Got some cup car toe links on the
05-10-2007, 10:20 PM
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Got some cup car toe links on the
way.
Going to put radiator inlet screens in.
Clear bra on today.
Going to start with manual's suggested track alignment as a starting point.
Forgetting anything before heading back out to the track? Lots of threads on understeer, but my local track is fast, 2.9 miles 15 turns so I thought I'd leave sways in stock locations rather than softening the front.
Going to put radiator inlet screens in.
Clear bra on today.
Going to start with manual's suggested track alignment as a starting point.
Forgetting anything before heading back out to the track? Lots of threads on understeer, but my local track is fast, 2.9 miles 15 turns so I thought I'd leave sways in stock locations rather than softening the front.
05-12-2007, 07:28 PM
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frayed -
I did exactly what you did: 'circuit alignment,' clear bra and screens. The car does understeer like crazy until you push the sport button on the suspension and the throttle. From that point on the car is pretty perfect. My car has gone through a set of rear brakes. It must be the traction control that is eating them up. As I am now much more acclimated to the car at my home track, I don't think I'll need the traction control any more. We'll see if that makes a difference in rear brake consumption.
Hank
I did exactly what you did: 'circuit alignment,' clear bra and screens. The car does understeer like crazy until you push the sport button on the suspension and the throttle. From that point on the car is pretty perfect. My car has gone through a set of rear brakes. It must be the traction control that is eating them up. As I am now much more acclimated to the car at my home track, I don't think I'll need the traction control any more. We'll see if that makes a difference in rear brake consumption.
Hank
05-12-2007, 07:39 PM
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Hank, so unless PASM was in sport mode it understeered pretty badly? Maybe I should go with Unitah/Apex's numbers as a starting point.
I gave Unitah the part numbers offline. Here they are, courtesy of Rad in case anyone needs them.
996.347.031.91.
I gave Unitah the part numbers offline. Here they are, courtesy of Rad in case anyone needs them.
996.347.031.91.
05-12-2007, 07:48 PM
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Frayed, I just got back from the trcack and my car has been transformed. Settings are:
Front neg 2.5 degreess, 0 toe
Rear neg 2.0 degrees 16 mins toe in per wheel.
Sway one from soft in front, full stiff in back.
The car now handles like the 996GT but I was a second a lap faster
without effort. Considering that the N spec 19 inch tires have less grip than the 18 inchers, I AM VERY PLEASED!
The handling is about the same with the shocks in normal and firm. Firm felt a little better on some turns, not as good on others.
Ron should stop dissing the RS and fix his alignment.
Best,
Front neg 2.5 degreess, 0 toe
Rear neg 2.0 degrees 16 mins toe in per wheel.
Sway one from soft in front, full stiff in back.
The car now handles like the 996GT but I was a second a lap faster
without effort. Considering that the N spec 19 inch tires have less grip than the 18 inchers, I AM VERY PLEASED!
The handling is about the same with the shocks in normal and firm. Firm felt a little better on some turns, not as good on others.
Ron should stop dissing the RS and fix his alignment.
Best,
05-12-2007, 07:50 PM
#7
Originally Posted by Hank Cohn
frayed -
I did exactly what you did: 'circuit alignment,' clear bra and screens. The car does understeer like crazy until you push the sport button on the suspension and the throttle. From that point on the car is pretty perfect. My car has gone through a set of rear brakes. It must be the traction control that is eating them up. As I am now much more acclimated to the car at my home track, I don't think I'll need the traction control any more. We'll see if that makes a difference in rear brake consumption.
Hank
I did exactly what you did: 'circuit alignment,' clear bra and screens. The car does understeer like crazy until you push the sport button on the suspension and the throttle. From that point on the car is pretty perfect. My car has gone through a set of rear brakes. It must be the traction control that is eating them up. As I am now much more acclimated to the car at my home track, I don't think I'll need the traction control any more. We'll see if that makes a difference in rear brake consumption.
Hank
Buy "through a set of rear brakes" I assume you mean pads only.
I suspected TC (but never see the "yellow circle of doom") so I did some temp tests with TC off and found no difference. I also ran some just straight line braking laps (in case there's something related to trail-braking into faster apexes) and some coasting laps with very little braking and the temps stayed low.
In short, no explanation other than the greater rear bias
The tiny little deflectors and ducting to the rears suggests it would be good to get some heavy plastic and pop-rivet some additional deflectors (like the 996 RS front deflector design) to get a lot more air to the rears.
By the way, I also did some soak testing (compared times in the hot pits versus cool down versus temperature over time as the car sat in the paddock. The fronts are cooling at lot faster and not soaked. The rears are cooling a lot slower and are soaked through at close to 500 def F while the fronts are at 300 and dissipate the heat while standing to the point of being around 100 deg and cool enough to touch.
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05-12-2007, 09:21 PM
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frayed - That's correct. The car had exhibited ridiculous understeer, most noticeable in slow corners. Once the middle button "Sport" was selected, the understeer went away completely.
I don’t know if you guys are using a Traqmate, but I have data from Road Atlanta. You can download the viewer. I’d be happy to share my session data.
