How to remove a brake booster permanently

[Mattt]

Right I’m wondering if the Oldschool experts can help with an issue I have. I’m wanting to run a non boosted brake system in my e21 bmw. I’ll be running aftermarket disk brakes all round. I’m hoping to remove the booster as the standard RHD setup the bmw uses pushes the booster away from the firewall towards the headlight using an extremely agricultural looking piece of folded plate. I’m guessing I’ll have to modify the brake pedal where it currently exits into the firewall and all that sort of thing which isn’t really an issue but what I really want to know is how to effectively calculate what size of master cylinder I’ll need to use to make the system work well. Any input from anyone?

[187inc]

I looked into this for basically the same reasons (escort though) and as far as I am aware, you need to calculate the leverage ratio of your pedal and the volume of fluid you need to push and compare those figures with the stock setup/modify to suit. In the end I couldn't figure it out to a point I was happy with so I gave up and am now rocking a booster. Mostly useless information but hope it helps. 

*Edit: also modifying pedals/pedal boxes needs cert but you probably know that already. 

[Mr Vapour]

Talk to Brent Parker on the e21 facebook page @Brentis 

Im going to do the same thing. My car has Holden disks and calipers on teh front and e34 rear brakes. 

there is a common bolt on off a e12 i think 

im going to be using the matching master off the Holden so i know it correct.  

have no idea how its going to be mounted yet. im thinking that im going to make a plate to bolt to the fire wall to ensure the fire wall is strong enough as they can flex if the master is bolted directly to it. not sure if it will pass cert. will check closer to the time. 

there is a guy on the aussie  bmw forum with a s52 in a e21 he had some great shots of how he mounted his.  his name is Nigel. But photobucket killed that thread. 

[Mattt]

Thanks boys. I’ll hit up Brent and see what he can tell me. I don’t mind running a normal booster if I have to, but I hate how bmw have done their stupid remote mount booster thing. It’s not great for engine transplants. 

[tortron]

Remote one in the boot ok? 

https://www.google.co.nz/amp/s/techtalk.mpbrakes.com/boosters/remote-mounted-brake-boosters-vacuum-booster-solutions-for-cramped-engine-compartments%3fhs_amp=true

[peteretep]

I think the rules are in the nz car constructors manual, from very vague memory, the pedal needed a ratio of 3:1 with a booster, or 6:1 without a booster. Get the manual and have a look though.

 

I removed the booster on my escort and fitted a landrover master cylinder which had a different piston size with a slightly modified pedal initially, and it juuust past cert. The brakes were OK but not amazing. Now I have made a bias pedal box and the brakes are legit

[sr2]

The correct way to compensate for removing a cars brake booster is to either increase the swept area of the caliper pistons or reduce the bore size of the master cylinder; the latter being the  preferable option. The trade-off for the increase in pedal leverage is an increase in pedal travel. 

Remote in-line boosters (hydrovacs) are another option but you'll need to fit two, you'll be stepping back to 1960's technology and they will still take up a lot of space.