hey guys have a 96 with a vortech v2 i had the stock 3.33 pulley earlier and saw about 5-6 psi i recently did a fmic set up over winter and changed the pulley on the unit 2 steps down which should put me about 9-10 psi. however i started it up yesterday and my guage showed no boost. I then searched for leaks im running 2.5 pipes with couplers and t bolt clamps checked all and found no leaks. i have a hks bov and when i revved it at idle it would blow off at high revs and i also would pinch a coupler and rev it and the coupler would blow up so i now the unit is blowing some air. next i drove it with the hks bov disconnected and no change, i then ran a pipe straight from the unit to the t/b just in case the innercooler was some how messed up..still no boost. i thought maybe my guage was messed up so i borrowed one from work hooked it the mani off a nipple and still no boost!
I checked the pulley on the unit to make sure the key way was lined up and that is fine. so now im thinking either the unit if messed up or the belt is slipping. i dont hear a slip but i am using the same belt from the 3.33 pulley set up which is a 8 rib 408 from gates i called up the local parts placed and ordered the next size down a 8 rib 400 which will be here tommorow. if this doesn't help what else could it be?

please help oh wise forced induction guys

 

I went from a stock Vortech pulley to a 2.95 (I think...) and went to a shorter belt. I can go look at the belt number if that would help. Sounds like this could be your issue. You probably wont hear 'slip'. But your belt tension should be (really) tight, no slop.

BTW. You really want to use a bypass valve on a blower. Blow offs are better served for turbos.

-Scott.

 

yea i dont hear it but also the belt doesn't look messed up so ill have to c tomm if the shorter belt helps i also have a new tensioner bought it when i put the pulley on so that should not be bad, did u have similar problems? also what diffence would a by pass or bov mater i dont see how it would make a diffrence

 

I didn't have any problem but I swapped belts at the same time I went to the smaller pulley.

The reason you want a bypass on a blower is just based on the way the a blower works compared to a turbo. Because a blower is mechanically linked to the engine, you can have real high impeller speed under light load situations. So its preferred to bleed off the pressure at idle, or cruising around at 2500rpm, or else you are making the compressor/belt/engine work harder than it needs to be working. With a turbo, the impeller speed is super slow unless there is a high load on the engine. With a turbo, there is not enough to bleed at low loads.

Basically a BPV is open under vacuum, supercharger can race along and bleed off pressure under light throttle condition. The valve closes as vacuum goes to zero and is closed under boost.

A BOV is closed all the time until a spike in pressure opens it up. Works real nice with a turbo to simply 'blowoff' air when the throttle blades close.

HTH
-Scott.

 

I also went with a smaller belt with the 2.95 pulley. Alot of the time you can see a little debris around the pulley from the belt slipping. Probably going to be your problem.

 

my mondo BOV is open, venting to atmosphere until the vacuum comes down and it closes to built boost. I thought the only difference was a bov vents to atmosphere and bypass recirculates within the system.

If it was running fine before it has to be belt slip, a major boost leak, or the BOV isn't closing. What size pulley did you go with?

 

A Vortech Mondo Bypass Valve?

http://www.vortechsuperchargers.com/product.php?p=24

Both types of valves work similar. They are manifold vacuum referenced and help to reduce/eliminate compressor surge.

With a Bypass, engine vacuum allows the valve to be open at idle and light load conditions.

With a Blowoff, engine vacuum lightens the valves spring force when you lift the throttle only allowing the intake pressure to escape. If you put a really light spring in a BOV, vacuum could hold the valve open and it could function just like a BPV. You wouldn't want that with a turbo though - at idle you would pull air in through the valve, not vent it. And that's just because impeller speed is low with a turbo and light engine loads. Impeller speed is quite fast even at idle with a blower.

If you vent under all conditions except WOT (or near WOT), you have a bypass setup. If you vent only when shutting the throttle plates form a boost condition, you have a blowoff.

 

well i changed the belt this morning and now i have like 3 psi?! i checked to make sure the intake wasn't constricted by removing everything from the inlet side and still no change, the car feels like it pulls hard but low boost on gauge. it also will blow the couplers up with air and make the bov operate or vent when i rev it at idle so i know the unit is pushing some air. if i didnt load the tune to the pcm yet would this affect it? i have the lt1 edit set up and have the tune from IOn but havent loaded it yet, but this would still make the car boost right? i mean it would just run lean but still boost right?
im not sure what to do now im thinking the unit itself must be messed up but it worked fine at 5-6 psi before the pulley swap and fmic
i did bypass the bov the fmic but routing a pipe str8 from the charger outlet to the t/b and still no change any suggestions?

 

I stand corrected!

 

Sounds like the gauge is bad or the plastic line that runs to the gauge is pinched or leaking.

 

I agree with boosted-lt1. If you say, the car still pulls hard, you have a burnt, cracked, missing line going to the guage and or by-pass valve.

Mike

 

well i kno its a bov, and it can be that b/c like i said i bypassed it and the innercooler by hooking a pipe from discharge str8 to t/b no bov or innercooler connected and still no change. i also thought the gsuge might be bad but ir reads vac fine and i hhoked up another gauge off the intake mani and it still read the same thing could something inside have broke? where it still pushes are just not enough?

 

Have you removed the inlet pipe to the supercharger and tried that? This sounds exactly like the problem I had with the T-trim, could only get 3 psi. I took off the intake pipe and it went to 12 psi. The Vortech intake ducting really sux *****. If that fixes it you will need a larger hard pipe. Superchargers are meant to blow, not suck, so the smallest restriction on the inlet will greatly effect the outlet.

 

that was it boosted now switched inlet set up

 

Glad to hear, now go kill some tires.