PseudoRealityX

If you change fuel load and gain 5mph through a corner, thats AMAZING. However, i dont think its true. :shrug:

What i mean by that is you should be able to play with tire pressures to get the car to rotate more. Keep your fuel loads about the same each time you autocross. Then you can tune with the pressures. Its a much better tool, simply because it doesnt add weight to the car.

0HP930

It is. Do a little research on light, tail heavy (44%/56%) mid engine cars with positraction and you will see that right after tires using front end fuel weight to adjust the weight distribution is at the top of the list for over/under steer adjustments. While I am working on the tire and suspension solution, for now all I can control is fuel weight.

I know you know how to handle your paticular car very well but 911 and 930 are very different creatures from the nose heavy automobiles most of us are used to driving.

Are you really trying to tell me that if I am understeering and I can reduce this by adding weight to the front of the car that I can not go through a particular radius turn faster than when the front end was plowing at lower speeds?

You don't have to belive me if you don't want to, but think about the physics of this for a while and you might want to reconcider your above statement.

PseudoRealityX

you can control tire pressures too, which is what i suggested. Yes, the Porsches are tail heavy, and very twitchy (from what ive read), but it still has to obey how a tire works.

This is true, ive only driven mostly front heavy cars, other than a formula ford, but that was only like for 6 runs...so it doesnt count.

What is said is that a 10mph difference is CRAZY. Maybe like 2mph. You'd be amazed at how close the speeds really are. Again, this is just my opinion. But if you look at it from a physics perspective, the difference in cornering Gs is really a very little amount of velocity difference. If you could really change your speeds by 10mph, you'd be beating Danny Shields all day long.

0HP930

On some of the wider turns (~20" Radius) at the miata event I would say I was able to gain around 5 MPH. That increase in speed only represents a 15% increase in lateral acceleration.

On a larger turn like the PCA's ~50" radius 180 degree turn I could see the benefits being as high as 10 MPH (this being an optimistic guestimate) since I would not need to brake as much to negotiate the turn.

You must keep in mind that the reason why the understeer is so bad in the 930 is not primarily because the maximum lateral acceleration the front tires can handle has been exceeded but because there is a strong posi and a heavy rear end trying to force the car in a straight line. You can also imagine what this does for accelerating out of a turn. Unfortunately having over 300 HP in a 2,700 LBS car makes a strong posi a necessary evil.

This understeer can always be counteracted by shifting the weight to the front by braking, but when you want to maintain a high apex speed this is not always a practical option.

If you are only thinking about the maximum lateral Gs my car can handle I can see why you may be skeptical about the possible speed gains. If you concider the fact that I have to battle strange non acceleration forces to negotiate a particular curved line while maintaining speed and control perhaps you can see why the 930 does not like really tight turns without some weight adjustment.

Tire presure changes just don't have same the tweak value of putting an additional 100 LBS on the front wheels.