Cobra Exhaust - Impreza STi

Enfield

Enfield

Enfield

Soldato
Joined
8 Nov 2003
Posts
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UK
Hi All,

I've been looking to increase the power of my 2003 Subaru Impreza WRX STi Type UK (and breathe). I've had it over two years now and it has been pretty much standard.

Currently, it has the following installed:

SuperPro poly bush kit
BC BR Coilovers (lowered~ -20mm)
Front & rear strut braces
Godspeed grooved discs and kevlar pads f&r
Goodrige braided brake hose
HEL braided clutch line
Walbro 255lph fuel pump
Vredestein Ultra Sessenta's
K&N panel filter

I think that's everything, I am going to uprate the anti-roll bars too at some point, followed by the clutch and new and possible uprated engine/gearbox mounts, but I feel it's time for more power...

Power wise it's standard. I'm looking at getting an ECUTek remap and full 3" exhaust system from turbo back.

I could go fully de-cat but that would mean swapping out the full exhaust system as the standard diameter is 2.5". So my likely option is to go for a system with a sports cat.

I've got a quote for a Roger Clark Motorsport system for £1360 with centre silencer, but I have found a system from Cobra for £730...

Is RCM really worth it, or should I go for a Cobra system? Anyone had any experience of them?
 
No the RCM kit is not worth the extra.. not that much extra! £1360 for a turbo back system is crazy..

Not sure what the Hayward and Scott prices are like these days so worth checking them out.

Nothing wrong with the Cobra system mind you. I ran their SB04 3" track day system on my old one for track days.
 
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Surely for that kind of money you can get a full titanium turbo back and still have enough left over to buy the MOT man a crate of beer each year for the remainder of the car ownership?
 
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H&S systems were £950 for a turbo back sports cat system five years ago, so I would imagine that they are a bit more than that now.

However...

Since you are only tuning up with the existing turbo, not replacing it with a bigger one, there's no real performance reason to change the one you have. If you really want to, then you could just replace the cat pipe (which has the second cat) with a straight through pipe, still at 2.5 inches. The remap should get you to about 330bhp on the standard exhaust, and fitting a full 3 inch system might just add 10-15bhp to that if you are lucky: the limiting factor in your car currently is the turbo, not the exhaust. Fitting the Cobra because you like the noise is one thing, but don't expect any noticeable performance gain.

However (again)...

If you plan on replacing the turbo later, then you might as well do the exhaust now. It will make getting 400bhp and up a little easier later. Although still not an absolute requirement.
 
I was thinking going for 3" to make it future proof, i.e. if I wanted to change the turbo. I'm not really after noise which is why I'm looking at the resonated system. Though I wouldn't mind a little, it's rather quiet...apart from the turbo. I removed the intake resonator a while back and I don't remember it being as loud as it is.

I've got also got in my basket:

SWRD intake hose
SWRD intercooler hose kit

All in all, it still comes to less than the RCM system.

Forgot to add that I have Whiteline anti-lift kit too.
 
If you are just after more power, but not after noise then don't bother doing a turbo back. As Meridian has said, removal of the 2nd cat (Still fine for MOT purposes) and replacing the Up pipe along with a map is the best course of action.

The above two will be enough to be making ~330bhp and will help with spool too
 
STIs don't have a cat on the up pipe, unlike (IIRC) WRXs, so there's no need to remove the up-pipe.

I forgot another possibility: replace the downpipe and cat pipe with a 3" sports cat down pipe and tapered 3" -> 2.5" plain cat pipe. What little restriction there is in that system is in the down pipe and the two cats. This would give you one single (sports) cat only, and get rid of the main restriction. You'd keep the original centre section and backbox, so it would be no louder. It would be good for at least 380bhp, and should only cost about £500. I know Hayward and Scott used to do this an an option.

Hose kits don't do anything unless you've already uprated the turbo. And they don't do much then.

If you are certain of getting a new turbo later, then yes, get a 3" system. Personally I'd get a H&S system (wait, I already did) or the Milsport pulsed one. Do the suspension bits, but then save all the rest of your money for a turbo. Factor in that you might need injectors as well at that point: you won't know until the turbo is fitted. In theory a good set of balanced factory injectors is fine; in practice, not so much. If you get a replacement turbo I'd also want a new intake. The default one is fine for anything you can do with the standard one turbo, but not for an uprated one.
 
No it won't. And they come with a life time warranty I believe.

However, some would argue that it may not perform as well as say the Hayward and Scott.
 
Enfield said:
That's not what I was getting at. The Cobra full system with sports cat is £730... will it last about a year and fall apart? Prices for exhausts confuse me!
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Sorry. My knowledge of Cobra exhausts is that they are OK, but they are aimed at the barry-boy market. H&S makes system for Porsches, amongst others. My H&S system is now five years old, and in perfect condition. That said, I've heard stories of them being slightly out of spec dimension-wise, making them hard to fit. Mine wasn't, I should point out.
 
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