I actually have the Grimspeed brace and I don't know if I felt much of an improvement. I preformed a similar test that shows it does have a very small improvement of 0.004 in (0.1016 mm) Can you feel that as a driver or is it more physiological?

From this result, I will probably stop using it as even the brace flexes by it's self. (Free up engine bay and driver corner weight.)

With - 0.030 in (0.762 mm)
Without- 0.034 in (0.8636 mm)

 

I actually made one of these 10 years ago. I put a smaller MC from a lancer oz on and modified the pedal rod. Autocrossed with it with hawk hps pads ( eek lmao).

​​​​​​Pedal effort isn't bad and it's an rs so no abs to deal with. Needed not to make any difficult tweaking to the brake lines.


https://www.evolutionm.net/forums/welding-fabrication/602821-brake-booster-delete.html

 

I've been ready to install mine for months, but I've been cringing at the idea of flipping the negative cable bracket that already has a broken loose copper strand. Maybe I should just ditch it and also ditch the catch can on the other side that never catches anything.

Thanks for sharing your experience.

 

I just read through that thread. Awesome!!!!! Thanks for posting that. I ordered the STM Brake Booster Delete and ordered a 7/8 master to give this all a try.

 

@awdboosted I had thought about doing this on my setup also, in my Evo 6.
The ABS action does wear out master cylinder seals fast, so you either replace them often or you go to the expensive ABS compatible master cylinders.
This is for pedal boxes i'm talking about.

Also if the ABS pump does have the proportioning valve inside, the master cylinder selection is easy.
Just use the same size front and rear.

It would be interesting moving to a larger master cylinder size while retaining the booster also, to reduce pedal stroke and increase effort required.

 

The extra cost of the ABS compatible master wouldn't be a concern to me, but I never realized this before. I feel lack of travel may make modulation a bit harder. I absolutely hate the feeling when you apply brakes abruptly. You can feel the vacuum assist catch up (like a delay) and I believe this can cause you to overshoots your original targeted effort. I'm confident this is caused by the brake booster and that's why I need to slow down and be smoother.

I'm also a bit on the fence about removing the booster because I like the pedal effort and travel. I don't know how much that would change.

Our ABS units would be perfect if we could control them an read CAN single from them.

 

It sounds like your booster is running out of vacuum or your check valve is leaking. I'd check the check valve first. If that's good you could consider adding a small vacuum pump to supply the booster. On track you're on throttle the majority of the time so there may be sections on certain tracks where your booster can't recover enough vacuum before the next corner. I can't say I've ever experience a delay in brake assist in my car.