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Oil pressure in right sweepers

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Old 09-20-2016, 01:14 AM   #1
Hella-Buggin'
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Default Oil pressure in right sweepers

I have an 06 997.1 S that I track about 8 times year. I'm running GT3 LCA's and rolling on Yokohama AD08R tires.

For piece of mind I've installed the third center radiator to aid in coolant temps. I also just installed a Mantis 1.2 Liter deep sump as I was starting to have oil ingestion issues. I figured this will allow me to run a lower level of oil to not overwhelm the AOS and still keep the same if not more actual capacity. Plus, I can worry less about oil starvation.

Anyways, I've noticed that in left handed sweepers the oil pressure remains consistent with straight line pressures of just over 1 Bar / 1k RPMs. I have noticed on a right sweeper, the pressure drops to about 2.5 bars and hold steady. On the corner in question I'm not hard on the throttle but just giving enough to hunker down the rear end.

I've read that the pressure is not only RPM dependent but also load dependent so I tried on a local looped onramp to give it more throttle but it still dropped to 2.5 Bar and only when I reached about 5k RPM's did it start to climb.

Thoughts?
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Old 09-20-2016, 08:48 AM   #2
Bill Lehman
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I would not run a "Lower" oil level and I would add a Motorsports AOS.
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Old 09-20-2016, 10:43 AM   #3
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Well, I used to run the oil level all the way up to the full mark but several people from the dealer to local race shops have said I should be at least a 1/2 quart shy from full. The Motorsport AOS is on my list but everyone said I should just wait for mine to fail first.
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Old 09-20-2016, 10:47 AM   #4
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I have noticed the same thing in my Boxster, and I saw a thread on P9 that suggested that the stock oil pressure measurement point is pretty far downstream and is on the front of the valve cover on the right hand side (on the Boxster/Cayman anyway, not sure if it is on the left since the engine is rotated 180 degrees in the 911 - edit: I just looked it up and the oil pressure port for both 9x6 and 9x7 is in the right valve cover), and the issue on right turns only may be related to that.

I have always wondered, is the pressure dropping in the right valve cover due to the oil pickup sucking air due to g forces, or is it a localized condition due to the location of the oil pressure point?

I am in the middle of an experiment where I am installing a sandwich plate with an oil pressure sensor and I am wiring it to my gauge with a switch that will allow me to toggle between the two oil pressure sensors. One lap I will run the oil pressure sensor in the OEM location, and then one lap I will switch and run in the oil filter sandwich plate location just past the oil pump. If we are sucking air I would expect to see the same drops at both oil pressure locations. When I get back to the pits I can watch my video and see what happens.

I got this idea from the thread on P9 and also from hearing from folks that added an accusump and wired an LED and saw it firing, and then once they added the deep sump, it stopped firing in places where it used to fire.

I run the 2 QT LN Deep sump, but only add an extra 1.5 QTs of oil, so that the electronic gauge reads 1/2 way between the two lines. I have found that if I run it full the oil quickly lowers down to this level (due to smaller amounts of oil ingestion that don't cause a smoke bomb?), and the one time I accidentally had it 1 bar too high I blew a giant smoke bomb at the track.

Last edited by steved0x; 09-20-2016 at 02:56 PM.
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Old 09-20-2016, 11:48 AM   #5
Frank 993 C4S
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Quote:
Originally Posted by Hella-Buggin' View Post
The Motorsport AOS is on my list but everyone said I should just wait for mine to fail first.
If you wait for the AOS to fail, there is a good likelihood that the engine will fail at the same time. My first Cayman engine failed for exactly that reason. Also, don't run the oil level low - you don't have to fill it up to the max but definitely don't run it low.

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Originally Posted by steved0x View Post
I have noticed the same thing in my Boxster, and I saw a thread on P9 that suggested that the stock oil pressure measurement point is pretty far downstream and is on the front of the valve cover on the right hand side (on the Boxster/Cayman anyway, not sure if it is on the left since the engine is rotated 180 degrees in the 911), and the issue may be related to that.
It depends on your model year. Pre-2008 Boxster/Caymans have an engine driven oil pump that is entirely RPM driven. Plus you need to install an aftermarket sensor to get true oil pressure as your factory OBD output reads a constant value until there is zero oil pressure (which unfortunately is too late to detect a problem).
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Old 09-20-2016, 11:49 AM   #6
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Mark - you said you were having oil ingestion issues before adding the deep sump. Can you explain further?
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Old 09-20-2016, 12:25 PM   #7
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Mark - you said you were having oil ingestion issues before adding the deep sump. Can you explain further?
OK, here goes....

