944 Turbo Master Cylinder on a WR

[RS6avant]

Read about this being used on a hillclimb car in PPC magazine.

Does anyone know if it can be done? or if there are any master cylinders that have a larger diameter piston than the standard WR version.


The car is a WR and I am going to fit the porsche boxster brake upgrade.

Also, when I replaced the master cylinder for a new standard one about a year ago, I noticed that the brake servo had a very slight leak, do you think this would affect braking performance? it may have been exacerbated by the fact that I disturbed the plunger/rod slightly...

Thanks in advance.

[Ian Simmonds]

There is, in every likelihood that this might work, I’ve no technical details to help, but in 1991 the Audi factory in Neckarsulm were building 944’s, so the commonality of parts might be closer than first appears. Likewise, Treser used certain 928 parts for their Ur conversions (mainly fuelling) so again, there could be a workable link. Let us know what you find out...

[RS6avant]

There seem to be plenty of secondhand 944 master cylinders on ebay, tempted to buy one and measure it up.

Only one that says its for the turbo....

Accoriding to a previous thread, there are two types of master cylinder that were fitted to the quattro:

443 611 021 is 23.81mm (earlier type)
447 611 021 is 25.4mm (later type)

944 BRAKE MASTER CYLINDER on eBay (end time 25-Feb-10 14:06:11 GMT)

The above link shows a 944 version that purpourts to be a 19mm and 23mm tandem cylinder.

Our master cylinder is also tandem is it not? so why can I only find one dimesion, do we thing 23 and 25 are the total and or average bore?

Also not yet sure if the 944 Turbo had a different master cylinder to the non turbo car.

[ralleyquattro]

Brake bias on a 924/944/968 is built into the master cylinder and matched to the calipers used. There is no external pressure regulator like on the ur-quattro.

[RS6avant]

There are only two types of cylinder for a 944 acording to Porscheshop.co.uk.

One is pre 86, the other is post 86 and used right upto the 968, 1995

This is the one in the link below.

Porsche 944 Turbo 968 ATE Brake Master Cylinder 1987-95 : eBay Motors (item 170167078033 end time Feb-24-10 13:44:37 PST)

[RS6avant]

Originally Posted by ralleyquattro

Brake bias on a 924/944/968 is built into the master cylinder and matched to the calipers used. There is no external pressure regulator like on the ur-quattro.

Sounds feasible, according to this person the bias unit can be removed:

944 brake master cylinder (ATE) on eBay (end time 24-Feb-10 17:14:24 GMT)

I'm not saying that they are right, but it's something said person claims.

[RS6avant]

"BRAKE BIAS VALVE: A 5/18 brake bias valve is used on the 944 Turbo and 944 S2. The '18' designates the pressure in bars where the slope of the pressure curve changes. Thus, when the pressure in the rear brake line reaches 18 bar, the slope of the pressure curve flattens a bit and any further increase in pedal pressure will result in less increase in rear brake line pressure. This is a safety feature designed to prevent premature rear brake lockup. Unfortunately, it also limits the effectiveness of the rear brake circuit. I replaced my stock bias valve with a 5/33 and this works well with the larger front brakes."

Taken from: Brakes

So it seems that a bias valve is fitted and can be changed/removed, as 944 and 968 owners sometimes change the valve as an upgrade.

Also:

"The bias valve is located on the front left port of the brake master cylinder on non-ABS equipped cars. On ABS equipped cars, its right on the ABS pump in the right side fender well. I dont remember what line it comes off though on the pump. I have a picture floating around of it somewhere, i can find it if you want. The valve esentially goes inline between the ABS / master cylinder and the hard line"

As per:http://forums.pelicanparts.com/porsc...e-upgrade.html

Again, all other people's information, but it would seem to be possible to remove the valve, I think its only a small restrictor type fitting

[swalker]

The different size down to a front rear split rather than diagonal ?
Posted via Nintendo Gameboy