Decats
 

Hi guys,

Is it mandatory to have a remap when installing a decat pipe?

Erm yup i would defo get a remap .

agree with scotty - with the extra flow, it would be beneficial to have it mapped :ok:

If it don't throw a CEL light, and you don't have induction kit fitted along with other mods and still running a standard ECU. I would say don't bother, as the ECU will pull timing and adjust fuel/air to a degree to compensate. But that's just me and all cars/models are slightly different and some more tolerant to small mods than others.

That said for the extra few ponies/spool/ and agro of decat and recat for MOT, and risk of getting pulled by Plod/Vosa I wouldn't bother with a decat at all any more.

I went for Sports Cat only on my Cobra System - passed the MOT on he Co2 limit - 0.20! so glad I kept it...

Thank god ive got 2 friendly MOT'ers :wedgie:

Me too plus the car was only MOT'd on Saturday so dont have to worry for another 12 months. Just looking into Cobra decats now as Surrey Rolling Road can dyno and set the car up on Friday.

Maybe on a classic.... but I disagree here - the scoob in question is a hatch, and we all know that you want to make sure everything is spot on with the 2.5 in those to save yourself grief further down the road ;)

Is it true the the 2.5's have a "learnable" ECU?

It would be fair to assume the newer the car the newer the ECU therefore the greater R&D. safety margins, and 'cleverness' of the ECU but a non profiteering mapper would be better placed to advise.

But regardless and agree with Steve, if it's a 2.5 with claimed weaker pistons and head gaskets, and to Maximize the benefit of a decat, its probably worth getting it mapped, as it sounds like you are on the slippery slope of modifications and will give you and your mapper a good benchmark for the next round of mods

It will run lean without a map the Ecu can only compensate so much and your asking it to correct after the event lamda says oh you're running lean let me add fuel, you've already run lean to start with,, not to mention at WOT the standard lamda doesn't work properly once on boost.
Have to disagree with robs first post about letting it be and just do it, this worked as stated on the standard map on the classics in part because the standard map was quite rich as a precaution by design. It is however far from ideal.

Spend the money and get a good map done for it. I would also advise not to chase dyno results ;)

as above most new-age cars benefit from a map but the leaner running Hawk and newer Hatch cars run very dangerous once the exhaust has been modified

Decats ordered and remap booked, hopefully i will see noticeable gains

:thumb: You could see 15/18hp gain from just the decat :) I'm not sure if the hatch WRX have cats in the up-pipe but assuming you have removed this already?

let us know how you get on. who is doing the mapping?

Duncan Graham at Racedynamix is doing it. I have been told with the set up and dyno I should see between 280-290bhp. Mods are:

Cosworth panel filter
Invidia N1 Street Exhaust
HKS SSQv4 BoV
Afterburner Catpipe (decat)
Afterburner Downpipe (decat)

Does anyone know what the Hawks 0-60s are with a similar set-up?

5 ish secs with a good launch

Does it already have the hks ssqv or have you not bought it yet?

The BoV has been installed already and been running it without any fuss for weeks

the days of 20bhp from cats alone are long gone due to the lean burn issues i mentioned above

no up-pipe cats, the "pre cat" was only ever fitted to new-age 2.0 WRX 2001-2005 cars

Are you meeting Duncan at Surrey Rolling Road? I live just around the corner and have a Hawk Wrx that Duncan's worked on. Need to pop up and ask him a few questions while he's there.

Give me a shout if you're heading there to meet him mate.

Yea im meeting him at 09:00 I think? I will be leaving Cody tech Park at 08:45 if your going?

Unless you have to have it for the noise.. The car will drive a lot better with the standard re-circ on it, even with mapping if your still using the MAF and standard ECU, by fitting pre map your effectively allowing the car to vent metered air to atmosphere, again throwing fuelling out, talk to Duncan when you see him though I'm sure he can advise better than I can.

I had advice about BoVs by Subaru4You and they told me the only ones that dont cause the engine problems were HKS and Forge. The car was running sweetly at first but last week or so i have been down on power and the exhaust has gone very silent and so im changing the CATs as its got all signs that they are blocked.