I was down at Buttonwillow and ran hard all day Saturday w/ issues. On Sunday I did my first session and everything seemed fine. I started the car for the second session and huge clouds of smoke started pouring out of both tailpipes. Everything sounded fine and I only noticed when I looked in my mirror to back out of the garage. I shut it down and began inspecting things. No leaks, or anything so I pulled the air intake apart and found oil in the the plenum.
The tell tale signs of an AOS failure. My car has 80k miles on it so I figured it's time was up and a friend trailer the car home as I was low on oil and I was five hours from home and didn't want to take any chances. Mechanic replaced the AOS and confirmed that the membrane was damaged. He checked everything out and said everything else looked good.

I get the car back and put it through it's paces as best as I can on some canyon runs to see if I can replicate the issue w/o incident.

A month later I'm at Laguna Seca. The oil was at the top "Recommended" level marker. First session was fairly mellow as there were a lot of cars and the grid pecking order wasn't ideal. Car ran great. I parked in my garage slot and when I started for the second session.... a cloud of smoke. Both tailpipes just like before. It quickly dissipated so I ran the next session towards the back of the pack and took it easy. A friend got behind me and said there wasn't anything while driving. I started up for the third session and another cloud of smoke. At this point I called it a day and my oil measured about One Segment lower.

I took the car back to the shop and had a compression & leakdown test done for piece of mind and had it looked over with a fine toothed comb. Everything checked out fine and I also had the Mantis installed.

I ran an event at T-Hill a few weeks ago and the oil level was showing up around the middle of the recommended range. Between each session I got a very small Puff of smoke that quickly dissipated. By the time I got out of the car with my phone to take a picture, it was done. I asked around and had several people tell me that it was fine and to just run a little less oil. A race shop that is very well respected was there and he told me that they track prep m96 & m97 engines a full quart low at the bottom of the recommended range. That given my run times I'm just sloshing too much oil and overwhelming the stock AOS.

After all the day's activities and puffs of smoke, the oil indicator didn't decrease at all and in fact is still reading the same amount of oil in the car a month later.

I replaced the failed AOS with the stock one because the motorsport version required some makeshift plumbing and my mechanic wasn't 100% confident doing it and I figured the factory one got me through 11 years / 80k miles and about 30 track days. A bad decision on my part.
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Old 09-20-2016, 01:17 PM   #8
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Quote:
Originally Posted by Hella-Buggin' View Post
I have an 06 997.1 S that I track about 8 times year. I'm running GT3 LCA's and rolling on Yokohama AD08R tires.

For piece of mind I've installed the third center radiator to aid in coolant temps. I also just installed a Mantis 1.2 Liter deep sump as I was starting to have oil ingestion issues. I figured this will allow me to run a lower level of oil to not overwhelm the AOS and still keep the same if not more actual capacity. Plus, I can worry less about oil starvation.

Anyways, I've noticed that in left handed sweepers the oil pressure remains consistent with straight line pressures of just over 1 Bar / 1k RPMs. I have noticed on a right sweeper, the pressure drops to about 2.5 bars and hold steady. On the corner in question I'm not hard on the throttle but just giving enough to hunker down the rear end.

I've read that the pressure is not only RPM dependent but also load dependent so I tried on a local looped onramp to give it more throttle but it still dropped to 2.5 Bar and only when I reached about 5k RPM's did it start to climb.

Thoughts?
i dont have any experience with the 911, but the oil pressure in the 928 will drop to dangerous levels with using Mobil 1 oil. redline or amsoil (or other good synthetics, fixes that ). seems its viscosity breaks down at track temps.
the g-loading issues could be foaming of the oil too that starves the pick up at high RPM.
oil pressure is not load dependant. often times many systems can have a lot of foaming of the oil and vapors can be brought back in the intake recovery system and then you can have a pool of oil in the intake. .. then, upon start up, you get a cloud of smoke. (or on some turns)
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Old 09-20-2016, 02:55 PM   #9
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Quote:
Originally Posted by Frank 993 C4S View Post
It depends on your model year. Pre-2008 Boxster/Caymans have an engine driven oil pump that is entirely RPM driven. Plus you need to install an aftermarket sensor to get true oil pressure as your factory OBD output reads a constant value until there is zero oil pressure (which unfortunately is too late to detect a problem).
Exactly, I have a 2000 and I replaced the Oil pressure switch with the VDO part that has oil switch and oil pressure terminals and wired the pressure sender to the matched VDO gauge and the pressure switch to the OEM connector. 996/997.1 folks have the dual sender already and the oil pressure in the cluster.
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Old 09-21-2016, 02:01 AM   #10
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First thing I did to my Boxster S was to add a 0.5qt oil sump extension and a baffle kit. I didn't add the 2wt as I feared I would lose ground clearance on the streets.

i also added a oil pressure sender and gauge.

i run my oil thick and full.

