Speaking of clutch pedal pressure.

[Erik Johnson]

Hey there everyone,

So I wanted to talk to everyone a little bit about clutch pedal pressure.

As some of you may have noticed the clutch system for your car can be a bit difficult at times.

Between getting all of the air out of the system and getting the correct Master Cylinder, pedal pressure can sometimes be an issue that people have contacted me about over the years.

So here is the deal on this. With the stock slave cylinder for the Porsche, bleeding this system is a bit of a challenge. This is due to the fact that the bleeding nipple is on the wrong side of the slave after you turn this assembly inverted. This can be resolved in one of two ways. Remove the slave completely and bleed the system by hand, or you can also use a different slave that has the nipple in the correct position.

Assuming that you are using the stock slave cylinder, one way to ease the pedal pressure is to go to a smaller diameter master cylinder. Think of a fire nozzle on the end of a fire hose, and I think that this will make this a bit easier to understand. If you go from a large volume to a smaller one the fluid is compressed, (your pedal pressure increases - gets harder to push) The opposite is also true. By going to a smaller volume master cylinder you will be compressing less fluid, which will reduce the amount of pressure required to push that fluid. Up until recently, this was really the only option available as there was no aftermarket company that I was aware of that made a larger diameter SLAVE cylinder.

Good news though, I have found one for everyone. Check it out here:

http://www.mpl-tuningparts.de/downloads/porsche_2009_eng.pdf

I just wanted to share this with everyone. I hope it helps some.

Erik Johnson
(303) 440-8899 work

 

[Cliff Beer]

Erik, looks like a nicely done piece of work.

The vendor's level of engineering and machining/finishing vastly exceeds the quality of grammar in their promotional flyer there. Wow. Reads like a google translation of a Chinese Instruction Manual for assembly of my kid's Whammo Big Wheel.

 

[Terry Oxandale]

I'm sort of dealing with these issues. In regards to the SC, I used a Mitsubishi SC (3/4") on the inverted case, which has the port on top of the cylinder (pusher configuration), and is fairly easy way to mount it to the adapter plate if you've got even the most basic mechanical or fabrication skills.

It is harder to push than I'd like, but the stroke is about perfect, which means I'd be compromising a pressure decrease for increased stroke, which for us short legged folks...

 

[Howard Jones]

Eric.....I have a flipped G50-03 with a Porsche upgraded turbo clutch. I know there is an issue with presure plate travel and therefor a need to limit pedal travel. I was going to deal with this when I get to it but here you are talking about clutches so could you clue me in on this?

Any pictures on the peddle limiter would be useful. I have a RCR floor mount peddle set that is more or less like a Wilwood set. I can do the welding/fab work I just need a target example or some direction.

 

[Erik Johnson]

Hi Howard,

I would always recommend using a pedal stop to ensure that you do not over throw the clutch and potentially break off the ears that hold the clutch fork in place, but you can control this by limiting the amount of fluid that you push through the system as well.

I would recommend that you go with a smaller diameter Master Cylinder, as this will help some.

With regard to the pedal stop, make sure that you reinforce the area that you place the stop in, as I have heard some people will install this and have the plate flex enough to still cause issues.

This used to be more of an issue but with most people doing the pedal stop now, it has become far more rare. I am not sure that I would spend too much time worrying about it.

Give me a call if you have more questions and I will be happy to help you with this.

Erik Johnson
(303) 440-8899 work

 

[Terry Oxandale]

At what point (OEM arm movement at the end of the arm) is considered adequate for disengagement, and how much is considered the safe limit for the pressure plate?

 

[Erik Johnson]

The issue here with too much throw against the clutch is not really a pressure plate issue, although I can see how this could come up too. The problem that most people see here is that the fork itself runs out of room in the gearbox and puts undue stress on the clutch fork ears that hold the pin, that keeps the fork in place. The ears while fairly strong, will not handle the kind of torque that a clutch hydraulic system can place on them and will eventually break. This is why a pedal stop if needed as well as the correct master and slave cylinder combination.

Erik Johnson