[gavinp98]

I have a 2008 wrx with mod list below. with the vf52 setup, should i add on some aftermarket uel or el headers? would they be a wise investment or no? I know if i do purchase them, ill be getting a new 91 tune as well as an e85 tune just not sure if headers are really a bang for the buck. Anyone have aftermarket headers on their subie?

 

[gavinp98]

iag air oil separator

Grimmspeed tmic

Ceramic coated Grimmspeed up pipe

Tial 36mm ewg

Cobb 3port BCS

Cobb SF intake

Gfb recirculating bov

Dw250 fuel pump

1000cc ID injectors

vf52 turbo,

invidia n1 dual exit exhaust,

catless tsudo divorced downpipe,

Gates timing kit,

grimmspeed lightweight pulley,

 

[gavinp98]

and yes it is pro tuned

 

[Gigs]

Yes

Equal length headers will change how the car feels , improve exhaust flow and gives you gains across the power band with no downsides.

This is why subaru changed to them in 2003 in japan for the STi.

 

[gavinp98]

I thought all rubies have unequal length except for anything after 2015. i really do love the sound so how are aftermarket unequal length in terms of gains?

 

[XJman]

Not worth the investment.

If you are replacing the header there is no reason to do anything besides equal length headers. There is a reason almost everything else in the world uses them. Better power, better efficiency, improved response, better exhaust scavenging, exhaust temperatures are stabilized across all cylinders.

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[EJ257]

It really depends. They're not really great bang/buck by themselves. I would not waste my time with a UEL tubular manifold; save your money and stick with OE cast manifold if you want to leave power on the table.

You're looking at $1250 for the KillerB EL manifold, $50 for gaskets, and $500 for calibration. $1800 is quite a bit of money. You could do a turbo upgrade (e.g., Blouch 440XT) for around that price, and get significantly more power in the upper RPMs. The EL manifold will broaden the power curve over the entire RPM band (midrange most impacted), where as the turbo upgrade will make 50+whp more up top and shifts the powerband higher into the RPMs

If you are already planning on getting a recalibration (e.g., going E85/FF), an EL manifold is a great addition to your stock turbo setup, and would be beneficial for future turbo upgrade(s), should you decide in the future.


As for the "sound" being the reason you want to keep your UEL manifold, don't let it be. Your car will sound more like a Porsche than a Subaru, but you won't miss the "rumble" after you see/feel what the new manifold does for you in the powerband. I made the switch 8 years into ownership, and my only regret is that I didn't do it sooner.

 

[racer70]

The theory of equal length headers on a racing engine is that they create a sort of pipe-organ effect that peaks at one rpm (the resonant frequency, determined by the header length and the tailpipe length) and can improve exhaust gas scavenging in the neighborhood of that rpm. You might ask the seller what peak RPM his product is designed for. If you don't get a clear numeric answer, shop elsewhere. if the peak is somewhere in a useful RPM range for you then there might be a small performance effect but it is not going to be some kind of big thrill. IMO they are not nearly as magical as xjman's post would lead you to believe.

A little more info here from kowalski71: https://www.reddit.com/r/AskEngineers/comments/1hqeyo/harmonic_tuning_in_engine_exhaust_system/

When I was younger and more foolish I put headers on a Volvo street (wannabe rally) car with a big valve, ported and polished head. Whether they actually did anything for performance I don't know, but it was only two or three years before the exhaust gas eroded the pipes from the inside. I had an exhaust leak and when I slid under there with a torch to weld it up, I found that the header walls were like tinfoil. Hopeless to repair. So ... bad investment.

From your list, it's obvious that you like to buy stuff for your car. So if you want to buy headers I'd say that's fine. Make sure the flange that mates to the head is really smooth and flat (check with an accurate straight edge) or you will have leaking gaskets at some point.

 

[zax]

The theory of equal length headers on a racing engine is that they create a sort of pipe-organ effect that peaks at one rpm (the resonant frequency, determined by the header length and the tailpipe length) and can improve exhaust gas scavenging in the neighborhood of that rpm. You might ask the seller what peak RPM his product is designed for. If you don't get a clear numeric answer, shop elsewhere. if the peak is somewhere in a useful RPM range for you then there might be a small performance effect but it is not going to be some kind of big thrill. IMO they are not nearly as magical as xjman's post would lead you to believe.

Not really... You're thinking of tuned headers for 2-stroke engines.

ELH are a solid improvement over the entire rev range. It's really backwards compared to your post -- the UELH cause exhaust pulses destructively interfere at certain rpms leading to reduced flow.

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[racer70]

Not really... You're thinking of tuned headers for 2-stroke engines.

Believe what you like. I know nothing about 2-strokes beyond having gone through a chain saw motor once. My experience is with 4- and 8- cylinder racing engines and, with my engine builder, checking/tuning my headers on his dyno. Also an undergraduate degree in physics and a masters in engineering. But, again, believe what you like. I am not here to argue.

