Which WRX Impreza Aftermarket Exhaust ?
Discussion
Hi,
I've had a bit of trouble finding some reliable and precise info regarding the best system / setup for my WRX. It's a 2007 Hawkeye model.
I'm considering a Miltek or a Japspeed, but I still have some questions, which hopefully someone can answer.
1: Do I need to change the short "up pipe" between the manifolds and turbo?. I understand this is always a non cat part, will this effect an MOT emissions test if I have a "Sports Cat" fitted instead of a Decat down pipe?.
2: "Sports Cat" - worth the extra expense?. Japspeed do one for £259, which is about £100 more than a non Cat one iirc (when purchased as 1 piece). Miltek more expensive and are a marked increase over a non Cat part. Is it worth getting one if the rest of the system is going to be Decat?.
3: Centre pipe to rear silencer, these seem to be all Decat systems , I've read that 2.5" give better results than a 3" - is this the case?.
If I were to purchase a Japspeed system, it would cost £580 for a system with a Sports Cat downpipe as opposed to £430 for a full decat. Is it a given that with a Sports Cat the car will pass an MOT? - the general consensus is that it might not.
Lastly, Can anyone suggest perhaps a different system which might be worth considering?. Miltek are not cheap, but I suppose you get what you pay for.
Cheers
Pete
I've had a bit of trouble finding some reliable and precise info regarding the best system / setup for my WRX. It's a 2007 Hawkeye model.
I'm considering a Miltek or a Japspeed, but I still have some questions, which hopefully someone can answer.
1: Do I need to change the short "up pipe" between the manifolds and turbo?. I understand this is always a non cat part, will this effect an MOT emissions test if I have a "Sports Cat" fitted instead of a Decat down pipe?.
2: "Sports Cat" - worth the extra expense?. Japspeed do one for £259, which is about £100 more than a non Cat one iirc (when purchased as 1 piece). Miltek more expensive and are a marked increase over a non Cat part. Is it worth getting one if the rest of the system is going to be Decat?.
3: Centre pipe to rear silencer, these seem to be all Decat systems , I've read that 2.5" give better results than a 3" - is this the case?.
If I were to purchase a Japspeed system, it would cost £580 for a system with a Sports Cat downpipe as opposed to £430 for a full decat. Is it a given that with a Sports Cat the car will pass an MOT? - the general consensus is that it might not.
Lastly, Can anyone suggest perhaps a different system which might be worth considering?. Miltek are not cheap, but I suppose you get what you pay for.
Cheers
Pete
I wouldn't bother with a sports cat if there's any risk at all of it failing the MOT, total waste of money as the de-cat is cheaper and offers better performance. My choice would be leave the original cat in.
Unless running crazy power levels a 2.5" centre section is better than a 3" I believe, something to do with throttle response/back pressure perhaps?
I have a Ninja 2 backbox from Scoobyworld with a 2.5" centre de-cat (original downpipe with cat) on my classic and the sound is perfect IMO and the backbox was very good value. They offer it in newage fitment as well I am very sure.
EDIT: Scoobyworld newage cat-back backage is £289.99 with the Ninja 2 backbox and a 2.5" centre de-cat.
Unless running crazy power levels a 2.5" centre section is better than a 3" I believe, something to do with throttle response/back pressure perhaps?
I have a Ninja 2 backbox from Scoobyworld with a 2.5" centre de-cat (original downpipe with cat) on my classic and the sound is perfect IMO and the backbox was very good value. They offer it in newage fitment as well I am very sure.
EDIT: Scoobyworld newage cat-back backage is £289.99 with the Ninja 2 backbox and a 2.5" centre de-cat.
Edited by HonestIago on Friday 20th September 14:45
My Choice for the Exhaust would be by by Hatward and Scott
Sports Backbox, nothing to obtrusive. http://www.haywardandscott.com/subaru/impreza-turb...
Deresonated Centre Section. http://www.haywardandscott.com/subaru/impreza-turb...
2nd Cat Removal Pipe. http://www.haywardandscott.com/subaru/impreza-turb...
The Hayward and scott Systems are Loud when you want them to be but on a motorway cruise they seem to quieten down around 80, not as quiet as the OEM exhaust but does not become so loud you need earplugs.
Removing the 2nd CAT does not affect the MOT. As the optional PPP Pack removes the 2nd CAT.
http://www.youtube.com/watch?v=8tQf5zKQF5k
http://www.youtube.com/watch?v=zPfsWatZ288
Sports Backbox, nothing to obtrusive. http://www.haywardandscott.com/subaru/impreza-turb...
Deresonated Centre Section. http://www.haywardandscott.com/subaru/impreza-turb...
2nd Cat Removal Pipe. http://www.haywardandscott.com/subaru/impreza-turb...
The Hayward and scott Systems are Loud when you want them to be but on a motorway cruise they seem to quieten down around 80, not as quiet as the OEM exhaust but does not become so loud you need earplugs.
Removing the 2nd CAT does not affect the MOT. As the optional PPP Pack removes the 2nd CAT.
http://www.youtube.com/watch?v=8tQf5zKQF5k
http://www.youtube.com/watch?v=zPfsWatZ288
Hi,
Thanks for the advice. Hayward and Scott are fairly local, and the products are high quality by all accounts.
I've asked a few Subaru owners, the general spiel is to firstly to remove the short "up pipe" between turbo and manifolds and replace with a non cat item, keep or replace the downpipe with either an STI unit or a 100 cell sports Cat , and then go with the H & S De res centre and rear, all at 2.5 inch if possible.
