When I'm not boosting, the Greddy boost gauge always shows 200 vacuum. It used to fluctuate anywhere from 0-700 mmHg as I'd accelerate. I checked all the vacuum lines and they look ok. When I boost, it works fine, just not when I'm off boost. I got the gauge used, do you think it's broken or something else?

 

bump.

 

200mmHg = how many Inches?

 

It's a Greddy gauge, so it's in metric. Let's say it equals .06 inches. What does that signify?

 

Hmm...according to an online metric conversion tool, you are pulling 7.8 inches of vacuum.

Sounds like a nasty vacuum leak - you should be pulling 17-22In Hg.

(That's 431-558mmHg on your gauge)

IanS

 

It normally fluctuates, but now it's stuck at 200 mmHg at all times except when I accelerate, then it goes anywhere from 200mmHg vacuum into the boost part of the gauge. I checked all my lines, no loose connections (except for the one that everyone agrees is the transmission breather line).

 

bump.

 

When you hit the gas at idle, does it go up, then when you let go of the gas, does it dip below 200mm for a little bit, then sit back at 200mm?

or does it never actually ever go below 200mm?

If that's the case, then either have a vacuum leak or your gauge is literally stuck.

IanS

 

I got 17in Hg during idling and 22in. Hg when the car is moving. is ur gauge a mechanical gauge? if so, I would check the hose and filter to see if there is any leak or the filter got clotted.

 

I think it barely goes past 200 mmHg at any time. When I accelerate, the arm goes up and into boosting. When I let off the gas, then it goes back to 200, maybe a little past, but it settles at 200 again. I just ordered a new gauge, so I'll swap them and see what happens.

 

I think it's an electrical gauge, but I could be wrong. I only see two electrical wires going through the firewall into the cabin.

I checked all the vacuum hoses and none seemed loose. I might have disconnected something when I was installing the Hyperground wires. I will try to follow the wires for the boost gauge from the cabin to the engine and see if somethings loose.

Thanks!

 

if u have mechanical gauge....even u disconnect the electric wire, it will still work. or if there is a vacuume hose going to ur guage, then u have a mechanical gauge. I think u have a mechanical gauge. Now the problem lies to 1)leaking 2)bad gauge.

Do you still get the correct readings when boosting?

I would take off the guage and install it right next to the throttle body and see if I get better reading. If not, I would try to find another gauge and do the same to elinminate the possibility of having a bad gauge.

 

I checked it today, the gauge is electrical, no vacuum hoses, just two sets of electrical wires going to the gauge. The gauge is ok I think. I can hear a hissing sound near the throttle body if the hood is open when the engine is running. I've never noticed this sound before. It sounds like air is escaping somewhere. I tried to feel for an air leak, but didn't feel anything. It's hard to hear the sound because of all the engine noise, but it's there. One weird thing I've never noticed before either, when I turn off the engine, I hear a short air rushing sound, and at the same time you can see the throttle body and acceleration\deceleration cables shake a little before they settle, and the air sound comes from this area. What do you think?

 

Get a 1/4 hose, stick it in your ear, then stick the other end to where you think the leak is - like a stehoscope.

That should help you find your leak.

IanS

 

I'll try that, but dang it's noisy in the engine bay, especially with the SC whirring .

 

Heh - when troubleshooting my SC, Czar stuck a couch cushion over my SC.



IanS

 

Ok, I found out the problem with the boost gauge vacuum reading. The Bosch recirculation valve wasn't working correctly, it was closed off and not opening. I found this out when I installed the BOV, because then the vacuum reading was normal. Then I had a problem with the BOV leaking, so I removed vacuum from the BOV to close it off, now the vacuum reading on the boost gauge is stuck at 200 mmHg again. So that means for the last few weeks while my boost gauge was stuck at 200 mmHg, everytime I boosted, I had no release mechanism to prevent backsurge of boost to the blower .

Currently I am running without a release mechanism, so I am just being careful not to boost.

 

Which hose did you guys tap the boost gauge in?
I tapped into the line that runs to the Hobbs switch. Is that correct?
I'm only getting 10 Hg vacuum so that must mean I have a leak? I also put a kink into that stupid plastic line that runs to the boost gauge. Should I replace it?

 

A shop installed mine, so I can't say where it's tapped.

I'd like to know though so I can swap the Greddy for an Apex'i.

 

Of course you can.

 

Of course I can what? Swap the gauges?

I've searched my engine bay to see where the boost sensor is located and tapped, but never found it. I'd guess it's drilled into the intake manifold, but I don't know for sure. There's a little black casing labelled "GReddy", but the wires leading from it disappear into the abyss that is the VQ30DE.

 

Sounds like an electrical boost gauge as opposed to the mechanical that most people have - you probably can't swap it.

 

Yeah, it's electrical. If I do swap to a mechanical gauge, I'll use the same tap point as with the electrical gauge, so it'd be good to find out where that is.