944 ls1 brake booster?

i am building a 944 with ls1 and idk if like im the only one who doesnt know what to do for the brake booster but i dont seem to find much on it so im going to ask. i see that most are useing hydroboosters that run off the the power steering pump, but what i want to know is where i am soposed to get a hydrobooster that fits? from what car do people get theres from?

Ford Mustang or BMW H31 boosters are most common, also there are electric units that work very well too.

thanks alot, and do i need a new power steering pump to go with it or does the stock ls1 one do the job just fine?


Travis

I don't know if you need to do anything for the Mustang booster. The BMW unit works on a system with similar pressure to the Porsche. If you are running power steering you can boost the LS pump pressure, there are articles on the web, or do like I and a bunch of other folks have done and get a pump from Turn One, setup for Porsche pressure.

that sounds good, i dropped my ls1 pump the otherday so buying a diifernt one dosnt bother me much

The advantage the BMW hydroboost has is that you reuse the stock Porsche master cylinder, so the brake bias is proper. The Mustang system uses the mustang master cylinder and it has too much rear brake bias.

However the mustang system is easy to find and is much cheaper than the BMW system...

if i do go with the mustang will i be able to make it work properly? and if i just plan to use my car as a dayly driver will the off bias even realy have that big of an effect?

I really didn't notice the bias issue until I was on the track. On the street it's fine, you can install an adjustable rear proportioning valve to get it good for the track, that's what I did.

In a non-ABS car, I think bias is even more important on the street. On the track, you get to threshold all the time and get a chance to adjust your driving style even if the bias is wrong. On the street, you will eventually end up in an emergency situation. If the bias is wrong you will either spin out immediately or, if you modulate the pedal well, experience very limited in stopping power.

In my opinion, stick with the stock master cylinder and bias control. If you do change things, plan to spend a considerable amount of time in a controlled environment tuning to get it right.

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Rich

In retrospect I wish I'd gone with the BMW system. I didn't really know that it was available and didn't realize it reused the porsche master cylinder and the bias issues that occur with the Mustang unit.

It's just one less thing to worry about with the BMW unit.

from the way it sounds the mustang booster is just a pain, but will the bmw booster be such a pain to my wallet that its worth all the fuss? how much do thoes go for?

Mustang units are cheap, $150. BMW parts are more expensive, however with the Mustang unit you need to factor in an adjustable rear proportioning valve, lines, labor etc.

This isn't a cheap swap you're doing and you'll spend more if you end up doing things twice.

Just plumb in a rear Wilwood Prop valve so you can use whatever caliper combos you have/use.

I think i will just go with the bmw one and just have it done right the first time i hve already done a few things twice so im going to try and avoid that. So what years did they make the bmw h31 i have been haveing trouble finding them.

1988 -92 or so 750 series, there are earlier years as well, back to 83 I think. Some of the earlier ones have part of the booster extend towards the firewall, which you need to consider depending on how you mount it. I'll be posting pics of my mount setup soon.

i found a booster on rockauto for a 1988 750il with hydroboost for $205 brand new. idk what all the fuss was about it being spendy but that seems like a fair price.

The booster is not the only part associated with the BMW unit. Mike, I thought you sold that?

Buyer didn't use it so I bought the system back. Booster is the easier part to get, the regulator with the nitrogen bomb, and the reservoir is needed too.

Does the reservior regulator and nitrogen bomb need to match the booster or are they universial?

Here is a diagram of the BMW systm, I think it will clarify things for you.

Is the GM pump enough to run the BMW system and power steering?

Yes, the BMW system sends very little to the booster, most of the pressure is used for power steering. I have some good articles I can post links to. I definietly think you need the modification to raise the GM pumps pressure to Porsche/BMW specifications.

so how would i try to search for thoes parts? would they be considered under steering, i dont see them listed for brakes.

87-944S wrote:Buyer didn't use it so I bought the system back.

I resemble that remark...

One way I found a system, that I didn't end up buying, was a local guy parting out a 740i. He was willing to let me pull the system out of his car in his driveway.

Here's another diagram:

Which I really appreciated Rich, so I didn't have to source this stuff again!