So, since I put my shanghai-s on I've had this wierd issue.

I suffer from slow spool, or rather, it spools to 3,5psi at 3000 rpm and then at 4500-5000 rpms it suddenly rises to 7 psi. 5th gear it is rather reluctant to get to 7psi, it likes to stay at about 5. Good vacuum on gauge when in idle/cruising.

AFR's are ~11.5 when flooring it, EMB, rx8 420s, divorced gases downpipe, t2856 churbo. Wastegate actuator is tight.

I'll be FMIC'ing it this weekend, but this ramping, jumping late spooling is so wierd I thought i would ask the pro's.

No ms because I had an e-manage and only have a power goal of 200-220rwhp.

Please help, This issue is confusing, is it as easy as a boost leak? Why then the different boost levels?

 

1st do a boost leak test.
Then make sure the wga flapper moves freely and is not obstructed.

 

Is your target 3.5psi or 7psi? I can't imagine you're shooting for 3.5psi, but there are some strange people out there.

I would say it sounds like a leak at the wastegate, like it's not closing all the way. Just beacuse the actuator is tight doesn't mean the actual flapper is covering the hole. Also check for exhaust leaks, though one big enough to cause this issue would be pretty easy to hear I think.

 

Sadly I dont have an air compressor, my first though was WG, I'll check the flapper during the weekend. Thanks.

Target 7psi, 12 on sunday

 

I had a similar issue when my recirc valve was not holding at mid boost levels. The valve would start to recirc at about 5 psi and then close again at higher boost /rpm.
A different recirc valve fixed in my case.

 

I do my boost leak tests using the air compressor at the gas station.

 

Fixed this yesterday, seems like a sticking flapper in the wg was the issue, same as the problem levnubhin had.
However, this only showed when the car was hot.
Dremel - issue solved.

 

Apparently not completely solved (see spool thread) now higher thresholds, but stll not building boost consistently.

Going to check both wg again as well as try to disconnect the blow off valve to try to find the culprit.