206.5hp on NA tuned with premium gas. 200hp NA barrier broken. :)

[2point0]

Originally Posted by NemeGuero

Its there in the 2nd post.

TL;DR

[industrial]

Originally Posted by w00t692

There's a few key critical points to making a good header.

1.) equal length!
2.) primary runner length
3.) stepped primary runners (finding the right point to step them)
4.) merge collector angle (divergence)
5.) venturi size and angle of convergence

Both the last 2 affect the rpm range the header works at, but not as much as the length of the primaries does.

longer transitions get the header to work over a broader rpm range.

Equal length isn't the end all be all. Either through superior engineering or serendipity, the Jdl header is making the best power of any header so far. Proper wave scavenging is probably the reason. Equal length in a NA motor is not the end all be all it is in a turbo manifold with a proper twin scroll setup. You want a constant negative pressure differential on the exhaust side of the motor(to prevent reversion) which can only be achieved with UEL. Then there are all the harmonics to deal with. It's not as simple as you think it is and it really shouldn't be dumbed down. It's complex and there is no easy explanation of the voodoo that is exhaust tuning.

[w00t692]

Originally Posted by industrial

Equal length isn't the end all be all. Either through superior engineering or serendipity, the Jdl header is making the best power of any header so far. Proper wave scavenging is probably the reason. Equal length in a NA motor is not the end all be all it is in a turbo manifold with a proper twin scroll setup. You want a constant negative pressure differential on the exhaust side of the motor(to prevent reversion) which can only be achieved with UEL. Then there are all the harmonics to deal with. It's not as simple as you think it is and it really shouldn't be dumbed down. It's complex and there is no easy explanation of the voodoo that is exhaust tuning.

I'm not dumbing it down. Did you know you can put those pieces i mentioned together in any combination in multiple different configurations in multiple different sizes and different venturi entrance and exit sizes... and steps in different spots... and the list goes on?

It's INCREDIBLY complex and you could spend ages finding the right setup.

But i'm sorry, you won't find ANY race car without an equal length header, and there's damn good reasons for that you will find in any book explaining why. But the main one? Testing methodology (explained a bit below). You can't tune a header for a specific rpm range (or broad rpm range) when you make all the piping lengths different.

When you speak of UEL vs EL headers you will ALWAYS be stuck with a million threads and posts turning up before you find anything actually explaining the reasoning behind it. But if you must know? The unequal length header will make some cylinders better at scavenging than others, while others are worse. And how do you know? You don't. The gain as a whole might be better, but it can always be better with an EL header. Scavenging is all about piping length to time your pressure wave to suck in the next cylinders air (valve overlap) with negative pressure to increase VE in an rpm range that you want. This gets so insanely complex when you bring a variable cam angle into play that it could take ages to find the right combo.

You realize that there are aftermarket headers with anti reversion chambers in specific spots to prevent reversion that affects power in specific rpm ranges poorly? On the ones i'm currently thinking of they are there to prevent poor reversion characteristics at high rpms. Otherwise, the pulses are bouncing back at valve overlap events at those specific rpms, resulting in lower volumetric efficiency.

tl;dr: exhaust tuning is SUPER complex and there's no answer to everything, but there's a reason they don't make UEL's when they actually care about making power.

[Coheed]

Why all this talk of reversion in an NA thread? The stock cams aren't going to have overlap values high enough to experience reversion. It would be rare to experience it.

I suppose it could be possible if scavenging really was that terrible, or if the exhaust was poorly engineered.

UEL outperforming an EL is nearly unheard of. Everyone sees EL as the superior because it allows you to get the best scavenging when things are perfectly symmetrical. But as we all know here, an EL can still suffer from scavenging issues if pipe diameter, collector, or bends are not completely ideal.

I'm going to check out the build thread now.

[w00t692]

Coheed: variable cam timing should allow some overlap and to be tunable at that!

This is the beauty of it, there's zero overlap when you have the cams at 0 cam angle so idle and low rpms are smooth and make torque, but once you get to higher rpms you increase those cam angles allowing some overlap to increase horsepower.

[industrial]

While I appreciate a good technical discussion, it's essentially meaningless because we are generally saying the same thing.

I think you are overstating the importance of el vs Uel runners in a header design. Things like the actual runner lengths (which affects velocity, heat, harmonics) and proper merge collectors are far more important than just ensuring all the exhaust pipes are the same length in my opinion.

If all things are the same, el will be better than Uel. But with so many variables this isn't the case at all.

[w00t692]

Originally Posted by industrial

While I appreciate a good technical discussion, it's essentially meaningless because we are generally saying the same thing.

I think you are overstating the importance of el vs Uel runners in a header design. Things like the actual runner lengths (which affects velocity, heat, harmonics) and proper merge collectors are far more important than just ensuring all the exhaust pipes are the same length in my opinion.

If all things are the same, el will be better than Uel. But with so many variables this isn't the case at all.

Essentially, the only reason uel headers exist for this car is ease of installation.

Once you find the proper piping length for the car it doesn't change from cylinder to cylinder. Hence... equal length.

[2point0]

Originally Posted by w00t692

Essentially, the only reason uel headers exist for this car is ease of installation and it sounds awesome.

Fixed that for ya.

[w00t692]

lmao, if you say so.

[bfrank1972]

Originally Posted by 2point0

Fixed that for ya.

Different strokes for sure

[2point0]

Originally Posted by bfrank1972

Different strokes for sure

I hear you there. My previous cars were a WRX and an STi, so I guess I'm a bit biased.

It's good that we don't all like the same things. Otherwise, there'd be no uniqueness.

[w00t692]

[ame="http://www.youtube.com/watch?v=drzwLPYPwXs"]2007 Civic Si Greddy Turbo - YouTube[/ame]

log manifold turbo civic si. Sounds like... what's that?

[industrial]

Originally Posted by w00t692

Essentially, the only reason uel headers exist for this car is ease of installation.

Once you find the proper piping length for the car it doesn't change from cylinder to cylinder. Hence... equal length.

Have you considered that it may not be possible to package ideal length runners given the way an exhaust has to be packaged? El and Uel headers won't differ much in installation unless you are talking about a radical redesign of the engine compartment. At what point do equal pipes become detrimental? When you have to utilize crazy routing schemes with less than ideal radius bends or less than ideal merge angles or longer than nessesary runners?

And Uel sounds much better on a 4 banger. That alone is worth the 1% difference in power between the two.

[jamesm]

Originally Posted by industrial

Have you considered that it may not be possible to package ideal length runners given the way an exhaust has to be packaged? El and Uel headers won't differ much in installation unless you are talking about a radical redesign of the engine compartment. At what point do equal pipes become detrimental? When you have to utilize crazy routing schemes with less than ideal radius bends or less than ideal merge angles or longer than nessesary runners?

And Uel sounds much better on a 4 banger. That alone is worth the 1% difference in power between the two.

that's entirely subjective. if you ask me, i think uel's sound like farty garbage. it's an opinion, and people's differ.

as for the endless uel/el debate, it's really simple: the ideal header design probably has equal length runners, certainly so if we're talking about a turbo manifold. many people have managed to package an equal-length header into the bay, and the 'best power producing' header around by far now is equal length (nameless). uel's also make great power.

really if you're buying a header you're probably staying na, and if that's the case i'd be more concerned with the sound preference, because you're not going to be making much power regardless of what header you buy. s/c guys might put a bit more thought into it, but even then i doubt there's much between them in real life.