong Either way, I�m sorry.

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Yes, standard Porsche protocol was maintained at 15k on 996 and 20k on 997 as stated in owners manual. I begged them to service sooner than that, but they conferred with Porsche and was told to go strickly by the protocol, and that also meant on center lock wheels used on the track to replace wheel bearings at 4k track miles and replace the wheel carrier and center lock mount and nuts at 8k track miles, quite an expensive maintenance item. Thicker oil does not cause a pressure drop, it does cause less flow though. Simple physics. Your incorrect, Yes I know the oil pump is a positive displacement pump, but it does displace more volume than the engine actually needs as a wear/safety/longevity factor, and hence one of the reasons for the pressure relief/by-pass valve of the oil pump, to limit the upper pressure to 5 bar and by-pass unneeded volume. Again simple physics. An increase in clearance (smallish) will lower the pressure at certain RPM's , but the volume of the oil pump is still over designed enough to reach full pressure of 5bar when the relief/by-pass valve opens. Of course if the clearance/leak is too severe , it cannot reach full pressure of 5 bar. There was an issue with the 986 m96 engines with a vibration/rattle noise. The cause was too much clearance between the crank carrier and the cases (machined fit). Test procedure was to connect a manual oil pressure gauge to the port on the head, engine at operating temperature, rev engine to 4k, engine should have above 4 bar pressure oil pressure, if not replace engine.. Your just saying the same thing in a different way, ( and your wife)..lowering the highest level in the sump also keeps more oil at the pickup tube like every one says.(with same oil volume) Think about it, simple..

But can the extra oil column affect supply to the oil pump? Maybe just less aereated oil because of the extra (positive) push it gets. Communicating vessels.

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Yes !! The oil is always aerated to a degree, the closer to the oil surface the higher the degree of aeration. With the location of the pickup near the sump wall on the g-force side, it will be further from the surface during turns and will receive the lowest aerated oil. The aerated oil is always lighter and the bubbles take at least 10 seconds to reach the surface and burst. These bubbles are less than 1mm in size.

Yes, most cars utilise this effect, just bypassing unneeded flow(check page 23 in the MIT document for example, fig 1-7....already at 3k rpm ). I think the 996 is not meant to be run like this, it's in the owners manual that you should have approx. 3.5 bar at 5k rpm....thus never really run in to constant bypass. Bypasses are known to cause aeration. I don't think it's that simple. You are blocking oil volume in pockets at each baffle step, that's where the lowering comes from. These pockets are made bigger on the X51 by moving the inlet ports up by circa 5mm. Everywhere on the internet when you read about baffles they show a nice picture where the doors/flaps are closed on one side. Initially it makes sense and is easy to understand. But, in an engine your pick-up will empty that 'high oil level' space in probably less than 2 seconds and new oil have to flow in. Imagine the oil level decreasing in that chamber, where does the new oil flow in from? and what do the levels look like in an equilibrium state? You really don't get a higher level more than just momentarily 1-2 seconds (depending on RPM). If these trap doors also introduce flow restriction there might even be lower oil in the chamber at high RPM. Remember, the flow can be roughly 1 liter per second, that's quite a lot. If you look at the inner chamber where the pick-up sits on our engines, it's very small. The engine case is marked by the black "V" in the cross section picture, taking up a large part of the inner chamber space.

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The Technical Service Bulletins from Porsche trump the owners manual. Don't take everything you read in the owners manuals to be absolute fact. I I give up, your like when my oldest son was at the inquisitive mind stage, no matter what or how I answered his question he would always say "why?".. Except you are more educated and don't really understand the complexities of the dynamic forces and the trumping of some theories by simple laws of physics.

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Yes. Tire tech has increased dramatically in the past 20 years. Also like it or not there are just inherent design concerns with a horizontally opposed engine. Unlike a V engine, gravity doesn�t help oil get back to the sump as quickly. The horizontal design also exacerbates bore scoring issues. These are the consequences of choosing Porsche for your fun car. Yes a flat design has better balance, a lower CG, but it has drawbacks too.

So, which relevant TSB have I missed? I will look it up.

Quotes source post: 16917049

The one I described above, for engine noise on the M96 engine in the 986. Since I have retired I don't have access to TBS's anymore. But there was a service you could buy access for a year, month, day, or even by the hour for like $8 an hour. I don't know if the serivce is still available, I did a post on it a few years ago and gave the link to it. Be forewarned that the TSB's are Porsche property, and some have been lost/deleted if they feel they are no loner necessary or beneficial.

