2000AZ5.0GT

Nope, you can see boost at partial throttle, you just wont see as much.

And if you're at WOT from idle, you will NEVER see vacuum, you will always be in positive pressure, or at 0.

teej281

Well yea, if your at WOT you will not see vacuum, and i know you can see boost at partial throttle, but you wont be running around at zero boost and zero vacuum just driving around not even getting on it. The more throttle you put into it, the closer to that point where it starts building boost it gets, but until youre pretty far into the pedal, i wouldnt expect to see much boost.

BTW 2000AZ, you get your car back yet?

2000AZ5.0GT

yeah, but the transmission sucks. I'm saving up to put another T-56 in it at some point

it's a true slushbox, it makes meh sad

teej281

At least you still own your car. lol and im now saving for a T56 myself. Good choice.

dennis_112

To fix where a couple of you went a little off track; in terms of reading boost/vac from the manifold. You will not see boost until WOT. If you were to drive in 1st gear up to 4500rpm with partially throttle your making boost BUT bypassing it, now mash the gas and the bypass closes and NOW your reading boost at the manifold. You have to be at WOT to for boost to be read at the manifold, even if your making boost doesnt mean your using it.

2000AZ5.0GT

again, this is wrong, but thanks for playing.

Alot of you seem to have misconceptions about boost. If you're bypassing all of your boost at partial throttle, there's something wrong, PERIOD.

Centri cars behave similarly to turbo cars in one respect, you don't need to be at WOT to see boost. IN the same way that a turbo car (with a properly sized turbo) can see full boost at partial throttle.

Think about it logically if you don't believe me. Lets take a hypothetical situation. Lets say in one instance, you're at 3500RPM at WOT, and in another instance your at 3500RPM at 60% throttle. The Centri is pushing the same ammount of air regardless of what throttle position your at, so lets say in this instance it's roughly 5PSI positive pressure before the manifold.

Your correct in that you will bypass some of that, but you certainly won't bypass 5PSI worth, leaving your manifold at zero pressure.

your engine WILL see boost at partial throttle, there's no way around that.

amoosenamedhank

My car will bypass all of the boost created by the centrifugal supercharger until I step completely on the throttle and close the bypass valve. As I understand the BPV, it's either open or it's shut. There is no partial open or shut. So regardless of the throttle position, be it 40%, 50% or 75%, until you put the engine in a 0 vacuum (WOT)state and close the BPV, you will not register boost at the manifold.

I can bring the car to redline at partial throttle and never register a pound of boost at the manifold.

darkmach1

+1 my car feels great while driving normally, I would say better than stock. I can drive around without going into boost and actually waste less gas.

Get a positive displacement blower, you wont regret it, instant torque FTW!!

2000AZ5.0GT

what BPV are you running. I guess I could see if you were using the Mondo BPV, it would actually take positive pressure to keep the valve close, but using the regular, even the mini-race, I see boost at 40% throttle, possibly even earlier.

I hate the trans though, so call it a wash?

Eagle2000GT

Yes, with all superchargers (twin-screws and centris) the throttle has to be open for the boost to get in. My supercharger generates about 8 psi at 5000 rpms but the vacuum gage will still show vacuum if the throttle isn't open very much. The boost is rushing out the blow-off valve because it can't get into the engine. The difference from an naturally aspirated motor and a supercharged motor is if I go WOT it at that rpm I instantly get 8 psi (on the boost/vacuum gage) because the blow-off valve closed as the throttle opened. On a n/a car it always reads vacuum.

Twin-screws are not faster than centris. The low end torque just makes the tires spin more. Other than launching from a dead stop, I do not know of a time when racing where the rpms drop below 3500 rpms.