This past weekend I was getting the car tuned, and while on the dyno the boost was hitting a constant 15psi at wot. After I left the shop, and did a couple of wot hits on the highway the boost started at 15psi, but then wouldn't go past 10psi. Later that same day while taking the wife to work It peaked out at 12psi? I'm a little confused with this problem? I was thinking a leak in the vacume lines?

Any ideas fellas?

 

Mods? Who tuned the car? Do you have a copy of the tune?

 

What size pulley?

 

That would... Sorry, I have 60's 2.8 pulley, full exhaust, and intake. The orgninal tune was a can from CA, then was tuned by HPT "Henderson Performance Tune Shop" The car was doing this before the new tune, but I was hoping it went away with the new tune.

 

Do you have a oversized tensioner or a stage 2 belt? Is the car making a high pitched sqeaul while in boost?

 

x2 could be slipping if you dont have a smaller belt and tensionizer

 

i don't know what your car is doing so if this sounds ignorant I apologize....

but it could just be perception. my car sometimes seems it's not as fast as it usually is, but then I realize that it's just where I am in the powerband. Sometimes I hit 17psi when I stomp on it, but don't hit that till about redline. Then if I'm running on the highway running in the "proper" gear for the speed I'm at and punch it, it may take till almost 6K till I hit 15psi and it doesn't crawl much beyond that.

So, if that makes sense and is what you're talking about, it could just be the powerband and how your running it at the time you notice the psi.

 

What cooling mods do you have on the car? If your IAT2 is too high the car could very well be pulling boost. It would be good to see some logs of when the car is doing this to see what is going on. I don't suppose you could take the car back to the shop, or if you know someone with HPtuners, and have them do a couple of runs and capture the logs when this happens.

 

i have the stage 2 belt. cooling mods are just intake, and waiting to install a cx racing heat exchanger. car doesnt squeel when boosting. i was thinking the same powerband theory. as for the shop i can go back free of charge. we did 5 pulls and all at a constant 15 psi.

 

that sounds like your best bet then. Go back to the shop and do 5 more pulls. This will garauntee you are in the same gear, same part of your powerband, and same mods. If your boost is sitll 15psi, you'll know it's all a result of how you were running it at the time you observed the boost. If it changes, then you know something has degraded in integrity since your last pulls since you haven't modded it since then.

 

I would take the car in, but you are going to need to do a couple pulls back to back, with little break in between to try and simulate road pulls. Doing a dyno pull does not usually have the same effect as doing pulls on the road as you aren't going through multiple gears. I would have them log the pulls as well so we can see them.



This could be true as well. You are not going to see PSI max out until you get into the upper RPM range. About 6000 is where my boost usually maxs out as well. If I floor the car at say 3500 RPM I may only see 10 - 12 psi; then the boost steadily increases as the RPM range increases. This in itself is normal and controlled by the computer.

 

that sounds like case. the pulls were all logged. my tuner said basiclly the samething. ill try to get ahold of the logs.