Was there one for the 996? While lots of parts are the same, the cylinder halfs and heads are not the same part number(what I can see). There could be a simple restriction(smaller passages for example) somewhere in there giving the Boxster higher oil pressure. Since this is for the 986, I believe the manual is still ok in this instance. If some one can find a TSB pointing the other way, do post. The M1 0w40 is a thin 40wt oil, it's 12.9cst when new. 12.5 to 16.3 cst is 40wt and 12.5 - 9.3 cst is 30wt. Reading UOAs the M1 0w40 in 996s, it is at 11.5-12 already around 3-4000mils, thus sheared to 30wt. If you follow the 15,000mil service, the actual oil weight in the engine would be mid to low 30wt at that time. When you change oil, there is some left in the engine. When doing a new fill of 0w40 after 15,000 mil you dilute your new oil with some old. Basically if following Porsche's oil and change interval recommendation, you run 30wt in you car. To all contributors to this thread, I'm trying to find the solution to this. Some times I will push you a little to get more/correct information. Sorry Porschetech3(and others) if you find it offensive, I'm not here to put anyone in a corner.

Quotes source post: 16917179

Nick, lets cut straight to the chase. YOU say you and Porsche wants 3.5 bar oil pressure max? IF so, why did Porsche even put the 5 bar pressure relief valve in the m96 engine? Why didn't they put a 3.5 bar pressure relief valve in instead like you want? Lets see if you can answer that simple question and make any since of it..

Quotes source post: 16917197

<<< Waiting....come on man, lets see what you got.

I have never said that I want 3.5bar max . 3.5bar at 5k does not mean it's max pressure, you can increase pressure by revving higher if you want. The 3.5bar at 5k is a measure and gauge point, like the 986 TSB. Let me explain. (on a side note, 3.5 bar at 5k follows the engine builders rule of thumb of 10psi per 1k rpm) When the pressure relief valve is open, you are wasting power. For highest efficiency you want a pump which delivers correct pressure all the time without wasting anything. Wasted power in this case turns up as heat and heats the oil, unnecessary. By setting the pressure at 3.5bar at 5k rpm you assure that the pressure relief valve is not in continues use while driving hard. The 911 is NA sports car, it's designed to run at high RPM for a long time. This is different from other cars you see which briefly accelerate and then keeps a steady economical RPM. Like the Ford in the MIT paper. That engine spends majority of it's life below 3k rpm and that shows in the oil pump. Not only does bypassing create heat, it also contributes to aeration. It's important, in a high revving sports car engine, to not run in to bypassing. The pressure drops I experience are at moderat g forces. My calculations show that it's highly unlikely that my pick-up sucks air, much much more likely that the oil is aerated. The X51 pan is not helping in this regard as the inlet ports sits higher and suck oil from higher up in the oil level.

Quotes source post: 16917239

That 10 psi per 1k RPM engine builders rule of thumb, is a MIN recommendation.You can get away with less but risky, most prefer more as a safety/longevity factor. If you want to tune your oil pressure to 3.5 bar at 5k operating temp, be my guest. You can use thinner oil, rebuild your engine with looser tolerance , or weaken the pressure relief/by-pass spring.( to 3.5 bar). If you just want to eliminate the drop on turns, I think Silks concept is the ticket.. In fact, a Partner (Rennlister) and I are considering designing a dual pick-up hardware/device using a similar concept but using g-force actuated simple mechanical valves instead of baffles, even though I don't have this issue on my 996 and have tracked it hard with oil temp up 250F..

No, you can not weaken the pressure relief spring. Then you will run in to bypassing much earlier(wasting more power) and not achieve the required 5bar at redline. Rebuilding with looser tolerances is just non-sense. You have yourself written that this car can run, in stock form, on track without pressure drops. You tune this by oil viscosity. Use 0w40 for 15,000 mil changes.... .or choose a 30wt oil and change more frequently. That's what I'm about to try out, it makes sense both logically and theoretically.

Quotes source post: 16917310

If you want to use 30w to lower your pressure, go right ahead!!! You're so set in your opinions no one can stop you.. hurry up and let us all know if it works.. I use 5w-50 in my 180k mile 996 and love my pressure, and don't have any issue with drops in corners with stock oil capacity.

Quotes source post: 16913198

But also earlier in the thread you mentioned the sump pan design being deficient, so does this mean despite that deficiency you don't think it needs to be addressed for most cars?

Quotes source post: 16917310

I would not try this idea if I were you...even if it gives you your desired oil pressure (whatever that is), it will cause other problems. My personal solution to this problem was running older, and therefore a bit slippery, Sumitomo HTRZ III tires. Less lateral Gs...

Quotes source post: 16917905

No, he really needs to try this. I have tried to talk since to him, Mike has tried, he won't listen to you either. He needs to stop reading and thinking so much and get some tools out and get his hands dirty. When he says things like "the oil pump drive is designed to break" and "the sump baffles are not to keep more oil around the pick-up tube".and so much more, I'd have to type for hours just try and correct it all.

Quotes source post: 16917905

Well, that is one solution. Can you elaborate what problems I might run in to? Maybe I have overlooked something. The condition of your car, they way you drive and the climate/terrain where you drive all makes a difference. Running thicker oil will work for some because of these different factors. By changing oil more frequently you are effectively running thicker oil also. What I'm going to try is within the boundaries of the manual, it just happens to disagree with the common belief here on Rennlist. I do think it's ok to follow the manual. Some information in the manual have been superseded by TSB information, but it's still in large part accurate.

