Equal length manfiold to unequal
 

What kind of power loss if any would I be looking at here?

Before I go any further, I've got an Impreza GX (2.0 Sport) and I've been umming and aahing with the idea of installing a stainless steel unequal length 4-2-1 exhaust manifold to replace the standard cast-iron equal(ish) one.

Obvious main reason I want to do this is acheive the genuine exhaust burble. However I've had conflicting reports of power LOSS and GAIN from different Sport owners who have installed this.

So, TECHNICALLY would I be losing power by changing the manifold? I'm only putting out 130BHP and really don't want any lower lol

Cheers for any help.

Tom


P.S. I've already been on Imprezasport.net looking for answers but found conflicting reports.

not sure for sports, but i read somewhere that turbo equal lengths can give you around 25ish + bhp extra. But as said, i dont think that would apply for sports

Thats correct and the easiest way to increase power by circa 30bhp... and when you think about it thats alot of horse power for such a simple cheap effective mod, BUT... equal length headers will do the worst thing possible to any scooby...

...you will LOOSE the burble and the scooby will end up sounding more like an evo!

(Altho this is all bases on turbo versions)

My mate had an 03 JDM STi with twin scroll turbo and equal length headers... absolutely NO burble, but I gotta admit it still sounded awsome (but very EVO-like).

It should be running an unequal length header as standard anyway :)

Tony:)

Cheers for the replies lads. Only reason I ask is because I don't know whether to fork out 250 big ones for the sound, especially if I lose a bit of power. What do you think? :)

Your not going to gain much on a NA car anyway, bit of a waste of cash when you can spend it on the brakes and suspension and make the car handle and stop better :)

Tony:)

As Tony says on all standard scoobys (apart from 05 onwards - the newer 2.5's dont have the burble at all) they come up with unequal length headers and thats how you get the burble... but I'm not sure you can get the burble on aspirated non-turbo's??

instead of spending the money on the headers, or suspension, or even brakes... open up the highest interest savings account you can find and start your WRX fund.
once matured and flowing with the deniro, buy a WRX and enjoy the burble to your hearts content! :D

Does a standard turbo subaru from 1997 ish have equal or unequal headers?

un-equal

arent all scoobs except sports, fitted with unequal

all turbo scoobys are fitted with unequal, apart from JDMs with twin scrolls... not sure about sports

Cheers. I just thought they all were but this post confused me a bit. The old Saab 900 turbos have unequal 'zorst headers and they have an awesome burble too :top:

Cheers for all the input lads. I think I'm gonan be sensible and not go along with this idea. Spending £250 for just the noise and losing already terribly limited power just doesn't sound great.

As for ungrading my brakes and suspenion... The brakes more than do the job with the OEM 2 pots with 277mm fronts and 1 pots with 266mm rears, mintex pads and Goodridge stainless steel hoses all round.

I'm also satisifed with the standard suspenion setup as I don't want to sacrifice any ride comfort by lowering. However I am planning on fitting a rear anti-roll bar in the near future, when I get help ordering the right one and fitting it :)

Tom

Do you have std back box, as that will make a difference to the burble..?

The burble has nothing to do with turbo/none turbo, it's purely a result of unequal length exhaust manifolds (headers). I'm not sure if the none turbo cars have equal or not as standard, but I recon they'll be more equal than the turbo cars as they don't need to go up to a turbocharger. Form a purely performance point of view, unequal headers are not a desirable feature (hence jdm car difference) so if I was you I'd stick to whats there, but as I say, an aftermarket BB would help.

The sports have as standard equal length cast iron manifolds. Changing to an unequal length manifold does increase the burble. I know because I did it to my old Sport. Sounded just like a turbo :) And I felt a good power increase, I RR'd it standard at 122bhp at Powerstation. Then after a decat, manifold, and induction kit got 145bhp. So there are some gains to make.

Cheers for that mate, yeah I've got a 2.5" catback with 4" backbox, sounds pretty decent but I want more burble! :norty:


Sounds promising, I guess I'm still 50/50 on whether to do thisor not. If I buy the manifold I'd also replace my current centre centre to a de-catted one but keep the downpipe cat in.

As for someone saying to save for a turbo, I can't get a reasonable insurance quote till I'm 25, I'm 21 now, so a bit pointless at the mo.

Decisions decisions! :cry:

There is no downpipe on the sport...

It goes Manifold, cat 1, cat 2, resonated section, backbox.

Sorry didn't mean downpipe, just meant first cat.

Yeah the unequal ones cause the exhaust gas pulses from both sets of cylinders to pretty much reach the up-pipe at roughly the same time - the burble noise is the shockwave of the pulses 'colliding' with each other.

With equal ones, the exhaust gas pulses line-up behind each other and are evenly spaced - hence the linear 'inline-4 sportsbike wail'-type noise, instead. As said, this is better for performance.

If it's currently running with the cat(s) in place then going full decat, without touching headers should release some power. Of course there's the hassle of MOT's- unless you know someone..;)

The only thing I'd do with headers is maybe port them in the way a lot of turbo guys do. Anything to help gas flow will help.

Other things that are easy/cheap and help the overall performance is to loose as much weight as possible, spare tyre, jack, junk in the boot/glove box..:)

Tom, eventho you got 4 more yrs til your 21... just think of it as sumin nice to save and wait for... slowly put away money anyway in a wrx/sti fund and in 4yrs time you'll of saved a fair bit and you'll really be able to treat yourself when you do hit 25... what a lovely bday present you can give yourself! :luxhello:

As for your sport, def try and pick up sum unequal headers... £250 is a bit steep... you must be able to get sum 2nd hand or flea bay jobbies for cheaper?

Cheers for that mate, it's cool to know exactly what produces that sound we all adore!

Well I'm not up for going completely catless as it's just too much hassle and I wouldn't want to lose to much back pressure. But the plan is if I go along with gettign theu nequal headers, I'll get myself a new decatted SS centre pipe to go with it.

Gotta love the weight saving!

Sound advice mate, cheers for that, and your right. A feq quid put aside each month will make a massive difference when the time comes. :)

Well genuine Borla manifolds go for a little over £300 and the "replicas" are at £250 on eBay, which are better. But I've never come across any second hand jobs which is a shame. Guess I'll have to keep looking!