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YOUR RESEARCHOk, my turn. White smoke today..
Reported or suspected cause
piston ring differences between the two engines
Reported cause
No successful repair reported for this finding.
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Reported cause
Another reason is due to the piston ring differences between the two engines.
Leading evidence: 'piston ring differences between the two engines' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'piston ring differences between the two engines' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check coolant reservoir' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed
Non x51 engines are only fitted with one oil scavenging pump on one side.
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Performed · outcome unconfirmed
That 964 was built by a company ran by Engineers, not accountants.
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Performed · outcome unconfirmed · Original poster
After I ran the second run, a friend told me it was smoking from the tailpipes throughout the entire course.
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Suggestion
Oil ring tensions are also different between the two, and the fish scale test will show that to any engine builder that deserves to hold a wrench and fill the role.
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Suspected cause
The reason why the auxiliary pump will seem to alleviate the issue is because it removes some of the pool of oil from the heads and routes it back to the sump, reducing the volume of the oil in the head just enough that it may not get sucked by the valve guides and lead to the smoking condition quite as bad, or at all.
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Porsche didn't invent the Gymbal Dyno, and it's use during the design of the engine didn't help, because we see the same old problems we've always seen.
Took my 03 996 to a Porsche Club AX today and got a lot of white smoke. The engine has about 1,500 miles on it since it was completely rebuilt last fall with new AOS, IMS, RMS, etc. and it runs flawlessly. After the first run, when I got back into the pits, I saw some smoke coming out behind me. I kind of shrugged it off and thought it might have been brake smoke. After I ran the second run, a friend told me it was smoking from the tailpipes throughout the entire course. I let it sit a few minutes, and then when I cranked it up a pretty good cloud of smoke came out of both tailpipes. You could hold it about two or 3000 RPMs and it would clear out and then if you revved it up, more smoke would come out. When I left the event, it smoked every time I hit the gas for about 10 or 15 minutes. After about 20 minutes or so on the way home, I couldn't see anymore smoke, and when I got home I checked it and nothing and then I let it sit for a while and started it after 15-20 minutes and nothing and right now it is clear with no smoke.
This is the first AX I have taken it to so I'm wondering if this sounds like a typical AOS issue? Or?
A month ago I was at an autocross and had similar. (also an '03 996)
First run, no smoke. Then, the car sat for maybe an hour until the next run. Huge cloud of white smoke that looked like a NASA liftoff. Smoked much of the run, but at a relatively low volume. By the end of the run, the smoke had stopped.
That was a month ago, not a wisp of smoke since then.
By the way, I changed out my AOS last year.
Also, it's never done that before (smoked) at either the track or at an autocross. Odd.
I had a similar experience at a track day. Was your oil level toward the high side? I think the aos more easily gets overwhelmed when the oil levels are full or overfull and then some oil gets burnt off in the combustion chamber and then the smoking stops. I've seen recommendations that the oil be to the low point of full on the dipstick for this reason.
Might all be anecdotal though.
But the stock aos isn't really built for high intensity track work. A new one is as likely to smoke as an old properly functioning aos. Check your coolant reservoir for oil and your oil for coolant. If both are fine you are probably fine.
Reads like the AOS got overwhelmed and gave the engine a good shot of oil. Probably wet the heck out of the intake manifold with oil which is why the smoking persisted.
Absent any signs the engine is not running right, and as long as the smoking doesn't return, that's what I would hazard a guess is what happened.
Be sure you check the oil level. I think you'll find it low.
Be sure when you attend another AX event you show up with the engine full -- but not overfull -- of fresh oil.
While I can't be sure I suspect the smoking episode was possibly partially due to oil that should have been changed before the event. While 1500 miles is not that many miles on oil depending upon how the car is used oil can still end up quite contaminated with unburned fuel and water (combustion byproducts) and these can have the oil more prone to foaming and thus creating more oil vapor in the engine which can overwhelm the AOS and the smoking was the result.
After everything JR has posted about tracking an unmodified M96, why are you doing it? I bet you even had the wrong oil in it too. Your lucky your car left the track intact (if it still is). Oil starvation and AOS/OVS issues for the stock M96 are no joke. Consider yourself warned for next time?
