Oil pressure issues at Road Atlanta - real or imagined
I just got a Go Pro camera, and so I used it this past weekend at Road Atlanta. I recorded a couple of sessions with the intent of watching my oil pressure, but the camera only picked that up during this (disclaimers be here) first warmup session with many awful driving issue, hand placement, etc (I would have sworn I had them at 9 and 3 but this video showed me where they really were). I'll post up the "good" video later for some critique on what to improve for next time - in this video, look only at the oil pressure issues I am describing.
Car: 2000 Porsche Boxster S, Hankook R-S3 tires, synthetic 5W40 street oil (not a "race" oil).
VDO Vision Oil temp gauge, sender in the extra port on the driver side valve cover
VDO Vision oil pressure gauge, sender in the port on the passenger side replacing the stock oil pressure switch.
Oil temp at 200, moving up to around 210/215 (the white hash mark is 200, the smaller one to the right is 220)
Oil Pressure - the big hash mark at 12 o'clock is 40, 20 on left, 60 on right, with 80 on far right. In between hash marks are smaller hash marks: 10, 30, etc...
I have the 2 Quart LN Deep sump kit installed as well, oil level is between the top and bottom hash marks but closer to the bottom since I don't like to run too full due to AOS smoke bombs. This may be the issue? I am still within the lines and carrying extra oil due to the 2 qt deep sump with the EBS baffle and windage tray.
Watch this video and see how much the oil pressure moves especially during right hand turns, even very easy turns. I could (and well next chance I get) video some street driving and see what happens. These turns were not extreme, I was getting no tire squeal or feedback, watch how much I am moving my hands around and pointing etc.. (another bad habit to watch for in the future), this was an easy warmup session and not a hard lap at all. If the oil drops this much during this sort of easy driving, how does it do when a person is going all out? I am not near the top fastest drivers but at Roebling Road I am doing low 1:30 high 1:29 on these same street tires, that is way more force than I was generating in this video.
Use HD and/or watch on full screen youtube to better be able to read the gauges...
Any thoughts. Are some dips in oil pressure normal? Is there any cause for dips (when the RPM is constant) that do not involve air getting sucked in? Is it because the oil pressure port is in the right side valve cover? (Don't see how but just thinking out loud...)
Edit: maybe the oil pressure is not instantaneous and the drop is just a reflection of the dropped RPMs due to the braking zone, like before 3 which seems to have an extreme drop.
Edit 2: 10B has a lot of drop, I am going pretty low speed through there and not squealing the tires. Much more drop than 10A. Seems like right turns are worse.
Looking at the oil pressures, running @ 5,000rpm on the straits you are registering +/- 50 psi, and even under braking @ 4,000 rpm its still around 50 psi. But even before you hit the apex of the curves (and as you say especially turning right), the pressure immediately drops to 30 psi. So you have lost nearly 50% of your pressure due to cavitation. This would not be acceptable under normal track usage - in all the cars I have had at the track that had an oil pressure gauge fitted, I have never seen a pressure drop so pronounced. Sure, pressure drops with high oil temps, but 210 deg is not too bad for modern 5W40 non competition oils but I would imagine the oil temps would go up considerably if you were driving harder. If the temp sender was mounted in the sump pan, I would think the readings would be higher.
The old acceptable rule of thumb for oil pressure (once up to track temps) is 10 psi per 1000 rpm so your OK on the straitaways, but way below that on the sweepers. No wonder people lose their M96 / 97 engines on big sweeping tracks.....
If the temp sender was mounted in the sump pan, I would think the readings would be higher.
I wondered that, I was only able to test up to 200F after installing the gauge by street driving and up to those temperatures the built-in sump temp reading (via durametric observations) matched the gauge.
For the rest of what you were saying, thank.you. It kind of matches what i thought. Dang...
Maybe that's why they left off the oil gauge I saw a video of a guy that installed a gauge on his Cayman and it was just like mine...
I have an accusump kit in the garage, might be time to put it on.
On a tangent, if/when my driving gets to a higher level and I am.pushing the car harder what would be the appropriate oil for track that can handle higher temps and stresses AND with a semi-decent service interval, like 2000 miles or so? the second part might be a pipe dream
i think the accusump kit is a good idea. Also i would recommend other oil for track racing. I would recommend 10W60. Which also gives higher pressure values in general. 20 psi at over 3.000 rpm is really too low pressure.
And please make shure that the gauges show correct values. Maybe it's a good idea to data record values via obd.
Regards, Markus
Last edited by Smallblock454; 03-14-2016 at 06:30 PM.
And please make shure that the gauges show correct values. Maybe it's a good idea to data record values via obd.
Regards, Markus
That is a good point. I believe the oil temp to be accurate based on comparison with the built-in temp sensor using durametric to compare, but I have no way to check the accuracy of the oil pressure, except that it seems to match the expected values most of the time.
Even if the gauges were (say) 10% inaccurate, they are still indicating the fluctuating pressures.
If the reading is 50psi, in reality it could be in the 45 - 55 psi range.
Most "real" instruments are calibrated to less than 1% accuracy, but that's what you are paying for.
The biggest question here is what to do regarding the loss of oil pressure on long turns during track sessions! The gauge indicates a real time loss which cannot be good for long term engine longevity, though there has been many owner who have hundreds of hours of flat out track time.
It would be interested to here from some of them. People like Brad Roberts who has been round the block a few times with the M96/97 engines and (I suspect) has had to rebuild a few after track sessions.
That is a good point. I believe the oil temp to be accurate based on comparison with the built-in temp sensor using durametric to compare, but I have no way to check the accuracy of the oil pressure, except that it seems to match the expected values most of the time.
