Subaru WRX Forum banner

white smoke from exhaust on start up

27K views 31 replies 9 participants last post by  jmb8806  
my set up is spt intake, hks catless downpipe, and spt exhaust, tuned to stage II with a cobb ap. does anyone think that this contributed to my problem. the only thing i can think is that i ran it for about 6 months without the AP after i did the downpipe, which caused y car to over boost pretty bad....thats the only thing that i can really think off...
Overboosting is only part of the problem. You were also running VERY lean every time you ran into boost.
 
well how would i fix the problem of running too lean?
Problem already solved, you got tuned. Removing the cats drops the post-turbo exhaust restriction significantly. This increases the pressure drop across the turbo, which spools it quicker. Because it's easier to spool the turbo, the turbo spools sooner (lower RPM). This means the stock delay the ECU uses before it switches to open loop fueling is now too large, which means the car will continue to stay in closed loop (14.7 AFR) well into boost, which can cause detonation/damage.