Disable the brake booster?

[exodus0784]

Thoughts?

Would like to get a more consistent feel while RXing. LFBing really does a number on the booster, and would rather just run without it. I think I'm fat enough to use unassisted brakes, at least at RX.

[Daox]

You REALLY have to mash a pedal down hard if you want to stop or slow a car w/o the brake booster. Its easy enough to test though, just disconnect the line to the booster and try it out. Just be careful!

Also, I don't see how LFB is any harder on the booster than anything else...

[exodus0784]

Yeah, I'm aware. After a good set of corners or a slalom, there's usually no boost from LFBing until I completely close the throttle, and yeah... kinda like pulling yourself into the pedal with the steering wheel...

I have a test'n tune session tomorrow, so I might try it out there and see if it'll work out for the points event on sunday.
Not sure which will be worse... randomly running out of boost, or having no boost all the time

We'll see how it works out, and I know a local rally guy who might be able to work something to change the pivot point on the pedal, giving some better leverage against the MC.

[Daox]

You could just make a reservoire to increase the amount of vacuum available. A simple piece of PVC with capped ends spliced in behind the check valve would work. I've seen that done before.

[petrified.rabbit]

that would work.. to sustain breaking for a few more times.

the thing about take off the vacuum line, is it is not actually manual brakes, just like power steering without fluid/pump isnt manual steering. To make it manual (and easer to push than just removing the vacuum line) you need to put a hole to open air on bother sides of the assist diaphragm. then you would not be fighting the residual either.

manual brakes arent "that" hard to push, i say if you know what it will cost you, do it. if you ever want to return it to stock, you will need a brake booster.

[ontarian_frog]

How about you get a vacuum pump or brake booster from a diesel car? That would solve the issue, plus you'd constantly have power brakes.

http://www.autoanything.com/brakes/69A3151A0A0.aspx

[exodus0784]

$280 for a pump, relay, and some fittings?!

Managed it a little better yesterday at the test and tune... still annoying having a different pedal feel everytime I touch the brakes.

To answer Doax question I didn't answer earlier about how LFBing effects the booster:

Unless I'm shifting I never let the throttle close 100%, combined with rapid and near constant changes in braking pressures, the vacuum line never gets to replenish completely until I close the throttle. At least that's my assumption based on reports from other FWD guys who experience the same issue. 4WD guys use LFBing in a slightly different fashion than we do, so they usually don't experience it.

To explain why:

During corner entry, never lift off the throttle 100% unless downshifting. Keeps your torque up, and keeps you from locking up the front end and stalling the motor. At the same time, it allows you to manage wheel slip when you get to your acceleration point. You can use it as primitive traction control to manage power induced under steer. This really isn't an issue in the Aveo, unless you dropped it down the 1st

[petrified.rabbit]

you could (after disconnecting anything else shared) put a T in before the check valve on the booster, and add a vacuum line to the venturi. then you might be producing enough vacuum during idle and open throttle to sustain the brakes? but make sure you put in a fail safe to not allow the vacuum to leak between manifold and venturi (two more check valves maybe?) could be a $10 solution.

not sure if that has been tried/dismissed before..

[xintersecty]

On the positive side of the booster, is that normal air pressure but closed? Or is pressurized just a little bit over normal sea level? If it's not pressurized then there should not be a need for a hole on that side.