Jake's posts are awesome, but badgering everyone with reminders of everything Raby has ever said gets old. The people who post here are some of the most informed Porsche owners on the planet, so maybe throttle it back one or two clicks?
If anyone needs me on 11/9, I'll be at the stadium tempting fate by autocrossing my unmodified 996...WITH THE WRONG OIL Z0MG!!!!
If the smoke started right when you started it up after it had been sitting after a run, then this could be normal. after a high rev run, tons of oil pools in the heads because the scavenger pumps cant keep up and pump the oil out, then at the next start up, it smokes. The solution is to let the car idle for a few minutes after a run so the scavenger pumps can clear the heads.
That is exactly what mine did.
This was an AX, not a track event and there were quite a few 'unmodified' 996s there, but mine was the only one that smoked like that. If I was going to track it, I would have already done the oil pan mod and Motorsport AOS. (which I am probably going to do anyway at this point) And I work at a shop and yes I used all OEM fluids.
Tell me more about this????
Thanks for the info. Would the motorsport AOS be a wise choice at this point? Does it do a better job at this, or is it just a tougher piece so to speak?
IMO for any serious track work, you should have X51 pan, Motorsports AOS, and either the Accusump or the X51 dual scavenging pump mod as to not starve your engine in long hard sweepers, especially if you are running good suspension and R compound tires.
Non x51 engines are only fitted with one oil scavenging pump on one side. The X51 motors are fitted with two on each side. It doesn't guarantee you won't have oil starvation but definitely reduces the chances of it. If you are paranoid, supplement it with the Accusump as well.
The motorsports AOS definitely costs more than the standard AOS. It is also a more durable piece of hardware.
Whether it does a better job of separating the oil from the (crankcase) air I can't say. My WAG is probably not. I say this based on the assumption it is probably the same basic design as the stock AOS and thus shares its inefficiencies.
At the risk of being accused of being wise after the fact, my opinion is the AOS is not really the problem -- as long as it is healthy -- it is the oiling system of the engine, and more specifically the oil scavenging system of the engine.
As alpine003 covered very well there are mods that improve the oiling of the engine and just as importantly the oil scavenging.
Were I preparing a car for track usage I'd do the oiling/oil scavenging mod's first. Then perhaps add the motorsport AOS if the stock one failed too often. IIRC the motorsport version runs around $900 (and can require extra work to install) while the stock unit can be had for around $120 and while the installation may not be a piece of cake easy it is easier than the motorsport AOS installation.
In case anyone's wondering, an autocross is not typically considered a track event. Autocrosses are generally tight courses that accentuate smoothness and precision, not high-speed. This is why Miatas and 914's tear up Corvettes and Turbos. Autocross is also one of the few driving events you can participate in with a totally stock car.
Oil system upgrades should definitely be considered when you're upgrading from street tires and stock suspension to racing slicks and adjustable suspension components. If you want to spend the money upgrading your oil delivery system on a bone-stock car, that's your prerogative, but to me it makes about as much sense as the giant red tow hooks you see screwed into Honda Accord bumpers all across America.
Track events generally can experience longer/higher/sustained g levels however both auto-x and track events can both see high sustained rpm's during your whole run. This is more of what's at play here.
Ha, funny you say that! I just now got back from a quick trip to Escondido, and two kids in an Accord pulled up next to me at a light. They had some crappy home-made air scoop on the hood, and as I passed them I noticed a red tow hook on the front, which gave me a chuckle.
+1 if the car has been sitting that long, i agree with the white smoke after initial start up and wouldn't worry too much about it. if it persists, then begin to worry lol
While an auto-x is not a track event per se, high g-forces and RPMs are common.
It depends somewhat on the layout of the course.
The auto-x held a De Anza College in Cupertino CA was a tight slow course affair -- the result of being laid out on the parking lot at the college -- and for lower powered cars speed and g-forces were not that high. (Although I saw a new Miata get up on two wheels one event.)
OTOH, the auto-x held at the Alameda County fair grounds in Pleasanton CA with much more room for a course was a much higher speed event with one long straight and a 180 turn at the end. Higher powered cars reached some impressive speeds at the end of the straight.
