Boost gauge reading -7 at idle

[b e z]

As the title states -7 at idle. When first installed months ago it read -12 and quickly went to -10. As of late the gauge has read on the norm -10 and after a bit if running down to -9.When the ac was turned on after the running for a bit it went to -8. It seems to me that i have a vacuum leak. I read that it is generally from maf to turbo, is that correct? This was just noticed late tonight and i have yet to go through all the clamps and connections. I did a WOT pull in 5th gear and boost read 14 then 13 and then 15 and i let off, not sure if that helps. Hopefully this is enough info for people reading but im sure i will hear a lot of check all the clamps and connections.

 

[Darth Vader]

Is it sitting at 0 engine off?

Those are pretty low #s for vac. What's your gauge calibrated in? PSI, I suppose. Often boost/vac combo gauges aren't that accurate reading vacuum. A proper vacuum gauge (couple bucks at an auto store) will tell you the truth.

 

[Kain]

What gauge are you using? If your vac is inHg, then you should be sitting at around -21 at idle, and -19 if the compressor is on.

 

[b e z]

i havent looked to see what it is at with the engine off, il do that on my lunch break. The gauge is called glowshift and its electronic, i looked on their site but i cant find it anymore. It is a combo boost gauge and air/fuel but i didnt hook up the air fuel.

 

[b e z]

And yes it is calibrated in psi. Im sure it is a cheaper gauge but the number is obviously dropping so i think there is a clear problem. I was hoping really for more insight on where to check if the number is dropping in the vac stage of the gauge and not being low while at full boost.

 

[b e z]

http://www.glowshiftdirect.com/Tinted-digital-boost-led-air-fuel-ratio-combo-gauge.aspx

There is the link for the gauge itself

 

[Kain]

Well, you pretty much answered it: you have a vac leak or the gauge is bad. See if you can get your hands on a Dash Hawk to see if the vac on it reads the same as your gauge.

 

[b e z]

Update: The gauge reads 0 while the engine is off. I went through and checked what connections i could get a hold of. All the clamps on the intercooler piping are butted up tight and the clamps are tight, same goes for clamps on intake and its tubes. I took a pic of the turbo inlet and once i figure out how to upload pics large enough then i will do so. I believe the loose looking turbo inlet is throwing off my long term fuel trims. Only things i could tell that could use improvement is the silicone hose going into the tee for the boost gauge. The hose is covering one barb and not the second on it, dont think that is the issue tho. Now to what i think the problem is. The line coming from the bov, not the recirc but the small one. It seems to make a short run to an elbow into im assuming the intake mani. I can grab the bottom of the hose and wiggle it, i tried pulling on it a little and it didnt pop off, but i believe i have a clamp on it. The part that wiggles is just past the clamp at the end of the hose and it seems to be lose. So maybe that is the culprit. I have an ultragauge scan tool, didnt buy it, received it as a gift. That is what i am using to monitor stuff. Unfortunately it doesnt have vac reading on it.

 

[b e z]

Update: Came home and changed the vac line from the bov. Turned on the car and nothing changed. Left it running and put my ear up to things and heard what sounded like air surging in the bov. The bov is a cheap one i already had from ebay, there type s knock off. Changed it out and boost gauge at idle went back to -10. I have never really had anything more than -10 unless engine breaking which bumps it to -12 briefly. So if there is a further leak then it is on the turbo inlet side. I also bypassed my boost gauge to see if it helped my fuel trim and to check for leaks. Right when i did that my fuel trims changed from 17.4 at idle to slowly decreasing and settling at 5.2. Investigated a little more and found the silicone tube to the boost sensor loosened itself up. Snugged that up and it stays at 5.2 at idle. Dont think it will get any better until i get tuned due to the added air from the cobb intake.

