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09-27-2007, 12:24 PM
catchacab wrote:
The main difference between what Bob and I am doing is that Bob is left foot braking, which I can't do on my e-gas car. About 2 seconds after I hit the brake, the throttle is electronically cut. This allows him to get on the throttle and modulate the throttle and brake to balance the car and keep it on the edge of the limit of adhesion through T4. I also think (I'd like to walk that track) that the camber falls off a little on the wider line, which contributes to the lifting problem.
I think the PSS9 is quite good for a compromise street/track car. I've replaced all of the rubber bushings on my car, so it's a lot more modified than most cars with PSS9's. I have the rear upper adjustable spherical control arms, spherical toe link, solid radius arm bushings (front and rear) and of course spherical upper strut mounts (front and rear). To me, I'd rather have NO rubber bushings and lower spring rates than rubber bushings and higher spring rates -- the latter just adds to an already existent geometry problem by causing even more bushing deflection!
All of these mods help keep the suspension aligned correctly throughout a corner. I'm able to run about 1/8" LESS rear toe-in (1/16" total rear toe in!) than someone on PSS9 with rubber bushings. They also allow the struts to do their job better because the bushings aren't deflecting (undampened shock). I was able to even adjust the length of the rear upper control arms to dial out most of the Porsche designed rear toe change with ride height.
Because the suspension is working so well, I'm able to maintain a decent contact patch -- I don't think many 996's on PSS9 w/sport cups lift tires there.
The main problem with PSS9 is that the spring rates are low, about 230 front and 520 rear, about twice the stock rates. The fronts are too low, causing too much front dive in braking and too much body roll on initial turn-in.
To keep that wheel on the ground, and solve these other problems, I'm thinking of upping the front spring rate +100 lbs, which according to Bilstein "is probably ok" without re-valving, and probably going to a smaller front sway-bar, which like Mike said, will help keep that wheel on the ground. Basically I want to keep the effective spring rate about the same but do it with springs instead of sways.
I really don't want to go to a double adjustable setup on this car right now because of the cost and because I don't want to spend the time necessary to maximize that kind of setup. I like 1 adjustment knob. If you ask guys in our club who have double adjustable setups, you'll find that very few of them make changes track to track, and most of them will openly admit that they don't know how to fine tune them.
Quote:PSS9's are not great for the track. You can get custom Motons, JRZ's or Cross adjustables with a spring package of your choice. You can also have your PSS9's re-valved and sprung. It will firm up the ride on the street, but you should be able to come to a good comprise. Performance had a PSS9 set re-valved and sprung. There is a 996 that runs in black that has the Cross system that is used for both street and track.
The difference between yours and Bob's style of cornering, shows the difference between what PCA teaches at DE's for safely driving rear and mid engined cars and what many racers do.
The main difference between what Bob and I am doing is that Bob is left foot braking, which I can't do on my e-gas car. About 2 seconds after I hit the brake, the throttle is electronically cut. This allows him to get on the throttle and modulate the throttle and brake to balance the car and keep it on the edge of the limit of adhesion through T4. I also think (I'd like to walk that track) that the camber falls off a little on the wider line, which contributes to the lifting problem.
I think the PSS9 is quite good for a compromise street/track car. I've replaced all of the rubber bushings on my car, so it's a lot more modified than most cars with PSS9's. I have the rear upper adjustable spherical control arms, spherical toe link, solid radius arm bushings (front and rear) and of course spherical upper strut mounts (front and rear). To me, I'd rather have NO rubber bushings and lower spring rates than rubber bushings and higher spring rates -- the latter just adds to an already existent geometry problem by causing even more bushing deflection!
All of these mods help keep the suspension aligned correctly throughout a corner. I'm able to run about 1/8" LESS rear toe-in (1/16" total rear toe in!) than someone on PSS9 with rubber bushings. They also allow the struts to do their job better because the bushings aren't deflecting (undampened shock). I was able to even adjust the length of the rear upper control arms to dial out most of the Porsche designed rear toe change with ride height.
Because the suspension is working so well, I'm able to maintain a decent contact patch -- I don't think many 996's on PSS9 w/sport cups lift tires there.
The main problem with PSS9 is that the spring rates are low, about 230 front and 520 rear, about twice the stock rates. The fronts are too low, causing too much front dive in braking and too much body roll on initial turn-in.
To keep that wheel on the ground, and solve these other problems, I'm thinking of upping the front spring rate +100 lbs, which according to Bilstein "is probably ok" without re-valving, and probably going to a smaller front sway-bar, which like Mike said, will help keep that wheel on the ground. Basically I want to keep the effective spring rate about the same but do it with springs instead of sways.
I really don't want to go to a double adjustable setup on this car right now because of the cost and because I don't want to spend the time necessary to maximize that kind of setup. I like 1 adjustment knob. If you ask guys in our club who have double adjustable setups, you'll find that very few of them make changes track to track, and most of them will openly admit that they don't know how to fine tune them.