chago996

Did my first STS event with POC on sat. It was a blast. Thanks to Don Neville for being such a great and patient instructor. Noticed on my '01 996 that the oil pressure was the normal (around 4) reading during the actual laps, but it would dip below the 1 bar when coasting to get out of the track on the way to the pits. No flashing lights on dash either. Is this normal.

Pac996

Well heated oil can do that. The car computer tracks temp and varys a restrictor that creates back pressure to make the oil pressure higher when cooler to get oil to penetrate tight spots better. After heated and the car should be well lubed the back pressure is dropped off which is why you can start at 5 bar cool then go to 1 at low idle after up to temp. Porsche figures as long as you have 3 bar at 5k rpms its cool. It is advised to not be rapping the engine up when the initial pressure of a cold start is high. AT least thats what porsche documents say.

ROK

Pac, great stuff. Do you have any official documentation to back up what you just wrote?

Pac996

Owners manual

Pac996

From manual
With a warmed-up engine and at a speed of
5000 rpm, the engine oil pressure should be
approx. 3.5 bar.

The fitting of racing tires (e.g. slicks) for sporting
events is not approved by Porsche. Very
high cornering speeds can be achieved with
racing tires. However, the resulting transverse
acceleration values would jeopardize the adequate
supply of oil to the engine.
Porsche therefore will not accept any warranty
or accept any liability for damage occurring as a
result of non-compliance with this provision.

If the vehicle is used for repeated short trips,
and consumes a normal amount of oil, the engine
oil measurement may not show any drop in
the oil level at all, even after 600 miles (1000
km) or more. This is because the oil is gradually
becoming diluted with fuel or moisture, making it
appear that the oil level has not changed.
The diluting ingredients evaporate out when the
vehicle is driven at high speeds, as on an expressway,
making it then appear that oil is excessively
consumed after driving at high speeds.

In the service manual pg 1-11 has the non-return vavle for the cams. It's backing up pressure to operate the vario cam with a 4 way valve. I figure during initial start besides the higher idle it goes along with the valve to increase penetration. A fringe benifit of the system I figure. Chevy in older cars was just using a ballbearing with a spring for back pressure.

chago996

Thanks. That all makes sense. Would Michelin Pilot Cups be considered racing tires and, therefore produce oil starvation on the 996 MK1? They are street and track according to Michelin. Thinking about them for next event at Fontana. Currently on PS2

Pac996

For the porsche guys I think somebody on here has mention before that just taking the car to a track is a failed on the owners part to honor not abusing the car. Sure its just driving the car like it should be but even with out the sticky tires I think the g's are always higher racing which ties into the mentioned stuff in the owners manual. What ever the facts have fun.

himself

I have run lots of sticky tires, Pilot Cups, RA1s, Hoosier R6s, even Yokohama and Pirelli slicks on my 996. Sticky tires can cause oil starvation problems. You can attempt to prevent this by running the X51 oil pan and/or a deep sump kit with pickup extender.

Also, I don't really think running Pilot Cup tires is a good idea for your 2nd event. They are really crappy when cold, so unless you are actually driving hard you will not have a good time as compared to the PS2s. In fact, I stopped running them altogether because of how long they took to warm up.

-td

robert r

Great explanation

I remember the old mazda mx-5 (miata in the US) at some point went from a oil pressure gauge to switch because of the number of owners complaining about low oil pressure? It still looked like a gauge but was either on or off.

Tbred911

how many laps do cup sports take to heat up? I thought they were good to go after 2 laps.... what track tires do you recommend that are not full slicks...

garrett376

Hey Chago, welcome to the POC - what a great group! PM me any questions you might have - I cup race an 02 996 as an MI car and do all the work myself so I might be of assistance with your setup.

Regarding your oil pressure, mine does that, watch this:
https://rennlist.com/forums/996-foru...-pressure.html

himself

2 laps is about right. But if you figure you get a 20 minute session, and each warm up lap is 2 minutes, that's 4 minutes gone just warming up - about 25% of your entire time. Figure in a cool down lap of 2 minutes and you get 14 minutes of lapping. Just too long for me Even in a 30 minutes session, that's 20% lost.

I only run Hoosier R6s now. But there are loads of "beginner" R-comps. BF Goodrich R1s, Toyo RA1 or R888, and Nitto NT01 are very popular.

Also, the only serious tire failure I have had to date was with the MPS Cups.



-td

Michael-Dallas

Uh, got any more info on this fancy oil system with restrictors? I have never heard of any modern engine having such system, but there's always a first. I know many Japanese cars have an oil bypass that will bypass the oil system when oil pressure is too high, trading oil filtration for engine lubrication.

But for the most part, oil pressure is higher when the engine is cold because the oil is cold. And cold oil is more viscous than hot oil.

Oil pressure is important to move oil around, but too much pressure becomes resistance to flow. Higher oil pressure does not mean higher oil flow.

///Michael

Pac996

Pg 1-11 in the service manual shows the vavle.