Improving vacuum assist.. a few questions
Thread Starter
Le Mans Master
Joined: May 2000
Posts: 8,729
Likes: 1,508
From: Redmond WA
Improving vacuum assist.. a few questions
I have two cars that pull about 10-12 inHg of vacuum, and the vacuum assist on the power brakes is fairly weak on both cars.
The part I -don't- understand is why if I let the car coast down in 1st gear, where it pulls probably 25 inHg, it doesn't have much better assist.
I would think that the vacuum booster would "store" that vacuum and the check valve would keep it. But it just doesn't seem to (on either car), at least not to the level that I'd consider a "stock" level of assist.
Can anyone explain why coasting down and creating a temporarily decent amount of vacuum doesn't provide a stock level of assist?
Thanks!
The part I -don't- understand is why if I let the car coast down in 1st gear, where it pulls probably 25 inHg, it doesn't have much better assist.
I would think that the vacuum booster would "store" that vacuum and the check valve would keep it. But it just doesn't seem to (on either car), at least not to the level that I'd consider a "stock" level of assist.
Can anyone explain why coasting down and creating a temporarily decent amount of vacuum doesn't provide a stock level of assist?
Thanks!
Safety Car
Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
That's one of the reasons I decided to go to C5 brakes on my C4. The C5 brakes have a larger diameter piston in the caliper than the 12" or J55 brakes. So, you have a hydraulic advantage to complement the vacuum booster.
Another thing to consider is an electric vacuum pump to assist the booster. The ZR1 has an electric vacuum pump to open the intake secondaries -- I wonder if it could produce sufficient vacuum?
Tom Piper
Another thing to consider is an electric vacuum pump to assist the booster. The ZR1 has an electric vacuum pump to open the intake secondaries -- I wonder if it could produce sufficient vacuum?
Tom Piper
