Modified 944's

[AndrewS]

ORIGINAL: 333pg333

For those who run slicks on their cars, Andrew and Paul, I'm interested to know what changes if any you've made to your sump to guard against the significantly higher chance of oil starvation. Also Andrew what suspension do you have in your car and what sort of springrates? From memory Paul I thought you had a stock sump? On one hand I'm delighted that you've not had any issues with your motor, but I'd also talk to Jon to cover off what he might think just as a precaution. If I'm out of line tell me to get back in my box. It's only out of concern of course. Then we get into what oils you use on the track..........perhaps leave that for another thread?

Hi Patrick,

Suspension:
Standard car with 1990 original Boge suspension suspension; later fitted with KW Variant 3. All road settings, but a little more front negative camber. Spring rates are standard.

Sump:
Standard baffled 951 sump. I never had any issues in 3 years of Porsche Cup racing (using very hard springs and ProTrac dampers) and have never had an issue (with oil starvation) in what has now been 11 years of track days.

Oil:
Fully synthetic - either Royal Purple 10W/40 Motorsport or Halfords 5W/50 Trackday oil. Trick is to keep the level just above the max mark on the dipstick.

Tyres:
Originally Pirello P-Zero Porsche Cup slicks and nowadays I use Avon hard compound slicks.

Driver:
Ask those that have witnessed the car or experienced a passenger ride. ;-)

Regards,
Andrew

 

[AndrewS]

ORIGINAL: 333pg333

Nothing wrong with a bit of slave labour. Do you remember what brand you used? Were they a proper slick with no grooves?

Hi Patrick,

Paul used the same tyres as I did, Pirelli P-Zero Porsche Cup slick tyres - these were the same control tyre used in the Pirelli Porsche Cup where there were two compounds available (hard & soft). I now use Avon hard compound slicks.

Both tyres types are full racing slicks with no grooves, just smooth ultra sticky rubber and super stiff sidewalls.

Regards,
Andrew

 

[333pg333]

That is amazing Andrew. As you would be aware, the archilles heel of our cars is the oiling and potential starvation. Good to hear though. Makes me feel a bit better about running around on almost slicks next year. I will have a highly modified sump though just the same. Those slicks sound like lots of fun. Do you think there has been any negative effect on the body as has been suggested in this thread?
cheers
Patrick

 

[sawood12]

ORIGINAL: Fen
Let's say on your road tyres you can generate 0.5g through a corner then what happens to limit you to that 0.5g? Your tyres lose adhesion; it is as simple as that. On your warm, sticky and stiff sidewalled slicks you might generate 0.85g through the same corner, so everything is subjected to an extra 0.35g.
That is so obvious to me that I really wonder if I am missing the point, but if I am then I can't for the life of me see where.

I agree. That is what is certainly what I meant. Some people seem to think that grippier tyres (or lower profice tyres) automaticaly subject your car to higher forces - but that is only true if you exploit the extra performance they provide.

Regarding this issue about oil starvation. This is one of the reputations that the 944 seems to have undeservedly earned. The thing is that if someone has a failure trackside which turns out to be an oil starvation issue then people automatically assume its a problem with the car rather than the owner. I think the statistics would show these cars make extremely reliable and good trackday cars if you treat them properly regarding making sure things like the oil is topped up properly - as you should with any car you are tracking.

I've see Andrew in his white chariot on slicks with standard and worn out gilopy suspension and it opened my eyes to just how potent and capable these cars are in the right hands. Believe me, if there is a weakness in the sump/oil pick up design then Andrew would have found it that day. Not only was the car seeing high cornering forces, but it was rolling like a 2CV which would have moved the oil even further away from the pick-up.

People seem to forget that these are Porsches and long before they went on sale they would have been tested (i.e. abused) over many thousands of miles on tracks such as the Nurburgring, by proper drivers long before us keen amateurs got anywhere near them. I think it is a case of look after your car and it'll look after you.

There are a number of 'myths' about supposed problems with the 944 that doesn't seem to be backed up by the sheer numbers of people who happily track their cars with little or no issues. For example, i'm still not convinced people fully understand the failure mechanism of the control arm ball joint. There is alot of circumstantial evidence about the failures (i.e. they do occationally fail), however what is the failure mechanism - is it the pin or the arm socket (they both have failed in the past)? the fact the cars are lowered (some un-lowerd cars have had failures)? is it the fact the ball joint is 20yrs old, is worn and has propbably seen zero maintenance over it's entire life and they have been subjected to it's fair share of bumps big pot-holes along the way - not to mention a few off-track excursions? Often with these things there is more to it than meets the eye.