 

[EJ257]

Not really... You're thinking of tuned headers for 2-stroke engines.

ELH are a solid improvement over the entire rev range. It's really backwards compared to your post -- the UELH cause exhaust pulses destructively interfere at certain rpms leading to reduced flow.

2011 STI S2 vs S2+UP+EL:

Why is there not power throughout the rev range? Maxed out fuel system.

Believe what you like. I know nothing about 2-strokes beyond having gone through a chain saw motor once. My experience is with 4- and 8- cylinder racing engines and, with my engine builder, checking/tuning my headers on his dyno. Also an undergraduate degree in physics and a masters in engineering. But, again, believe what you like. I am not here to argue.

Are you dealing with N/A or F/I manifolds? Completely different animals.

Yes, an EL manifold that's designed for a 400whp Subaru will be a restriction on one built for 1000whp.

You're dealing with a street car which will likely never even see 500whp in this thread.

 

[XJman]

Engineer and physicist, "pipe organ effect" okie doke.

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[zax]

Believe what you like. I know nothing about 2-strokes beyond having gone through a chain saw motor once. My experience is with 4- and 8- cylinder racing engines and, with my engine builder, checking/tuning my headers on his dyno. Also an undergraduate degree in physics and a masters in engineering. But, again, believe what you like. I am not here to argue.

I will resist the urge to piss on you just this once. Like you, I am an engineer with a physics degree. I respect fact, not belief.

Yes, you are thinking of acoustically tuned headers. Of course these exist and assist with exhaust scavenging improving flow. They are also used almost exclusively for naturally aspirated engines.

A turbo engine, OTOH, is quite different. Instead of an expansion tube like you'd see on a NA motor, the header sits between the head and the turbine. When in full tilt, the manifold pressure can rise to roughly 35 PSI above ambient. As you can imagine, this makes the design strategy different.

UELH were chosen by OEM primarily for packaging reasons and secondarily because of a slight spool advantage. When selecting an ELH, one should match the primary tube diameter to the flow characteristics of the turbo. This is to conserve exhaust gas velocity which is very important when considering transient response. The cardinal mistake novices make is to throw big-diameter primaries on the car expecting a performance jump. In likelihood the opposite will occur.

That said (and directed to your original comment) when comparing properly-matched ELH and UELH, the ELH will offer greater performance across a broader rev range, hands down.

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[gavinp98]

With a turbo 4 cylinder, how beneficial are headers for my car? Ive heard it reduces spool time very minuscule by as little as 300rpm and with my car already having a protune, I'm not even sure if my tuner will throw more timing earlier in the power band (Nor do i want him to). I do know this is a heated debate but if i were to do this, I would definitely be getting the invidia turbo manifold. Im currently making 325whp 360 tq. With an E85 tune and new headers, I would imagine 400+ but thats majority of the e85 doing its job. 400 hp is the most I will put in this car especially since its running oe internals and oe block.

 

[gavinp98]

Ive heard the equal length gives a better spool advantage but not by much.

 

[gavinp98]

Now those gains on the dyno sheet really show a difference. From 3250 to 5000 you can see a huge jump in power. Was the boost increased here? or do the EL really make that much of a difference?

 

[gavinp98]

It would be about 1500$ for me with the headers I want after everything all set and done. I like Invidia's manifold. I was wanting to add a little more oomph in the car without stressing it too much and I know touching the exhaust is usually reliable and full of results. Ive already swapped the td04 for a vf52 and I'm very happy about it. Im only running 16 lbs of boost.

 

[racer70]

I will resist the urge to piss on you just this once. ...

Thank you. I now realize my error: I totally forgot that these little guys are turbocharged. Everything I have ever done has been with normally aspirated engines, buy, build, and race. My wife has had a couple of turbo engines (Audi TT and Mini) but this is my first. So, OP, please ignore my post unless someday you get a normally aspirated engine to play with.

 

[EJ257]

Now those gains on the dyno sheet really show a difference. From 3250 to 5000 you can see a huge jump in power. Was the boost increased here? or do the EL really make that much of a difference?

Less boost, actually.

It would be about 1500$ for me with the headers I want after everything all set and done. I like Invidia's manifold.

I'd recommend going with KillerB over the Invidia/Perrin.

 

[gavinp98]

Now those gains on the dyno sheet really show a difference. From 3250 to 5000 you can see a huge jump in power. Was the boost increased here? or do the EL really make that much of a difference?

Less boost, actually.

It would be about 1500$ for me with the headers I want after everything all set and done. I like Invidia's manifold.

I'd recommend going with KillerB over the Invidia/Perrin.

What about tomei? KillerB are $$$