boost drop off

[BADINBLACK6]

Boost is set a 23lbs with alky. At WOT it hits 23 no problem but drops to 20lbs and stays there for the rest of the run.(on a back street almost 1/4 mile long) Why does the boost drop off? No KR and all #'s are good. And on one of the runs it dropped to around 16-17 lbs.

 

[Turbo Brian]

i had a boost drop problem. took a few months to track it down. it was actually a vacuum leak. plenum/intake leaked and later found the big leak, my egr gasket was shot and the egr had loosed up and could walk around quite a bit. check your vacuum lines, then move to things like a plenum leak, intercooler hose leak, intercooler leak, etc.

 

[BADINBLACK6]

Thanks Brian, I just put the alky kit on a few weeks ago and have been beating on it alot. I just noticed the boost drop last night and today the idle was real bad too. I always had good idle with the t-92 chip so I guess the the bad idle all of a sudden is from the vac leak too.

 

[8UWITH6]

Thrasher Chip, to my knowledge it pulls the boost down in 3rd gear. On my ttype (when I ran a thrasher for a while) Id run 17psi in 1st and 2nd, then it would drop to 15psi in 3rd. Try another chip and see if your boost stays solid. HTH

 

[TurboDave]

Because just about all chips pull some boost out at the shift into 3rd gear, and some more at the shift into 4th. It's a safety feature because the engine is less tolerant of boost the higher you go in gears and the higher the load becomes.

The only chips that don't do this are race chips, or chips that have been specifically requested to run full boost through all gears.
The Thrashers have independent boost control in all 4 gears and reduces it a little with each higher gear.

 

[BADINBLACK6]

Took Thrasher chip out today and put in jc 93 chip, idle problem seem to go away but I don't know if it is because he just raises the idle in his chips. Haven't been able to give it WOT yet to see if I get same drop off on boost(been raining since I put the chip in, who didn't know that!)Anyone know what timing or boost for a JC 93 for stock inj? I've had the Thrasher in for so long I forget what the JC had.