 

[333pg333]

Scott,
I think in this case most people would increase the G forces on their cars given the difference between say road and slick tyres so I would assume that whatever possible outcome would be reached with higher stresses on the cars with slicks.

As for the oiling situation, I guess it would be nice to have some stats to corroborate one view or another. I would also defer to people that know a lot more than me on the subject but given good reason or fact, I'm prepared to believe either. At this stage I'm still in the '944's do have an inherent oiling issue potential' camp.
I'd also like to know what sumps the Cup cars had? I'll try and find out for curiosity's sake.

 

[AndrewS]

ORIGINAL: 333pg333

That is amazing Andrew. As you would be aware, the archilles heel of our cars is the oiling and potential starvation. Good to hear though. Makes me feel a bit better about running around on almost slicks next year. I will have a highly modified sump though just the same. Those slicks sound like lots of fun. Do you think there has been any negative effect on the body as has been suggested in this thread?
cheers
Patrick

Hi Patrick,

I have heard about some early none baffled sumps having that issue. However, during the Porsche Cup in 1998, 1999 and 2000 (when the 944 Turbo was campaigned) - all cars were 250bhp models and used the later type sump. I remember two engine failures - one threw a #2 rod through the block at Spa and another suffered bearing failure when the oil cooler was punctured at Brands Hatch. I personally never had a single engine issue.

The use of slicks has no impact on the cars that I have used them on. My current car (1990 model) with KW V3 suspension works very well on the track with Avon slicks. I have had no stress or reliability issues to date.

Regards,
Andrew

 

[333pg333]

Thanks Andrew. It's nice to hear this as it gives me one less thing to be concerned about. I am actually going for 10" all round. I may even use the same width tyre front and rear. There are quite a few racers who do this. Having never looked at proper slicks before rather than the Hoosier type '2 liners', I wonder on the costs of slicks compared and their lifespan? Perhaps I should just go for them instead?
Oh this is on a lowered car with KW 2 way race setup.
Just a bit of OT. I had a current Carrera Cup guy as a passenger for a few laps recently and amongst other things he remarked "Because you're car is so soft and doesn't have much grip, you need to be more subtle with your braking". This was a slight shock as I have 255/285 Toyo R888 and spring rates of 616lb/in 708lb/in eff rear !! Soft.??? Then I thought, what is this guy used to? Ah yes, massive slicks and 1500lb/in springrates. []

 

[AndrewS]

ORIGINAL: 333pg333

Thanks Andrew. It's nice to hear this as it gives me one less thing to be concerned about. I am actually going for 10" all round. I may even use the same width tyre front and rear. There are quite a few racers who do this. Having never looked at proper slicks before rather than the Hoosier type '2 liners', I wonder on the costs of slicks compared and their lifespan? Perhaps I should just go for them instead?
Oh this is on a lowered car with KW 2 way race setup.
Just a bit of OT. I had a current Carrera Cup guy as a passenger for a few laps recently and amongst other things he remarked "Because you're car is so soft and doesn't have much grip, you need to be more subtle with your braking". This was a slight shock as I have 255/285 Toyo R888 and spring rates of 616lb/in 708lb/in eff rear !! Soft.??? Then I thought, what is this guy used to? Ah yes, massive slicks and 1500lb/in springrates. []

Hi Patrick,

I ran spring rates of 700lb front and 600lb rear with 8" slicks (wide) at the front and 9" rear. My car at one point had 11" rear slicks and 9" fronts and the spring rates were then too soft to really work the tyres. I increased the rear spring rate to 800lb and left the fronts as was and it was fine. So yes, slick tyres require hard spring rates to really work them effectively - but you still need some compliance for bumps and changes in the level of the circuit. Using a tyre pyrometer and doing a lot of testing is the only way to determine if the tyres are being worked effectively and not overheating at specific points on the tyre.

Slinks are generally cheaper than road tyres and will last a long time, before you hit the wear limiters. However, you will only get 100% of the maximum grip available for a short window before it falls away to about 90% - which is then sustained pretty much until the tyre physically wears out; hence why many races sell part used slicks (that have been used often just once!)

Regards,
Andrew