Exhausts, remaps and tuning?
 

After buying a 2001 wrx (bugeye) and peviously owning a 1996 turbo 2000 I have found that I am dissapointed with my new cars performance. This has spurred me on th release the beast I know is lurking within by carrying out some performance modifications.

I've already done the snorkel modification and fitted a green cotton air filter. My next steps are going to be an exhaust system and then a remap.That is all for now. I've already got someone lined up to do a custom remap but my query lies with the exhaust.

I've been doing my homework but everywhere I go I get mixed opinions. The make and manufacturer is not my concern. My problem is figuring out what diameter tubing is going to get the best performance, 2.5" or 3", and wether removing all the CAT's (including the up pipe) is really the best option.

Emissions are not a problem as I am a mechanic;) but I preferably would like a combination that is road legal. Now I have been told by the man who is doing the remap for me that he thinks the best combination is to have 2.5" tubing and to remove every CAT apart from the the down pipe. This includes removing the up-pipe CAT. This way it will have increased airlow but will still have the necessary back pressure to maintain good torque figures.

I deffinately dont want to lose any torque. Improving acceleratiom is my main aim. Im not concerned with top speed.

If you've got this far thanks for reading. any advice welcome.

2.5 should be fine, 3" is only recommended above 350 BHP or there abouts, thought about a sports cat for your down pipe? a bit expensive but almost as efficient as a decat, think they only loose a few BHP over the decat downpipes

I have thought of a sports cat but i've heard that alot of the sports cats, fitted by themselves, wont be sufficient to get it through an m.o.t test.

If that was the case then I would preffer just to go without a cat as getting it through the m.o.t isn't critical.

But again. Is removing every cat the best option for performance? The tuner I spoke to seemed adamant that a complete cat removal would increase my bhp but my torque would suffer. I would much preffer torque over bhp.

Can anyone confirm this or is he talking nonsense?

Normally the best cat to get rid of is the one in your down pipe, I noticed a big difference in midrange torque with mine out.

Fit the STi uppipe, prodrive sport cat downpipe and go for a decent aftermarket centre pipe and backbox. That combination will net you 270-280bhp and over 300lb/ft. It'll also easily pass an MOT too.

Turbo's need as little back pressure as possible downstream of the turbo, is this tuner Subaru specific? Removing all the cats spools the turbo up quicker and allows for higher boost, both contribute to higher torque, not lower.

He specialises in tuning subaru's. I've not had a full conversation really but over the phone his recommendation was to leave the the downpipe cat in and go for 2.5" piping.

I may have misunderstood and he might have suggested that as the best option to keep it road legal. I'll try have a better conversation with him tomorrow.

Is it the general consensus that the less cats and the bigger the tubing the better. Baring in mind that I wont really be pushing over 300bhp?

The less cats yes, you don't need a 3" exhaust for your power goals.

Thanks for your advice guys.

I'm looking at a milltek cat back system but there downpipes seem very extortionate.

Could either of you suggest a cheaper alternative that goes down to 2.5"?

There are loads to choose from, Hayard & Scott are pretty decent though.