cs jeff

TD... I'm bone stock as far as the engine, but I just redid my suspension -AST 5100 coilovers (550/700# springs) and GT3 bars. I'll probably keep running BFG R1s. I haven't been out yet, but I expect to be going a tad faster w/o my floaty old suspension. That's why I'm a little concerned about the oiling issues, with what I see happening to so many 996s lately...

ervtx

How are you measuring "oiling issues"? Oil pressure drop? My oil pressure always dropped in sustained high g turns, just by a larger amount with the R6's. Kind of blunt instrument, so it would be hard to say how much of my problem was caused by all track days combined vs. just the last DE, or the last few on R6's.

I do know this much: John said that I had no category 2 over revs on the engine, and the number of category 1 over revs were statistically improbable as the leading to the failure. He concurs with the high g turn theory and the R6's as the leading contributor. Just saying...

Also, my car is very heavy compared to every other 996 out there. That is why I am dog slow in the straights. You, mglobe, and everyone else pulls away from me on the straights, yet I always make up ground in the turns. So I may have been putting a higher lateral load on my engine that you guys despite having lower lap times. Said another way, if you found another few seconds per lap in the turns, wouldn't you see more "oiling issues" by whatever measure?


Never tried the R1's. I only know that going from MPSC's to R6's was like getting a cheat code on a video game!

Re: your suspension... Same reasoning as my reply to Tom. I don't think the suspension upgrade is going to do much to your speed in the straights.

As I've inferred in my posts before, I do think that the 996 engine issue is overblown (pardon the pun) for the vast majority of stock 996's you see in DE's. For those of us who are running in the white run group with the same kind of after-market suspensions, tires, etc. that some racers use, well... that's another story altogether. Where's the inflection point? Who knows? I'm sticking with my R6 theory. But let's not scare off the 996 owners who will never take their cars to the level of mods that we did. My guess is that statistics would prove that we're talking amongst a pretty small sample size here.

cs jeff

I hope that you are right about that. i guess I'll find out when I get on the track with all my new stuff...

mpaton

Looks like Porsche may be improving the wet sump engines.

http://www.youtube.com/watch?v=fv53RbvgfGc

Michael

stuttgart46

Michael,
They probably are getting better and I am sure it will help with street cars. However, once you have installed sticky tires it seems that the G forces are too much for the stock oiling system. Not to mention the HP losses from the wet sump.

himself

I doubt anyone really knows what the oiling threshhold is for our engines before something goes bad. So, while the car is being worked on, you might contempate additional oiling support. Will you be pulling enough Gs with R1s or R6s to potentially cause a problem? Maybe. Is there any way to know for sure? Probably not. But an ounce of prevention and all that jazz.

-td

Olcha911

Let's talk Gs. This is an interesting comparison. I have the Cayman S and the 93 RS America. At the most recent club race, based on my competition, I decided not to use new Hoosiers. I used two sets of used tires - the best was one that had 3 races from TWS in March, the worst had about 3 track days on them. The RSA is no doubt fast, but not blinding at 255 HP at the rear wheels and 2920lb with me in it in full race trim. I turned a 2:00.4 as my fastest lap, and had several 2:01.1's. At the same track I have run 2:03s in the Cayman S with the same wheels, but usually a little more worn R6s, which I no longer would use to race. I have lowered the Cayman S with H&R springs and had a Gladwill alignment. Otherwise it is our daily driver. I have not done anything to increase power, etc.

I had huge problems with Cayman S smoking, which really decreases the horsepower since oil is not as combustible as gasoline- I could feel the car getting slower towards the end of each run session form oil ingestion and sloshing. What I did to address the oil and power steering overheating issue is 3 things 1) Underdrive Pulley 2) X51 Oil Pan and mods 3) Motorsports Oil Separator. The Cayman runs really well now for the money invested.