You could record the sensor voltage via an analog interface to a smartphone. This way you could make shure that the gauge doesn't shop crap. Also same time you could record g-forces to compare and evaluate data.
Indeed via OBD it's a bit difficult to get the oil pressure. But it's there - in PIWIS you can see it as data. Should be identifiable via an obd port sniffer. But that is not an easy and quick to solve thing. Analog conversion and recording from sensor is much easier.
@Steve Tinker: agree. Would be interesting to get oil pressure and temp values from other users that track their cars.
Regards, Markus
Last edited by Smallblock454; 03-15-2016 at 02:30 AM.
I think your rpms are a big factor - you were going easy and not flogging it. I think if you were driving harder your rpms would be up through the corners and you wouldn't be seeing as much of a drop. it seems to drop more on the rights, but the rights seem to be slower on this track, so again is probably tied to rpm.
Here is a video of a Cayman with an oil pressure gauge installed in the sport chrono center dashboard display. You have to watch in HD to see it, that needle is moving around like crazy too.
I have a couple of experiments I am going to perform:
Street driving on 300TW street summer tires and watch the oil pressure gauge
Possibly install a second oil pressure sender somewhere else and see what it says, and compare it with the one that is on the passenger valve cover. I have a sandwich plate for accusump, I could put the gauge there.
Maybe go ahead an mount the accusump, and put a pressure sender on the air side instead of the dial that is there. Use that to compare readings.
I'm telling you, if you were in the car and felt how gentle these right turns out you would be amazed. If I had a G-meter I guarantee I would be at way less than 1 G. Even my fastest laps at Road Atlanta are only in the 2:03 range. That leads me to wishfully think there is some issue with the reading.
I wonder if the 996 oil pressure gauge in the cluster is buffered? They read the oil from a similar point on the driver side. Or if it moves with every little change in RPM.
I watched about 5 min of the video and to me it looked like the pressure was tracking RPM, with the gauge slightly lagging. Can you point me to a time in the video that demonstrates a large drop in pressure?
FWIW, I log oil pressure in my SPB and oil pressure holds up ok (IMHO) with a deep sump.
As for oil, I tried DT40 for track use and oil analysis showed the viscosity was breaking down pretty quickly. I suggest you find something else. For me, XP90 holds up much better, but I change it every 10-15 hours.
As far as I noticed (on regular streets): My 996 oil pressure gauge constantly fluctuates with changing RPM/loads (quote Steve Tinker: ~10 psi per 1000 rpm), but values are pretty stable with constant RPM.
__________________ Original Owner | PORSCHE Boxster 2.7L (MY01) | Seal Gray
Perhaps slightly off topic, but I've got a question while we are on the subject of gauges.
I want to mount oil temp, pressure and coolant temp (or at least the oil gauges) to my center console. I don't want decorative crap just to see needles moving around, I want a good gauge.
What are some good choices of instruments/sending units?
flaps,
I've fitted VDO on a couple of bikes and cars with good results, but what may be a better installation is to have a look at Pedros gauge install kits
pedrosgarage.com-Site-Technolab.html
Interesting issue. Pedro has discussed it re. Sebring Turn 17. Ask him ? He removed his Accusump and used a system similar to yours(he calls it Technosump).
With your LN 2 qt. deep sump + EBS baffle kit + correct oil level + correct grade(??) of oil- there should be no substantial drop in oil pressure due to the pick up being above the oil surface in the sump at your g-force.
It does seem like the issue is windage/baffling not foaming ?
Are you sure the EBS kit was correctly installed ?
Extended pick up tube would be the #1 question.
#2 would be the horizontal baffle
#3 the baffle flaps are closing correctly ?
Foaming would exacerbate an incorrectly functioning baffle/unmodified oil pick-up.
Drop the sump and inspect?
I definitely have got the oil pickup extension installed the baffle flaps were free when I installed it, and the windage tray is present.
I was running the oil a little too low I think due to fear of AOS smoke bombs. That may have been an issue. I wish I had a data feed for RPM and oil pressure, because it seems like if I take a corner at 4000 RPM and up, I get barely any drop. Under 4000 the drop seems like a lot. If I could graph it on a line I wonder if I would see the RPM falling to sub 4000 on a brake zone, followed shortly by a corresponding dip in oil pressure, that then catches back up tot e rising RPMs? Above 4500 or so I am at the max pressure I think and the oil pump relief valve kicks in?
I watched about 5 min of the video and to me it looked like the pressure was tracking RPM, with the gauge slightly lagging. Can you point me to a time in the video that demonstrates a large drop in pressure?
FWIW, I log oil pressure in my SPB and oil pressure holds up ok (IMHO) with a deep sump.
As for oil, I tried DT40 for track use and oil analysis showed the viscosity was breaking down pretty quickly. I suggest you find something else. For me, XP90 holds up much better, but I change it every 10-15 hours.
I like this thought, and re-watching the video with this in mind, it seems to correlate pretty well.
I would love to go to XP9 but I drive to and from the track so I could only get 1 track weekend per XP9 oil change since the closest one is 3 hours away. I read it has a 750 mile lifespan. I wondered if that was 750 racing miles lifespan, with longer if there was street driving in between, but Lake Speed Jr told me it was not. I guess a person could get a UOA after each weekend and see if there was more life left?
If I could find an oil that was good for around 2000-3000 miles that was XP-9 like that would be perfect - I change the oil now every 6 months and my mileage is right around that.
Redline 10W40? It looks like it could be pretty good and says:
Best choice for high-performance engines that see street/strip or track activity
Great for engines with high oil temperatures
Oil question for spec boxster folks - what are you running?
I saw a video of a guy that installed a gauge on his Cayman and it was just like mine...
"GRAY"
Linear Mode
