Boost issues-Stuck BOV?

[ksd9000]

Hello all. Just got done rebuilding the engine and running into some issues. All components are stock except for the 3" turbo back exhaust. No CAT and just a free flow muffler at the end.

The issue I am having is that the intake soft pipe (where it comes out of the right fender well to the 3000 pipe) keeps blowing off when I push it hard. Stock boost gauge shows 8+ psi when this happens. Double checked all vacuum lines and made sure the bypass valve is connected. Looked through the TSRM and didnt see any info on how to test it. It also sounds like there is no pressure relief when I let off the gas after hard acceleration. I can hear the intake charge resonating in the intake after the hard acceleration and let off the pedal.

Maybe I'm not tightening the intake tubes enough, but I dont want to chance it and not have ANY pressure relief if the BOV is not working correctly.

Car is not being driven for street use. Track only. Not that it makes a difference.

Any help is appreciated.....

[cre]

Yup, sounds like the BOV is to blame.... that and a dried out or dirty IC coupler. Use a vacuum pump on the BOV's signal line to test the valve. If this is an aftermarket BOV refer to the manual to see if there's a trigger adjustment.

[ksd9000]

Its the stock bypass valve. And the IC rubber piping is surprisingly still soft and pliable. Plus I cleaned all the piping out thoroughly before reassembly.

Applying vacuum at idle should make the valve open and cause the engine to stumble correct?

[cre]

Originally Posted by ksd9000

Its the stock bypass valve. And the IC rubber piping is surprisingly still soft and pliable. Plus I cleaned all the piping out thoroughly before reassembly.

Pliable or not it shouldn't even be coming off at 14+psi. Something's wrong with it, the clamp or your arm strength.

Originally Posted by ksd9000

Applying vacuum at idle should make the valve open and cause the engine to stumble correct?

No. the valve dumps back into the intake AFTER the KVAFM, so the air is metered and accounted for.

[ksd9000]

Thanks for all the help CRE.

Did some more testing and found that the BSV is not closing. Relieving pressure all the time. I have been looking into the Saab BSV P/N 0 280 142 110 as an alternative. Any suggestions on where I can get one without getting robbed? I'm leery of going used because the used one may have the same issue as the one I have now.

I'm tired of messing with this thing. I have a race in 3 weeks and this is driving me nuts!

[cre]

I wouldn't run a used unit either. Did you apply pressure to the BPV's trigger/signal line before drawing the conclusion it isn't closing?

The Bosch BPVs are decent units. There are two commonly used, the less expensive one will handle about 9 or 10 psi on a regular basis and the more expensive one will handle 14 - 16psi regularly without failure. I don't have the part numbers handy. Both are used by Saab.



Can't even get the IC piping to stay together and you're already setting race dates... and .... Supra owner through and through.

[ksd9000]

Ok, so I got a BOSCH BPV and installed. Now I dont have the same noise as before. However, i think I'm hitting fuel cut???? In 2nd gear at WOT the boost pegs past the stock gauge limit and the engine bogs down. However, after letting off the gas, the car still hesitates and doesnt run properly. I have to nurse it along for about 30 seconds before it will just barely respond to throttle inputs without wanting to die. Shut it off for a minute and start back up and it runs fine until WOT issues again.

Questions:
1. Isnt the waste gate actuator supposed to open at 7psi? Should this not regulate the boost pressure to remain under fuel cut? I have not shimmed the WGA and there is no boost controller installed.
2. Do I NEED a boost controller?

BTW, I tightened the IC piping a lot more and its staying in place now. I didnt tighten more earlier for fear of breaking the plastic tubing. Didnt realize it had a metal sleeve inside to take a greater load than just the plastic would bear. All piping and lines are staying on now.....

[cre]

Put a real boost gauge on it, if only temporarily with the hose running out from under the hood into the passenger window.

Test the actuator with a bicycle pump. It should open approx 1cm by 9psi max... It should start opening sooner (5 to 6 psi but may not initially crack open until 8 or 9 when cold). Disconnect the actuator linkage while testing the actuator and check that the waste gate armature moves relatively freely.

Next would be to make sure the vacuum line from the compressor housing to the waste gate actuator isn't rerouted or obstructed.

No a boost controller is used to INCREASE the pressure needed for the waste gate to open it cannot reduce pressure.

[ksd9000]

***UPDATE****

OK, so I got an aftermarket boost gauge and hooked it up. Did some more testing and found that the WG actuator was not moving. BTW I bought a blood pressure cuff at CVS and used the pump off it to make a SST that worked exactly like the one in the pic for the TSRM. Just tee'd off the boost gauge and was able to see the pressure at which the WGA opened...

OK so back to the testing... I applied pressure to the WGA and no movement. Some investigation showed that the new turbo came with an adjustable WGA rod. Well whoever put it togehter at the factory adjusted it to the shortest length. In essence it was like shimming the WGA so that it would never open. Some adjusting and pressure testing and the WGA moves freely and correctly.

Test drive.....she dies again around the block and neighbor has to tow me back to the house...

Feels like a fuel delivery issue now. Some more testing and find that there is so much vacuum build up in fuel tank that when I open the fuel cap, it sounds like a jet taking off...WOOOOOSSSSHHHHHHH. Ok, Start up and she runs fine now. Test drive and starving for fuel again.

Went out and bought a new fuel filter and fuel pump. Installation to ensue tomorrow...will post again with more details....

CRE, you help has been on point so far...thanks for your insight!

[cre]

Your love of TLAs is killing me. What do you mean when you say CVS? It's not ringing any bells for me.

Vacuum in the tank? Sounds like someone either tried to delete the evap control system (the charcoal canister is part of it) and didn't have a clue or it's plugged up... either way it can result in cavitation of the fuel pump impeller.


EDIT: ROFL!!!! Bought it AT CVS.... the store... never even seen one but heard of them in the past... I feel like a tool.