Quotes source post: 16917941

What kind of information/video/test/pictures/report etc do you need to change your mind? You need to think for hours to get it, not typing for hours. Look at the drive of the head scavenge pumps, same designed break point there. Isn't that a coincidence.....

Hey Nick...just do it. Quit yacking. Do your study and in five (5) years get back to us. Be sure to include a full tear down of your engine and UOA. "hands over ears" la la la la laaaa laaaa laa la la la lala la la la.......

Quotes source post: 16918018

^^^ And, in the mean time STFU!^^^

Quotes source post: 16912223

Your mechanic could spin up a business very quickly. Maybe under the UAOS brand with @Porschetech3

Quotes source post: 16917948

You are aware that "the manual" was written over 20 years ago...right? And almost every year Porsche releases an updated recommended and approved oil list for our cars. Why? Because over 20 years things have changed, blends have changed, brands have changed, quality has changed. The newly released Porsche Classic Oil for our cars is 5W-50. I'm going to trust the Porsche engineers and all of their testing.

For the experts. I am still not convinced about the oil pump and the oil level. But please consider me as not an expert. However I can be easily convinced by the right technical reasoning. From what I understood from the earlier answers I derive that the oil pump is perfectly able to PROVIDE pressure. Given that there is enough oil to supply. Supply is affected negatively by aeration. But is it sure that suction power on the supply side for the pump when the oil level is much lower compared to the pump. For example it would be interested to compare output pressures in a test set-up when the pump position is 5 cm lower or higher. Again I have no practical knowledge about these type of pumps. And I am unable to find some additional info about this. So I am happy to believe that it makes no difference if someone can confirm this from his expert knowledge.

Quotes source post: 16919331

What you are playing with by moving the pump inlet up or down in the sump is net positive suction head (NPSH). Moving the pickup without lowering the pump does nothing to increase NPSH. Even moving the pump inlet down further does nothing for pump performance when discussing a positive displacement pump, until the point where the pump inlet pressure is below the vapor pressure of the liquid. Read up on NPSH for positive displacement pumps and you will better understand.

Lots of talk, just like the previous 20 years. Gents, I solved this problem. I had a dry sump kit for sale for a couple years. I had about 10 sales and gave up on it. It is too expensive for this market, and not usable on a street car. I sold kits for $8500 and barely made money on it. The tech support alone made it not worth the trouble. This market wants an easy solution that can be installed in a day for under $3000. IT IS NOT EVER GOING TO HAPPEN. Most of the content of this thread is completely, 100% wrong. Just guys talking on the internet. If you want your M96 to have oil pressure in all conditions, contact me. I have what's necessary to make that happen, but it costs as much as a decent used Boxster S. Also, even after you solve this problem, there are other technical issues standing in the way of GT3 type reliability. Don't bother with the intermediate steps like sumps, auxiliary pumps, and Accusumps. They are a waste of time and money. Chris Cervelli Cervelli Technical Service

Good for you! You made your point. But I think it is not because you solved it that we cannot talk anymore about alternatives or even just discuss the technicalities of the problem.

Quotes source post: 16920711

You guys are not actually doing that. You are just rehashing the same crap that's been on Rennlist for 20 years.

Quotes source posts: 16919331, 16920378

Rockhouse66 is right, moving the pump or inlet up or down a small amount will not have much effect as long as its not extreme enough to cause a dramatic lose of inlet pressure or cavitation. For a scientific look at forces/pressures, and for simplification assume water and oil weight the same instead of oil weighing less by 0.91.. Start with Atmospheric pressure of 14.7 at sea level Then with engine running, subtract crankcase vacuum of about -4 inches of water ( if using the UAOS) which equals 0.15 psi..so 14.7-0.15 =down to 14.55 psi on the surface of the oil.. Then to see the pressure at the bottom of the sump/pick up tube, add the inches of water/oil column, say 4 inches depth , So 4 inches wc or oc = 0.15psi so 14.55+0.15-14.7 ,so back to 14.7 psi at the pickup tube/bottom sump. Then if the pump rotates enough to remove trapped air from the pickup tube, the oil level will rise to surface level with no additional suction needed. Then if the pump inlet center is located 1 inch above oil surface level, then the pump will only need to lift 1 In water column or oil column to reach the pump inlet,To lift 1 inch requires a suction or negative 0.037psi. So the absolute pressure at the pump inlet would = 14.663psi. at sea level. On the outlet side of the pump the pressure is determined by the efficiency of the pump and the pump volume, and is developed by the resistance to flow using clearance and oil viscosity.

For the track, isn�t one solution to use racing oil at the track? Aren�t there oils that simply don�t aerate nearly as much as good ol� Mobil 1 (Street) oil? As Jake said, it doesn�t solve the temperature problem, but then again, racing oil can generally withstand higher temps anyway.