Carrera GT – My car has steel brakes and “by through a set of rear brakes,” I do mean the pads only. I do see the yellow circle of doom, but I use it on purpose. It sounds like you have some very good data on the brakes and I know the bias was changed to increase braking at the rear. Perhaps it isn’t traction control and just part of the ‘charm’ of the new GT3.
In any case, I find the car to be as advertised. It is extremely competent on the track and very fast. My times at Road Atlanta on stock Pirelli Corsas [the ones delivered with the car] with nothing more than the published ‘circuit alignment’ are less than one second off the winning fastest lap of the Club race in class B. Not bad for a full on street car. Conditions were very similar and one week apart.
Hank
I don’t know if you guys are using a Traqmate, but I have data from Road Atlanta. You can download the viewer. I’d be happy to share my session data.
Carrera GT – My car has steel brakes and “by through a set of rear brakes,” I do mean the pads only. I do see the yellow circle of doom, but I use it on purpose. It sounds like you have some very good data on the brakes and I know the bias was changed to increase braking at the rear. Perhaps it isn’t traction control and just part of the ‘charm’ of the new GT3.
In any case, I find the car to be as advertised. It is extremely competent on the track and very fast. My times at Road Atlanta on stock Pirelli Corsas [the ones delivered with the car] with nothing more than the published ‘circuit alignment’ are less than one second off the winning fastest lap of the Club race in class B. Not bad for a full on street car. Conditions were very similar and one week apart.
Hank
05-12-2007, 11:02 PM
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frayed...are you headed to TWS? My car was sublime there. PASM in sport mode. Air pressures were critical to balancing the car....it has Corsas. No change to alignment or roll bar settings from factory. I guess the car can get better with attention to those details....its running 2:00 lap times now without trying hard....
05-12-2007, 11:17 PM
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One thing about brakes, I will have to reread the manual. Cars with Electronic Brake Force Distribution (EBD)wear out rear pads much faster than fronts because the system has much higher rear bias.
05-13-2007, 12:21 AM
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I ended up with 29psi front, 33psi rear hot (after a 20 minute session in 85 degree sunny weather). One of the instructors that owns a 997 GT3RS rode with me and he also thought my car was well balanced through the turns.
He was running his tire pressures about 1 psi different front/back. I believe it was 29/30 hot. Again he owns a RS...may be a different animal (I have the regular GT3).
I didn't like the feel of the car as much at higher air pressures. It felt stickier at the lower pressures but had to be careful to warm the tires up before pushing too hard.
Again I haven't messed with any setup regarding alignment or sway bars. Any change there might require different pressures.
He was running his tire pressures about 1 psi different front/back. I believe it was 29/30 hot. Again he owns a RS...may be a different animal (I have the regular GT3).
I didn't like the feel of the car as much at higher air pressures. It felt stickier at the lower pressures but had to be careful to warm the tires up before pushing too hard.
Again I haven't messed with any setup regarding alignment or sway bars. Any change there might require different pressures.
05-13-2007, 12:29 AM
#14
Brake Bias
My 997 GT3, steel brakes, came back from 330 track miles at Watkins Glen last weekend with ~70% of the front OE pads remaining, but only ~20% of the rears left. Interestingly, there was almost no sign of heat stress in the rotors, which is hugely different than a friend's '04 GT3 did last fall at VIR.
I'm not aware of the traction control invoking itself, and my guess is that we have a brake balance issue here. I'm going to Road America over Memorial Day, and I'll try running w/o traction control. I'll be using Pagid RS29s and SRF this time.
I'm not aware of the traction control invoking itself, and my guess is that we have a brake balance issue here. I'm going to Road America over Memorial Day, and I'll try running w/o traction control. I'll be using Pagid RS29s and SRF this time.
05-13-2007, 01:03 AM
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997_GT3 - That's interesting. Thanks for sharing. I tried lower pressures - even the one you settled on - and found the car to be less responsive with regard to directional changes than at slightly higer pressures.
Karl - I don't necessarily think it’s an issue (not trying to be argumentative at all). The car is very heavy and requires a lot of brake to slow it down as it is also very fast. The car is easy to control and feels well balanced under even maximum braking. I am not an engineer, but I would guess that Porsche struck the best balance they could between rear brake bias and braking performance vs. rear rotor and pad size (i.e. weight). The cost of this great braking and Porsche’s compromise to the owner/user is frequent rear brake pad changes. Now that we all know it we can be prepared and check them often. They’re a frequent wear item just like the front lip spoiler.
Hank
Karl - I don't necessarily think it’s an issue (not trying to be argumentative at all). The car is very heavy and requires a lot of brake to slow it down as it is also very fast. The car is easy to control and feels well balanced under even maximum braking. I am not an engineer, but I would guess that Porsche struck the best balance they could between rear brake bias and braking performance vs. rear rotor and pad size (i.e. weight). The cost of this great braking and Porsche’s compromise to the owner/user is frequent rear brake pad changes. Now that we all know it we can be prepared and check them often. They’re a frequent wear item just like the front lip spoiler.
Hank