My son want to put an aftermarket catless Downpipe on his Wrx. Will he have to buy a tuner and retune it to trick the cel or can you retune it with the stock port.

 

Dp213

He should have a tune when changing the exhaust beyond a Cat- back.. And on a WRX, the first pipe he should change is the up pipe if he wants to put any extra boost thru it since the up pipe has a Cat in it too, and that's pre turbo

He's not going for more boost, he wants a better sound. He loves the sound and isn't worried about more power

The Uppipe is a potential turbo killer as they wear out internally and send their contents....lots of places it ain't 'sposed to go.

 

But to answer your question. You can get a Tactrix Cable ($100), download free ECUFlash and ROMRAIDER software and tune it yourself via the OBD2 port, get a Cobb AccessPort (AP)$300(used)-600 (new) , or do nothing and probably be fine......but I wouldn't risk it as these 2.0/EJ205 are known to spin bearings even on the stock tune. You can also get those 'anti-fouler' plugs for the O2 sensor which usually work to eliminate the CEL.

And not sure just a DP will get him the noise he's after....new muffler?

He did the cat back already. Sounds way better than it did stock be he's wanting a bit more. (Kids) oh wait, I put loud exhaust on everything I can :-)

The thing about turbo engines in particular is that they need a certain amount of backpressure.  Doing what he's wanting to do is dangerous for these engines.  Trust me: we won't even give a warranty on one if the exhaust isn't stock.

 

Emily

The thing about turbo engines in particular is that they need a certain amount of backpressure. Doing what he's wanting to do is dangerous for these engines. Trust me: we won't even give a warranty on one if the exhaust isn't stock.

 

Emily

 

 

Hmmm...didn't finish this.

 

Hoping she means NA / Non-turbo engines.

Although I'm not the one w/the expertise to dispute this, there are more than a few that will in the below links. Backpressure  is created by the turbo, so no other back pressure is required after the turbo. Exhaust velocity - discussed in the links, is what is @ issue, and that comes from the header/exhaust manifold and up pipe.

 

Link1

Link2

Link3

Edited March 14, 201610 yr by wtdash

he could consider running without a muffler and do a 'turn down' on the exhaust.

Wow, so after reading ALL 3 links, I have come to the conclusion that a cat delete down pipe is a good thing for any turbo car. The bad is emissions, and since we don't have emissions here the only problem I see is the cel. So once I figure out how to deal with the cel, I'm good. I can't just ignore the cel because of its importance, so I will figure out how to get it off.

 

Thanks for all the info from everyone.

It's an '02, so you can use an 18mm spark plug anti fouler, drill it out and put the rear O2 sensor in it. the ECU does not use that sensor for anything else except tripping a catylist inefficency code

^^^ yep - or possibly a coupla resistors at the end of the harness.

 

but, with ECU Flash or some other tuner software, you can 'un-check' the P0420 and other codes I think.

A couple of things to add to this thread:

 

A 2002 WRX does NOT need a tune to run a full turbo-back exhaust (TBE).  They run a 16-bit ECU that is primitive enough that it's factory software can compensate for the change in airflow.  The later 32-bit cars ('06+, IIRC) MUST have the ECU retuned when any aftermarket downpipe is installed.

 

As far as the backpressure comment from CCR: FALSE.  Normally aspirated engines do benefit from backpressure, but a turbocharger is it's most efficient when you have a large pressure differential across the turbine wheel.  (High pressure before the turbo, low pressure in the exhaust).  It makes sense as a business to only warranty engines installed with 100% stock components, and I understand why they do this (See comment about 16 vs. 32-bit ECUs above), but the reasoning is just plain wrong.

It doesn't sound like your son changed the uppipe yet? it's not part of the catback exhaust.  To reiterate what matt167 and wtdash said, please make sure the uppipe is changed to catless before changing to a catless downpipe. If this was done already, go ahead and change out the downpipe.

Right, and a stock used STI up pipe won't be expensive at all.. STI's were exempt from the strict emissions crap since every manufacture was allowed 1 model to exempt back then.. You could use one off any '02-'07 STI and it will be a catless up pipe