UEL vs EL Headers

[peadya100]

I've recently purchased UEL headers, as recommended by MSR.
He led me to believe that UEL was an improvement in top end power and EL is an improvement in mid range power.

Owen just mentioned that it was the other way around?

So can someone please tell me which way it is?

MSR's website has a few paragraphs on UEL vs EL:

Should I upgrade the headers? If so, which type would be best?
The standard headers in your Subaru are a 3-piece unequal length (UEL) type. This is essentially what makes the unmistakable boxer rumble. So if you love the boxer rumble (whoever doesn't is just mad!), stick with the UEL headers. UEL headers work extremely well if you are running a small to medium sized turbocharger. Porting the standard headers slightly also increases turbo spool up and engine response. That being said though, back-to-back testing against equal length (EL) headers showed that although the UEL headers offered slightly more top end power, the EL headers promoted stronger midrange power without compromising top end power too much. However, you do lose the infamous boxer rumble if you decide to run EL headers.

So the verdict is, if you are going to run a small to medium sized turbocharger, stick with the UEL headers. A small to medium turbocharger will spool up quickly with a good turbo-back exhaust system so you won't notice the slight loss of mid-range response when compared to running EL headers. The UEL headers will also promote as much top end power as possible from the small to medium sized turbocharger and you also retain the awesome boxer rumble!

If you are going to run a large sized turbo, EL headers would be recommended to promote quicker spool up for midrange power although you do lose the boxer rumble. The large sized turbocharger with a good turbo-back exhaust system will effectively take care of the slight top end power loss that EL headers tend to have.

[jacks-GTB]

MSR did a back to back on his 2 door...both were ceramic coated...

https://www.facebook.com/16920221647182 ... =3&theater

[peadya100]

Alexei just put me onto that one... MSRs testing definitely backs up his claims.
Weird that other tuners get different results but can only assume that's to do with the brand of headers?

[GONEWALKABOUT]

the common belief is that EL is better for power and spool as well as evening out EGT, which is better for the engine perhaps. Downside is.. well depending on preference, the sound.

Unless you going for raw power and lots of it i wouldnt lose sleep over it, you probably wouldnt have been able to feel the difference without large boost, large turbo and large kw's.
just my $0.01

EDIT: heres a quote i found on a subie forum:Tomei, I believe, did a research project a number years ago that compared an UEL header and their EL header.
Spool was the most noticable difference. Peak boost (I think it was a 35r turbo) came on almost 400 rpms faster
with the EL than the UEL. When tuned for, the UEL made 29whp over the stock exhaust manifold and the EL made
31 whp respectively.

[peadya100]

Yeah that's what makes me think the brand/design has an impact. I've seen a Tomei graph which I assume is that test.
That could be the only reason a very reputable tuner like MSR could get different results.

[GONEWALKABOUT]

from what iv seen physical design between brands of EL and similarly UEL do not differ that much but there must be something else going on. Whether maybe one brand has some how found the mm perfect diameter and it really does matter, who knows.

EDIT:In a rough sense in design:
-primary pipe diamter = rpm of peak torque; smaller diameter, lower torque peak, larger diameter, higher torque peak
-primary pipe length = "lean" of torque curve; short length, high rpm emphasis, long length, low rpm emphasis

[KiDo_Tuning]

It is also dependant on cam timing shape as well as to the result. Higher flow or more header volume affects cam overlap which affects timing and VE

[peadya100]

It is also dependant on cam timing shape as well as to the result. Higher flow or more header volume affects cam overlap which affects timing and VE

Although I know zip about tuning. That makes sense Matt. Different tuners run different timing in different places so it would effect the results.

[dr20t]

Matt is correct so if cam timining wasn't optimised for the el header compared to uel then you won't see gains

But just putting it out there that most aftermarket Subaru headers (psr, kando, tomei, Kobe ) come from the same factory

So header design doesn't come into it unless you're talking about full race or killer b

[peadya100]

I can only assume that in MSRs test that he tuned for both headers... wouldn't be worthwhile otherwise.

But I think it's safe to rule out brands then if they're mostly all the same.

My UEL headers go on in 2 weeks so I guess I'll see soon enough what the difference will be in performance.. be it mid range or peak. Shame it's not the only mod with that tune so I could get an exact sign of where the gains are... which is what started this whole thing in the first place hahaha

The thing is MSR is so pro mid range over peak power it's not funny. So if he recommended the UEL header to me I trust him

[GONEWALKABOUT]

I can only assume that in MSRs test that he tuned for both headers... wouldn't be worthwhile otherwise.

The thing is MSR is so pro mid range over peak power it's not funny. So if he recommended the UEL header to me I trust him

Did he though?

Probably a good thing for majority of people!

[peadya100]

Only he knows for sure... ill ask him in 2 weeks for you.

[dr20t]

I can completely appreciate and understand why Michael says the uel header is better for auto

My personal, untested and purely hypothetical opinion on this is due to the taller gearing in first and second gear of the 5eat compared to a 5mt/6mt, and combined with the way the torque Convertor multiplies load in an auto, that you want the best scavenging for low down torque (I mean 1500-2500rpm range)

The uel will help promote that as the irregular exhaust flow and pulsations in the uel header will help scavenge down low

Its much the same effect as higher exhaust backpressure in an n/a car up to a point of peak torque / airflow as it assists in "bunching" exhaust gasses (for want of a better term) to assist in building volume and exhaust energy (heat) to spool the turbo as compared with a manual

[peadya100]

Man, I really need to learn more about tuning and these things... I struggled to keep up there Mick! Haha

But i trust you so that's making me even more confident about my purchase

[shav]

I cannot add anything to this thread other than I am intrigued and fascinated with the science behind the 2 designs of headers.

I have no interest in changing my UEL headers. I love the sound. Plus im not looking for every poofteeth of a kw. But to read of the differences and learning how best they operate is very educational.

Thanks guys