When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Cross posting this from the 996 forum. I am not freaking out about this, seems like most of these motors behave similar and they kind of are what they are - that said, I would be open to anyone that was actually able to resolve the pressure dip. Most of what is suggested I've done - so next up would be accusump....
One thing I should note - it was cold on this day, 43 degrees at the time of the video, I would imagine in the heat of the summer with the oil running hotter this issue would be further exacerbated along with a planned change to a R comp tire mean I should take some steps to address.
Post from 996 Forum:
So I was reviewing the footage from my last track day a little closer, since I had not adjusted the camera properly for a preferred outside view (was more washed out than I would have liked) I got a better cockpit view than I generally do and I could get a pretty clear look at my gauges. I watched a session back with an eye on the oil pressure gauge and noticed a constant dip down to 2 Bar and change at the same point on the track. The pressure did not drop quite as far, about 2.5 Bar on first couple laps of the day and also did not drop as far or consistently when I was slower than capable due to traffic.
Sweeping right onto the brakes and then a tight right, as soon as I get off the brakes and turn in for the right hander a quick drop of about 1 Bar in pressure that builds back up rapidly as G's are bled off. The drop is quite noticeable as the pressure falls away.This is on PS4S tires, 2QT Deep sump and baffle, XP9 oil. You can see RPM at the time at about 4K, coolant temps are good and I am at WOT at this point. Clean magnetic drain plug and filter was inspected and free of any debris as well.
Below are the screen shot, showing RPM and pressure as well as the track map showing the point on track of occurrence. I also added the video as well. If you leave it in small screen you can zoom in and watch the gauge.
Having tracked a 2003 C2 quite a bit before selling it and moving on I will say that this can happen with this engine, but after I did the upgrades you also have done (deep sump, XP9, etc) I didn't see it anymore, even running on R7 slicks, at least not often. The gauges and sending units are known for not being very accurate either so may be worth checking the sending unit. One important point - If your oil scavenge pumps are not keeping up then the deep sump won't do you much good as the level could still be lower at high Gs...they have to pump it back from the heads fast enough to keep the oil in the sump. Sometimes I would see this late in the session on a hot day when the oil was thin and the scavenge pumps would slowly get overwhelmed throughout a 25-30 minute track session. Did you get rid of the swirl pots when you did the deep sump and go to the 997 style straight return tubes? That is supposed to help.
Having tracked a 2003 C2 quite a bit before selling it and moving on I will say that while this can happen with this engine, but after I did the upgrades you also have done (deep sump, XP9, etc) I didn't see it anymore, even running on R7 slicks. The gauges and sending units are known for not being very accurate either so tough to say here. If your oil scavenge pumps are not keeping up then the deep sump won't do you much good as the level could still be lower at high Gs...they have to pump it back from the heads fast enough to keep the oil in the sump. At one point I would see this late in the session on a hot day. Did you get rid of the swirl pots when you did the deep sump and go to the 997 style straight return tubes?
I do run the 997 return tubes.
And as I mentioned, it seems like many had luck with the combo I'm currently running resolving their issues, but as you can see if you watch the video - the dip is clearly present... as to if the stock gauge is reflecting reality - that's hopefully something I will be addressing in the off season with better methods of data collection and review. For now, I got the stock gauge and a video...
I have gauges on the top od my dash along with deep sump, x51 style baffle, horizontal baffle, and 997 dump tubes. Problem not solved. the only thing ive seen work is keeping the oil very cold.
And as I mentioned, it seems like many had luck with the combo I'm currently running resolving their issues, but as you can see if you watch the video - the dip is clearly present... as to if the stock gauge is reflecting reality - that's hopefully something I will be addressing in the off season with better methods of data collection and review. For now, I got the stock gauge and a video...
FWIW - Oil level 1/3 up the dip stick.
I thought LNE recommended running the oil level higher?
The sending units get old, dealing with the heat and pressures. Put a new sending unit in.See if this fixes the problem. If not, then go on to more complicated and expensive fixes.
No worries, the whole how full to run your oil is a whole debate amongst itself. If you’ve found what works for you, maybe best to forget all the bull**** the internet says anyway.
I tracked my 997S for several years and came to the conclusion that this is based on the Scavenger Pumps in the heads. On one side of the engine it's at the front of the head and the other side it's on the rear. Whenever a right sweeper is in play the oil is pulled away from the pump in the head so it can't return it to the sump fast enough. I have the Mantis deep sump and it slowed he drop but it still happened. I just learned to short shift and ease up on problematic corners until I could get a GT3. An Accusump should help.
If you follow the normal pattern this is what will happen:
Your videos show that you are driving pretty hard and I get the impression you are a motivated guy so you will continue to get faster. You'll have an engine failure in 2021, probably at a track that you are visiting for the first time. You'll decide to install a used engine or perhaps an expensive new build and get back on the track after missing most of the 2021 season. This new engine will last only 10 hours or so, because you, as a driver, are not going to reduce the intensity level (and I am not even remotely saying you should) that you achieved with the last engine.
Everyone will try to convince you that this second engine had some fatal flaw and that going forward with a third engine is going to yield a different, and better, result because reasons. (Accusump, deep sump, scavenge pumps, bearing coatings, AOS, oil, oil level, oil cooler, short shift, etc).
The 3rd engine will last about as long as the 2nd engine. When it fails, you will move on to something else.
Don't do this.
You have all the data you need already. Your OP gauge (as inaccurate and imprecise as it is) is showing you what is happening and it is very simple: the oil pressure is dropping because the oil pump is sucking air for some percentage of the lap.
That is fatal to ANY race engine. There is no way around that. If that is occurring then an engine failure is only a matter of time.
It has become very darkly humorous to me to watch these threads attempt to avoid this obvious fact. Two decades of the same discussion with the same result is frankly bizarre.
I will help anyone dealing with this problem any way I can, except by denying what is obvious.
That was funny, and I believe you have seen the same play many times over, I’m not planning on sticking to that script as far as compounding errors with the same error repeatedly.
I was thinking something probably equally stupid when the motor fails involving a totaled GT3. But that’s a story for another day.
That said, the longer this motor holds out, the better so I reached out to the group. I know you have done a lot for these engines, the knowledge and experience is only learned the real hard way for people like me so your input is much appreciated.
11-23-2020, 09:43 PM
M96 Oil Pressure Drop
