Still struggling with boost gauge

theconductor · Feb 11, 2010

No one was able to help last week, but I'll try again....

I just installed a boost gauge and need some help as to where to cut in the boost/vacuum line. I currently have it cut into the vacuum line that comes off of the neck of my manifold and runs to the charcoal canister. It reads vacuum fine, but nothing on the boost side.

Any ideas? Where are you fox guys routing it?

Thanks,
Kyle

Grn92LX · Feb 12, 2010

tap into the fuel regulator line, any line off the manifold or look for a spare port on the vacuum tree.

87AODGT · Feb 12, 2010

there should be a port on your vacuum tree that is capped off and says b/r right over it, which I always figured was perfectly marked for boost reference

theconductor · Feb 12, 2010

87AODGT said:
there should be a port on your vacuum tree that is capped off and says b/r right over it, which I always figured was perfectly marked for boost reference

I've seen that port. It's broken, so have to get a new vacuum tree. Oh well, I'm sure I can find one.

RatStang · Feb 12, 2010

You can tap ANY of those lines that come from the bottom of your intake (assuming stock upper plenum). If your intake is aftermarket, tap one of the lines that feed from the manifold's main chamber (if at all possible).

A small tip: It's best to install and inline orifice in the line going to the gauge. The orifice should be roughly .050 in. (tiny drill bit). You can make one out of just about any metal or plastic plug that will fit INSIDE of the vac line going the gauge and is 1/4 in or so long. What this does is keeps your gauge from "bouncing" erratically from sudden changes and also prevents the gauge from "stealing" vac/boost pressures from other items if the line you happen to tap happens to be low in air volume for some reason.

Works great, lasts long time.

theconductor · Feb 12, 2010

DontGivaRatz said:
If your intake is aftermarket, tap one of the lines that feed from the manifold's main chamber (if at all possible).

A small tip: It's best to install and inline orifice in the line going to the gauge. The orifice should be roughly .050 in. (tiny drill bit). You can make one out of just about any metal or plastic plug that will fit INSIDE of the vac line going the gauge and is 1/4 in or so long. What this does is keeps your gauge from "bouncing" erratically from sudden changes and also prevents the gauge from "stealing" vac/boost pressures from other items if the line you happen to tap happens to be low in air volume for some reason.

Works great, lasts long time.

My intake is an older edelbrock. The line I'm using now comes right out of the neck just behind the throttle body flange.

I'm not sure I follow your tip. Are you saying I should find something that fits inside the line going to the gauge to plug it, but drill a tiny hole in it to allow just enough flow to/from the gauge?

frcefedlx · Feb 12, 2010

I have ran mine off of the vacuum line for the FPR on this and my last car. I can't say that I have erratic guage readings either. Just t into that and should get boost readings no problem.

theconductor · Feb 13, 2010

frcefedlx said:
I have ran mine off of the vacuum line for the FPR on this and my last car. I can't say that I have erratic guage readings either. Just t into that and should get boost readings no problem.

Okay, I admit it. I'm a douche....

What is the FPR?

frcefedlx · Feb 13, 2010

FPR is the fuel pressure regulator on the fuel rails on passenger side of car back behind the throttle body. Just T into that line going to the regulator.

bmo37 · Feb 13, 2010

another note once you finally have the gauge plumbed, it's possible you won't see any boost at idle and think it's broken. Generally it's working as it should just that you won't see it build enough boost on the gauge untill you rev the engine high enough to build pressure. This usually happens on smaller blower apps 8lbs or less or if you have a larger engine.

frcefedlx · Feb 13, 2010

Good point about the boost at idle. Also motor should be under load so free revving won't give boost either.

RatStang · Feb 25, 2010

theconductor said:
My intake is an older edelbrock. The line I'm using now comes right out of the neck just behind the throttle body flange.

I'm not sure I follow your tip. Are you saying I should find something that fits inside the line going to the gauge to plug it, but drill a tiny hole in it to allow just enough flow to/from the gauge?

Sorry, didn't see this question but YES. The tiny hole allows more than enough volume to operate the gauge and helps to prevent any "wierdness" from other items that might otherwise 'lose' vacuum as the result of being plumbed in-line with the new gauge.

Just a preventive measure that's worked well for me in the past.

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