gary_phd

I finally got around to installing a boost gauge (Cyberdyne Digital VAC/Boost with memory), and was excited to see what I'm boosting at. Complete the install, took my car out for a quick sping. See VAC, good so far...accelerating...seems like positive boost doesn't occur until the upper rpms. Did two runs in 2nd and 3rd gear, max boost is only 3.7! I'm like "wtf!!" Is this normal for an AP2? I would have searched, but the fx is out of order right now.

Background on my car:

Stock Comptec SC w/ AC
Modified stock exhaust (refabbed Y section with Magnaflow rears)
JIC Test Pipe

Dynoed (dyno jet) at 278 whp and 185 wtq, when first installed (85*, 29.42 inHg, 26% humidity) - Didn't have the test pipe at this dyno

Once I installed the test pipe, my car felt stronger. This was supported by my ability to pull on my bro-n-law's 05 GTO (1-4th run) by a car. I wasn't able to do that before the test pipe.

I wish I had installed the boost gauge when I first installed the SC. Today's conditions: 96*, 29.59 in-Hg, 26% humidity.

Should I expect more boost? Will boost levels change if it get cooler? It shouldn't matter should it, as the boost is regulated by the pulley size?

I will be dynoing again tomorrow, however, it's going to be on a Mustang Dyno I believe.

Scorpion

Check the belt, might be slipping.

gary_phd

How would you check for belt slip? How much tension should I be feeling? The Paxton is pretty noisy, so it'd difficult to hear for slipping. Also, my exhaust get a bit loud, especially after vtec.

slamar1

Belt might be slipping or the intake piping may be leaking boost

FF2Skip

Temperature and humidity do play a part in boost level potentials, but I'm sure it's probably the belt. As you're looking at the engine, reach in below the 'charger bracket and twist the belt. If you can twist it more than 90*, then it should be tightened. There is an actual measurement of tautness, but I have no flippin' clue what it is or what instrument needed to measure it.

I found it easiest to remove the airbox for tightening the belt.

Asura

Have you checked the calibration on the gauge?

If you remove the blower belt, the boost (manifold pressure) should be zero at WOT. I know it sounds like a bit of work, but it is one way to decide if the problem lies with the gauge or the SC. You could also re-dyno at the same shop, but you are going to get higher #s with the TP.

revhi

Where you hitting redline during your two runs? Max boost isnt until absolute redline.

gary_phd

I'll have to check everything you guys suggested, from the belt the boost gauge calibration. If it's the belt, I'll have to get back to the shop and have them retighten it, as I don't have any way of knowing how tight it should be. As for the gauge, I hope it's not that. I'll have to return the damned thing and get a new one.

I went to the rev limit on both times. I also double check the couplers, and retighten all the clamps. Seems like the couplers are bit too narrow, can't really apply the clamps on well. I'll probably change them out.

How do you remove the belt? I can give that a shot to test out the gauge.

Asura

To release the belt you need to release the tension on it from the belt tensioner pulley. Then you have to fish it out carefully.

revhi

I know on a hot day, I wont reach full boost until 4th gear max rpms.

Even with that 3.7 sounds pretty low, what type of boost gauge is it?