some specs,
1990 1.6
new act hd clutch
greddy kit running an fmu with the following additons and upgrades

turbo clocked down
FMIC and 2.5in piping
Ebay purple BOV recirculated to intake
ball&spring manual boost controler
Boost set to about 6-7psi
No ac or power steering

Car will reach full boost with out a problem at about 4k( stock exhaust) as i start to go over 5k the psi steadily drops. will drop to 2psi sometimes less sometimes more.

what are some ways to diagonosis this problem, its a real burden as this is the autox car and boos starts to fade right when it motor starts to make power.

 

search "helper spring" or greddy wastegate their know to suck and need a helper spring to hold boost to redline

 

ive seen this on mycar when the compressor was leaking.

 

i'll look into that...

magna where was your compressor leaking at?

 

Check for a boost leak. Or a non closing bov... It can appear to be sealed and leak on pressure. Check all ic conections.

A stock greddy set should be able to make 6 psi with oem exhaust all the way to redline.

 

Remove the rubber hose connecting the wastegate can to the compressor. Block the compressor outlet with a plug. Install a nipple in the pipe between the intercooler and the throttle body, and run a new hose from this nipple to the WG can.

 

the ebay bov;s leak,, buy a real one

 

you have a manual boost controller? tried running without the MBC fitted?

 

I disagree.

All BOVs purchased from any eBay vendor are completely reliable and trouble-free. I base this upon my experience of having purchased one BOV from one vendor, said BOV now being two years old and still working perfectly.

 

could this just be the common case of the greddy wg
(helper spring)

 

Why do you do this Joe?