By the way, the Helix system rocks! That big bellmouth DP is just so pretty.

 

With a WRX you can run with the stock ECU on a catless car. According to Cobb Tuning, the up pipe is within the learning capabilites of the engine computer. To get the most out of the downpipe you need to have engine management of some type: reflash, utec, accesport. STi's have been known to have problems with boost creep after installing a TBE, but I haven't heard any of this for the WRX.

 

Eric - What did you go with for a hi-flow cat? I'm either going to get a 2.5" universal and weld it onto my Scoobysport midpipe or go for one of the Random Tech Subaru kits that bolts right on:

 

From going to the local suby meets and seeing and smelling other guy's exhausts... I have asked LOTS of questions..heheh Most of the guys are running a catless dp, uppipe, and have either a highflow cat or a regular cat... This is what I have noticed... with a only 1 cat or even a highflow cat their exhaust still stinks, smells like fuel or something.. can't really describe it, but I don't think it's bad, not like say.. B.O., that is a different sort of stink..lol... personally I don't mind the smell... I have asked them and they have all failed emissions even with a hi-flow cat... so they told me to put my stock stuff in before I get it inspected...

I have a full TXS TBE exhaust that is all catless along with the crucial racings uppipe that is also catless... this will all be installed on the 18th... so I'll let ya know the smell and how it runs :-)

-Nigel

 

nice, yea, i just insatlled a gutted downpipe two days ago, and i can't believe how much earlier the turbo spools. it's hard to explain, kind of like, theres not more power, it just starts earlier and increases smoothely. where as the with stock down pipe, there power wouldn't come right when you floored it, but wait a couple seconds then hit pretty hard. either way i like it alot, but not enough to be satisfied. i wanted to get an aftermarket downpipe, but the way i drive coupled with the loud exhaust and flourishing amount of cops, i know im going to get pulled over. and if they look under the car and are competent enough to see that i have no cats in the downpipe or the mid pipe, then the fine is 2500 or something like that. so i like the stock look. i guess im going to gut the third cat or replace it with a high flow. luckily, the up pipe is out of view, so i can put my vishnu, or anything else down there.

-tj

 

According to Vishnu, boostcreep is an issue with catless turbobacks and stock turbos. They recommended that I get one with a highflow cat in the downpipe.

 

I'm pretty sure all the Stromung products are made to bolt to the stock pieces, so it should fit. Unless Stromung has changed in the past year. Regardless, whoever is selling it to you should be able to tell you.

 

wrxless: Are you required to have a cat in the dp? I thought the main cat was enough

 

In CA, all three factory cats are supposed to remain in place unless defective. By the letter of the law they are not even supposed to be changed for high-flow units if they are functioning properly. Other states have different requirements.

As far as passing smog with one cat, I've heard of one person who passed the sniffer test here in CA but don't know anyone personally who has had to smog their cars yet. Catless definitely won't cut it come smog time.

Worth noting - generally, if you have to run a restriction in the exhaust, whether it's a cat or a muffler, it's best for performance to place it as far back (close to the tailpipe) as practical. The problem with cats is that they function best when mounted close to the exhaust port (or turbo) to get hot enough to achieve light-off temperature for the catalyst.

--
0==WW==0
"…axles of evil…" - george w. bush

 

I just don't get it. Why are all of you taking your carefully engineered LEV vehicles and removing the cats? Is a few extra horespower worth the harm you are doing to the air quality? Sounds terribly myopic to me.

Why not strive to have both? There are ways to achieve horsepower without excessive HCs and NOx. The Cobb stage II keeps the all important up-pipe cat for light off emissions and includes a high flow in the downpipe. This type of system offers horsepower gains while maintaining exhaust catalysts.

But even Cobb doesn't quite get it...I've asked them if they've done emissions testing and they're response was "It doesn't set off the check engine light."