05stangguy

Hey guys. I think I may have an issue with one of my gauges in my car. When starting the car or when my foot is off the gas, the gauge reads around 20-22mmhg/vacuum, which I believe is normal. The problem is however, even at wide open throttle (or extremely cloes to it around 4-5000rpm) I can't seem to get to 10lbs of boost, which is what the car is tuned for I believe. Now, I do have an sct tuner that supposively has 3 tunes on it, maybe I am running the lesser of 3 tunes? I do not know ANYTHING about the tuner, so I have not used it yet. I do not believe I have a vacuum leak anywhere, due to the vacuum gauge reading normal readings. With the kenne bell 2.6H, at what RPM range should I be at 10 lbs or boost, or is it more complicated than that? Thanks!

Chris

BruceH

The best way to see boost is by driving uphill in a higher gear. Drive uphill in 4th and give it some gas, you will see the boost. Unless the motor has a load on it you won't see boost.

05stangguy

hmmmmm, this is alittle hard to do in FL, as it is so damn FLAT . The best I will be able to do is an onramp to a highway! What about in like 2nd or 3rd gear? I don't think I'll get to 4th on an onramp.

BruceH

It doesn't have to be a hill, it's just easier to quickly build boost that way. Try a 4th gear pull on an open stretch of road starting at about 50 or so.

05stangguy

How long should it take to get to a full 10lbs of boost? I thought the beauty of the twin Screws is that they get full boost almost instantaneously no?

onederful100

what is your pulley size?
what is the most boost you have seen on your mustang since putting on the SC?
is your exhaust stock?

onederful100

how much boost you seeing now?

onederful100

if you have LT's and o/r midpipe, you may not see the psi that correlates to your pulley size. that is normal with decreased backpressure from the free flowing exhaust. psi isn't an accurate measure of the power level at which your mustang is putting out.

and with a TS, you will see full boost instantly at about 2500-3000 rpms.

05stangguy

I bought the car as is. It came with an SCT xcalibrator tuner with supposively 3 tunes, however I have not messed with them because I have no idea about this tuner, or what the tunes actually are. Supposively the car is making 10 lbs of boost...I am using af full mac exhaust or/h pipe..As far as pulley size, I am not sure what size pulley it is, how do I measure? just use measuring tape and go across it horizontally?

BruceH

I don't know how long it should take. Boost is a measure of restriction. It's pressure the motor can't process so it backs up and is measured as boost pressure.

I can show you one of my dyno sheets with the boost logged. The green line is boost. The pull was done in 4th gear and the dyno simulates the load that would be on the motor while driving. You can see it took some time to build. Also note this was at wot. Just driving along at 2000 rpms there won't be any boost.