Question for racers with FI
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From: Marysville, WA
Question for racers with FI Ever since I started racing my blown stroker motor combo, I find my brakes don't work properly at the end of the 1/4 mile. One of our tracks up here has a pretty quick exit, so I have to lay into the brakes early & hard. Problem is, the pedal feels like a brick for about 3-5 seconds, and then releases & the brakes work. Which leaves me barely enough room to slow down! 
I'm figuring it's the power brake booster getting pressurized by the s/c. And I've heard there is a module you can add to fix that, but I can't find anything on here that talks about it. Since I'm new to this forced induction game, I thought I'd ask you guys what works for you.
I'm figuring it's the power brake booster getting pressurized by the s/c. And I've heard there is a module you can add to fix that, but I can't find anything on here that talks about it. Since I'm new to this forced induction game, I thought I'd ask you guys what works for you.
I am going to be running a really large cam and FI. I am expecting to have power brake booster problems, so I went ahead and bought the vacuum pump kit made by SSBC. The last thing I need is my brakes not working at the end of the track.
Your brake booster should have a check valve on it where the vac. hose plugs into it. This is there to hold vac in the booster, but will also prevent positive pressure from getting in. The hard brake pedal is probably caused by that valve going bad. So your getting psi in the booster untill the motor decels enough to create enough vacuum.
Id simply start by replacing the check valve (its the 90* elbow that connects your hose to the booster). If the problem persists, you prob arent making enough vacuum with the cam your running and would then need a vac pump.
Id simply start by replacing the check valve (its the 90* elbow that connects your hose to the booster). If the problem persists, you prob arent making enough vacuum with the cam your running and would then need a vac pump.
Thread Starter
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From: Marysville, WA
Vacuum pump by SSBC.....I thought there was something on this board. And I checked my check valve once, but that is a good point. And a cheap thing to try. Thanks!
Even tho I am only trapping around 125, it's pretty spooky to step on the brakes & have basically nothing happen for a few seconds.
Even tho I am only trapping around 125, it's pretty spooky to step on the brakes & have basically nothing happen for a few seconds.
if the ABS is still hooked up and you run slicls/skinneys it will do exactly what you describe. Pull the ABS fuses at the track and it will be OK.
Never had any problems with the brake booster or blower, if you are off the throttle you have a ton of vacuum there. Its possible the booster could be bad or the check valve too..
FWIW I had a 414 inch solid roller (268/278 @ .050) and never had a problem with the stock booster. Only time I would notice it was at the starting lineagainst the converter the brake pedal would start to get harder.
Never had any problems with the brake booster or blower, if you are off the throttle you have a ton of vacuum there. Its possible the booster could be bad or the check valve too..
FWIW I had a 414 inch solid roller (268/278 @ .050) and never had a problem with the stock booster. Only time I would notice it was at the starting lineagainst the converter the brake pedal would start to get harder.
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Could this be a problem that is just created by a cam? I have a problem similar to this before I even got my turbo installed. I thought it was just because I dont have a stall but this makes me wonder.
Same thing happened to me on my last outing at the track
Never had decel issues in the shut down area with the S/C or turbo before?
I have new pads and rotors and was wondering why I couldn't slow down. That was running on the street tires/rims as well. I had to let the car "coast" pretty far for the brake pedal to come to life...pretty eye opening.
Guess I'll replace the brake booster check valve and see if that does the trick.
J
Never had decel issues in the shut down area with the S/C or turbo before?I have new pads and rotors and was wondering why I couldn't slow down. That was running on the street tires/rims as well. I had to let the car "coast" pretty far for the brake pedal to come to life...pretty eye opening.
Guess I'll replace the brake booster check valve and see if that does the trick.
J