Also, I would be remiss if I didn't point out that the speeds/g-forces involved are also somewhat dependent upon the skill, or lack of skill, of the driver. With the wrong driving technique higher than normal (what is normal for the event) g-forces can result which can exacerbate any oiling weakness in the engine.
The key to solving these issues is first understanding exactly what happens as the underlying condition. Those issues start with the crankshaft oil passages and end with oil temperature, loss of viscosity to thermal breakdown and seldom are primarily rooted with G forces.
I learned all of this while developing my dry sump oil system for the M96 engine. I learned it the hard way.
What I was stating is that treating symptoms doesn't solve the problem. This isn't the common cold.
Everyone thinks that G forces are the ONLY problem, when in face they are very, very little of the problem.
Even if the answer is "buy the following products that will make me fabulously wealthy and force you to rub my bare feet with rare and expensive oils" we would all love the knowledge.
Apparently, LN Engineering thinks a bit differently as they sell all the parts I've mentioned. I don't know why people would waste money on this stuff for the tracks if it didn't help. I do agree that G loading isn't the only thing and maybe even the fact that the m96 motor was never truly designed with racing in mind. I dont know if this was what you were implying about solving the problem but for peeps that dont want or cant afford one of your engines, these "treatments" are a good interim solution. For the peeps that wanna track this, i feel those additional components are helping prolong reliability to some degree.
I've just started research on the secondary pump but most of the threads I've read state that the 3.6 motor has better oil flow through the heads and doesn't need that kit??
And Jake, so what's the cure with problems like mine? It seems a few us on here have the same issues but at the AX there were several other 996s that didn't have this issue that day on the same course.
First off, guess who develops products for LN and helped found the company? That would be me. Those products don't hurt anything, and of course they can help alleviate some of the issues, but they are not going to solve the problem entirely; because that can't be done without invasive, internal procedures.
That said, the issues that are experienced during AX, and those experienced on a road course are completely different. Neither are treated in the same manner, but the good news is I can't remember the last failure call I received that started out "I was at an AX on Saturday, when..." That never happens here. On the other hand, almost every Monday morning we come into a message from someone with a failed engine that occurred at a DE.
Worn valve guides and valve stem seals couple to cause most of the AX issues, especially with 3.6 engines. The 3.6 sees higher valve stem side loading, due to the vario cam plus arrangement, which the 3.4 engine does not incorporate. Another reason is due to the piston ring differences between the two engines. The 3.4 engine has a different means of "parking" the second compression ring into position than the 3.6L engine has, and this can effect ring seal greatly. Oil ring tensions are also different between the two, and the fish scale test will show that to any engine builder that deserves to hold a wrench and fill the role.
Other than the AOS beginning to fail, worn valve guides account for most of these "white smoke" issues that we see in AX conditions. The reason why the auxiliary pump will seem to alleviate the issue is because it removes some of the pool of oil from the heads and routes it back to the sump, reducing the volume of the oil in the head just enough that it may not get sucked by the valve guides and lead to the smoking condition quite as bad, or at all. Because it removes the symptom, does not mean that it eliminates the root of the problem.
Also, different oils will respond differently in the AX environment, some are more prone to being pulled by the valve stem seals and guides than others. This was another consideration when developing DT40, XP9 and XP5 oils.
I've kept M96 engines alive in Grand Am and never employed a single "oil system fix" except the X51 sump plate mod. No accusump, no auxiliary pumps, and nothing else "bolted on" to the engine. We've never had a single Grand Am engine failure.
Yes, as the last poster mentioned, pick up locations for the oil system means everything in regard to the effectiveness of the secondary oiling system. The more pick up points you have, and the more optimum they are positioned, the more effective the system will be.
My engine was rebuilt last fall with all new valve guides, rings, etc. but also the smoke comes out equally of both tail pipes which would make me think it more intake or something related to both cylinder banks. I would think that it would be separated to just one pipe if there was a part failure on a certain cylinder? But either way, after 15 minutes of highway driving on the way home and not a wisp since.
G-forces are not everything but they play a role. I note Porsche built a dynamic engine dyno to whip and thrash an engine around in order to subject it to the same g-forces encountered the the 'ring.
Yeah, it is a really interesting and informative post and one I am glad Jake took the time to write.
Not sure why I am being told to shut the f*ck up though.