Quotes source post: 16921003

Not really, just because it hasn't been much improvement in 20 years doesn't make it impossible. The AOS hadn't received any technical advancement in 20 years until I designed and invented the UAOS, you can look here. https://ultimateaos.com/ I agree the factory concept of " Integrated Dry Sump" missed the mark, but with a little technical advancement it will work .

So, the investigation continues. I had one of the scavenge pumps out today for inspection/measurement. It's properly worn(177k km) so a new is on order. So, what would the effect be of a worn scavenge pump?

Quotes source post: 16921251

Why don't you ask the person that told you that Scavenge pump snout right there was designed to break off on purpose, or the one that told you the main oil pump drive was supposed to break to save the engine? Or just go away, and stop spreading false stupid information, you're hurting the forum badly..

Porschetech3. How many years have you been here on this forum telling people to use thicker oil, baffles and deep sumps etc to stop the pressure drops? Like Cervelli said, rehashing the same crap over and over. Here we are in 2020, still people are having the same issues to this day. Makes you look quite stupid. DEAL WITH IT.

Quotes source post: 16912855

This is a cool diagram. Your basic assumption is wrong though. There isn't 100mm of oil level in the sump under track conditions. I don't know the exact number, but I expect it is closer to 2 cm, which is why modifying the sump or pickup is a waste of time. Chris Cervelli Cervelli Technical Service

Quotes source post: 16921317

Nick,I usually don't give out advice like that, unless I know it will help someone in need. You on the other hand go out of your way to say things like" the oil pump drive is designed to break on purpose to save the engine" and "the Scavenge pump snout is designed to break on purpose" and " the sump baffles are not there to help keep oil around the pick-up".. I know your wife told you the last one, but who told you the other two? Oh and" the IMSB problem is made up, the factory bearing is best !!" Did you dream it up? I know for sure Porsche hasn't written any thing of the such !!! How long have you been interested in M96 engines? If you would get off your "high horse", you might be usefull to the community, as it is you are just spouting stuff you read out of context, and making your self look ignorant..

Quotes source post: 16920572

Do you have inputs for improvement that don�t include putting a boxster S under the 996 hood ? External oil cooler ?

Quotes source post: 16921626

As Mr Raby says, cooler oil is better. He does not say what temperature he prefers, but I would like to see a normal operating oil temp of 200 degrees. This is not going to happen unless you are racing in 30 degree weather and the cooling system remains in the control range of the coolant thermostat. Maybe in Canada, but I doubt it. It seems very unlikely that you could run oil lines to the front of the car, install an air-to-oil heat exchanger there, runs lines back and have that arrangement be an improvement over the stock oil-to-water heat exchanger, which works very well. With the stock cooler and with a 3.4 engine, expect to see an oil temp 40 degrees F higher than the coolant temp when you are racing, which means the oil is likely to be over 250 on a hot day. So the engine and everything else has to be able to withstand that temperature, and all you can do is try to drop the coolant temp and drag the oil down with it. It would be great if the stock cooler were more effective and could shrink that 40 degree delta, but it is what it is. It is not going to happen. On a hot day, the coolant will be 210 and the oil 250. Plan accordingly. I have raced these engines many hours with the coolant temp at 235, and they will sustain that without damage. The resultant high oil temp is a much greater concern, even with a dry sump. Chris Cervelli Cervelli Technical Service

a lot of people have stated out of hand that accusumps don't work. i think some of that is internet lore due to initial misapplication of the product. there was some good real data-based analysis on 986forum measuring pressures at different points of the engine with/without accusump, with accusump introduced at different places, with/without the automatic pressure switch, etc. i think if implemented properly an accusump is a viable solution IF oil QUANTITY is the issue (ie pickup tubes can't find oil because of lat-g or pooling in heads). if however it is not quantity but rather the ability of the oil pump to get the oil to the far reaches of the engine (ie, oil pump is going into bypass) then another soln needs to be found. here's the thread ... http://986forum.com/forums/boxster-r...some-data.html

Quotes source post: 16921251

Your AOS will be swamped. Oil will start collecting in the head. The drivers side bank will be worst as due to the location of the scavenge pump and oil return and an AOS vent line which gets flooded with too much oil there. It will start slowly. But every right (or left hand for bank 2) hand turn more oil will start flooding the AOS and eventually the in the crankcase will eject the oil out via the AOS outlet. Your engine will become an oil injected engine. I have been there and seen it. Luckily my AOS is rerouted via the air filter box and saved my engine. The oil came into the air filer boy (no catch tank at that time) and caused some nice BBQ smoke, This AOS mod is maybe not the most perfect. But it is a very safe one.

Quotes source post: 16921765

Got a link for this....?