Never had any oiling issues.

mike
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Old 09-21-2016, 02:16 AM   #11
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How thick is thick. I'm running Motul Xcess 5w/40 but have heard maybe I should switch to a more "race" based oil like Millers CFS NT and blend a 60/40% mix of 5W-40 & 10W-50.

The oil pressure sender unit is in the upper right corner on my car.

Very helpful info here.
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Old 09-21-2016, 02:26 PM   #12
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fwiw, at a DE, in july, my student drove a stock 996 cab, and had oil pressure light up. Talked to local shop owner (runs PBOC in fla), He said oil foaming. They recommend running 1/2 qt over full.

he was 1/4 down, we added oil, and no more warning lights.

fwiw...
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Old 09-21-2016, 02:55 PM   #13
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Quote:
Originally Posted by Hella-Buggin' View Post
How thick is thick. I'm running Motul Xcess 5w/40 but have heard maybe I should switch to a more "race" based oil like Millers CFS NT and blend a 60/40% mix of 5W-40 & 10W-50.

The oil pressure sender unit is in the upper right corner on my car.

Very helpful info here.
im running 15w/50 Amsoil Dominator racing oil with 1 qt 60W Dominator racing oil. It gets hot here in Texas.
my pressure gauge is plumbed on passenger side with a tee I think where the general oil pressure gauge is. Since it's a Boxster that would put it in the drivers side for your 996/7.
this is into the cam tower. It's a pita to tighten as it likes to interfere with the fuel rail.

i plumbed the temp sender into the opposite side, but it interfered with the air box and I snapped the terminal on top.
i hate 8mm posts!
so I don't have a working oil temp gauge. Haven't gotten around to replacing it.

after the hottest of track sessions I'm seeing low teens at idle. I'm usually a little busy on track to read those gauges so I can't speak for corner readings ... But never any dash lights.

i really want to get my temp sender fixed.... But I've got too many other projects with higher priorities.

mike


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Old 09-21-2016, 04:06 PM   #14
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I just got back from a little experiment drive on the long back roads after dropping the kids off at school.
The amb. temps are around 65 degrees and I kept revs down to try an eliminate the foaming factor.

I think my pressure findings are more related to the location of the pressure sender unit's location than I was considering. It's located on the passenger side towards the front of the car above Cylinder 6.

Oil Temps reading 205 degrees. Measurement is midway on the recommended indicator so about 1/2 qrt below max.
I tried to keep rpm's around 4k which under normal circumstances I get about 4.5 Bars of pressure.

On and uphill right sweeper: The pressure drops the most to around 2.75 Bar.
On and uphill left sweeper: The pressure drops a tad but holds at 3 Bar.
On and downhill right sweeper: The pressure holds at around 4 Bar.
On and downhill left sweeper: The pressure increases and pegs at 5 Bar.

There was a steep incline and a long uphill pull for about 1/2 mile. I started in second at took it up to about 6500 rpm's the pressure stopped climbing at 4 Bar when I got to about 4k and held there. Once I shifted to third, it was still pegged at 4 bar. Up to fifth, still pegged at 4 bar. Once the hill leveled out, it pegged at 5 Bar. It's almost like the internal pressure system maxed out but the gauge didn't reflect that accurately.

If the pressure is mechanically driven, which I think it is, this should result in a constant pressure at a constant rpm, assuming, foaming isn't a factor here.

I feel like the location of the sender is effecting the gauges readout. The pickup tube location is pretty symmetrically located in the sump and a left vs. right turn should have equal effects. A uphill or downhill trajectory should also have equal effects on Pickup pressure.

I'd be really curious what would happen if I installed a more centrically located sender.
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Old 09-21-2016, 04:23 PM   #15
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thats interesting Mark, because you would think that any variation in oil pressure at a given RPM would be due to the pickup issues. however if the pressure sensor is reading from something other than the output of the oil pump, then all bets are off. maybe thats the issue here with the 911
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