corvet786c

iTrader: (6)

I have a 2002 A4 corvette D1SC LS6 only seeing around 5lbs of boost on an autometer guage. I know I should be making more than that on a 4.38 pulley especially in cold weather. Anyway I should be making around 10 lbs boost, but the guage is showing only 5lbs. I checked the piping and also got new Fast 102 gaskets which I did not need. No other leaks, I also checked the boost guage and it works so I am thinking its the blow off valve not fully closing. Is their an adjustment screw somewhere? Its very frustrating trying to find this problem. Is bob here? Any help would be great Thanks in advance.

ddnspider

iTrader: (26)

What's the rest of the setup? That's an awfully large pulley so I wouldn't expect much more boost. I only make about 7 or 8 with a 4 inch pulley but I have a healthy cam. What size crank pulley? If you suspect the the bypass valve, I got a good tip from Bob at Brutespeed that you can just plug it or remove it and seal it off for a quick pull just to check if you make way more boost. It won't hurt anything for a brief pull.

Also have you checked for belt slip?

corvet786c

iTrader: (6)

1 3/4 headers 2.5 down pipe, upgraded A&A bracket, there's no slippage or dust around the head. There's is a blower cam but don't know the size. Crank pulley is about 7.5in, patriot stage III 243 heads ported.

ddnspider

iTrader: (26)

So blower cam ported heads and a fast 102? I don't think your boost level is unreasonable given how large that pulley is. You need to step it down.

corvet786c

iTrader: (6)

I understand but I am still having this issue where my boost guage is not reading boost so back to my original question is there an adjustment nut on the BOV, maybe it became loose and is not holding pressure?

Side note I have your issue in GM high tech performance mag. I seen your turbo car.

ddnspider

iTrader: (26)

Maybe that's what I'm missing. You said you're seeing 5psi. Are you saying you're not seeing 5psi? With a centrifugal you should see a relatively linear increase of boost with rpm. If you're not or it's leveling off you either have belt slip or a vacuum leak. There is an adjustment nut on the bypass valve that deals with how easy it opens. You could try adjusting that first. If it doesn't work I'd plug it and make a pull. Just be careful if you all of a sudden make more boost.

Side note...thanks, my avatar pic is from the 1st time it was on a cover. The 2nd time it was on the cover of high performance Pontiac. That's when it actually ran a decent time. Lol. Tough to launch a turbo stock with a 10 bolt. Once I got the 9 inch in it, different story. I think it's changed hands a couple times since I sold it, but the current owners having fun with it to my knowledge. It was a solid car.

corvet786c

iTrader: (6)

The guage is showing about 5lbs now, but a few months ago in cold weather it showed 10lbs, I just looked over the BOV and it seems fine good spring pressure closed, No leaks in vacuum line I just don't know where else to look. Had no intake seals installed on Fast 102 car runs great otherwise. Doubled checked hoses, everything is fine. On a normal 85 degree day it shows around 7lbs.

ddnspider

iTrader: (26)

Ah ok that makes more sense. Have you tried retensioning the belt or is it an automatic tensioner? Is the belt worn? You do have the option of pressure testing the cold side too.

dlandsvZ28

Vacuum pulls the valve open, so simply removing the vacuum line will close the valve. Simply pull the line off of the valve. At idle, you can stick it back on, the valve should open, pull it off the valve should close easily if the hinge mechanism isn't binding.

If you can't feel any air that's a good sign with the line removed. If you can feel some air as you rev it a few rpms, it's probable the gasket has deteriorated and has a pinhole and/or the blade mechanism is binding or is not closing completely.

How old is the valve? My Proflow valve is the first version purchased in ( 2007. I understand there is a newer version of the ProFlow. Don't know production date.

Having the same issue as you thinking the valve wasn't closing, I replaced the bladder. However, when I took the valve apart, the bladder was in nearly perfect condition with no holes. ProCharger sent me a new bladder overnight and I replaced the old bladder, however.

My Proflow valve has a nut extending out of the valve. But all I found is that it adjusts the butterfly to full open. So after reassembling the valve with a new bladder (the new bladder wasn't as soft and plieable as the old) I discovered that at idle with no boost the butterfly was only open about 45 percent. After adjusting the nut, the adjustment allowed the valve to open so the blade was exactly 90 degrees (full open)- same as the position of the throttle blade on the throttle body at full throttle.