Quotes source post: 16921608

I have explained all of that in detail during discussion but you are too stupid to understand(or actually don't read my explanations), that's all. IMSB, read here from post #492 and some 10-20 post forward: https://rennlist.com/forums/996-foru...-first-33.html The things that are meant to break: Well, when you'r an engineer you see certain designs reoccur over and over, this is one of them. I've used them myself many times. It's there to have a controlled break down, you know what will break if something goes wrong. It's good design practise. It's like using fuses in an electrical circuit, you protect stuff. The oil pumps on this engine bolts to the outside of the engine and connects to the inside via a weak link, protecting the inside if something goes wrong. Get it? Thanks for your input. I pulled the scavenge pump to investigate the oil return as I suspect the running level is too low.

Quotes source post: 16921900

See for example https://rennlist.com/forums/996-foru...l#post15569721 The issue with the scavenge pump is more discussed here. I also mentioned this modification in other threads on this forum where it is commented on. You can find it probably easily looking for posts with my name and ‘AOS’ ‘modif+’ as keywords Below is a photo how it looks like. The modification can be further extended with an overpressure relief hose going from the oil filler cap to the catchtank. That is the capped hose on the right you see. In the event of an AOS vent block, crankcase overpressure can get relieved via this connection. The catch tank is not compulsory but it helps a bit with keeping the air filter box clean. As you can see the weakest point at this stage is the material of the tubes which doesn’t like the tight bends, it tends to crack. When taking the photo just now I see it cracked again. Need to replace it The use of a rubber-like flexible hose is also not ideal as they tend to fold/collapse in a bend due to the extra elasticity from the heat of the engine. I notice I need to clean my engine bay I more thoroughly. But it is my daily car, outside sleeper. The AOS modification I have is probably not the most ideal following the expert’s opinions here. Check also PorscheTech’s thread about the ultimate AOS modification where my setup has also been discussed and conceptually been reviewed. There are advantages compared to other modifications/solutions: the AOS will never fail. I mean that the weakest link, the diaphragm is not subject anymore to the harsh vacuum application. If any oil comes out from whatever other failure it will not go into the intake. Your intake stays free from oil dirt Idle is much smoother as there is no more 'unmeasured' air form the crank int he intake Disadvantages: Your air filter gets a bit dirtier quicker, and you need to clean out the lower part of the air filter box once a while. There might be some dirt get past the air filter onto the MAF the experts says the crankcase pressure is not ideal. Related to disadvantage 1: never had any problem. I change air filter more often. Related to disadvantage 2: no issue for me. I check the Hot Film Voltage regularly. If it comes near to 1.05 or 0.95 I change it anyway. For me the MAF is just a wear item. It is one of the most important sensors in the car. Till now I replaced it every around 40.000km I think when you are tracking your car it is a nice solution to get rid off ALL the the risk of the most common AOS failure. I have this AOS modification on my car for 80k kms / 50k miles now. It has been further done on +300 cars by now. From what I heard no problems so far. At least mine is still going very strong. Total 135k miles now Okay lengthy post. Deviating form the original topic

Quotes source post: 16921732

I was thinking NACA in rear bumper behind wheel feeding into a shrouded heat exchanger mounted off the old muffler hanger. Shroud would be simple CF surround (prob NASCAR surplus ) with heat reflective foil on the outside. Exhaust vents cut into back of rear bumper. N for duct inlet

Quotes source post: 16922498

Because of the shape of the car and the proximity to the wheel that's a low pressure area, which is why the Turbo's intercooler exhausts are located there. I don't think you would get much if any airflow into a duct located there, even a NACA duct. You could exhaust there though I don't see an obvious way to supply intake air. Were it me I would locate an oil/air heat exchanger on the driver's side of the transmission with fan forced airflow. That is where the oil/air heat exchanger for transmission cooling is placed when adding pumped transmission cooling to the G50 gearbox. Another choice would be an oil/water heat exchanger with a separate water circuit. A third possibility would be keep the existing oil/coolant heat exchanger and improve the cooling system. When I ran Lime Rock in my Turbo on a 90 degree day I had coolant temps max out at 195 degrees and oil temps at 220 degrees. That's with the stock Turbo heat exchangers - and the Tiptronic ATF cooler is also in the water cooling system. It does seem that a classic air/oil heat exchanger would be the simplest if it could be made to work.

Had the new scavenge pump installed this morning and I'm just back from the test drive. I test drive the same route all the time when testing this issue, it'a 10km road climbing around 500m up a mountain side. The pressure drops are now very much muted and some of the turns where it used to drop it stayed steady. Still not perfect but then again I have only replaced one side and seeing the condition of that one I think the other side is probably equally bad. Bank 1-3 seams a bit tricky to change tho, not enough space to pull out...or is there a trick to it? At the top of my test drive I stopped on a level surface and checked the oil when idling, it was reading at the bottom tip of the dip stick. When checking according to the manual (hot and level) it's at 4/5 full. Thus, just at idle on a level surface there is roughly 1.5L in circulation.

