Accurate boost reading

[merlinx]

This mught sound like a dumb question to some of you but I need to ask. I have a 99 gst and Im trying to determine my boost reading. Is there a special way of doing this? I have a boost guage, high flow cat, 3" Apexi N1 cat back, 2.5 down pipe, K&N intake, Upper and Lower IC pipes. When I accelerate rapitly the boost sometimes goes up as high as 19psi but then quickly drops down to 14-15 PSI. Its hard to keep up the boost cause the car usually reaches its wanted speed really fast and the PSI drops or I just run out of road . I live in LA so there is a lot of traffic . Can I accellerate in a lower gear and check the boost that way? Please help, thanks


Jason

 

[Grimis]

all stock except what you said??? if you have the boost gauge installed to the P or the fuel press thing, then your getting the right readings. I have mine taped into the fps and i get 16psi at wot and it then drops back to 14, so yours sounds about right. your getting the normal for the T25

 

[99gst_racer]

It sounds like your boost is set at 19 PSI. The reason it drops off is because the stock T25 turbo is not capable of holding 19 PSI all the way to redline. So it drops off and hold the best it can. When I had a T25, mine was set at 14 PSI and it would fall to 12 PSI all the time. Dont be alarmed if it falls back a few PSI everytime. It happens.....

 

[merlinx]

Ok thanks guys. What im trying to do is get an accurate reading from the boost gauge. I just installed a MBC and the readings have not changed much. I have the damn thing screwed all the way, the screw is about to fall out if it wasnt for the lock nut. Under hard acceleration I actually managed to keep the boost at 16-17 acter spiking to about 19 psi, is this normal? I do not want to blow my turbo or engine. Im not sure if Im reading the guage correctly, most guys say they do 15 psi max with a stock turbo. Do they mean maintained or spiked to that level? Do I even need a MBC? or should I plug the stock stuff back up? I dont think I will do any more mods for a while

Thanx

Jason

 

[Spln_Hrd]

how long is the hose that "feeds" the mbs and how long is the line that the mbc uses to "feed" the wastegate.

sometimes using to long of vac hoses will make it spike.

 

[merlinx]

the Wastegate line is about 19 in and the line from the BOV to the MBC is about 15in


will that make a difference?

 

[Spln_Hrd]

no, sounds fine to me.

what kind of mbc is it?

 

[merlinx]

just a regular ball and spring I picked up on ebay

 

[leet]

My 25 did the same thing, until I ported out the wastegate passage on the turbo, and ported the O2 sensor housing.

 

[merlinx]

so will this damage my car? Also please, how do I get an accurate reading of what Im boosting?