993 RS calipers ?
11-17-2016, 08:26 PM
#62
Banned
I was able to experience the MS 40/65, RS rears, and 4channel (same pad f/r) last week. The additional rear bias is staggering compared to the stock setup I've been familiar with (C4 w/4channel). The car lays pretty flat digging deep and with some finesse, one can rotate the rear on nt01s whilst trailing.
It took some getting used to, but its worth it if you have a setup geared like an "replica" or "track" build.
Only thing i would like to do is add some rear scoops to the rotor.....Will look up
It took some getting used to, but its worth it if you have a setup geared like an "replica" or "track" build.
Only thing i would like to do is add some rear scoops to the rotor.....Will look up
Last edited by Sword_of_the_Spirit; 11-20-2016 at 02:07 PM.
11-17-2016, 11:00 PM
#64
Banned
Thanks Patrick. I never have either at RA or Mid. Same can be said with Autobahn. But the courses out West are short and fluid.
I'll have to do a bit more research. I know the 996/997 GT variants had a scoop/duct.....
I'll have to do a bit more research. I know the 996/997 GT variants had a scoop/duct.....
11-18-2016, 12:28 AM
#65
Rennlist Member
Well, technically that is not necessarily correct. The 993 ABS system is designed to operate with tires of the same diameter, in about 645mm in diameter. Through the evolution of the series, they began to run taller rear diameter tires in about 680mm in diameter with some of the cars with the widebody work running as much as 710mm in diameter. This can present a problem with the ABS control unit recognizing wheel slip when there is none. Since the rear ABS teeth are part of the stub axle and cannot be changed, Porsche offered a set of 45 teeth rings from the 964 for the front of the car. which returns back to normal the operation of the ABS control unit. So, a car with 645/645 would run with 48/48 and a car with 645/680 or 650/710 would run with 45/48. This is outlined in both the 993RSR and 993GT2 racing manuals.
On my car, I run 964 axles obviously which have 45 teeth on the stub axle, and I run 640/680 tires. I cannot easily change the number of teeth on the rear so I made a set of 43 teeth front ABS rings and run 43/45 to restore the ABS control unit operation. Since my speedometer is through the MoTeC unit, I just calibrate the speedometer using 43 and 45 teeth so all 4 wheel speeds show correctly in the MoTeC data acqusition which is also sent to the MoTeC ECU for traction control and pit speed limiting. The ABS functions normally and without issue on my car.
On my car, I run 964 axles obviously which have 45 teeth on the stub axle, and I run 640/680 tires. I cannot easily change the number of teeth on the rear so I made a set of 43 teeth front ABS rings and run 43/45 to restore the ABS control unit operation. Since my speedometer is through the MoTeC unit, I just calibrate the speedometer using 43 and 45 teeth so all 4 wheel speeds show correctly in the MoTeC data acqusition which is also sent to the MoTeC ECU for traction control and pit speed limiting. The ABS functions normally and without issue on my car.
11-18-2016, 03:34 AM
#66
Rennlist Member
Well, technically that is not necessarily correct. The 993 ABS system is designed to operate with tires of the same diameter, in about 645mm in diameter. Through the evolution of the series, they began to run taller rear diameter tires in about 680mm in diameter with some of the cars with the widebody work running as much as 710mm in diameter. This can present a problem with the ABS control unit recognizing wheel slip when there is none. Since the rear ABS teeth are part of the stub axle and cannot be changed, Porsche offered a set of 45 teeth rings from the 964 for the front of the car. which returns back to normal the operation of the ABS control unit. So, a car with 645/645 would run with 48/48 and a car with 645/680 or 650/710 would run with 45/48. This is outlined in both the 993RSR and 993GT2 racing manuals.
On my car, I run 964 axles obviously which have 45 teeth on the stub axle, and I run 640/680 tires. I cannot easily change the number of teeth on the rear so I made a set of 43 teeth front ABS rings and run 43/45 to restore the ABS control unit operation. Since my speedometer is through the MoTeC unit, I just calibrate the speedometer using 43 and 45 teeth so all 4 wheel speeds show correctly in the MoTeC data acqusition which is also sent to the MoTeC ECU for traction control and pit speed limiting. The ABS functions normally and without issue on my car.
