Exhaust Power

[nikkinokkinoo]

Hi, I know there is probably not a straightforward answer to this as the response is probably dependant on a re-map, does anyone know an out of the box power increase for the various different aftermarket exhausts that are available - so in stock form just replacing the exhaust which gives the best results? Thanks

[Steve_PPP]

Which part of the exhaust? Complete turbo-back? (normally 4 sections).

Are you looking to buy an exhaust with a sports-cat or go decat? Both would really need a remap if you're running a newage.

[555_Si]

I put a jap speed back box on my bugeye when it was standard and power went from 220 to 239bhp without touching anything else.

[BIG"E"]

Originally Posted by Steve_PPP

Are you looking to buy an exhaust with a sports-cat .

WR1s come with a sports cat

[555_Si]

The difference between exhausts is probably negligible, decating will see gains but you should probably remap, and that is going to make the biggest difference.

Scoobies easily make more power when modding, not like a naturally aspirated car.

You need to make probably at least another 20bhp to feel a difference anyway, remapping can change the characteristics of the power delivery which make the car feel different.

[nikkinokkinoo]

I'd probably go de-cat but can't be 'doing' with a switch each time for an MOT. I'm after bit more sound but straight exit. Sounds as though there is no clear winner in the power stakes. I quite like the look of the miltek's but some say there is little difference in sound. So de-cat or cat, no standard performance measures from a stock sti out there?

My aim is to not get mugged off by an M3 on a straight which is what happened at Bruntingthorpe - only by the slightest of margins. I dont want to go changing internals of the engine, but would like to get it to a safe improvement. May mean a new turbo as reading the forums the WR1 is probably getting to the top end of its turbo capabilities. Then it may make sense to have a twin-scroll to avoid the lag - thoughts most welcome as I find my way through this maze!

[555_Si]

Have you looked at Andy Forrest's website as it gives some guidance to what is required for certain gains, I used it as a guide when I first got my car.

I have milltek centre resonated section and back box on mine because they are quiet, I have decatted and got RCM manifolds on mine. Changing the manifold and up pipe made it a lot louder. Can't remember what Dave (Ginola) had on his STI, that sound nice, straight exit and looks well built.

[ScoobyStu]

Originally Posted by STIWR1

I'd probably go de-cat but can't be 'doing' with a switch each time for an MOT. I'm after bit more sound but straight exit. Sounds as though there is no clear winner in the power stakes. I quite like the look of the miltek's but some say there is little difference in sound. So de-cat or cat, no standard performance measures from a stock sti out there?

My aim is to not get mugged off by an M3 on a straight which is what happened at Bruntingthorpe - only by the slightest of margins. I dont want to go changing internals of the engine, but would like to get it to a safe improvement. May mean a new turbo as reading the forums the WR1 is probably getting to the top end of its turbo capabilities. Then it may make sense to have a twin-scroll to avoid the lag - thoughts most welcome as I find my way through this maze!

Find a friendly Mot tester to get around the decat issue. Get an uprated fuel pump, panel filter along with the decat, get it remapped and you will make anything from 320-360bhp. As regards to M3's, you should be quicker to 100-120 but after that they will come past. Switching to a twin scroll is way too much work and expense for what little you'll gain. Another good mod to do before messing with turbo swaps is to get some ported headers and up pipe which will see you on boost sooner. My 03 Sti makes 343bhp 348lb/ft with decat, panel filter, fuel pump, Harvey ported headers and up pipe remapped by JGM. Hope that is of some help

[SpecB]

I have the full 3' Miltek sports cat system on mine and it's around 90db at Goodwood.

[555_Si]

Mine has the 3" milltek with centre resonated section, no cats, RCM headers and up pipe. 92db fit Brands.

Guy was confused after everyone else had gone through with 102db upwards, I told them they were hooligans, especially the blue WR1 that failed scrutineering. Can't think who that was .

[Ginola]

Originally Posted by Wagon_Si

Have you looked at Andy Forrest's website as it gives some guidance to what is required for certain gains, I used it as a guide when I first got my car.

I have milltek centre resonated section and back box on mine because they are quiet, I have decatted and got RCM manifolds on mine. Changing the manifold and up pipe made it a lot louder. Can't remember what Dave (Ginola) had on his STI, that sound nice, straight exit and looks well built.

I have a Cobra 3" "Track day friendly" system on mine, full 3" turbo back, with custom 4.5" exit (you can specify changes if you order it new) think I paid £550 or there abouts for the lot. system has 2 resonators in the center section one small one large, and a silenced backbox, it is straight through though no bends etc.

Went with track friendly as it means no fuss when visiting various circuits for a bit of fun. and failing noise tests.. it sounds nice on full chat too!.

I believe Revolution also do a full 3" system with no restrictions but that is slip jointed rather than flanges.


Think mine is roughly 96 / 100db