i recently noticed that an increase in black soot from the inside of my exhaust tip. i just did an oil change so i don't think that is the problem. a search came up with the possibility of running lean. would that be the case? if so, why all of a sudden, and how do i correct it?

this is on an 05 wrx. mods are turbo back with catted dp, k&n air filter, and stage 2 ap. i have been running this setup for about a year but the soot has just appeared recently.

 

could be the summer gas?

 

I would think that any exhaust system with a less restrictive cat/no cat would expel more soot. I have seen visible puffs of black soot frequently on other cars running catless. Also have heard that soot on the bumper/trunk area means your running rich I dont think thats the case though. So long as your car runs trouble free with your setup I wouldnt worry too much about it. Just monitor your oil consumption...GL

 

Black exhaust is caused by running rich. Mine does it as well with a cobb catted dp, stock cat back running stage 2. Mine has been protuned also so I'm pretty sure its normal. I don't think its too much to worry about unless you notice something wrong. If you get worried though you can get a scan tool and check your fuel trims. Those will give you a good indicator of how you car thinks its doing at least.

 

yeah, i am now thinking that i am running rich because it looks like my mpg has gone down a bit. just don't know what could have caused it to happen all of a sudden. the only thing i have done differently is put in a tank full of 76 after using chevron regularly. while i doubt that did it, i am going to wipe it down and go back to chevron and see what happens. i should also check my air filter to see if there is any kind of blockage.

 

i thought turbo back didnt have cats

but your right from your last post, running rich not lean

 

Lean would be white residual soot