rear mounted turbos?

[Boyraceruk]

I'd have a chat with Gunni if I were you Murran, he's got the technical chops and who knows, running without the servo might be cheaper than the pedal box or the oil pump?

[GeoffBob]

There's no such thing as master cylinders small enough in diameter to regain the mechanical advantage lost after the brake servo is removed!

There are many people on this forum (myself included) running servo-less brakes on track-cars, and it requires the pedal ratio to be increased and the use of brake calipers with larger than standard pistons (4-pot calipers on the front at least, and typically M3 calipers on the rear) and bigger discs.

Don't go down this road unless you know exactly what you are doing and you have money to spend Murran. After you've f**ked up your brakes it won't be anyone on this forum sharing the hospital bed with you.

Probably your safest and cheapest route (provided you have a working PAS pump on your car) would be to follow E21Jason's earlier advice and use a hydraulic booster from an E28. You can locate this basically anywhere you want, provided you can get your pipes to it.

[Gunni]

By relocating the pivot point on the brake pedal against the master cylinder it is possible to adjust the ratio, even make it adjustable. And suit the stock stuff.
This will likely require raising or lowering of the master, but that shouldn´t be a problem.

This way no new unknown parts are added . Only the mechanical efforts multiplied by the brake pedal is changed.

[GeoffBob]

You are sooooooooo wrong about this Gunni its laughable. Have you even tried what you are proposing? I have.

With the standard callipers and the smallest master cylinder available you'd still require a pedal ratio of around 10:1 to reclaim the mechanical advatage lost when the servo was removed. Think you've got room down there for a 10:1 pedal - think again. And even if you did the resultant pedal travel would be just ridiculous. Modifications done your way require over 100lbs of pedal force to achieve what should only take 30lbs.

Go search the trackday section of the zone for properly calculated and executed examples of what you proposing.

And for goodness sake, you're advising someone who's just starting out in the FI game to remove their brake servo! Have some common sense man, it's not you who will have to pay his hospital bill if he gets hurt.

[Gunni]

What I proposed has already been done on E30´s a number of times with solid results.

Any way it´s done you always swap pedal travel against input force.

For less travel = more input required and vice versa

http://r3vlimited.com/board/showthread. ... ual+brakes

Notice what trent did.

[GeoffBob]

What I proposed has already been done on E30´s a number of times with solid results.

Yes Gunni, with larger brake calipers. Otherwise you need at least a 10:1 pedal, or smaller M/C's than are manufactured, or 100lbs of pedal force in place of 30lbs of force.

I have servo-less brakes on my car - do you?

[Gunni]

He doesn´t mention anywhere that he´s replaced the calipers.

I totally see where you are coming from and it´s all true.
But I can try and dig deeper and see if he did at all change calipers at that point.


EDIT.
I have driven a E30 with a failed remote booster and know the feeling of pushing a brick against a wall.

I´ve done plenty of brake system calculations to know where I´m coming from and you as well. What is unknown here is the added force by the vacuum booster.
Which leaves it a unknown of how much mechanical change is required to not go nuts on the pedal travel for easy input or having to grow some serious legs .


EDIT.
I notice that he´s not really using his rear brakes.
So the effort goes to the front´s only.

[murran]

the cars got standard 323i calipers with green stuff mk1 lotus elise front pads (trimmed to fit) (they were free) at the front.
standard drums at the back but all newish shoes cyl. etc
im not just gunna fook about drilling holes in the pedal and bodging things with the brakes.
id buy this.
http://www.rallydesign.co.uk/product_in ... ts_id=4030
like this......

[GeoffBob]

Murran, Epic pedal-box/brake discussion here

Take note that, even with a motorsport type dual master cyclinder pedal box, you will still need to super-size your calipers.

[e301988325i]

All I have to say is that you get what you pay for. Murran you'd be better off spending the time doing this conversion with questionable results, earning money, and spend that money doing this properly. Fair play you want to do it yourself, and the sense of accomplishment when you're finished and I respect that, but are you going to get that sense of accomplishment when it just doesn't work very well?

[quote="gunni]By relocating the pivot point on the brake pedal against the master cylinder it is possible to adjust the ratio, even make it adjustable. And suit the stock stuff.
This will likely require raising or lowering of the master, but that shouldn´t be a problem.

This way no new unknown parts are added . Only the mechanical efforts multiplied by the brake pedal is changed[/quote]

I'm afraid I have to disagree, there is force added by the servo and the system is setup around this. Removing the servo from a stock system will need a much greater pedal force or a much greater pedal travel, for the same retardation. As you wouldn't want to extend brake pedal travel, that means extra force is required.

Pedal effort for a given brake function, with servo removed will depend on the size of the caliper pistons, of course influenced by pad friction and rotor size.

[Gunni]

You must always extend brake pedal movement if you want more leverage from the same force input.

[murran]

but are you going to get that sense of accomplishment when it just doesn't work very well?

of course i will! im always faffing about with it.
im buying that pedal box at the end of the month. get all that fitted and working then think about turbos at a later date. as somone said by fitting the pedalbox im making provision for a proper turbo set up at a later date while improving the brakes.

for those that are interested this is dr jims car that the pedal box is on.

[turboe30]

oil pump is 200 then theres pipe work and getting it to run on std ecu just put a £300 m50b25 in and have done . or listen to gunni the guy has some ide what hes talking about and a remote servo is cheap and easy

[murran]

naa dont want no e36 engines spoiling my car! i have a good m20 that can take some sh1t, in the new year i'll be modifiing and i'll be posting results. but yes ive been put off the rear/mid mounted turbo idea.

i have new plans, just need money of which i have little!

[bss325i]

I would go with the E28 brake booster set up, its cheaper than a bias box.

[murran]

i dont like or want the e28 system, i dont want power steering pumps and boosters with hydraulics cluttering the engine bay with hoses and sapping power from the engine.
plus with simplicity comes reliablitly...... sadly a concept that is lost by modern car manufacters. same applys to retro fitting s/h components from an e28.