I have an AP2 running the 4.5" Pulley for over 2 years in my Vortech V3 Sci. Ive been seeing a max of 8.3psi at 8200 rpms. Car made 372rwhp. Last night I installed a 3.8" Pulley from ASP. Put in the base tune I received from my tuner, and saw that max boost was only 9.7 psi@8200 rpms. I find it kind of low. My car has a berk header, test pipe and T1R Dual sparrow exhaust 70mm. I double checked the belt, re-tightened and still same boost level, it climbs with rpm, never drops until I shift at 8200rpm@9.7psi. Is having a better flowing exhaust setup maybe making me see so less psi? I was really expecting at least 11psi with my setup.

2006 AP2
Vortech V3 Sci 3.8" pulley
Flashpro
Upgraded bigger watercooler with bigger pump
AEM Water Meth 50/50
Berk test pipe and header
T1R Dial 70mm Exhaust

 

Yeah that’s really low, id expect closer to 12-13psi with that pulley. No your exhaust mods aren’t the issue here with the low reading. Belt slip obviously comes to mind first, but if your sure that’s not the case then im not sure what else the problem would be, unless what your using to read boost is off? Are you looking at a gauge or data log? It would be best to compare the two for accuracy, make sure the gauge isnt a problem.

Also are you sure you were only seeing 8psi before? Unless you were on Churches dynopack, that is an abnormally high amount of power for the minimal boost, it just makes me think you were making more boost then what you were being shown. Could be a gauge accuracy issue. Not sure what else it would be.

 

The Dyno was a dynojet. I'm using the flashpro datalogs to monitor boost. Gauge reads the same. There is a chart here that states that an Ap2 Vortech with the 4" pulley makes 11 psi. So my 3.8" should be around the same. Checked all after cooler pipings, checking the datalogs is definitely making more boost at all rpms just that the peak is a little under what's expected.

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Boost guage off?
Belt slip?
Loose hose clamp?

Thats all I got.

 

Typically when your belt starts to slip first, its in the upper range where the motor spools up the quickest, also one thing to check for is that your yielding the same boost in all gears. Many times I know my belt tension is off when I accelerate in 1st or 2nd gear and see I am making a lower peak boost then if I were to redline in 3rd gear. Point being, the slower the motor accelerates the easier it is for the belt to maintain grip on the sc pulley. Its a simple test you could do on the street in a safe area to see if and how much fluctuation there is.

 

Good advice everyone. After tightening I only did a 2nd gear pull, I'll check again tonight on 3rd gear and see if it makes more boost.

 

Have you used a boost leak detector on it yet?
Well worth the effort. I was amazed when I checked mine out.
I had several leaks including throttle body x2, couplings x4 and aftercooler/bov interface.

If your shop or buddy doesn't have one you can use, they are available for less than $40 on e-bay. Check out turboboostleakdetectors.com

 

You just gave me an idea, maybe I should tighten a little more my BOV? It may be opening at higher psi..

 

3.8 asp pulley will only give 10 psi @ 8k rpm.

i had same pulley n exact same setup on my car for years.

 

You just gave me an idea, maybe I should tighten a little more my BOV? It may be opening at higher psi..

That adjustment impacts closing not opening.