jackal2513

what about the LSD ? does the RS have one ?

Bill Verburg

the g50/3x transmissions used in the RS & Cup cars has a much more effective lsd than the g50/2x trans lsd optional lsds

RS is 40/65 w/ 4 plates
tt & n/a have a 25/65 or more usually a 22/45 2 plate that wears out quickly*

GT transmissions can rebuild these w/ 4 more effective plates

bobesser

Bill,

Can you elaborate how the brake bias and the LSD interact and balance or unbalance braking? This is a very interesting discussion to me and I am having a bit of trouble visualizing it.

Thanks,
Bob

Bill Verburg

993 use a variable lockup lsd, 40/65 means 40% lock on acceleration and 65% lock on deceleration. These are nominal #s and only hint at the actual break away torque between the wheels. Generally 4 plate will have more actual break away torque that 2 plate but it depends on many factors from the plate material, to preload, to wear.

Additionally lsd equippped cars have 4 channel abs , open diff cars 3 channel.

lsd helps to stabilize the rear of the car under braking, awd also does this as does the 4 channel abs, all contribute to allowing an lsd equipped car to brake later and deeper using more of the rear brake potential than non lsd cars.

pure race cars like the RSRs also use 40/60 but w/ 6 or 8 hd plates and far more brake away torwque than is used in the street oriented cars

V

Very interesting thread.

Did the 993 GT2 in it's various forms have 993TT front and rear calipers and not the 993RS rears?

If Porsche did not use the 993RS rears on the GT2 or the turbo, I don't see how then can be a good alternative on a turbocharged car. I agree the 993TT and 993GT2 are very different cars, hence my question.

I am all for stopping power and have considered the 993RS calipers for the rear but I don't want to screw up the balance too much. I though if the change would make sense on a 2wd TT with some weight reduction and a nice LSD, why wasn't it standard on the GT2 in the first place?

Bill Verburg

Street 993 GT2 used the sma e barakes as 993 tt ie 36/44 Big Red on 322x32 and 28/28 big red on 322x28. This setup is extremely front biased
~2:1 front, rmemeber used 911 has always been ~1.6:1 front

GT2 Evo used a 34/42 race caliper on 380x32 and the same big red 28/28 on 322x28 as 993tt, this again is very front biased.


Use what you want, I've had both and IMO tt rears are leaving a lot on the table

rsa964

If anyone has a set of 993tt rears available - let me know - am interested.

Thanks,
Dan

Geoffrey

The 993 RSRs have only a 4 plate LSD and the 8 plate version did not come out until the differentials found in the 2004 RSR (9E) and 2006 997 Cup (9C). Even the 96-98 911 GT1 ran with 4 plates. I've found that with the racing brake assist module, racing ABS, and no pressure limiting valves in the circuit, the RS calipers have way too much brake bias, even with less agressive pads in the rear.

Bill Verburg

Actually I was was referring to the late 997RSRs wrt the 6 & 8 plate lsds

the 993GT1 used 996.332.083.80 which was a 50/80 but could also be set up 60/40 or 80/80 by changing the outer pressure pieces. I've never seen one apart so I have no idea what the plate count is. The point of the discussion being the use of an effective lsd which the older RSRs certainly had w/ their sintered friction plates


and of course your issue w/ RS rears can be summed up, you should be using the RSR twin master setup w/ it's base 50bar/55 bar setup

Geoffrey

The 993 RSR and GT2 uses the same master cylinder as a TT or C4s (993.355.903.00). The GT2 parts manual lists the brake servo and master cylinder assembly as one part number, but the master cylinder is physically the same as the street car. Neither racing system in either the 322 or 380mm brake setup uses pressure limiting valves. Pressure limiting valves are crap for track usage.

Bill Verburg

agreed, but most of the folks here have dual purpose cars

one more question what is the tooth count on your abs rings? f/r?

Geoffrey

What are you thinking?

Bill Verburg

993GT2Evo used an ideosyncratic set of abs rings

Geoffrey

ideosyncratic?

Bill Verburg

GT2 Evo use 45/48 not the usual 964 45/45 or 993 48/48