BicuspiD

I had a friend drop off his 93 today at my house. My old shop (UPRD) had done a ton of work done to it awhile ago, but hes having problems.. so I tell him to drop it off with me for a few days to check it out.

First off - mods

Redline streetported/dowelpinned motor, S-AFC for fuel ( thats IT!), STOCK 107k mile turbos (non ported wastegate) AVC-R boost controller dialed in for 14 psi, downpipe and midpipe, stock catback

The car idles a little lopey, and takes a while to warm up, but thats pretty apparent with most of the streetport motors I have dealt with, so no biggie.

Once you get on it, it will make boost to 7psi (rather quickly even), regardless of whether the controller is on, off, full , 1/2 whatever.. It feels like the second turbo never comes on line.. When shifting at 7krpms ( and boost never past 7psi) There is a loud popping from the exhaust and a (BIG) black smoke cloud puffs out. Progressing through the rpms in the next gear, and its not smoking at all, until, again, at the shift. Same black cloud. I did this 4 times, so Im pretty sure I can re create it again.

I am assuming the S-AFC is probably set wrong, and there are vacuum line issues, possibly even a dead second turbo, but any ideas on the smoke cloud?

The motor only has 20k on it, and it idles at 14-16 in/hg.. seems normal for a street port.

Tomorrow when I have some light im going to check the plugs and the coolant system for telltale bubbles, as well as pull the UIM off and see if anything is apparently wrong. I am dropping the car off for him at RR&R monday, but would like to give them a heads up and possible issues..

Anyone ever experience this? I hope its the turbos so I can see the BNR's up close and personal!

SnowmanSteiner

I would think you're on the right track. Maybe the secondary turbo is gone and the smoke is from oil build up or something of that nature. That when the pressure is let out all of the oil has built up and then just blows out once released. Anyone else with a better more experienced opinion?

- Steiner

skunks

What is the setting for the superafc? even with the first turbo, it should beable to get easily to 10psi. double check if the turbo precontroler door is stuck open/closed.
Why not trying to go non-seq?

BTW: the black cloud and backfire is cuz your runnign super rich when you shift/deacel, perfectly normal for a stock ecu with a super afc.

Oh yeah, if your running a street ported engine, how come your not shifting at 8-8.5k rpm? this is a manual car right?