Quotes source post: 16922353

That is the perfect example of your preposterous statements !! 1. If the main oil pump drive breaks, what exactly are you protecting? Nothing !!! 2. If the Scavenge pump snout was designed to break, it does a poor job !! Many many times when the scavenge pump ingests a piece of valve spring or lifter debris it will lock up and instead of the snout breaking the timing chain will break !! This is not Porsche Engineers intention, this is your imagination !! Give it a rest....

Quotes source post: 16921732

When I ran the m96 engine, I had the Mantis 2qt sump and plumbed some -8 lines to the front where an oil cooler lived. The oil was being fed up there through a Mocal electric pump. The result was oil temp staying around 220-230* at the track (with 70-80* ambient temps). Water temps were roughly 210-215 regardless of what I did (3 CFS radiators). I used JoeGibbs racing oil in part due to the advise on this board (which didnt change temps or pressure). What i noticed is oil pressure dropping down to 1bar (sometimes 0 bar) with anything above 1.1G turns (so 80% of the turns on my local tracks). This was with 200tw 225/265 Hankooks. I was taking temp from the sump so it was pretty accurate. I tracked the m96 for 2 years before I realized nothing short of a dry sump would solve my issue. An accusump will help with most tracks, but some will still be an issue. I see tons of people track their 996's over the years and some do fine, some blow up. To be fair, of all the cars I've seen come off the track with issues, the 996 is up there (boxster, cayman 996...any m96 engine). I gave up trying to mess with the M96 and sold it. A common mind set I've seen shared between people who track these things is: "I'm running on borrowed time". People are willing to accept that these engines can let go at anytime. If you can stomach that, I see no issue. I can't...there are significantly better platforms for racing (chassis and money wise). These cars are terrific for the road though

Quotes source post: 16922943

+1. If folks want a real race car, they should get a real race car. The stock 996 is not that.

So you used a discrete pump to move oil from the sump to the front of the car ? How did you ensure that when the sump volume was compromised due to cornering that you weren’t exacerbating the issue by pumping what oil was left in the sump to the front mounted cooler ? Where did the oil re enter the oiling system after leaving the cooler ?

Quotes source post: 16922976

good question. Oil cooler pick up was farthest away from the actual oil pick up (engine oil pump) and return was closer. Sadly, only real data I can share is that oil drop happened quicker and more severe without the oil cooler. Prior to the cooler, oil temp would get to 250-260 in similar conditions and oil pressure would never get above 2.5-3.5 bar in the straights. After the cooler, it would take longer for oil pressure drops to get to 1bar (they would usually only drop to 1.5-2bar) but it would always eventually get there...I was just buying time. At the end, I may have made some things better while others worse, which is probably what your question was eluding to. Mantis recommended this set up claiming that it solved some of their issues. Never solved mine. This may not have any relevance on the current thread, but I now run an LS3 engine in the 996. I use the same oil cooler set up (just on a ls3 pan). at the track, temps are managed within reason.

Quotes source posts: 16922974, 16922994

I don’t get what the $hit that has to do with anything. Thread is about addressing a weakness with the platform, Some really smart guys have provided their thoughts - that is a benefit to the community regardless purpose of use of the owner. If only race cars were used on track, Track attendance would be pretty low huh... Jason I applaud the ingenuity but I would. not run setup a system like that. 1. I would never want to rob the sump of oil 2. your dumping cooled oil back in with hot instead of letting it soak heat by running through motor first 3. Long lines/external pump Good input though as not a lot of folks have seemingly tried the external cooler method.

Quotes source post: 16923001

you're not really robbing the sump since the lines are never empty to being with (and if they are, its because they failed to pick up oil from the sump, so there is extra oil in the sump). If you're continuously running the pump, the oil in the sump balances out temperature wise. I agree with your third point on extra stuff to break/fail but that was the only way I could make it work. Going on 4 years without any issues.

I've been looking for what way the oil that goes to the heads can travel inside the engine. The pictures below have been to great help. What is obvious is that there isn't any good way for gravity(without the scavenge pumps) to drain oil from the heads back into the sump. The green arrows(four small holes) are the main way for gravity to get it back there.( I think there is also bigger holes, where the top of the swirl pots are located, but they are located above the cassette drain holes. )This can be compared to the big cut outs just above which drains the cassette (rod and main bearings, sprayers etc). There is, as you can see marked by the red line, a small passage where oil can travel between left and right head, meaning that both pumps kind of work to scavenge the same oil, in parallel. If you are constantly turning hard there is only one scavenge pump working at a time as the other will run dry. One idea can be to increasing the gravity drain back holes. I believe this will help keeping the sump level higher(avoid pooling) as this off-load/help the work of the scavenge pumps. The cavities for the cam chains is the only big place I've found so far that could pool any significant amount of oil. Correct me if I'm wrong, I might be, I've just spent a few hours on this.

