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Will a turbo back exhaust with sports cat need a remap?


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As the title says, I have a down pipe with sports cat to fit (I already have a cat back fitted), my main worry is will it over boost and damage the engine if I don't get it remapped. I know it's advisable if fitting a full de-cat, but not sure about high flow cat.

Thanks for any advice, its greatly appreciated

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What year /model is it ? 

Think the classics tend to run safer than newage, with a few minor mods .

As my v3 UK ran fine with a sports cat and cat back for 10k or so , until I got it mapped .

But you can never be 100% sure what's going on with un mapped mods, until its dyno health checked .

If you need a new cat and want to buy a aftermarket sports cat ,as its probably cheaper than a new subaru one ?

Then I'd say fit the sports cat and get a dyno health check asap .

If you want to just fit a sports cat to get "gains" I'd say buy it and wait to fit it until you have the money to get it mapped in .

As although the ECU will adjust the map a little bit (learn) it won't add timing and change fuelling for more power . It will Just add fuel (drown power) and pull timing to lessen the chance of knock /detonation,  to "try" and stop the engine eating itself if it detects something dangerous and outside the oe map parameters. 

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Thanks for both reply's

Sorry should of said it's a 07 WRX Hawkeye.

Everything's fine with the cat, the down pipe and sports cat where a bargin off eBay, only paid £77. Had been looking at a Cobra one at £430 so just bought it on impulse really.


I've only had the Hawkeye 9 months, I am planning on getting a remap done but was thinking after a couple of MOT's, get a feel for the car first and root out any niggles if there are any. Not really wanting any gains, guessing any would be negligible anyway, as my insurer doesn't even charge for changes to the exhaust, another reason I bought it.

Bottom line is, if I fitted it it'd have to go on a dyno/rolling road, Can anyone recommend one in west Yorkshire, only 4WD one seems to be RS tuning in Leeds.

If I wait to fit it, whats the best way to store the downpipe for 18 months?

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If the car is standard I would recommend a remap that is bespoke to your motor (not a £30 ECU flash) anyway as there are midrange gains and fuel economy (only a couple of mpg but every little helps) to be had. 

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My Hawkeye is completely standard bar panel filter, AOS, and big brake Brembo front calipers, and a back box. Mapping is worth every penny. Mine went from 227 to 269 bhp and the difference is very noticable. The torque gained 90 ft lbs at its peak and now pulls like a train compared to stock. 2.5 engine responds quite well to map due to the extra torque. As for mpg i managed 282 miles on 50.28 liters (full tank) which works out at just shy of 25mpg. 240 miles were 70+mph (u know what i mean by +) motorway speeds, put it this way i did worry about my MPG on this journey. Rest was town driving which I know drops below 25.

Cost me just over £400. Your hardest part is finding the correct mapper. I used Race dynamics and i know his name is mud with some people. I had no problem with him at all. It is used daily as my only car and has done approx 12k since without any issues. 

If you look up any mapper you will find horror stories, blow motors, mapping with faulty sensors, blah blah blah. There is some very damning evidence against many so called Subaru specialists and the main dealers are a joke in my experience. Mind you my car only had 36k (47K now) on the clock 3 years ago when it was mapped so car was mint. I also have some mechanical sympathy, and I would hazard a guess some of these horror stories are down to idiot owners. Knowing what I know now I would go with a mapper that did both rolling road and real road mapping.

Map it you will not regret it.

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