Funny boost gauge reading

[Turbojuice]

Umm, my boost gauge reads at a -25psi vacuum while at idle, and under high boost, it reads a whopping 0psi. I just installed the gauge today, using the how-to on the forum. Used the same vac hose used in the pics and everything... Wtf?

While the cars off, it reads -1psi vacuum.

 

[43975]

Either your not making boost or the gauge is broke. I used the same how too. Check your intake pipes to make sure they are not cracked or not sealing

 

[blueprotegelx]

What brand is gauge?

 

[Turbojuice]

Its an autometer. Pro-comp Ultralite sort of thing.

i dont think I have any sort of leak or anything... Car runs great. I can tell that I am boosting... No idle issues (cept for the dirty EGR valve) and car is fast as all hell...

 

[Turbojuice]

Vac hoses are good... Most the hoses were just replaced.

 

[Wagonbacker9]

gauge is prb f'd up... or the line is pinched?

 

[Turbojuice]

Dont think the line is pinched... I sent AutoMeter an email, so hopefully they will get back to me.

it is reading almost exactly 10psi too low i think. Most of you guys idle at about -15psi vacuum right?

 

[J_Naoto]

should be around -22 to -20

 

[Turbojuice]

should be around -22 to -20

Can someone verify this? Maybe my car is not getting boost. How can I find out if my car is failing to boost? I hear it in the intake, but my car is idling at just about -22 and boosting up to 0.

 

[Turbojuice]

Either your not making boost or the gauge is broke. I used the same how too. Check your intake pipes to make sure they are not cracked or not sealing

I will try this when the sun comes up tomorrow.

 

[Sp33dFr33k]

Vac is usually 22 to 23.5 for me.

 

[greasemonkey524]

Are you t'd off the brake booster line? Could it possibly be on the wrong side of the check valve in that line?

 

[orng1]

I used to get 22 average, what does it say when it's off? Oh wait you said -1, that's fine + - 1 is not a big deal. I bet one of the fittings is loose.

 

[jersey_emt]

If you tapped into the brake booster line you are probably on the wrong side of the check valve.

 

[Turbojuice]

Noob question time. Whats the brake booster line? I think I'm in the right one. I am plugged into the vac line that is on the far right side of the top of the intake mani.

 

[Turbojuice]

If you tapped into the brake booster line you are probably on the wrong side of the check valve.

Check valve? Brake booster line? Noob to turbos am I

 

[43975]

He said he used the "How too" on here. That "how to" has you tap the short "U" line that is under the Brake booster line near the back of the Intake mani.
20-22 Vac is normal...-1 vac when car is off also normal as well for non electric needle type boost gauges.
The Pro feels fairly quick due to is weight in general. I can almost guarantee one of your pipes is either cracked or popped off.
Are you running stock plastic pipes and stock SMIC? If so check where the pipes connect to the turbo, intercooler and intake mani. also keep in mind the top and bottom of the intercooler where it connects is plastic you could crank down on the crank to hard and crack it.
Also what line did you use to run the Boost gauge? Did that gauge come with the hard plastic "tubing" or did you run actual hose? There is a small chance that you have a small hole in that line or it's not sealing well. but I would expect to seen a vac leak at idle as well, unless it only leaks under pressure.

 

[Turbojuice]

All the piping under the hood is stock with the oem smic. I'm using the hard nylon tubing that came with the gauge, and I'm pretty sure it is working because my car is not showing signs of a vacuum leak. I'll check the pipes now.

 

[Turbojuice]

ok I think I fixed it. All of my hoses were just replaced (still basically stock) with new ones when they started cracking, and I guess I didn't put one of em back on all the way. it had almost completely slipped off.

I can't tell for sure if this has fixed it yet though, cause my car is out of battery but I'm pretty sure this will fix the problem. Thanks guys!

 

[Wagonbacker9]

if that had been your problem, you wouldn't have been showing low vacuume. a boost leak will show up LONG after a vac leak (though they're really the same leak, I'm just differentiating direction of the leak)... because the turbo can usually pump enough air to keep up with a boost leak... where as the engine runs like crap if theres a vac leak.