Oil pressure difference on each bank

Hi all, new to the forum, my 996 C2 99MY has just undergone an engine rebuild, the cylinder head was cracked on the plug tube on number one cylinder, this was repaired and the heads refurbished. New rings, bearings, chains, guides, IMS, engine is running well and pulling strong, however noticed going round a sharp bend, not quickly or high revs, the oil pressure gauge dropped to about 2 then recovered after bend, I can replicate it at low speed also. The indy who rebuilt the engine wasnt happy with the rattle on startup from chain tensioner until pressure was up, they measured the oil pressure on each bank and the left bank (repaired head) had a lower oil pressure than right bank. The sump was dropped but no obvious issue found, oil pump ok, pick up ok, baffles ok etc. They are now going to check scavenge pump and tensioner, any thoughts or suggestions welcome!!

Well, clearly of course NOBODY here can give you any sensible advise without a picture of your car. Then after that thoughts can start to pour in...... :-)

This was the initial cause of oil in coolant, that prompted engine build.

10-15 PSI of delta between Bank 1 and 2 is normal on every M96. This is why the IMS Solution doesn�t rob oil from a Cam cover location, as this delta is designed into the engine�s hydraulic system. This is also why the chain tensioners are different left to right.

Thanks for that info, thats really helpful, any ideas as to why oil pressure is fluctuating on sharp turns?

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Internal clearances are likely too loose, the oil is too hot, or the oil is improper viscosity for the internal clearances of the components. Or all of the above, or more. If the shop was the builder, they should be able to answer these questions with proficiency. That�s what you paid for, not Just bolting a box of Parts together.

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Its pretty common for M96 engines to have a pressure drop on the track with long sweeping turns. Even some have reported this on the street as well. Both scenarios, though, are usually under more extreme conditions (higher load g-forces and/or engine revs and elevated temps).

This is fluctuating on any sharp turn at any revs, so theres definitely something mechanical up, the engine has completed 1000 miles since rebuild and was pulling really well. The engine builder has great experience with these engines, but hasn't seen this issue before, and have not worked with a repaired head before, only used or new replacements. The engine is being dropped again tomorrow, so may have a better understanding then.

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If he hasn�t dealt with repaired cylinder heads due to cracks, or oil pressure deviations between banks, then he really doesn�t have �great experience with these engines�. sorry.

Unlikely a Pro would make such a mistake but..... It is possible that some components are missing or loose. For example the oil pickups/swirl pots.Drop the sump plate and inspect ? Don't drive it until it is diagnosed? Oil starvation can be an instant (expensive)death

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sorry to bump an extremely old thread but this statement sheds some light but is extremely confusing at the same time. Is there documentation/info as to why there is this difference?

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The oil passage that feeds the bank 2 head is on the side as the main galley that feeds the crankshaft. From that main galley there is a passage that goes through the crankshaft carrier to the bank 1 side galley and the bank 1 passage to the head feeds off that side... So to follow the oil path from the sump, the oil goes up the pick-up tube into a galley that feeds the oil pump, then to a galley that feeds the oil filter, then up to the oil cooler, then down into the main galley that feeds the crankshaft,( this is where the bank 2 head channel connects to the head), then across the crankshaft carrier to bank 1 side ( this is where the channel that goes to bank 1 head connects)...So there is quite a drop in pressure from the oil pump to the bank 2 oil pressure port, then another drop in pressure to the bank 1 oil pressure port due the port channel sizes along the path..The bank 2 variocam needs more pressure due to being on the drive side of the timing chain..

Interesting setup there. Not sure what to think about it lol. Does that include feeding bearings on the way across etc? If so I'd suspect any bearing wear causing even more of a drop to Bank 1. In other news, I've noticed that Bank 1, once warmed up, has some fluctuations on my 04 C2. About 7psi and it seems random though not at idle or low pressures/rpm. FYI, I have an aftermarket gauge and sensor on bank 1. Bank 2 might have the same thing happening but the stock gauge may not update that fast etc... hard to say. Any thoughts on the fluctuations? i also notice oil temps seem high for just driving around at like 3k. 220-235 though that was 90+ ambient. Going up mountains even just at a casual pace will show temps of 240-250. Just overall temps seems high to me overall. I'd like 180-200 just cruising but I'm not familiar enough to know the norms. Coolant temps are 180-200 though. Thoughts on typical oil temps in different street driving conditions? I appreciate you letting me pick your brain lol. My first P car. Only other flat engine car was an 05 Subaru Legacy turbo but I never ventured into monitoring things to this degree.

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No, all the crankshaft bearings and piston squirters are fed from the main galley on the bank 2 side. Any wear on the crankshaft bearings will lower the pressure at ANY location ( ie lowers the resistance to flow).. The 7 psi fluctuations are probably from the varicam functioning. On my 3.4 5 chai engine the variocam activates at 1200rpm and deactivates at 5200rpm, also it switches on and off if the throttle is fully lifted then e-applied and cause a 10 psi very quick drop every time you are on/off the throttle. This can be seen easily on a manual gauge or high speed gauge, but the factory gauge is too dampened to see this quick of a drop.. Where are you getting your oil temp from ?, it makes a big difference. On my 3.4 I get the oil temp from the factory sensor that is in the Sump, it is the hottest place... during cruise the oil temp will run about 220-230* at 80* ambient temp coolant temp about 200* 210*, but very agressive driving will make it go way up. On the Track at 100* ambient I had had it over 300* oil temp...and the coolant temp up at 240*...

I get my readings from the same place. So the oil temps are to be expected? The oil pressure start doing funny stuff when the temp goes up so I'm trying to think of ways to keep it cool. Like some sort of oil cooler setup... but would rather have something close to the engine bay in back there.

Yep, those oil temps are to be expected. And the little 7psi fluctuations are probably from variocam...If you have serious fluctuations it will even show on the factory gauge . Mount a phone/camera to record the fluctuations and post them up to verify... Oil cooling is always a good thing.( but it will raise the coolant temps a little) You can install a 997 oil cooler and it will help .. LN has a new remote mount oil cooler that needs some testing to see how much of a change it will make, but has to be ran with muffler deletes..

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I'll get the video. I need to get that oil temp thing working. I got that one kit from someone who makes them on here where you tap into the stock probably that measures temp and level...but it's not been working the last week or so. And interestingly enough, I am running a muffler delete. I might look into the LN oil cooler setup. Happen to have a link handy? I guess I could Google lol

I don't know how available the New LN oil cooler is because they are looking for people who can test it and post results/ data to see how effective it is. I'm sure it will be beneficial and they may have several available, so if you can provide some feedback/testing they may select for you to receive/review/purchase one of them, you just need to inquire to LN.. Yea, CoopDuc's little oil temp gauge is a good one and gives the same values that Porsche designed into the system....

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Here's a video... You Tube

I would want to see a lot more time than just 13 seconds of operation. Also what is the ambient temps/climate ? Also would be good to see some aggressive maneuvers at high oil temps to verify safety..

That was fully warmed up after getting off highway and driving backroads... mid 70's. It'll be a bit before I can get more. Had to hold the camera while driving hard etc. Might be early November