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bholmes
05-30-2012, 10:31 PM
Hey guys, I got a kinda silly question that I can't really find the answer too via the search function. Anyhow... I know how the bypass valve works and all, but are there any DOCUMENTED consequences of just keeping the bypass closed and constantly compressing air. Theoretically I could see how this would increase heat, prematurely wear out the bearings, and kill gas mileage. But has anyone just corked the bypass vacuum line and left it closed?

Second question, which is sort of related. I don't build much more than 5psi of boost generally, but I disconnected the bypass valve vacuum line and it boosts to ~11 or 12psi. I did not alter the set screw/bypass valve stop screw so I don't think the bypass valve could be leaking because it fully closes (apparently) when disconnected. Is it possible the spring in side the bypass valve is shot? Well, thank you for indulging my ignorance.

SUPERVIC
05-31-2012, 11:44 AM
If your making that much more boost with out a tune becareful:)

bholmes
05-31-2012, 11:49 AM
If your making that much more boost with out a tune becareful:)

I thought they were supposed to make 11-12psi? Hmmmm...:confused: may explain my recently blown headgasket! LOL. It's not showing any symptoms as for running rough, but I was pulling the air silencer out today and thought I'd check my fluids....the antifreeze has just a hint of oil in it... the blower looks to be very low on oil.... looks like my "good deal" car just turned into a "crappy deal" car.

David Neibert
05-31-2012, 05:02 PM
I thought they were supposed to make 11-12psi? Hmmmm...:confused: may explain my recently blown headgasket! LOL. It's not showing any symptoms as for running rough, but I was pulling the air silencer out today and thought I'd check my fluids....the antifreeze has just a hint of oil in it... the blower looks to be very low on oil.... looks like my "good deal" car just turned into a "crappy deal" car.

Yes, it's supposed to make around 10-12 psi. The warmer weather will generally make less boost, because the incoming air isn't as dense. You can leave the bypass valve closed, but doing so will generate more heat and the constant whine of the supercharger will drive you nutts after a while. The added heat also kills power. The bypass valve system also circulates air through the intercooler and tubes during normal driving which cools them.

If working properly, the bypass valve should start closing at about 2 inches of vacuum and be fully closed at about 1" of vacuum. The valve linkage will sometimes stick on the backside of the supercharger top, and that may be preventing it from closing all the way.

You may also want to search "Cross Talk Tube" for pictures on how to make the bypass valve more responsive to throttle input.

David

90sc35thann
05-31-2012, 05:36 PM
I thought they were supposed to make 11-12psi? Hmmmm...:confused: may explain my recently blown headgasket! LOL. It's not showing any symptoms as for running rough, but I was pulling the air silencer out today and thought I'd check my fluids....the antifreeze has just a hint of oil in it... the blower looks to be very low on oil.... looks like my "good deal" car just turned into a "crappy deal" car.

If you have oil in the cooling system your best bet is to look at the oil cooler. Remember the oil pressure is greater than your coolant pressure. That said when that oil cooler craps out that is one part at which to take a closer look.

Coolant in the oil is a different story. That would be indicative of something different.

bholmes
05-31-2012, 10:39 PM
Great info guys! Very helpful. I'm not at all new to mechanics and I have had an SC before in the past, but I didn't do much work on it so I'm still not as familiar with them as I would like to be.

I only have oil in the coolant, so that's good news! Oil cooler is a much better scenario. I don't have much at all, just enough to start making it cloudy green rather than clear green. I'll have to do some more research into that. Thanks alot!

As for the bypass valve, what you said made sense about increasing the air temps. I'll have to look more into how to make it more responsive, I appreciate you guys help alot. I try to search as much as I can but sometimes it's hard to turn up the results you want. It's not a major concern now, since I found my supercharger was low on oil I unhooked my belt and rigged the bypass valve open for now. No sense in tearing my supercharger up worse than it probably already is.