KeithC2Turto

Mabie you C2/4 guys can help!

I would like to reduce the power brake "assist" on my C2Turbo brakes so they are not so toutchy, if possable. When I have my toe on the brakes and try to heal the throtle for a down shift I over apply the brakes. I found refrence for the Turbo-S Lithtweight that states "anti-lock brake system as before, but with screw-in regul. 965.355.305.01 on hydr. unit".

Has any one played with this?
Were is it?
What was the stock part number on the 91 C2T?
Is there a part number on the existing regul?
Is is adjustable or can it be made addjustable?

I know putting a spacer block on the throtle pedel will help w the "heal-toe".

Bill Gregory

Keith,

I don't think playing with the regulator will help you. The regulator determines how much pressure goes to the rear brakes when you brake. It doesn't, directly, affect the sensitivity you're describing with your brakes.

I use the Wings Third Foot on my gas pedal to provide more area to be able to heal/toe on. Goes on in a minute or two and can come off just as easy, if need be. They advertise in Pano, or if you do a search I posted their ad in the archives some time ago.

joey bagadonuts

This might not sound very helpful, but I think you need to focus on your technique.

I have a C4 and I've driven an M3--the two are night and day in terms of brake feel. The C4 requires a reasonable stomp while the M3 is rather touchy and doesn't require much effort. I'm rather adept at heel and toeing with my C4 and had no problems adjusting my technique for the M3. In fact, it seemed dramatically easier with the more sensitive M3 pedal.

A friend of mine raised his throttle pedal to make it easier for him to heel and toe, but it produced disastrous results. He found himself easing off the brakes way too early at the turns as he tried to blip the throttle of his 996. He said it was horrifying.

I believe the stock set up is fine. I have smallish feet, 9D, and I don't have any reach problems. (No cracks about small feet! <img src="graemlins/nono.gif" border="0" alt="[nono]" /> ) Are you breaking with the ball of your right foot? That's really the key. Good luck!

Cupcar

One could theoretically change the Turbo master cylinder and brake booster parts to the Euro RS units. I say theoretically as I don't know of anyone who has done it, but it should be possible as the basic system is the same.

The RS has a larger 25.4 mm master cylinder and a lesser 3.6:1 booster ratio (Turbo has a 23.18 master cylinder and a 4.8:1 booster ratio).

The RS parts will give you a significantly harder pedal(~40%) but are $$$$$. <img src="graemlins/yltype.gif" border="0" alt="[typing]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

KeithC2Turto

Thanks to all for the help.

Will work on my skills & try shimming the go pedel.

I am used to dirving a 72 S on the track with no power assist, what a dif. I added two painters sticks to the pedel and it helped a bunch. I would never shim the go pedel above the Brakes when fully engaged.

The RS parts look like the solution I was looking for! I like factory solutions. If Porsche did it on speciality, race or cup cars - it is a winner!

<img src="graemlins/c.gif" border="0" alt="[ouch]" /> As the regulator is for the back, is there opertunity here???

I read years ago that a company, I think called BDR or BRD, removed the rear regul on there RS race car for better stopping.

My C2 Turbo has a full suspention kit, which should reduce the forward weight shift. The rear is over 120 lbs lighter w cup seats, no back seats, lt wt exaust, no air pump & a plastic air box. I have changed the tire sizes and have bigger brakes all around. Thus, who knows if the balance is right or not.

Options could be to remove the regul, is there different ones that act at different pressures,or could I install an adjustable one in its place? the goal being,to better tune the brakes???

Any thoughts
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Cupcar

The factory proportioning valve is a 60 bar unit, (1 bar=14.5 psi). Wilwood Engineering makes a valve that is adjustable from 100 to 1000 psi. This valve has been installed by others on this forum. Valve is small, has a **** adjustment and can be installed using some pigtails of -3 braided stainless to adapt with AN to metric fittings. A bracket could be fabricated to attach to area where the original Adel clamp goes for factory valve. Make sure the braided stainless lines are pressure tested after fabrication!

BTW the weight transferr under braking is a function of: CG height/wheelbase X decel G. The suspension kit changes the chassis response to the weight shift (less nose dive) the amount of weight transferred stays the same. <img src="graemlins/yltype.gif" border="0" alt="[typing]" /> <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

KeithC2Turto

Cupcar.

Thanks again.

Where is the proportioning valve located.

Was going through an old mag last night and saw an artical on the Cup Cars that were going to be shipped to the US. Do you have one of these??

Nice...

Also, said that they left the rear regul off of these cars. Is that the case?

Does the ABS work on the back?

I like the Willwood idea. I have so much more brakes in front with my up grade that mabie I should remove the regul all together. I guess I am thinking that if I put the Wilwood prop valve in that I will just end up setting it at its least restrictive setting any way.

For liability reasions I belive that Porsche has dialed in more understear & less rear brake bias than is ideal. If you drove it off the road it is your falt... If it goes off backwards then the lawers say it is a deadly design & Porsche ends up paying.

Adrian

Dear Keith,
The bias valve is mounted on the ABS hydraulic unit. Yes the ABS works on the rear brakes as well. You do not want the rear end skidding either,
Ciao,
Adrian
911C4

Cupcar

Keith-

Like Adrian said the valve is in the front trunk on the ABS unit. Follow the line that goes to the rear brakes and you will find a little cylinder mounted vertically that is around 1" diameter and 2" long and held by a rubber sleeve (adel) clamp. That's the valve. It's behind the spare at between 12 and 2 o'clock as I recall.

Yes, I have an American Cup. As sold to the public it came with Euro RS brakes with a 55 bar valve. During conversion to Carrera Cup spec by Andial the valve was removed and replaced with a bypass pipe, Porsche racing part number 964.355.315.70 (probably NLA). I have installed this bypass and the front brakes still lock up first with my ABS off.

Since ABS works front and rear, ABS can cover up a lot of brake proportioning sins people are making when they indiscriminately install various brake components on their cars. I think you are right in your assumptions about both the Wilwood valve and Porsches conservative approach to vehicle stability. After all, the Porsche chassis is an arrow flying backwards! <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />