Equal or Unequal Headers?

Robert Viehweger · Jan 26, 2012

.. and why please

Scott said the problem with cyl 4 on so many cars are the unequal headers, so why stay unequal?

Grinder34 · Jan 26, 2012

As far as I can see it, the only reason to stay unequal is the sound. Many people associate the subaru with a "boxer rumble." The reason for the rumble is UEL headers, so many people stick to that. The truth is most (all?) of the highest performing factory subarus come with EL headers and have no "rumble." But I dont think the US has ever gotten a factory EL header, so over here people shy away.

From a performance standpoint I dont think there is a single justification for UEL headers.

ZachTTLM · Jan 26, 2012

Its a choice in what you want to have basically.

Unequal length header will allow you to keep the Subaru Boxer rumble sound,

BUT unequal length header is a poor choice for high horsepower when you want to maintain equal EGTs among all cylinders.

The reason for problems on cylinder 4 is because the runner for cylinder 4 is the longest on unequal length headers, this gives you the highest EGT in that runner and on cylinder 4. This is because the hot exhaust gases take longer to get out of the chamber. Cylinder 2 runner is the second longest. Since you are continuously subjecting cylinders 2 and 4 to higher heat than other cylinders it is very common to see various cylinder 4 and cylinder 2 failures in Subarus.

Equal length manifold smoothes exhaust pulses of the Boxer engine, thus changing the exhaust note to smooth vs. the rumble. Some say it makes it sound like a honda or ricy, but I dont think it's really not that bad.

Equal-length header is the best for maintaining equal EGT between all cylinders and delivering a constant, lower-temperature exhaust gas to the turbo. Equal length header is a must have for any higher horsepower Subaru WRX STI.

Hope this helped!

ZachTTLM · Jan 26, 2012

As far as I can see it, the only reason to stay unequal is the sound. Many people associate the subaru with a "boxer rumble." The reason for the rumble is UEL headers, so many people stick to that. The truth is most (all?) of the highest performing factory subarus come with EL headers and have no "rumble." But I dont think the US has ever gotten a factory EL header, so over here people shy away.

From a performance standpoint I dont think there is a single justification for UEL headers.

EL actually is an improvement on performance compared to UEL because of the reasons I posted above

Robert Viehweger · Jan 26, 2012

Interesting, thank you both for the responses! Question becomes, at what hp range do you want to switch to EL?

Grinder34 · Jan 26, 2012

ZachTTLM said:
EL actually is an improvement on performance compared to UEL because of the reasons I posted above[/INDENT]

Did we ever contradict each other?

HolyCrapItsFast · Jan 26, 2012

Also the EL headers promote exhaust scavenging where the velocity of the previous exhaust pulse actually creates a negative pressure down stream and aids the next pulse in line. This doesn't occur throughout the entire rpm range though and not every EL header is created equally. You can find headers that are tuned for mid range, upper mid range or high range but you need to figure out where you want to maximize power and make your decision based on that. The tube size also determines the power range of the header.

So many people make the mistake of thinking that bigger is better. With exhaust that is not at all the case. IMO I don't think there is enough exhaust tuning and research for our cars. Manufacturers are just bending tube without putting physics behind it.

Grinder34 · Jan 26, 2012

^ good point about size. Some people go to huge primaries/secondaries that can actually hurt performance over a smaller header.

The only other thing that hasn't been mentioned is spool time. THEORETICALLY, an UEL header can have a lower volume and therefore pressurize sooner than an EL header, providing you with a slightly earlier turbo spool. I highlight the "theoretically" because I'm pretty sure there are lots of counter-examples of the opposite being true. I'm not citing my sources well, but I think I remember reading that KillerB's header spooled earlier than a factory header everywhere (on the setup they tested).

Anyways for performance, the chain usually goes something like this:
Nominal UEL < R&Ded UEL header < nominal EL header < R&Ded EL header.

ZachTTLM · Jan 27, 2012

Grinder, we never did contridict each other. I was just trying to be as detailed as possible in the explination and used your statement to also help my reasons. You are also correct about the spool time being less on the unequal however this also causes more heat and stress onto the turbo.

sinister · Jan 27, 2012

For a daily driven car, my personal opinion is... stay stock.

There's a reason why the stock collectors are cast iron. They won't crack easily. I've never heard of a stock collector cracking. Almost all aftermarket headers come with the risk of cracking at welds. almost always the weld to fail is on the flange where the collecters meet the heads.

I've got the grimmspeed pnp header+crosspipe combo, and was EASILY able to get 380whp on 21psi with e85.

Robert Viehweger · Jan 27, 2012

Thank you all for the information! So I guess I'm good until I get to about the 350 whp range then.

Still in the low 300's

Grinder34 · Jan 27, 2012

sinister said:
There's a reason why the stock collectors are cast iron. They won't crack easily. I've never heard of a stock collector cracking.

KillerB recently made a post over in iwsti about cracked headers:
http://www.iwsti.com/forums/3471163-post96.html

I think you're probably right that it's less common...but apparently nothing is immune to cracking.

EDIT:
I dont know of any 321 SS headers other than the KillerB ones, but if I had the money those are the ones I'd get--hands down. The 321 was designed to withstand the extra heat. If you wanted to go really crazy you could get Inconel headers.

R3V · Feb 23, 2012

What's everyone's opinion on the Litespeed UEL header? I can post links to info about it if you'd all like. I also know Nameless has a EL header in the works that is aiming to dethrone the KillerB.

Grinder34 · Feb 23, 2012

Cool vid fuji. Anyone know where to find a little more info on that? Material? Release date? Rumors and wild speculation?

R3V · Feb 23, 2012

Ouch. When I get headers, if nameless is out, it will be strongly considered.

Grinder34 · Feb 23, 2012

I've got a 2nd hand set of GPMoto EL headers waiting to go on. I want the powah, don't like UEL as a concept, and dont care about the rumble. Plus i got them cheeeeap.

DierwulfBL · Feb 24, 2012

Im addicted to the rumble and refuse to give it up unless someone makes an EL that gives me 500rpm earlier spool and 25whp extra through the powerband

, it's probably the ricer in me. Also it sounds more like a harley and they seem to be able to get away with loud exhausts so we should be able to as well right? RIIIIGGHHTTTT :-D

R3V · Feb 24, 2012

DierwulfBL said:
Im addicted to the rumble and refuse to give it up unless someone makes an EL that gives me 500rpm earlier spool and 25whp extra through the powerband , it's probably the ricer in me. Also it sounds more like a harley and they seem to be able to get away with loud exhausts so we should be able to as well right? RIIIIGGHHTTTT :-D

My main concern is long term engine efficiency and reliability. EL lends itself to that, UEL does not.

DierwulfBL · Feb 24, 2012

R3V said:
My main concern is long term engine efficiency and reliability. EL lends itself to that, UEL does not.

This is true but at lower power levels the difference isnt much, I just personally prefer my car to sound like a bulldozer over a chainsaw

the boxer rumble was actually one of the reasons I got the sti over the evo :lol:

R3V · Feb 24, 2012

DierwulfBL said:
This is true but at lower power levels the difference isnt much, I just personally prefer my car to sound like a bulldozer over a chainsaw the boxer rumble was actually one of the reasons I got the sti over the evo :lol:

It could be argued that with the stock piston configuration the manifold plays a role in the piston ring failures, but for the most part I agree. I know big power people that still religiously stick to UEL.

Equal or Unequal Headers?

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