Have any of you FI users lost brakeing force due to loss of vac, and, what did you do to fix it???

 

Never had that problem. Brakes work just as good as when I was NA. When my car is decelling its pulling 20" of vacuum. Are you sure your brake booster isn't ruptured or some other problem?

 

This depends more on how large your cam is more than the fact you are FI.

 

Cam... 231/ 240 @ 0.050 .540/ .560" lift 114 lsa 110* In CL. 13 inches @ 2k rpm no load. 3 inches @ 1k idle. Could be the vac booster check valve.

 

Or even just a leak, that cam shouldn't have any problem stopping.

(granted if you went from bone stock to that it may feel different)

 

I agree. Usually if your cam is big enough, it will lead to enough vacuum loss to equal a loss of braking performance. Yours isn't big enough to make that much of a difference.

+2 for looking for a leak.

 

3" at 1000 rpm. Somethings wrong. You should have around 14 inches. Are you sure your vacuum guage is right?

 

I put that same size cam in my 1992 LT1 corvette and I loss vacume presure for my brakes. I have to push the brake petal to the metal. Not sure of the fix. Just got the cam installed?

 

The only time you make boost is when your on the gas when your off the gas the vacuum would be the same as it would be without the blower on.

 

I saw a big change (low vac @ idle) with new hard pipe compressor intake ducting. During road tests, throttle off results in about a maximum of 13 psi vac. on the gage. I may try another PCM flash with more IAC counts and less opening on the throttle valve. The brake vac booster holds, so, I believe it is OK. From the data I have, usually a minimum of 16psi vac is needed for the booster to yield 1200 psi brake line pressure. Possibly an aux electric vac pump will be required to get 16psi+ vac. I see other options are use of Pwr_steering pump and hyd accumulator to power the master cylinder (lot of work).