Is there any level of brake lag associated with superchargers when going from full throttle to brake. How long does the supercharger boost last once you take your foot off the throttle before you've got enough vacuum to generate brake force? Is it noticeable or greater than with a NA engine?

 

Whenever I autocross, I cannot go into any turn hard on the throttle, then go immediately to my brakes. I HAVE to let of a half second sooner than I like, to make sure I have enough vacuum so my brakes will work properly.

Before I got used to the way my L would brake, I would frequently miss the turn and wipe out cones.

With my new built engine, and the custom grind cams I have, I can bet it will be a bit worse, so I intend to purchase a Hydratech Hydraboost setup to cure what ails me.

Stewart

 

Vacuum for the brakes is pulled from above the blower, so there should be no lag at all.

Stewart, have you tested the check valve on your brake booster? It sounds like it isn't holding vacuum at high throttle. I've never had the problem you are describing nor have I heard it from other auto-Xers.

 

superchargers use a belt drive off the crankshaft, or in exotics gears. No effect on brakes other the speed and weight of the vehicle. Turbochargers use the exhaust gases to power them. When the throttle plate closes vacuum should return and accesories work; or have a vacuum reserve tank and maybe an auxillary vacuum pump.

 

It doesn't matter how it's spun, when the vacuum goes away at WOT there's nothing there to boost the brakes if the check valve is bad. If the vacuum line is installed under the blower it's even worse.

 

OK that pretty much answers my question. So if I made a schematic you would see...Throttle Body - Vacuum Take Off - Compressor - Intake manifold (or plenum). The compressor would really have no impact on the way the vacuum operates correct?

 

Yep, that's it.

 

I never thought about checking my check valve.

I learned about the Hydrboost from Ian (Pitstain) because we were talking about the brakes on our L's a while back and he told me about the time he lost his brakes at Watkins Glen one time.

That's when he decided to go with the Hydraboost setup.

If it is the check valve, you may have saved me some cash.

I'm not completely convinced it is my valve though. Because once again, while discussing this prob with Ian, he pointed out there is a brief instant when the upper plenum is pressurized from the boost bypass when you lift off the pedal. When the throttle snaps shut, and the boost bypass simultaneously opens, that's when the upper plenum is temporarily pressurized. If I hit my brakes at that exact moment, voila, brake loss.

That scenerio does seem more plausible to me too, because even though it happens all too often to me, it's not happening ALL the time, just when the stars align!

Stewart

 

Hydro boost brings with it its own set of problems. They tend to fade out as your power steering gets hot and they also link the two collision avoidance tools you have to the same power source. If that source fails you are left with failure of your power steering and your power brakes. I don't like that scenario. Before I did that, I would be very tempted to look into a vacuum reservoir for the brake booster.

 

My buddy Martin went that route. He picked up a Comp Cams res canister from Summit.

COMP Cams 5200 - COMP Cams Vacuum Canisters - summitracing.com

Stewart

 

Actually, you won't lose brakes, you'll lose vacuum assist. The brake will still operate but require more force.

 

I said you would lose your power brakes. It really doesn't matter, on these trucks it's one and the same. With no power assist you might as well drag your feet.