Quotes source post: 16923503

Nick, you are on the right track. The intermediate shaft channel, along with the chain areas (I call this the "Z") is full of oil, all the time. You need to consider what happens to this oil with respect to those drain holes under acceleration, which you will be doing 90% of the time on when you are on track. You are wasting time and money replacing the scavenge pumps. Yours were functioning fine. They don't wear out. Any data you think you are gathering by watching the OP gauge is garbage and is worse than useless. You can skip right to the end of this exercise by roughly calculating the internal air volume inside the engine. That's how much oil you need inside the engine to guarantee that there is sufficient oil in the sump for the pickup to remain submerged in all conditions. When the engine is running at high rpm, it can hide 15 qts of oil in its internal volume. I have data that proves this. The crankcase environment is dominated by the air moving around, and how the chains are moving the oil, not so much by gravity. In other words, there is no guarantee that oil flows downward. Chris Cervelli Cervelli Technical Service

Quotes source post: 16913559

^^^^^^That's a pretty good idea , I wonder where you got that? Do that and lets see how it works on your car, mine is fine.

Quotes source post: 16923646

Did you solve the drain back on your dry sump systems or just accounted for 15qts pooling? Why is the OP gauge garbage? And, what should we be measuring? I measured my old pump, it is most definitely worn. In the pictures above you can also see the wear in the main pump body(alu piece on the right), it's worn away almost 0.1mm. Normally this kind of wear reduces pumping capacity.

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My data shows that with the current system, which includes some small mods to the engine itself to improve oil scavenging, the oil tank level (average level over the course of a lap) is around 1.5 qts lower than the level in the tank when the engine is idling. The system is doing a good job of scavenging the oil out of the engine and returning it to the tank. There are 3 additional scavenge points and the stock pump is repurposed to be a scavenge pump so there are a total of 4 scavenge pumps. The two stock scavenge pumps are still in place also, but I don't count those directly because their output has to be re-scavenged by the stock pump. The stock OP sensor is very slow to react to pressure changes. The pressure drops are likely to occur when your eyes are on the road ahead of you, not watching the gauge. If you see pressure drops on the gauge while driving, you can be sure there are bad pressure drops happening. Also, the oil pump will create about .5 bar air pressure at high rpm even with NO oil in the sump, where guarantees that the idiot light will never illuminate at high rpm. You should redraw the above diagrams with the horizontal lines tilted to show the influence of .25G in acceleration and 1G in braking. Show the lines for mid engine and rear engine applications. The drain holes there are not significant. Regarding the movement of the oil within the engine, consider the case of a mid engine car in an accelerating right turn: On the left side of the engine, the scavenge pump on the front of the head is dry due to the accel G forcing the oil into the rear of the head. No return to the sump is occurring. On the right side of the engine, the cornering G pulls the oil into the intermediate shaft area, away from the scavenge pump on the rear of the head. No return to the sump is occurring. There is another factor at work here. The stock oil pump is really big, and runs at 66% of crankshaft rpm. It pumps much more oil than the pair of scavenge pumps, which runs at 50% crankshaft rpm. Because of this disparity, the engine does rely on gravity to return the oil to the sump. The sump shape is really bad too. I think they had to do this to get the necessary volume without reducing the ground clearance. Chris Cervelli Cervelli Technical Service

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I found this hard to believe. If the scavenge pumps was pumping slower than the rate that the oil arrives, we should all be pooling oil and running the sump dry. The gravity drain is as mentioned earlier, rather insignificant. Not plausible. I measured the scavenge pump and it will pump around 42L/min at 7000RPM(crank RPM). I assume (I'm lacking any exact number here, please fill in if you have) that the main oil pump pumps around 70l/min at 7000RPM(crank RPM). If we assume 2/5 of the oil goes to the heads(slightly more if running an oil feed IMSB) that is a flow of 28L/min. So, if both scavenge pumps work properly we have a scavenge rate of 84L/min which is an over capacity of 3 times. I wrote earlier that my pump was worn but after further investigation it is badly worn out. Numbers I found would indicate a reduction of 30-40% of the pumping capacity. If we calculate that both pumps are toast(-40%) we still have 1.8 times the scavenge capacity, well enough if driving straight. If we further look in to driving, we don’t drive straight all the time. And here is the interesting thing. If we assume a very twisty road where basically you never drive straight but corner hard all the time, then only one pump will scavenge at any time. If we only have 1.8 times over capacity(both pumps toast) that means we are running in to pooling since one pump is not able to scavenge all the oil by itself. After running the numbers I’m more certain this is an issues of worn scavenge pumps. EDIT: If you have this problem when driving a stock car on road tires.

