Greetings there, i own a 2006 mcs with alta cai, 16%+2% pulleys, grs cooler and forged wossner pistons. I have just logged the car with Innovate Logworks through my iphone and i can see that at 4850 rpm i have almost 17 psi and as the revs go up it is gradually dropping and at 5970 i have 15 psi. Is that normal? What should i check? Could the computer read wrong numbers through the obd port? Thanks in advance.
George

* I have a 1375 belt. Is that too big ?

 

the boost leak will happen at boost pressure, not neccesarilly at RPM, so if you do spike at 17lb then drop to 15 see when it starts to leak, cause that does sounds like one, could be a vacume hose, could be the intercooler couplings, i can hold 16.5 psi all the way to redline

 

Thanks for the reply, so what you are telling me is to check the intercooler couplings and the vacume hose. What is the vacume hose you are reffering?Should i check the bypass valve too? or its not causing that kind of problems? Might be the belt sliping?

 

could also be the belt slipping, my intercooler boots were starting to crack so i replaced mine, the rubber does degrade over the years. it could be any vacuume hose, they degrade as well, doesnt hurt to take a look, but the car would run iffy if the leak was large. if it was the bypass valve, again you would have yo yo issues at lower boosts, i dont think you would have problems up top. belt slipping is also another idea. turn the AC on and see if it does the same thing. extra load of the compressor should either make it slip more( less boost) or keep more tension on the belt (same boost or even boost)

 

But how do you explain the 17psi at that low rpm? Normally my car would gradually boost up to 17psi near the redline not at 4000rpm...

 

i can hit 16.5 psi at any rpm, so long as my foot is in the floor, thats the benefit of a supercharger. i also have a mechanical gauge. about 40-50% throttle i have 10 psi across the range

 

Im monitoring the boost through the ecu via OBD not with a mechanical gauge. So i dont know if its the same. Im looking at the boost my map reads.