Thread: Boost reads in the negative?

So I just hooked up my boost gauge and it reads in the negative -20 -10 range? It sweeps about 10psi in the negative but I just cant figure out what could cause this. I bought the gauge from a member and it was said to be new so maybe I have a bad gauge?

Its late and dark now, ill post a vid of it tomorrow, I taped the line under the snout and bought nice couplers for the T but it just reads in the negative.

Where did you hook it up? Needs to be on nipple by the coolant elbow underneath the supercharger snout.

It doesn't read pos if you get on it

When idling you should pull around -20 VACUUM. You don't want to see boost until you get on it. That's completely normal.

Originally Posted by Sandman

When idling you should pull around -20 VACUUM. You don't want to see boost until you get on it. That's completely normal.

Ok that makes sense I guess ill rip up the freeway a bit and see how it goes. On a side note, and this could be unrelated. My MPGs went down the tubes? Car is running just fine and it could be cause its a fresh tank and I havent had a chance to take it on the freeway but my MPGs is in the 16s and its typically 20-23 range mixed. Could these be related?

How old is the vacuum system? You could've broken brittle lines with the installation.

Well that makes sense, the car is a 97 and im assuming its stock. What else is weird is I cant seem to floor it while in the 65mph range the pedal feels hard could these be linked? Or is that maybe while I was rooting around under the dash cause a kink?

Im assuming replacing the specific vac line I taped into isnt too tough?

My MPGs are somewhat back to normal. I drove it on the freeway and she was climbing up back towards the 20s, Havin an aeroforce is trippy!

see now i have mine tapped into the right spot, but will only ever read max +2psi boost
not sure if the gauge is shot or not, but i don't even have any kinks or anything in my line either....

Ill try to take a vid and show you guys whats up.