glade

iTrader: (2)

Guys, don't want to seem retarded, but why not use a vacumn pump off of a late model Ford diesel. Weighs under 1 pound, runs of switched battery voltage, and is oem reliable/rebuidable for 100k miles...

Not that I have any direct knowledge of boosted brake problems, just thought I would throw out a possible situation.

miata_racer

A friend has an autocross car with a neat trick...it's a vacuum box sort of thing on the brake booster line so that his car will ALWAYS have consistent brake operation. It is THE COOLEST mod I've seen on braking consistency

The one on his car is off an Audi turbo.

hector

Back in the good old days when I had a GM G-body and a rowdy cam V8, i used an electric vacuum pump from early 80's Cadillacs (diesel or not) to run my booster. Nowhere near under one pound but thats progress for you. I didnt want it running all the time so I hooked it up to a timed relay. It would turn on with the brake light switch and turn off 30 seconds after the brake lights turned off. I ended up going with manual brakes on that car anyhow. Will do the same to the Miata when I hit SSM even though I have no plans on tracking the car. I just dont like boosters I guess. One more thing to fail and oddly enough, at the last autox I was at a guy had the booster fail on his 08 C6Z06 in SS. Would hate to have that happen on a track.

MartinezA92

iTrader: (4)

I really don't think booster failure is a valid concern here. That's like saying I'm scared to put gas in my car because I might start a fire.

hector

Not a good analogy: you cant run your car without gas.

All Im saying is that the brakes work well without a booster. Is it absolutely necessary to go without one, no. Is the lack of vacuum easily fixed, yes.

However, if you find the easy fix not to your liking or you are getting imprecise assist, there is a solution. Maybe not an easy one or cheap but a solution none the less.

And it will also eliminate a failure point. Maybe not important to you, but it would be to me if I were tracking. And if you run two masters, it would make it safer yet since you divorce the front and rear. It also get the brakes away from the heat of the turbo if you were to run inboard mounted master cylinders.

wildo

iTrader: (1)

Back from the dead.

Just read this for the first time. I've had some funky braking issues going on with my naturally-aspirated 11:1 midly-cammed IRTB '99 motor. I suspected it may be a vac assist issue (lack of), and installed a Vaccusump™ last year. It helped.

Here's something I've never seen before. This is front brake pressure under braking at T1 at Summit Point. My brakes felt like crap there for the duration of the event, with an inconsistent pedal feel and sometimes I felt that I couldn't lock up the brakes even with my foot pressed hard enough to be poking through the radiator. This is a fairly heavy braking zone, down from ~125 mph at entry to 55 mph at the slowest point in the corner.

Dark blue trace = speed
brown/green trace = throttle position
red trace = longitudinal g
light blue trace = brake prressure

The peaks & valleys of the light blue trace (brake pressure) are not normal. Normal brake pressure traces are usually fairly flat, with sometimes a quick dip if heel-toe shifting.

I can't explain the pressure fluctuation, but I know it wasn't driver induced.

thasac

iTrader: (3)

Soooo ... what's a reliable small booster vacuum pump?

I've been contemplating doing this since I've had issues in the past with pressurizing my booster due to a failed check valve.

I was thinking about mounting a small pump inside the wiper/cowl area and running a short line through a grommet in the fire wall - nice, clean and consistent.

The Audi/VW pumps are a dime a dozen but I really hate the idea of having a piece of Audi on my reliable japanese vehicle

-Zach

hector

Maybe warped or otherwise not trued rotors causing the pressure fluctuations? Just a WAG