Whack in a panel filter and a decent Remap (I was thinking of Race Dynamix or Jolly Green Monster) and it's expected to give around 280 BHP and 400 or so Ft Lbs of torque from the 2.5 WRX Engine.
Am I on the right track or perhaps over estimating the results?. Fwiw I'm aware of the issues with the 2.5 engine, however they seem to be limited to the STI models and not the WRX's apparently.
Cheers,
Pete
Thanks for the advice. Hayward and Scott are fairly local, and the products are high quality by all accounts.
I've asked a few Subaru owners, the general spiel is to firstly to remove the short "up pipe" between turbo and manifolds and replace with a non cat item, keep or replace the downpipe with either an STI unit or a 100 cell sports Cat , and then go with the H & S De res centre and rear, all at 2.5 inch if possible.
Whack in a panel filter and a decent Remap (I was thinking of Race Dynamix or Jolly Green Monster) and it's expected to give around 280 BHP and 400 or so Ft Lbs of torque from the 2.5 WRX Engine.
Am I on the right track or perhaps over estimating the results?. Fwiw I'm aware of the issues with the 2.5 engine, however they seem to be limited to the STI models and not the WRX's apparently.
Cheers,
Pete
Hi Lefty
Yep, I'm probably getting my figures mixed up, I think I got the 400 from Powerstation's dyno graph they publish (http://www.powerstation.org.uk/uk25wrx.pdf), as even though they're a fair distance from me, I was considering going to them for the upgrade (the Miltek nearly swung it for me).
More realistically, Race Dynamix predicts around 350/360 lb ft with a full decat system / filter and around 270hp. I've heard good things about RD and am considering calling him. If you don't mind, what set up are you running? 370/370 must turn the car into a bit of an animal on full chat. Are you on the threshold of needing to run forged pistons etc?.
When doing the above, would you advise changing the Y pipe on the intercooler as per the PPP as well?.
Cheers
Pete
Yep, I'm probably getting my figures mixed up, I think I got the 400 from Powerstation's dyno graph they publish (http://www.powerstation.org.uk/uk25wrx.pdf), as even though they're a fair distance from me, I was considering going to them for the upgrade (the Miltek nearly swung it for me).
More realistically, Race Dynamix predicts around 350/360 lb ft with a full decat system / filter and around 270hp. I've heard good things about RD and am considering calling him. If you don't mind, what set up are you running? 370/370 must turn the car into a bit of an animal on full chat. Are you on the threshold of needing to run forged pistons etc?.
When doing the above, would you advise changing the Y pipe on the intercooler as per the PPP as well?.
Cheers
Pete
texaxile said:
Hi,
Thanks for the advice. Hayward and Scott are fairly local, and the products are high quality by all accounts.
I've asked a few Subaru owners, the general spiel is to firstly to remove the short "up pipe" between turbo and manifolds and replace with a non cat item, keep or replace the downpipe with either an STI unit or a 100 cell sports Cat , and then go with the H & S De res centre and rear, all at 2.5 inch if possible.
Whack in a panel filter and a decent Remap (I was thinking of Race Dynamix or Jolly Green Monster) and it's expected to give around 280 BHP and 400 or so Ft Lbs of torque from the 2.5 WRX Engine.
Am I on the right track or perhaps over estimating the results?. Fwiw I'm aware of the issues with the 2.5 engine, however they seem to be limited to the STI models and not the WRX's apparently.
Cheers,
Pete
If you have a 2.5 WRX 2005 on the up pipe does not have a CAT in it. The CAT in the Up pipe was only 2001-2005 WRX Models with the 2.0 engine. Thanks for the advice. Hayward and Scott are fairly local, and the products are high quality by all accounts.
I've asked a few Subaru owners, the general spiel is to firstly to remove the short "up pipe" between turbo and manifolds and replace with a non cat item, keep or replace the downpipe with either an STI unit or a 100 cell sports Cat , and then go with the H & S De res centre and rear, all at 2.5 inch if possible.
Whack in a panel filter and a decent Remap (I was thinking of Race Dynamix or Jolly Green Monster) and it's expected to give around 280 BHP and 400 or so Ft Lbs of torque from the 2.5 WRX Engine.
Am I on the right track or perhaps over estimating the results?. Fwiw I'm aware of the issues with the 2.5 engine, however they seem to be limited to the STI models and not the WRX's apparently.
Cheers,
Pete
The standard STi cat is the same as the WRX one. If you are going to replace the CAT it needs to be a Prodrive Downpipe as this was a performance CAT fitted as part of the PPP Pack.
you can easily get 270Bhp and 280Lb/Ft from a remap + a Cat back exhaust. you do not need to do anything more to get that amount of power. you may want to consider a decent airfilter + Walbro Fuel Pump + a uprated hose hose connecting the topmount intercooler to the inlet housing.
Remap 500,
Exuast 550 Fitted
Walbro Fuel Pump 70 Fitted
Uprated Panel Airfilter 40
Uprated Hose 40
I modded my own Impreza many years ago have a look at my garage for details.
Edited by ThePlanner on Friday 27th September 20:34
Thanks for the help and advice everyone, I've now got a good idea the setup I want and the results I can expect. In terms of "bang for the buck" I'm surprised at what just over a grand or so can achieve. Once I've finished the Lancer Turbo, sorting out the Scooby is next on the list.
Cheers again,
Pete
Cheers again,
Pete
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