I've now put the car to test with both scavange pumps replaced. The right side pump (passenger side) is very easy to replace but the drivers side is very tight. It is possible to replace it with just taking the wheel off. The old pump can be disassembled in pieces and easily taken out but the new is built different and needs to go in in one piece. The trick is to file away some material as shown in this picture, then it's possible to get it in without removing anything: Removed material On my normal test drive I had 4 turns in which I usually could provoke oil pressure drops. They all had in common that the precursor was several right/left turn and then a strong right i.e no straight driving just before. I guess this caused pooling of oil because of the old/worn scavenge pumps. After changing both pumps I went for a test drive and only in one turn showed a slight drop. After the drive I checked the oil and it was only half full. Then came the second corona lock down here. Last week I was able to get out again, this time with full oil and now there is zero pressure drops. Rock steady. I guess not everyone will have worn scavenge pumps but it's dead easy to take off the passenger side pump and check. My passenger pump had scoring and very loose tolerances, in the area of 0.12-0.15mm on the internal clearances and >0.25mm on the rotor-to-case clearances. On top of this scoring/pitting. The driver side was significantly worse compared to the passenger side. this is what my driver side pump case looked like: Driver side scavenge pump scoring driver side scavenge pump scoring

Folks, this is an incredible thread that I hope will become active again and updated with additional info. For those of us that don't have the engineering/mechanical knowledge and experience of the contributors, we truly appreciate your insight. Thanks to Nick in referencing it in De Jeeper's "Another One Bites The Dust" thread.

My next step is to implement more cooling... as can be seen below - hotter oil = more pressure instability.

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Jason, After reading the complete thread, it looks like it may be a an important preventative step that most of us haven't taken yet. I know with the AIM system you integrated, you have been measuring and ultimately traveling down this path. At this point I certainly wish I had an engineering background to fully understand the details. But at least I can follow along with the concepts and potential application. Appreciate your approach and shared findings.

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I've come to the same conclusion, and purchased the parts for an external oil cooler, but haven't had the time or energy to install it. And while running the heat exchanger, dropping coolant temps with better flow, center rad, better rads like CSF, low temp thermo, etc, will make an appreciate difference to oil temps.

Zbomb, looking at your graph the oil pressure is constant from say 4500rpm and up. This indicates the oil pump by-pass is open and the flow of oil is constant. It will reduce the efficiency of the oil cooler. You probably want to run a thinner oil to increase the flow at high RPMs, this should bring your oil temp down.

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With whatever i do u will be adding a cfs center rad and remote larger 997 cooler per Charles' advice. I already have a low temp and cfs side rads. Just considering it as part of the upgrade costs.

I would NOT recommend using thinner oil to increase flow,( It reduces pressure )there are other ways to increase flow that are much more desirable, if that is your intension. Increasing flow by using thinner oil and reducing pressure will cause more "dessolved air" to be released from the oil to form bubbles that can block flow. Oil always has air in it that can be dissolved in it or entrained in it. The higher the pressure the more air can be dessolved in the oil. Dessolved air in the oil causes no problem, "entrained air" (bubbles) will be formed if pressure is reduced (thinner oil) and will cause overheating and flow restriction. The oil pump by-pass does not by-pass untill 5 bar pressure is reached

How would you increase flow and what minimum oil pressure would you say is safe?

Isn't there an x51 oil scavenge pump that helps the high g pressure drop, also I'm sure I saw a thread where someone was also making a modified scavenge pump cover to replicate the x51 pump , also is this the best route to solving the problem, doesn't the high g keep the oil from draining back to the sump and stays collected in the head ?

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I believe the X1 adds a 3rd pump, but I think 4 head pumps are ideal, along with improvements in the swirl pots. And by the time that�s done, you still want a deeper sump and AccuSump, not to mention racing oil.

The X51 pump sits on top of the passenger side pump and sucks from the front of the passenger side head. It's basically two pumps stacked on top of each other. It's purpose was to avoid pooling in the front of the head during hard braking in a left hand turn. Together with the X51 sump plate/baffles this was dropped on the later 997 X51 kit. I've seen someone produce(or maybe just built a one off) replacement pump. I used to have pressure drops but not any more. The combination of new chain tensioners, scavenge pumps and full oil solved that. I see I forgot to mention in this thread that my chain tensioners are new and I think this also important since if they leak they add to the pooling in the internal space.

So this thread kept going long after I found it interesting, but in the end is the answer under $1k there's nothing worth doing?

Sorry the world let you down, Marlinspike. Next time we'll try harder to maintain your interest. Chris Cervelli

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If you thought this one was bad - try this https://rennlist.com/forums/996-foru...stability.html 700+ posts of put you to sleep medicine.

I remember when being the original poster meant something! Kids these days....

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You Tube

Hate to see this thread, Jason's thread on Oil Pressure Stability, and Skips threads on the UAOS and UIDS get lost. Too much good information and experience with testing different configurations with cooling and aos usage. He'll, Chris' back to back 8 hour races in the Boxter without a dry sump system was enough to get anyone of us thinking. Further, Skips UIDS could be a game changer in many ways. My wife tells me I need to develop other interests than oil starvation and oil pressure stability. But call me crazy, are we not a few steps closer to further mitigation?