Exhaust advise

[Sirspidey]

Hi all I have a 2005 wrx. It's got a prodrive exhaust, but as far as I know not the complete ppp (still trying to find that out) , but it was at 250bhp before I remapped it, so I guess it could be the ppp, but I have no certificate to prove it.

I've changed the panel filter to a cosworth one and had it remapped and is now at 285hp. It's my daily runner, so I'm not looking to get anymore hp as I think I'm at the max for the car, but if the exhaust needed replacing what should I go for? If I was to go up to 3" would I need to remap again? Would this push the hp to high for the gearbox etc?

Many thanks

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[kershaw-330s]

A remap would be recommended to maximise any gains you may get but from what I'm aware your good for about 330lbft I'm not sure maybe more , on the factory 5 speed I don't see an exhaust pushing you over that , also your tuner should be able to tune appropriately within the tolerances of the gear box

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[Sirspidey]

Ok thanks that's good to know. I thought the limit for the gearbox was around 290.

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[Tidgy]

Alot depends on mechanical sympathy. i mullered 3rd gear in my old classic at 280ftlb, but was on the mountain pass on the isle of mann hahaha, its torque that kills box's rather than bhp.

I ran my type r 5 speed at 330bhp/380ftlb but was only for about 4k miles and i knew it was being pushed so no hard launches. As said 330-350ftlb is typically as far as you'd would push a 5 speed, only exception being a hawk 5 speed, for some reason they seem to be taking alot more punishment than others. I ran 400/420 on one for about 14k miles with no problems and know a few that have been run over 450ftlb without problems.

 

[Sirspidey]

Sounds good to me. Mine is 285 on both bhp and torque. I'm. It looking for a 400hp car, 300 is more than enough for where I live. Most of the road around here are small A roads, mostly B roads and unclassified roads. The car is very quick for here. I can hardly use all the power now lol. But 300hp might be a way to go ;-). Anything else I could do to push it over 300?

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[Tidgy]

turbo is gonna be your limiting factor no mater what you do I'm afraid.

[Scooby1972]

2.5 inchpipework is more recommend unless going over 350 bhp as gives more low down torque v35 turbo and a map should make a reliable 320 330 lts if you do a lot of heavy launches and are not very sympathetic the gearbox can go bang on a standard car😎😎

[Scoobyghost]

I have a 3" turbo back decat and made 280ft-lb on a 2.0 TD04. not sure having a 2.5" would give more torque.

[Sirspidey]

Thanks for all the advice. I will leave it as it is for the mo. If exhaust, turbo etc needs replacing, maybe I'll do upgrades then. I'm haven't got thousands to spend. Very happy with what I have, was just getting prepared for any changes that have to be done.

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[kershaw-330s]

I have a 3" turbo back decat and made 280ft-lb on a 2.0 TD04. not sure having a 2.5" would give more torque.

Yes I second that I'm not convinced a 2.5 would produce more torque on a turbo car the less back pressure, the quicker the turbo will spool quicker therefore producing more lowdown torque

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[Scooby1972]

When i got my exhaust i did a lot of Google and phoning specialist and the majority recommended 2.5 over 3 inch bore piping there answer was 3 inch loses to much back pressure unless running high power ...i,m not saying 3 inch is wrong and 2.5 is right its just what i learnt,if you google it you will see thats the feeling regarding subaru,s among the gurus😎in reality theres probabley no difference your happy with 3 i,m happy with 2.5 and life goes on 😂😂

[kershaw-330s]

Haha yes life goes on . I'm running a 3 inch front half with a standard 2.5 centre section and prodrive back box would be interesting to compare the readings when I eventually get a 3" lol

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[savage bulldogs]

A friend of mine had a 3" unbranded exhaust on his 98 wrx and kept getting low 200flb torque figures once mapped .

Went back to 2.5 h&s cat back.... 240 flbs but did drop 7 hp to end up with 265hp instead of 272 hp with the 3" .

From what I've researched a good branded 2.5" exhaust isn't restrictive on spool untill 350hp ish and some . I think it was "engine tuner" or "Harvey (rip) did a dyno test and found that 2.5" didn't restrict hp @ just over the 400 mark .

[Sirspidey]

Old thread, but one quick question, if I decided to change to 3" cat back, I assume that it would fit into the standard 2.5" cat?

[stants]

Not unless it was tapered to fit 2.5

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[Sirspidey]

Thanks

[wrxstandard]

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[wrxstandard]

Will this 3' fit on a 2.5 decat without a 3'decat...some seller on eBay telling me a story...kinda confused

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[wrxstandard]

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[stants]

That cobra system looks like 3" all the way through,

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[stants]

That's a 3" cobra dp to midsection so I doubt very much if it will fit on a 2.5

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[kershaw-330s]

The bolt holes will line up and you may just need to buy a reducer or get inventive with some putty

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[wrxstandard]

Is there any power gain difference from a 2.5' cat-back setup to a 3' inch catback?

I got the ninja 2 back box (2.5) ordered but saw this on eBay. Might have to get a 2.5 centre pipe with no res.

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[Sandals]

44 minutes ago, wrxstandard said:

Is there any power gain difference from a 2.5' cat-back setup to a 3' inch catback?

I got the ninja 2 back box (2.5) ordered but saw this on ebay. Might have to get a 2.5 centre pipe with no res.

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I doubt it since the cats are the most restrictive part... if it's decat, probably a slight power increase

[Scoobyghost]

I managed to fit my 3" centre onto the standard cat before going decat. Wasn't the best fit and only just managed to seal with gasket. Was only temp for me so wasn't worried.