rjparth

I've been out of the f-body world for about 10 years, but recently returned to it with the purchase of a '98 SS convertible. It has a "few" mods as follows:

-Vortech Polished, V9 G-trim Supercharger kit (w/ 13 pound pulley)
-Procharger Intercooler
-GM Performance Gen III Camshaft
-Richmond 4.10 Gears
-SLP Long Tube Headers
-SLP High Flow Cats
-Borla cat-back exhaust
-Autometer air/fuel and boost gauge

The car produced 450 rwhp on a dyno test done by the previous owner, but without the boost gauge showing boost. When I drive the car I see various vacuum readings on the gauge, but never positive boost values.

I'm totally new to superchargers and the extent of my mod experience in the past has been light intake, exhaust and tuning. I'm curious what thoughts / reactions you may have.

ohshixgoat

iTrader: (14)

a electronic boost guage has a senser that then goes to the intake. check to see if the senser has a loose connection or the hose popped off a port on your intake.

rjparth

Thanks - I'll take a look at the line and sensor. Here's another way of putting the question. Based on the mods and the dyno result, do we think I'm making boost and the gauge isn't showing it OR do we think I'm really not making boost?

98legendws6

iTrader: (5)

i would say you are making boost to make that number...but no where near 13lbs.. The odd part is if the boost gauge is showing negative manifold pressure then there is no reason that it shouldnt show positive pressure. I wouldnt think it was a vacuum leak. You are certain that all of the piping is hooked up and secured and that your bypass valve is working properly? If the bypass valve was stuck open the car wouldnt really see any boost pressure because all of the extra pressure would be ejected through the bypass valve. That is deff worth checking.

rjparth

Everything appears to be fitted properly and the craftsmanship appears good. The bypass valve is the black plastic Bosch on which I've been reading some not-so-favorable reviews. The vacuum line is a T off the brake assist and, within inches, another T to continue on to the BPV and feed the gauge.

Is there an easy way to test the BPV? Should I consider upgrading the Bosch BPV?

98legendws6

iTrader: (5)

Is the bypass valve piped back into the intake? If it isnt then you can easily feel if air is coming out of the bypass valve when the car is at idle. Then have someone rev the throttle and see if the air stops coming out of the bypass valve. You could also remove the valve from the car and see how the bypass valve is oriented. The valve should be closed when no vacume is present and open when a vacume is applied.

ModularTurbo

iTrader: (14)

I have seen dry rot cracks that show vacuum but not boost (vacuum sucks the crack closed but boost blows it open). This almost caused me to destroy my EVO's motor. LOL

The 90 degree rubber elbows that come with autometer gauges become brittle and crack. Check your vacuum/boost lines wiggle them around and check for cracks etc.

boost27

iTrader: (3)

i would check the connection on the line going to the boost gauge. as ModularTurbo said the rubber fitting that they give you for the gauge dry out and crack really fast. last month i blew mine off my vacuum tee. It was only 6 months old

ModularTurbo

iTrader: (14)

yep yep he speaks the truth my friend