I don't see why the informative post couldn't have been written the first time instead of what was written. I think Jake has done a ton of development and rightfully uses this forum for advertising of his services. But I also think that a post that doesn't provide information about the OP's question isn't useful. Do you really disagree?
It was your taunting nature on your 3 or 4 posts that didn't sit well with me. I had your opinion a few years back....Let's just say I've learned a lot since.
How do you feel about posts discouraging paying sponsors from posting the most valuable info available to the OP & everyone else reading the thread for free??
STFU !!
imo 1500 miles is not enough miles to be doing any type of tracking etc. i would guess the rings[ and other things] are not seated in yet. the aos may have been over whelmed by blow by .are you still on the oil from the rebuild ?
In that case, the only person that you should consult, is the engine builder. Its his role to support what he has created, and no one else's role to stick their nose in the middle of that.
I extend this courtesy to every engine builder in the world, because I know first hand that there's nothing worse than a room full of experts who know nothing about how the engine was built, offering their opinions on the subject.
Porsche didn't invent the Gymbal Dyno, and it's use during the design of the engine didn't help, because we see the same old problems we've always seen.
Its funny, all that work to develop the oil system, then they just dump the same old oil back into the engine, and expect a different result.
i got a great kick out of this post ['fish scale term]. i have done many,many harley motors and i brought back cylinders that were not bored to specs by a machine shop.the owner of the shop said real snotty,how did in know they were not bored straight. i told him about the feel gauge stock and withdrawl tension .he said thats dinosaur mearsuring......20 minutes later of him miking the cylinders he said he would hone them straight .us old timers still rule....once inawhile
I agree and already knew this but glad you pointed it out to the newbs. However what I was referencing was not really LN but Charles more specifically in the slight philosophical differences he might have. There are numerous quotes he has made right here on Rennlist that doesn't 100% line up with your beliefs/philosophy. People can search for them and find them if they have the time.
Either way, thank you for the explanation on this subject.
That still doesn't change the fact that you and him might not have the same philosophy on everything. Like I said it's well documented here right on Rennlist if people are willing to do a search.
Regardless, are you ever planning on coming out with an aftermarket dual chamber AOS you were testing a couple years back?
Neither do me and my wife (who holds 4 Land Speed Records set in a 996) and I've known Charles longer than I have known her.
Strong willed people never see 100% eye to eye with other strong willed people, even if they are on the same team.
And the point is?
No, it costs too much to manufacture, people won't pay for it.
Dozens of products face the same challenges, and we refuse to send the parts to China just to make them affordable.
I would take my 964 and 993 to the Streets of Willow and do 45 minutes sets non-stop and never had any of these issues. Seems like an awful lot of mods are needed to make the modern 911s track worthy. I raced a 1958 Alfa Romeo Spider Veloce for several years in vintage events...8000 rpm every gear every shift every lap every race...and never burned a quart of Kendall 40w oil in an entire weekend, never a dnf. Denise McCluggage used to driver her Ferrari SWB from the Village in NYC down to Sebring Florida...tape up the headlights, race for 12 hours, and then drive the same car home to NYC. This whole thread reminds me of Nasim Taleb's new book "Antifragile." Perhaps technological sophistication has become a weakness rather than a strength.
That 964 was built by a company ran by Engineers, not accountants. It had a true dry sump oil system and could be ran near 5 quarts low on oil before it had any oil related issues on the track.
The same goes with the 993.
Neither pertains to the M96 engine.
First of all you have to indicate why the AOS is being overwhelmed. Then you have to treat that condition, it's the evil underlying root of the problem.
For the guy who doesn't know the secret handshake, hasn't kissed the ring, and genuflected in the aura, is this a way of saying 'get the X51 engine oil baffle kit, as it will help reduce oil packing in the cam/valve chamber'? I sort of gathered that from a prev post, but as I intend to do some AX and maybe the occasional track day with a 3.4L engine 996 I would like to be prepared.
Some history may help. I own, maintain, and operate a 928GT(I know, really sorry that). They have a problem with oil starvation of the 2/6 rod bearing and part of the solution is the GTS engine oil baffle. Well, lucky me - on my first track event after buying it and without the GTS baffle in the pan my rod bearing seized and destroyed the crank and rods of my engine. So - maybe a bit less wink-wink, nod-nod is in order.
