Does the E21 booster suck?

[5mall5nail5]

So I got back to driving the '87 325 I swapped with an M50TU and E21 booster. The brakes feel pretty un-assisted. Not horrible, but going from any one of my E34s to the E30 leaves me noticing that the brakes take some effort.

I am kind of considering the swap done - don't really want to seek out other solutions necessarily... but, would a remote vacuum reservoir help at all?

I was thinking about welding up a cylinder and fitting it where I can and having it add to the volume of the E21 booster... or is it not a volume thing?

Trying to realize what my options are to make these brakes feel more natural.

[brenE30]

just swap it out for an IX booster. IMO easier then trying to fab up something to make up for the lack of vacume pressure in the small e21 booster. I personaly noticed a big differance between the e21 to the e30 IX boosters

[5mall5nail5]

Hrm - is IX a direct swap? No pedal shenanigans? I am going to rock the E21 unit since its in there, but just thinking ahead. If it's simply a volume thing I really think I'd rather just make a reservoir and T into the line after the check valve from the intake. Then, I can hold as much or little vacuum as I need. But, I feel its not simply a volume thing.

[Cyrix2k]

Hrm - is IX a direct swap? No pedal shenanigans? I am going to rock the E21 unit since its in there, but just thinking ahead. If it's simply a volume thing I really think I'd rather just make a reservoir and T into the line after the check valve from the intake. Then, I can hold as much or little vacuum as I need. But, I feel its not simply a volume thing.

A) I think it's a surface area thing. If your intake vacuum isn't dropping while coming to a stop (and it shouldn't, much), then a vacuum reservoir isn't going to help. B) If the iX is the same as the e32 booster (I think it is), it requires a different master cylinder. If you don't want to deal with the pedal shenanigans, it also requires the use of a spacer which should be included and a remote mount reservoir. Honestly, the whole thing is a pain AND the booster won't clear the intake without some serious grinding. On top of that, with the spacer, the booster & MC are right up against the throttle body so you need a throttle cable with a 90* bend in it and the remote mount lines rub. I'd forget about that boost IMHO.

If you a close to direct swap, use the 944 booster. It provides more assist than the e21 booster, clears the intake with light grinding, and leaves stock amount of room around the brakes. If you get the ATE (I think, the one with the correct diameter shaft), all you need to do is a run a die down it and cut the shaft to the stock length. It's a 5 minute mod. The girling needs the shaft ground down so the die with fit, still like a 30 minute mod. Brake assist feels good to me, it's firm so not e34 like, but it stops well.

Here

http://www.r3vlimited.com/board/showthread.php?t=243829

[brenE30]

Ix is a direct fit, i didnt need to make any modifications to the pedals. I think it is the volume only for the fact that with the bigger booster you get more pressure assist then out of the smaller e21 booster. But if you are going to play with a reservoir then please post up your findings as i am very interested in this. i would love to have the smaller booster, looks cleaner in the engine bay IMO then the big IX booster

[5mall5nail5]

Yeah I think I might just grow accustomed to the E21. I put new brakes (literally rebuilt / powder coated + new pads and rotors) on it and it felt un-assisted. I thought I had air in the system so I bled it with a pressure bleeder again a few times. It just feels unassisted-ish. I can bring the car to a halt I just need to remember what car I am in.

[Cyrix2k]

Yeah I think I might just grow accustomed to the E21. I put new brakes (literally rebuilt / powder coated + new pads and rotors) on it and it felt un-assisted. I thought I had air in the system so I bled it with a pressure bleeder again a few times. It just feels unassisted-ish. I can bring the car to a halt I just need to remember what car I am in.

Sounds like my dad's '69 442 with manual brakes. My e30 with the 944 booster stops like normal; I never have to think about stopping or plan stops. The pedal just isn't luxury car light. I have an e32 booster in the new e30, but I think I'm going to swap it out for the porsche booster because it either has a leaky vacuum line or a hole in the bladder the size of texas, and the space requirements are just too awkward for me. I can't see you wanting to deal with a remote brake fluid reservoir either.

[Mr.SWISS]

Yea first swap was an M50 NV and a e21 booster.
Wasn't gonna make that mistake again.

IX ( mines an e32 actually) booster FTM. Cheap too gave the guy $40 he was parting a 740i on the clist.

[Danny]

I like my e21 booster.

[VinniE30]

Of course it sucks! But so do all other brake boosters, since they need a vacuum to function.;-)

[328ijunkie]

E34 V8/Thread.
;)

And theres nothing you can do to make the E21 better. Its not the volume of airflow (i.e. adding a vac res) its the diameter of the diaphragm. Its just too small.

[Mr.SWISS]

I like my e21 booster.

Bet u like Revshift mounts too.



Bahhhhhhhhh!!!!

[5mall5nail5]

I should just turbo this thing and put wilwood 6 pots on it and be done with it.

[Roysneon]

I have an e32 booster and short of the e34 v8 booster Dave is using I feel it's the best solution. If you take out the 'spacer' then you need to shorten and thread the rod and slot two of the mounting holes to fit it directly to the firewall, but you don't need to mess with a remote fluid reservoir and you keep stock feel. Actually, it's even better since you'll need the larger iX/m3 style master cylinder.

[Jand3rson]

My e30 with the 944 booster stops like normal; I never have to think about stopping or plan stops. The pedal just isn't luxury car light.

Same, I didn't even really notice much of a difference in pedal feel with the 944 booster. They can be a little harder to find, tho. But you can get lucky, I put an ad on CL looking for one, and had a response in 48 hours. P-Car guys (especially those into the old ones) will be chomping at the bit to get rid of the surplus parts they have. :D