I recently rebuilt my 88 TII.
I've kept it under 4000 RPM for the past 1400 miles or so, so now I'm starting to boost a bit and it won't boost more than 5 lbs.
At 5 lbs it seems like the wastegate is venting the extra boost.
Is there any way that the wastegate could be stuck or maybe the wastegate actuator not working properly? How would I check?

I know very little about turbo-chargers, so any help would be appreciated.

 

Are you using an aftermarket gauge to monitor boost levels? Check the vac lines, I had a leak in my previous mechanical boost gauge line that limited me to 5lbs. I used a mitty vac to hunt the leak down.

 

If you scroll down this thread, you'll find an expedient method for testing the actuator. The thumbnail shows the FSM instruction for doing so.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/wastegate-actuator-543490/

Edit: I think Jimmyv has identified the more likely problem in his post.

 

1400 miles is too soon for boost. Full brake in isn't complete until about 3000 miles & it really should see boost before then. It will cut down the life of the engine.

 

last I checked, 5 PSI or so was the correct level for a stock TII..

 

that is all relative to who built the engine, i have boosted fresh engines with no miles on them with no side effects, for my customers i tell them 1000 miles but 3000 miles is just rediculous. reduced lifespan? the engine has already lost 3000 miles to babying, what more can you ask?

5.5psi is stock for a S4 T2, what mods have been done?

 

No boost for 3000 miles? That seems a little extreme. I've kept it under 4k rpm for 1200 miles and plan on allowing *some* boost between now and 1500 miles.

Anyways, I've got a hybrid turbo, 720 secondaries, sport cat, sport exhaust, RB downpipe, 3" TID, WI, dual stage mbc, rtek 2.0 and other stuff.

I've removed the rats nest, installed all new vacuum hose, caps and clamps. Triple checked them all.
I'm going to redo the plumbing on the WI where it meets the IC as that's the only place I could find any possible vacuum leaks.

 

tighten down the adjustable wastegate arm to put more tension on the flapper door. i have found almost every hybrid does not have enough tension on this door.

 

do you have an adjustable wastegate actuator arm it could be too long just tighten it up some when i bought my turbo from bnr it was not adjusted to where i held boost and all i could see was 5psi also try adjusting it and you should see more

 

You sound like you know more about turbo's than alot of the people in here claim to...

 

the 5 psi limit is probably what bought you a few extra days of driving time, lol.

 

Not really. Just trial and error(mostly error), but thanks to the search button and you guys on this list for answering my sometimes stupid questions I've been able to keep it running and actually have some fun with it from time to time ;-).

 

5.5 psi is factory boost for a s4 t2
thank god i thought mine was just not boosdting good but releif to hear that if its true ive hit 7 lbs like 2or 3 times but i think it was cold and lus i have 3inch exaust from down pipe back and i have the down pipe but no fcd yet