Thread: 2 different vac readings?

Ive always had a boost/vac gauge and this whole time I thought I was getting 4 psi of boost. Is that low? I just bought the Bluetooth obd2 and torque app. My gauge in my car reads 8 for vac while parked. The vac reading in the app says im at 24.5 Do I have a vac leak?

4 PSI is way low. I am getting 9 psi on a 3.4 & feel that is low. Does your car feel like a dog?

I tied the gauge in right in the back by the firewall. on the line that wraps around the s/c and goes under the snout. it doesn't seem like a dog at all. it kicks it right in the ass when you get on it. isnt 8 psi normal for stock?

ya that boost number seems low stock is like 5-6psi, like they said you should be at around 8-10 psi... im at like 10-12 on a 3.0.. plus your vac seems off too it should be sitting at like 20ish at idle.(-20 inHG)

take a pic of where you tapped into, you should be after the supercharger like the lim

Maybe I should try to find a better way to tie it in.

If you see -8 vac.. that's likely pounds, and if you see -24 vac..that's likely HG

What do you mean by parked? Are you idling or is the engine not running?

I

yes. its idling, engine running.. and the -24 vac is not in hg. I checked the settings. its in psi both ways. is there a way to see if its leaking at the T for the boost/vac gauge?

My aeroforce usually reads around -18.5 (-) -20 when idling.. WOT stock pulley for me (10°F-20°F) is around 8-10

I lied. the settings are on psi but the gauge itself on torque app is in hg... I inspected the T in the vac line and it looks fine. I don't know what to do.

Isnt that line just picking up from afted the bbv? You wouldnt see any boost from there except from bleed off. Right? Boost would be created after the SC.. can you tap into the lim? Or before the bbv?

Also have you tried spraying all lines and connections with carb cleaner yet?

I did it right where this guy did it.

does anyone know why my boost reading is so low?

im at half the boost I should be at. im gettting about 4.5 lbs of boost when I should be at about 9

I told you why... your tapped into a line that is on the bypass... you need to be after the supercharger where the boost is made

so the guy in the picture above did it wrong too?

its not in the wrong spot. It is right between the T on the lim and the map sensor. on the back side of the sc. bill even said so in a thread on here.