How did I know something was amiss after assembly? Less noise at idle from air exiting the Proflow.

If you had 10 lbs at one time and now don't, I suspect a vacuum leak or leak in one the silicone pipe connections. Or even perhaps a leak in the intercooler(s) or piping.

Intercoolers are easy to test for leaks. Fill with water and wait. If there is a leak water will find its way out. Bar and plate intercoolers are more durable than tube and fin but imagine under worst case scenario an object kicked up off of the road might create a pin hole leak.

If there is a minor leak at a silicone connection, I have noticed that dust will collect inside the silicone hose at the leak. Will even see dust on the pipe at the connection where the leak is. Note the flow of air at each pipe connection. Is it sucking in or blowing out?

IMO cold temps allow a worn out belt to slip more easily that warm temps so you might have some belt slip even thought you don't see any belt dust. Pipe connectors aren't as pliable and soft either.

HTH

So what was my issue? Dry rotted vacuum line at the tip at the vacuum source along with leaks at two silicone pipe connectors. I also had a tranny with a pump that was failing on the dyno.

corvet786c

iTrader: (6)

Thank You Z28 for the detailed response. I do have good vacuum on the guage about 10 mg at idle, but boost is low. The proflow valve is the procharger one probably the earlier one Stage 1 kit, It is older. I do have some nicks in the silicone but does not look like it protrudes thru. I also inspected my proflow valve and the spring inside looks new, I performed some tests on it and seemed to operate correctly. I do hear it working when I let off the gas after a hard pull and hear it relieve air. I tested the clear small tube from autometer and everything seems to work fine, no pinholes so I am guessing either the proflow or a leak somewhere. I already checked everything, this is very frustrating, I am really stuck on this one.don't know where else to look. Other than this the car runs really good.
I guess I am going to have to inspect all the hoses and connections sometime. My Fast 102 has new gaskets and was sealed with rtv a couple of yrs ago, it should be fine right?

Forcefed86

iTrader: (4)

Cap the BOV and see if you get more boost. A little surge one time isn't' going to hurt anything. This was the issue on a friends car. It did pop the air filter off onto the header when he let off though, so might want to pull that.

ddnspider

iTrader: (26)

The other option I mentioned is to pressure test the cold side. This will show whether or not there is a leak that only shows up when in boost. Pressure test it for 10psi and see what leaks.

corvet786c

iTrader: (6)

OK Thanks for all the responses will try that and inspect the hoses.

ls3fox

on a buddy's procharged car we boost tested the whole system found the maf adapter leaking, the bypass valve was leaking and the head unit it self was leaking

corvet786c

iTrader: (6)

ok Thanks will also look into that also.

Any other suggestions?

forcd ind

iTrader: (7)

A couple things, hoses can leak, I have had them pull apart (conns.) and go back under boost, def hard to find.
Also, are you sure of 100% throttle, sometimes on the street you may think its 100%, but self preservation takes over and you are not 100%-when I switched to data logging, I was surprised, lol.
Easy enough to eliminate the surge valve, but I suspect that isn't it.

corvet786c

iTrader: (6)

Thanks for the response, ok so I started car and sprayed windex over the front by the MAF and massive leak. Just bubbling like crazy. The band was tight but in a akward position air coming out of both sides, I am not finished yet and going to check underneath and spray the hoses. I know this is a cheap way but did not suspect the windex would do the trick so far. It help the boost guage some but still can't go past 5lbs yet.

corvet786c

iTrader: (6)

Found another leak coming from the I/C to the y-pipe it was a pin hole leak at idle. I used the windex. Could imagine how it opens up during wide boost. Also I am still getting some air coming from the MAF. I wonder if the coupler is the right size?

forcd ind

iTrader: (7)

Are you using T bolt clamps or radiator clamps on the conns.

corvet786c

iTrader: (6)

Large radiator clamps. when I bought the car the passenger side 45 degree hose was flimsy to begin anyway I guess something penetrated the hose causing only a pinhole leak during idle, I am sure under full boost it would blow up. Here are a couple of photos of the hose, its the 45 degree hose, and the straight hose has a gash in it.