 

[MSMS3]

Bez: When you say -10 or -12, what unit of measurement is that? Does the gauge say inches of mercury on the vaccuum side? Like inches-Hg for example? It would say psi most probably on the boost side, although some measure boost in bar or megapascal units. Confusing. And some boost/vacuum gauges do read the vacuum side as minus psi. So we need to know what unit of measure is printed on your gauge for the vacuum side. If it's psi then a -10 psi might be normal. But if it's -10 inches of mercury, then there is probably a leak somewhere. If it is a leak, that needs to be located and fixed before you mod further. On any tune you need to be seeing idle vacuum something very close to -19-20 inches Hg or its equivalent. If not, you do not need to be trying to fix this with a tune. Ain't gonna work that way.

 

[b e z]

^ On the website i linked earlier it shows the gauge and the description says it is measured in inhg. Also if there is a leak i cant seem to locate it because i have checked out everything i know except things on the turbo inlet because space is tight. That i can notice it seems the turbo inlet is a little loose could that cause it? I have yet to try and spray things down with carb cleaner and see if the idle changes. Ive contemplated buying a turbo inlet pipe so i have a reason to take out the battery and ic and check everything but im holding back because this possible leak issue.

 

[b e z]

Another thing here, will splices into the wires from the boost sensor to the actual gauge make it read off some. At the time of install we didnt have a lot of good wire.

 

[Domino81]

If you have a vac leak it should run pretty rough. Like mentioned above, I'm always at -20 in/Hg (-20.37/.67) at idle.

 

[b e z]

as far as shifts and things it runs fine and it idles ok, shows it idles anywhere from 688-701 once warmed up. Is there any other places i need to check that are accessible? I have checked: the ic couplers, the bpv, the vac line from the bpv, the recirc line has a small tear on it, clamps on intake, the maf looks like it is on tight but i didnt snug it up, clamps beyond maf, all connections on the silicone hose for the boost gauge.

 

[Domino81]

Anywhere it's suckin' in air has the chance to leak.

 

[shcernsise]

What gauge are you using? If your vac is inHg, then you should be sitting at around -21 at idle, and -19 if the compressor is on.

If you have a vac leak it should run pretty rough. Like mentioned above, I'm always at -20 in/Hg (-20.37/.67) at idle.

Your vac/hg will be different depending on the load of you car. I would bet you dont have a leak. If your lights are on it will be different. If your ac is on, it it will be different. If there is no load on the electrical system at idle then it will be at its lowest, but start turning on stuff then the idle will adjust and your vac will be different. You most likely do not have any problems as my cx7 does the same thing.


Usually the deeper the vac you have at idle, the better condition your engine is/ pistion, rings, ect. Usually..... there can be other reasons that this statement can be false.

 

[b e z]

With the ac on it runs -9 so just one lower and when we hooked up the boost gauge the power is hooked into the power wire for running lights, yea i know dumb but it was freezing when installing it and we got tired of messing with it.

 

[shcernsise]

With the ac on it runs -9 so just one lower and when we hooked up the boost gauge the power is hooked into the power wire for running lights, yea i know dumb but it was freezing when installing it and we got tired of messing with it.

Just wondering when you installed your boost gauge, did you disconnect the neg battery terminal from your battery. You could have shorted something somewhat out during the install causing it to misread. Especially if it is an electrical boost gauge. I have the mechanical one so there is less worry for me. You should have used an add a fuse and tapped into your 12v acc fuse. It will turn on every time you turn the car on. You would not have to drive with your lights on always.

 

[b e z]

yea it was disconnected during the install. We were looking for the right wire to tap into so we just used a wire that went to one of the switches where the dsc is.

 

[shcernsise]

yea it was disconnected during the install. We were looking for the right wire to tap into so we just used a wire that went to one of the switches where the dsc is.

I mean if it works, it works, but not the ideal method I would use. Glad that the battery was disconnected. I believe that what is happening is normal. My boost gauge fluctuates based on the load the car is at - ac, lights, ect. You would almost know if you had a vac leak. Perhaps your gauge is faulty. I had to send my prosport back once so far because when it was off it would not be at 0. It would stay at -2 so it was 2 psi/hg off.