Not looking for a $35,000 race prep engine, with dry sump, giant AOS, dual scavenge setup, but something a relatively normal person would pursue to enjoy their car as it was designed... thankyou -- thankyouverymuch
I think that was JR's point. The 996 NA (except for the GT3) was not designed nor intended for track use. Porsche probably assumed if your intent was track use, you would be buying the GT3 or GT2 TT. Porsche and experts even sternly warn against tracking the 996 NA M96. Those that choose to ignore the warning should not be surprised when things go wrong.
I did not know that. No excuse on me of course, but knowing that the 996 was actually designed to get groceries from the Piggly Wiggly, and take grammy to the train station speaks volumes.
Where does one find these stern warnings in the product literature?
My take is there are too many possible factors.
I note some owners apparently avoid seeing the signs of an AOS being overwhelmed.
Is this due to AOS differences? Possibly. Some AOS's are better (or worse) at what they do.
What about engine differences? Possibly. Engines can have some variation in the amount of oil that flows out at various places. There is also some variation in how effectively the scavenge pumps work. This can result in more oil being in the engine and being whipped about and more oil vapor being created. There is also the differences between engines and the amount of blow-by they have.
There is the oil to consider. Approved oils are high detergent oils. But they also have a good anti-foaming additive package too. If one ventures off the reservation regarding oils well, he may exacerbate the AOS's problems. Not only which oil is used but also its condition (oil with miles and contamination foams more readily) and its level are important.
Last but not least there is the driver. I have watched videos of Porsches on the track and in some cases I am considerably impressed with the smoothness of the driver. The smooth driver is not slow not by any stretch of the imagination. In other videos, with other drivers driving, there is an obvious lack of smoothness.
IOWs, the driver is partially to blame.
So there are at least some of the factors involved.
Now while there are too many factors to believe only the luck of the draw would have one picking the magic bullet there are things one can do to reduce the possibility the AOS gets overwhelmed.
At the top of the list I would think oil selection, freshness, and oil level.
Then there is the driver. The driver needs to get proper instruction or if possible to work on his own to improve his driving seeking to be smoother with the car, to avoid sawing away at the wheel, being all over track, to brake at the proper times, and do, or avoid doing, all the other things that go into being a smoother and a faster (and a safer) driver.
Doc, you've been on the Rennlist for a while...so you should know that 996 thrives as a garden ornament only.
I've read enough posts from Jake Raby ( go through the post history and verify if you want) to realize that almost every type of operation is hazardous to the M96 motor. The following is a short list of the information I got about M96 from F6I. I am not making this up, go through the F6I's posts and you will find posts listing all of the things I list here.
- Starting motor when it is cold outside is BAD. Uneven metal expansion in M96 kills them all the time.
- Idling M96 in traffic is bad, as timing chains cannot handle the stress. Idling is BAD.
- 1/4 mile runs are BAD as they stress the engine too hard and launching in straight line is too much for M96. You can score the cylinder walls. BAD.
- Driving M96 in hot weather is COULD BE BAD as oil can break down and motor can lose oil pressure. Hot weather is BAD.
- Taking fast turns is BAD as oil lubrication system is **** and your motor will starve for oil.
- Lugging the engine is BAD. Low RPM operation is BAD for something in M96.
- Sitting unused is BAD as oil drains from the lifters and on start up you get no lubrication for a few seconds.
What is GOOD for M96 according to F6I is running at high RPM when warm, but not too high, and no turns. So, highway (only in straight line though) driving at around 75-80MPH is where M96 feels the best and has highest chance of surviving.
This would be funny if it was a joke, but this is a reality of the $75-$90k car engine. LOL.
Where would you recommend having the oil level before an AX or such? I added about 1/2 quart to bring it right up to the full mark exactly that morning. Would it be better to run it a little lower, or?
Slap shot and a beauty!
Post of the century vis-a-vis the 996. I guess I will shop for the auto so I can let the wife drive it back and forth to the job at 35-55MPH. It should last to 300k miles.
thankyou,,,thankyouvermuch
p.s. I've been mired in the lesser mortal world of the 928 for the most part.
