Brake Booster Kaput

[decoupe]

On the cross section of the brake booster photo attached - the angled and tapered cylinder that the booster attaches to is what I refer to as the mounting neck and that is what you have to shorten to get more clearance for your triple webers. The other link shows the entire mounting bracket.

First step is to determine how much the Tii booster would have to move back towards the firewall to give you the clearance you need - somewhere around 3 1/2". Put a centre line down the length of the neck and mounting plate so you can get it back together with the correct orientation.

Next is to cut/grind the plate (with the four bolts that the booster attaches to) off the neck - cut it as close to flush as you can. Make a block equal to what you want to cut off and mount a utility knife blade to the block with the blade projecting about half it's length beyond the face of the block. You use this to scribe the cut line on the neck. Stand the neck upright on a flat surface with the newly cut end down. Scribe the cut line. The neck cylinder is tapered and sloped so this is the easiest way to get the cut in the vertical axis/plane. Cut the neck on the scribed line, orient the mounting plate to your centreline and weld it back on.

Next is to shorten the linkage the correct amount and there is something that needs to be done with the connector at the Tii booster I have to think about but this can get you started.

http://i54.photobucket.com/albums/g120/decoupe/M30B35 EFI/P1000167.jpg

http://www.realoem.com/bmw/enUS/showparts?id=3435-USA---E9-BMW-3.0CS&diagId=35_0222

 

[Honolulu]

I think the effect of the booster depends on the amount of vacuum you pull on the intake side, and the diameter of the diaphragm in the booster itself. Simple hydrostatics...

Not having seen a cutaway of the tii version, and since others are much thinner, I'd speculate that the tii version may be using two diaphragms in it. Anyone know?

BMW did make a two-diaphragm unit for later cars and I have, somewhere, a cutaway diagram of it. At the moment it is not handy nor does memory relate what car it came with. Anyone?

 

[aguirola]

What baffles me, is that the original CS booster is on right now, and yesterday, while rebuilding the calipers, we realized that the new master cyl. that we installed, is stuck and most likely the root of all the problems.

Will let you know what happens when the old one goes back on.

Now, the original M.C. had a check valve whereas the new old stock unit, did not and could not fit the check valve as it has no provisions for it.

The pancake filters I use for the Webers are a decent fit, only the center one has created its own clearance with a 3/4" ding, but I would prefer something with more room and install shorty airhorns.

What confuses me is, why the regular 2002 and the tii had different boosters? For racing, we don't even use a booster on Alfa Romeos, and the braking is perfect.

If I could do the same with the Coupe, then I could even fit airhorns...

Please post opinions, as knowledge is everything.

Thank you.

Regards, Alberto

 

[HB Chris]

The regular 2002 booster interfered with the Tii air box, hence the smaller diameter.

 

[aguirola]

Thank you Chris, but is the braking effect equal?

Regards, Alberto