Brakes suck. Its the camshaft robbing vacuum.
08-09-2010, 04:51 PM
#1
Brakes suck. Its the camshaft robbing vacuum. Been chasing a hard braking condition under panic stop conditions. All braking components have been determined to be good including the master and booster. I have to stand on it to make the ABS kick in under panic stop.
FTR I have 12" LS1 brakes too.
For giggles I put a vacuum guage on the intake and I have:
12" at idle with AC off
10" at idle with AC on
Stock cam made 20"-22" IIRC.
I am confident I dont have any vaccum leaks. Motor runs well and BLMs are near perfect. So its the cam robbing my vaccum that is affecting my braking. I have a 224/230 which aint that big. But its on a 107 LSA with lots of overlap and according to folks who are smarter than I am, thats what is doing it.
What are my options here other than replace the cam with a tamer LSA??
FTR I have 12" LS1 brakes too.
For giggles I put a vacuum guage on the intake and I have:
12" at idle with AC off
10" at idle with AC on
Stock cam made 20"-22" IIRC.
I am confident I dont have any vaccum leaks. Motor runs well and BLMs are near perfect. So its the cam robbing my vaccum that is affecting my braking. I have a 224/230 which aint that big. But its on a 107 LSA with lots of overlap and according to folks who are smarter than I am, thats what is doing it.
What are my options here other than replace the cam with a tamer LSA??
08-09-2010, 06:41 PM
#4
08-10-2010, 12:13 AM
#7
I had a vacuum canister installed and saw little to no improvement in braking. I sold it for a profit considering I got it for free. Again I am not convinced it did any good.
Idle is 950 but I dont expect to see a big improvement by increasing it. I am going to bump it up a bit just to see what happens for giggles. Seems like vacuum bump is the best cheapest fix.
Idle timing is around 25-28 or so. How much for the pump? I cant really speak to the overlap other than to say my vacuum is ****.
Please PM me.
Please PM me.
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08-10-2010, 12:32 AM
#9
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The idea of a vacuum canister is to give you multiple brake pedal hits, not to give you any more braking power. In a panic stop, where all you do is stand on the brakes, if you lack braking power then you need different brakes and not more vacuum.
08-10-2010, 01:25 AM
#15
raybestos ceramic pads willl not give you that problem at all. My buddy Speed has them on his wifes car with ls1 brakes and those brakes are hard as a rock. Even the cam is similar to what you have. You might have something else goin on. How much pad life is left on all pads. If they are really low or your rotors are almost done then you will have a very crappy pedal. It will take more effort to push the pedal down for them to engage.
08-10-2010, 02:14 AM
#17
raybestos ceramic pads willl not give you that problem at all. My buddy Speed has them on his wifes car with ls1 brakes and those brakes are hard as a rock. Even the cam is similar to what you have. You might have something else goin on. How much pad life is left on all pads. If they are really low or your rotors are almost done then you will have a very crappy pedal. It will take more effort to push the pedal down for them to engage.
08-10-2010, 06:26 AM
#18
To clarify. They are Napa Safety Stop ceramic pads made by Raybestos. They are the cheaper grade of ceramic pads too. I would guess there is easily 80% plus pad material remaining. I will most likely put some HPS pads on prior to considering the vacuum pump.
The booster is good. The MC is replaced and it made no improvement. Calipers are rather new considering I rebuilt them. ABS module is fine considering I parked the pistons at the top and pulled the fuse which essentially bypasses the ABS functions. Lines are well bled too so I really dont think there is any mechanical issue with the brakes. The disks look a bit blue so that might indicate a problem with the pads as well.
The brakes work better when the car is decelerating (clutch out) and vaccum is at its greatest. Its worse decelerating (clutch in) and vaccum is essentially the same as at idle. So obviously vaccum is playing a generous role here.
The booster is good. The MC is replaced and it made no improvement. Calipers are rather new considering I rebuilt them. ABS module is fine considering I parked the pistons at the top and pulled the fuse which essentially bypasses the ABS functions. Lines are well bled too so I really dont think there is any mechanical issue with the brakes. The disks look a bit blue so that might indicate a problem with the pads as well.
The brakes work better when the car is decelerating (clutch out) and vaccum is at its greatest. Its worse decelerating (clutch in) and vaccum is essentially the same as at idle. So obviously vaccum is playing a generous role here.
