Boost gauge vacuum?

**bigduck187** · 02-17-2013

Not real familiar with boost gauges let alone with a supercharger but my gauge reads 0 when I'm off the supercharger. Shouldn't it have a vacuum reading? I've talked to a couple old school guys who said they tuned their cars to a 0 idle reading. But I'm seeing pics of people with -20 vacuum!? I'm at a loss on this. What is the "proper" boost my gauge should be reading?

**Erik Adam Rodriguez** · 02-17-2013

17 to 20 at idle

**bigduck187** · 02-17-2013

So now I need to figure out what's wrong with my lines lol yay more work. Thanks though!

**dsmuts** · 02-17-2013

You likely have the gauge hooked up wrong

**bigduck187** · 02-17-2013

I didn't install it so now I get to fix someone else's mess

**BillBoost37** · 02-18-2013

Follow the line to the motor. It should be connected into the line from the T under the snout. Whether it's up front or at the back, that's the line it should be hooked into somewhere. Any other place and it'll give you no vac

**jayroca** · 02-19-2013

Im also fairly new to the install other than following the line to the snout can i use the fuses on the passenger side? How properly to do this?

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**BillBoost37** · 02-19-2013

A fuse won't help you with vacuum. Typically a boost gauge only wants a ground and the dimmer circuit for the light. Unless you are working with an electronic one.

It would help if we know what you were working with and which year car you had.

**blueguy** · 02-19-2013

I'd post pictures...especially if you don't know what's going on.

This is why I say do your own work.

**Explicit_Spade** · 02-19-2013

There's no such thing as negative vacuum.

Vacuum is read in kPa (kilopascal) and Boost is read in PSI (Pounds Per Square Inch). Zero is the middle mark, where neither exist.

To convert pounds per square inch to kilopascals(PSI to KPA), multiply the PSI value by 6.894757293168361.
To convert kilopascals to pounds per square inch(KPA to PSI), multiply the kpa value by .14503773773020923.

**jayroca** · 02-19-2013

Originally Posted by BillBoost37

A fuse won't help you with vacuum. Typically a boost gauge only wants a ground and the dimmer circuit for the light. Unless you are working with an electronic one.

It would help if we know what you were working with and which year car you had.

Sorry lol its a 2001 GTP as far as the dimmer circuit where is that located? Ground is the black wire near the front by the battery/passenger headlight right?

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**BillBoost37** · 02-19-2013

There are plenty of places to ground inside as well. Any piece of metal behind the dash will work for the ground. Trying to remember, I think the small yellow wire off the headlight switch is illuminination, or the grey one. Test those two and you'll have power for the light with dimming.

**jayroca** · 02-19-2013

Originally Posted by BillBoost37

There are plenty of places to ground inside as well. Any piece of metal behind the dash will work for the ground. Trying to remember, I think the small yellow wire off the headlight switch is illuminination, or the grey one. Test those two and you'll have power for the light with dimming.

Ok gotcha so i can use the interior harness those are on the passenger side or driver side sorry for endless ques.. Im not by my car right now...also i have glowshift 7 color series boost gauge can i use the dimmer feature with this gauge?

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**bigduck187** · 02-21-2013

Hey guys thanks for the info and the help! Been too busy to visit the site lately but I will get some pictures posted tomorrow as I still haven't figured it out. The "T" under the snout is just that, a T. But I can't see where anything is going to the supercharger. One line is running to the nitrous module. Another to the fuel rail. I don't think that's the right "T" I'm looking for lol I have a 97 gtp