On my car, I run 964 axles obviously which have 45 teeth on the stub axle, and I run 640/680 tires. I cannot easily change the number of teeth on the rear so I made a set of 43 teeth front ABS rings and run 43/45 to restore the ABS control unit operation. Since my speedometer is through the MoTeC unit, I just calibrate the speedometer using 43 and 45 teeth so all 4 wheel speeds show correctly in the MoTeC data acqusition which is also sent to the MoTeC ECU for traction control and pit speed limiting. The ABS functions normally and without issue on my car.
11-18-2016, 11:13 AM
#67
Drifting
I have 4S so 4 channel ABS with tt brakes. I now learned that rear brakes do very little (over 30 track days on rear pagids). Front last about 12 days.
My shop recommends taking the p/v out to move bias to the back. I also read that this mod is reversible. This is not a race car but I'm planning to do 10 or DEs next year. This seems like a lot more cost efficient alternative to rear RS calipers at $700 a piece.
any words of wisdom...looking at you Bill. I'm not looking for best alternative, but something better than what I have now. And yes LSD will get rebuild if I shift bias to rear wheels.
My shop recommends taking the p/v out to move bias to the back. I also read that this mod is reversible. This is not a race car but I'm planning to do 10 or DEs next year. This seems like a lot more cost efficient alternative to rear RS calipers at $700 a piece.
any words of wisdom...looking at you Bill. I'm not looking for best alternative, but something better than what I have now. And yes LSD will get rebuild if I shift bias to rear wheels.
11-18-2016, 07:39 PM
#68
I have 4S so 4 channel ABS with tt brakes. I now learned that rear brakes do very little (over 30 track days on rear pagids). Front last about 12 days.
My shop recommends taking the p/v out to move bias to the back. I also read that this mod is reversible. This is not a race car but I'm planning to do 10 or DEs next year. This seems like a lot more cost efficient alternative to rear RS calipers at $700 a piece.
any words of wisdom...looking at you Bill. I'm not looking for best alternative, but something better than what I have now. And yes LSD will get rebuild if I shift bias to rear wheels.
My shop recommends taking the p/v out to move bias to the back. I also read that this mod is reversible. This is not a race car but I'm planning to do 10 or DEs next year. This seems like a lot more cost efficient alternative to rear RS calipers at $700 a piece.
any words of wisdom...looking at you Bill. I'm not looking for best alternative, but something better than what I have now. And yes LSD will get rebuild if I shift bias to rear wheels.
bias goes from 1.997 to 1.426 below the knee of the proportioning valve
and 3/697 to 2.64 above the knee. In your car the knee is 55bar
11-18-2016, 09:06 PM
#69
Drifting
I'm not following the "and 3/697 to 2.64 above the knee" part.
11-19-2016, 01:14 AM
#70
Rennlist Member
11-19-2016, 01:35 AM
#71
Banned
11-19-2016, 08:21 AM
#72
3.697
you have 2 p/v one for each rear corner, both would need to be removed
if they are removed the bias is 1.997, under heavy braking at speed you can use more front but it's a step in the right direction.
11-19-2016, 10:10 AM
#73
Drifting
so are you saying that without p.v. the bias will go from 2.061 to 1.997? Yea doesn't seem to be worth the effort. Is that because the rear pistons are just 28mm? Anybody has a pair of used RS calipers they want to part with?
11-20-2016, 12:34 PM
#74
11-21-2016, 11:30 AM
#75
Drifting
Here are the basic 993 choices w/ oe calipers and rotors, Ideal fixed f/r ratio for track use is a bit under 1.5, w/ a proportioning valve +/- that w/ more rear at higher line pressure is desirable. The more rear bias the lower and stiffer and the more an effective lsd is desirable. The difference between the tt and RS is the rear caliper pistons, 28/28 on tt and 4S, 30/36 on RS
If I understand correctly now, at 70 bar pressure with 55bar limiter the bias is 3.697 and without the limiter (p.v.) it would be 1.997. While not ideal 1.5, it looks like a def improvement. Please correct me if I got it wrong again.