boost gauge shows 0 psi at wot

DUSHER

I am out of solutions at this point and I'm about to go insane. I just had installed topgunz a2a kit and have leak tested 3 times now. I also tightened the supercharger belt as much as possible. The first time I found two leaks. One small one on the block off plate and another small one coming from the maf sensor. After that I ended up checking it two more times and found no additional leaks.

Seb says I'm only getting 4.5 pounds peak boost. My boost gauge that I've tried on two different vacuum lines shows 0 psi at WOT. The only part I didnt check for leaks is the supercharger itself.

Also mineral oil smells like ****!

Senna-F1

How are you testing for boost leak?
Here is how I tested https://www.youtube.com/watch?v=-7ZPmLl_7xI

Are you saying the block off plate on the manifold was leaking? How did you test that?

0 PSI at WOT is actually not necessarily a problem with a centrifugal SC, it depends on at what RPM this is happeninig. Boost will = 0 at WOT below a certain RPM.

Does your boost gauge EVER see boost? Seb sees 4.5 which is coming from the MAP sensor in the manifold. Your gauge is being fed from a vacuum line coming off the manifold. If Seb see's boost, but your gauge never does, that might be a pinched/torn vacuum line.

Not sure why he only sees 4.5 psi though. Maybe your manifold not sealed, but not sure how you tested that it's OK.

DUSHER

yes. Where the manifold cooler once was. I work at a dealership with two different smoke leak testers.

What exactly am I watching here? Is this showing the car has no leaks?

yes it does. At idle it shows 24 and when I give it about 25-75% throttle I usually see 8. As far as the type of vacuum line that I'm using, its just a regular air line. I made sure there were no kinks in it. I got the gauge for free since it was used so I'm not 100% sure if its faulty.

Like I said up above I tried two different testers. One produced more pressure than the other. I also tried to hook it up to the pipe that connects to the supercharger, T'd it off of the BOV line, and the last time off of the port on the back of the intake manifold

Senna-F1

Ok, there is a lot of info and statements here that are conflicting and confusing. And, and I’m not sure what your main complaint is. Instead of pointing out all of these here and asking a bunch of questions, can you send me the log you sent Seb? PM me if you want.

turtle64b

You say that at idle it shows 24 and at medium throttle range shows 8. This sounds like vacuum? Maybe in inches H2O or Hg? Even at WOT, you won't see any manifold pressure until you're above maybe 3k RPM (off the cuff, I'm sorry if not exactly accurate).

My pressure meter is T'd off the line that goes to my BOV and fuel pressure regulator.

DUSHER

I had my info all ****** up. It was at -24 at idle. I found out that the gauge was uncalibrated/broken. When the gauge was uplugged from the vacuum line it showed -6. I have a new gauge and I'm going to check it. Thanks for the help

turtle64b

Hell yeah, glad it is an easy fix. I've chased all kinds of leaks on all kinds of cars and they're never fun...

Jetsimple

How would that faulty gauge change the fact that Seb was only seeing 4.5 from the ECU?

Girald

So, a proper boost gauge should show you what is happening...full stop. If you arent generating boost it should show 0psi or negative. to indicate the engine is running on vaccuum, the way most NA cars run...

If you are spooling, then the the psi should build and indicate +psi on your gauge. ....



Now, that said. where did you plum the vacuum line?

For my vacuum line, i bought a 1/8th NPT tap kit... i took my plenum out of the car and carefully made the threaded hole at the back ( with a vacuum cleaner hose to suck out any plastic while i was doing it and a shop rag stuffed in there just in case i miss anything.)

Then I bought an 1/8 NPT threaded fitting to whatever size nipple for the hose you are using) teflon and not over-tightened since you are dealing with plastic. I ran the hose to the gauge MAP sensor. and wired to the gauge of course.

So a coupe of things... The gauge MAP sensor.. make sure the nipple is pointing down as not to collect debris in the air or water condensation... try to buy an inline vacuum-line filter to further help that situation., Also, make sure that the gauge is hooked up to its own power and not piggy backing the stereo or other 12v devices for power.

Another thing: Most gauges, if not all require calibration for barometric pressure so you dont get false readings... Check the handbook to calibrate your gauge AFTER you check the other things i mentioned.

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AAM tt'ed // Soon: Moving back to the East Coast