I wish I could have a car with the following characteristics - Cayman S turn-in, and 911 track-out. But I digress- I really think the engine problems are tire related. The better my tires on the Cayman the worse the smoking and the subsequent loss of power. On street tires, I drove down to Harris Hill Road in San Marcos for the day, and things were fine (Before the mods), a few weeks later at MSR, I was smoking like a bandit on track tires (BFG R1 this time).

I believe it is not just turning, it is the combination of hard stopping followed by the hard left-hand turn that pulls the oil away from the pickup and sloshes it upwards on the chain rails towards the oil separator. Hard braking with track tires brings the oil to the front of the sump.

-Keith

TRT41

good post, I like the "Cayerra" idea. I think the posts on the effect of tires are getting to one major cause. I need to do some researh on your under dirve pulley and oil separator ideas. Thanks

TR6

Do 944's suffer from any of these oil starvation issues?

mglobe

Directly from the 997 owner's manual:

"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."

I don't have a 996 manual handy, but I'm pretty sure the same warning is there and also in the Cayman/Boxster manuals.

ervtx

Excellent observation, and something that Gladwill mentioned to me as well.

At ECR last year, I wore the pads more quickly than at any other track, and ended up wearing one down to the backing plate - it disintegrated at the entry to T9. I had not been back to ECR until Memorial Day again this year, and this time, T9 figured into an equipment failure once again. As you all know, 8 - 9 - 10 is all down hill. So the sequence of events leading up to my engine failure went like this:


Hard on the brake into T9, going downhill.

Relatively sharp transition to lateral g's at T9 turn in, but with a mix of negative longitudinal g's.

Hold lateral g's during the long left hand turn thru T9 exit.

Moderate braking before T10, but the transition of g's from lateral right, to negative, to lateral left is pretty quick.

On the gas up the hill (AWD on Hoosiers!) - lots of lateral g's left and rear.

Repeat.

Again.

Again.

The whole track is hard on the car, but the combination of braking and turning in 8 - 9 - 10 may have done the lion's share of the damage leading up to the failure. (which happened going up the hill at T10).

The 996 manual would not have helped me Mike. If I ignored mpaton's warning, I would have certainly ignored the manual!

BTW, the engine has to be dropped to install the Motorsports oil separator - something I never had to do until it now. A classic case of pay me now or pay me later.

Veloce Raptor

These are very good points. And I have seen how your car smoked before you fixed it. In my M3, doing 01's and 02's at ECR, I purposely add approximately an extra quart +/- of oil for just tis reason. I do the same thing at MSR. And you and I have had some really fun dicing at both tracks. At TWS not so much--maybe an extra 1/2 quart or so when going CW, but that's it. And this is irrespective of tire--RA1's, NT01's, Z214's.







Professional Racing and Driving Coach

stuttgart46

Good find Mike. I'll see if I have a Boxster owner's manual laying around. I'm sure it says something similar or the same exact thing.

mglobe

My point on the excerpt from the manual was just to note that the type of tire probably is part of the story. That said, I just got off the phone a bit ago with a guy with a lot of experience running 996's in the Koni Challenge, and they have never had a problem with oil starvation. On thing he did mention however is that they replace their engines about every 18 months. So... probably has something to do with the age of the motor, and tires, and the particulars of the deceleration vector, etc, etc, etc,...

JW in Texas

I "thought" the mid-engine cars had less of a problem with this due to a lower moment of inertia. All this Cayman smoke talk makes me wonder. I have run used R6s in the low :02s @ ECR w/o issue on a stock 2.5 Boxster motor other then underdrive pulley. No X51 pan or Motorsport Separator. Could this issue have something to do with the larger displacement of the Cayman? Don't the larger displacement motors have a more aggressive, multi-stage oil pump. I wonder if the oil capacity under G load can't keep up with the higher pump volume?

PS: The Kumho Hoosier knock off is within a few tenths of the R6. Turned :02.8 on those first practice session Memoral Day & they were VERY used up. Not a bad tire.