car makes vacuum not boost

[GT/CS]

Went to have my car dyno tuned yesterday and it ran like crap. Threw a boost gauge on it and realized it pulls 11" of vacuum @ WOT...haha, not boost.

Mods:
-intercooled vortech V3 Si w/ 3.48 pulley (blow thru w/ 50mm tial BOV)
-BBR stage 1 cams
-LT's

Right now I am in the process of ripping the front cover off of the car to retime it since I really have no other idea what could be wrong. Just wanna see what you guys think. Would hate to rip the motor apart and then find out I had a bad phaser or something similar.

Thanks.

 

[VTXFrank]

Could be the boost sensor is wired backwards. Reversing the wires will reverse the readings on most gauges.

 

[GT/CS]

it was a manual gauge hooked to the vacuum line.

 

[white05gt]

Went to have my car dyno tuned yesterday and it ran like crap. Threw a boost gauge on it and realized it pulls 11" of vacuum @ WOT...haha, not boost.

Mods:
-intercooled vortech V3 Si w/ 3.48 pulley (blow thru w/ 50mm tial BOV)
-BBR stage 1 cams
-LT's

Right now I am in the process of ripping the front cover off of the car to retime it since I really have no other idea what could be wrong. Just wanna see what you guys think. Would hate to rip the motor apart and then find out I had a bad phaser or something similar.

Thanks.

I would start by looking into the tial, you would be nuts to tear the timing cover off to look at the timing if it's not throwing any codes and is running good besides the boost issue.

 

[fdjizm]

If the SC is spinning something has to be leaking or the BOV is staying open.

 

[TheKurgan]

Sounds like you might of had a coupler popped off ever so slightly. Did you hand-check all the tubing and couplers ?

 

[GT/CS]

too late...haha. just gotta pull the balancer and the front cover will be off (only 2.5 hours into disassembly)

How would the tial malfunctioning make the car make vacuum? If it was NA, the guage would read "0", right? Something def has to be wrong since it is making 11" of vacuum and only 149 rwhp on the dyno (used to make 317rwhp NA before cams/SC).

 

[GT/CS]

everything is tight, no leaks. When it was WOT I could hear the BOV bleeding off some. It has a 8 pound spring in it.

If the BOV is leaking, wouldnt the car still make some boost? The whole vacuum thing really has me scratching my head.

 

[fdjizm]

Every engine makes vacuum when out of boost even at WOT (NA).

 

[GT/CS]

When I left the dyno the tuner said that one of the cams might be off 180 degrees. I dont know how that could happen, but that is why I am retiming the motor. Is it possible that the engine was at TDC according to the harmonic balancer, but the #1 piston wasnt at the top of the stroke meaning it wasnt at TDC when the cams went in?

 

[Swarzkopf]

Every engine makes vacuum when out of boost even at WOT (NA).

At WOT an N/A engine will read 0 on a vacuum gauge. Vacuum is created by the pressure of the inducting cylinders pulling against a closed or partially closed throttle blade.

So...OP, are you sure that the TPS and throttle body motor are working correctly, and the throttle body is actually opening? LOL

 

[Embalmer]

When I left the dyno the tuner said that one of the cams might be off 180 degrees. I dont know how that could happen, but that is why I am retiming the motor. Is it possible that the engine was at TDC according to the harmonic balancer, but the #1 piston wasnt at the top of the stroke meaning it wasnt at TDC when the cams went in?

Hmmm...I've never tried to time a motor with the balancer on, I always used the crank keyway method.

 

[GT/CS]

Yeah I would assume it is working properly. No codes and i have put a hundred or so miles on it now and it runs fine during casual driving (didnt want to get into boost before the dynotune).

 

[GT/CS]

Hmmm...I've never tried to time a motor with the balancer on, I always used the crank keyway method.

Wasnt timing the motor, i was putting the cams in without pulling the front cover. I used the wrong terms, just had to put the motor in the correct orientation for the cam install.

http://home.comcast.net/~cookpaging/hammeron/cams/hotrodcams.html

 

[05roush0090]

Are you running an air to air intercooler or air to water. with air to air and a 3.48" pulley you should be seeing 10.5 psi,.......air to water (vortechs kit) and a 3.48" pulley you should be seeing about 12 psi so putting an 8 lb spring in your BOV is hindering some of your performance. I dont know for sure if should keep you at 8lbs or it will just strait up malfunction since you are overpowering it. But I do know if the BOV does not perform as inteneded you may not be getting any boost through thus your lack of power. With an air to air kit I highly recommend using t-bolt clamps instead of the worm drive clamps as mine failed often until I switched to t-bolts clamps. if they fail you once again have a lack of boost making it to the intake manifold. Same scenario,,no boost = lack of performance.

 

[TheKurgan]

putting an 8 lb spring in your BOV is hindering some of your performance. I dont know for sure if should keep you at 8lbs or it will just strait up malfunction since you are overpowering it. But I do know if the BOV does not perform as inteneded you may not be getting any boost through thus your lack of power.

It's not going to hurt having an 8lb spring. I doubt the problem is the BOV unless it has a vacuum leak around the seal.

 

[TurboX]

Really sounds like a timing issue, what has me confused is the car should be running like shit. What kinda vacuum does it have at idle ?

 

[GT/CS]

Are you running an air to air intercooler or air to water. with air to air and a 3.48" pulley you should be seeing 10.5 psi,.......air to water (vortechs kit) and a 3.48" pulley you should be seeing about 12 psi so putting an 8 lb spring in your BOV is hindering some of your performance. I dont know for sure if should keep you at 8lbs or it will just strait up malfunction since you are overpowering it. But I do know if the BOV does not perform as inteneded you may not be getting any boost through thus your lack of power. With an air to air kit I highly recommend using t-bolt clamps instead of the worm drive clamps as mine failed often until I switched to t-bolts clamps. if they fail you once again have a lack of boost making it to the intake manifold. Same scenario,,no boost = lack of performance.

it has the paxton air-to-air intercooler in it. Wow, didnt know the 3.48 makes that much boost which explains the BOV bleeding off boost @ WOT. I plan on getting t-bolt clamps, just want to get the car running 1st before I dump more $$$ into it. All the connections are tight right now.

 

[GT/CS]

It's not going to hurt having an 8lb spring. I doubt the problem is the BOV unless it has a vacuum leak around the seal.

No leaks around it and Ill def change the spring out once I finalize the pulley/boost im running. I also have a 3.33 pulley that I might slap on depending on the kinda power it makes when everything gets sorted out.

 

[GT/CS]

Really sounds like a timing issue, what has me confused is the car should be running like shit. What kinda vacuum does it have at idle ?

I had the cams in the car before the blower went on and it seemed to run fine. Got horrible gas mileage but it ran strong. Im gonna just finish retiming it so I know it is right and then go from there.

Not sure what vacuum is at idle, dont have a gauge and forgot to check it when i was at the tuner yesterday.