hey guys i have an 86 gxl swapped with a series 5 turbo engine but running series 4 turbo and electronics as well ecu to work with he body harness. my question is what a safe boost for my car to be ? i know the stock hitachi is only good for 14 psi and you need a fmic,rtek,720cc injectors,fuel pump and a fuel cut defender to run safely at that boost as well porting the wastegate to control the boost creep. my concern for my car is what would a fcd, ported wastegate, fuel pump, front mount and 3 inch catless downpipe and test pipe with stock NA catback be good for with stock injectors my only concern is that my ecu is meant for the lower compression s4 not the higher comprerssion s5 motor so im not sure if that will change what would be safe to run for my car any input on what i should do would be greatly appreciated thanks !

 

with a stock fuel system, i wouldn't go more than 10psi, although between 3800-5000rpm if it went a little higher thats ok.

what happens is that when you mod the car the AFM is going to be 100% open earlier, so any rpm over where the AFM is 100% open, the ecu won't be able to add more fuel. so if the boost is a little high between where the secondary injectors turn on (3800rpm) and where the AFM is 100% open (depends on your setup), boost could be a little higher, because the ecu can "see" it.

and then the stock turbo is so small running more than 10psi is not a great idea anyways. if you looked at compressor maps you'd see that the stock turbo is already spinning really fast, so more boost is just shortening its life really. one of the advantages of running a bigger compressor (BNR style turbo), is that you keep the turbo RPM stock, but it moves more air.

 

oh ok well thank you with the response as of now my car has a walbro 255,fmic,fcd and soon a 3' downpipe and test pipe just waiting to install, will porting the wastegate be enough to keep it at the 10psi range or are their other measures to prevent boost creep other than replacing turbo ect.