Headers Long tube vs Short vs Stock

Armhunter

Just thought some might want to know.

Headers

theDreamer

End of the day, LTH > all still, not very shocked by the results.
I think the main thing is how poor the aftermarket short headers did with very little gain showing the quality and improvement OEM manifolds are today.

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Armhunter

I take it though.. Since they eliminate the Cats, they are illegal? At least in CA.. right?

theDreamer

Correct, LTH by themselves are illegal in some states.
Now you can add a CAT to the system and generate a legal exhaust system. Fast Intentions has created a LTH+CAT system for those who need a legal system.

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MicntaeG35

I want to revive this thread because I'm curious on something. I've done a little searching and can't really find an answer (unless I'm missing something). I want to know what the results are for these 2 combos. LTH with a true dual exhaust vs Shorties with ART pipes plus true dual. I know some combos offer more high end power > low end and vice versa. So can any one shine a little light on this subject?

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Rusty

FI LTH's, 12" resonators, FI CBE, Stillen G3 intakes, port matched intakes and tune gave me 334hp.

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Jordo!

As I understand it: All else being equal, maximum torque/power is determined by the diameter of the runners; where you see those values produced in the rev range is determined by the length of the runners (typically, longer = peak lower, shorter = peak higher).

A good merge collector will make all the difference for scavenging.

Also note that diameter of piping requires a bit of a compromise between low speed and high speed power -- gasses slow down when going through a wide opening relative to a narrow one, but the volume of gas expelled will be greater at WOT than at partial throttle...

On a NA DD this usually means leaning towards narrower diameters (or, put another way, as wide as possible without sacrificing too much low speed torque), whereas a drag car (especially FI and most especially if turbo FI) should probably run the widest piping it can without losing peak power, even at the cost of some low speed grunt.

Anyway, all the LTH's should all be (theoretically, anyway) shifting peak torque range down and bumping the peak value by virtue of diameter of the primaries. Its a balancing act between the change in increased diameter and the change in the increased length of the primaries, which (again, theoretically) should be responsible for the overall peak gain.

Design of merge collectors, smoothness of transitions, and other design-related resonance factors will probably account for any other differences you see, such as evidence of greater or poorer scavenging and bumps or dips in torque at various points.

All of this can be further adjusted by playing with intake set-up and of course valve timing and lift.

I might be able to shed some light -- see here to compare and contrast highly similar set-ups, TP's vs. LTH:

Here is a comparison between my 2010 370Z with resonated TP's and Nismo weldina (Y-pipe version) + OEM headers vs. my 2011 370Z with PPE LTH + Nismo take off (H-pipe version). Both runs are under nearly identical ambient conditions and both have K&N panel filters plus the smooth tubes and a tune.

Because these are technically two different vehicles (although, of course, same engine model and on the same exact dyno...), these results should be interpreted with caution -- but I think are informative, nonetheless.




Much more detail to be found here: Proven Power Dyno Database Thread


Tentative conclusion: LTH is far superior up top, presumably due to wider primaries, but possibly a bit inferior down low, as compared to OEM headers + TP's.

On LTH's, primary length and scavenging effects from collector design are most likely what keeps flow from slowing down too much due to the wider primaries at low speed.

If the momentum headers are wider diameter shorties, that plus TP's might be an even better combo for gains throughout the rev range, but again, things like the intake set-up, rest of exhaust, and tune will affect things too. It's all a bit of a juggling act and compromises are unavoidable (especially where there are space constraints -- its all still gotta fit).

I know of no clear back to backs with different LTH's or shorty headers with everything else being approximately equal.

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MicntaeG35

Wow I couldn't have asked for a better explanation! It all makes sense now. I'm just not quite sure what I want though. Do I want more power up top or down low? Tough question ha but I think I might try to do a motordyne or FI exhaust with motordyne test pipes and shorties to see what kind of results it might bring

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Jordo!

Frankly, I think its really a matter of cost more than anything.

Having had both combos, I am much happier with the performance characteristics of the LTH than the OEM headers + TP combo, but TP's tend to be way less expensive than headers and much easier/cheaper to install/have installed.

Bang for the buck, TP's all the way. Just make sure you get ones that are resonated...

As to headers, I think the LTH's tend to overall perform better, but again balancing primary diameter with length and also effective scavenging is tricky, so its hard to say without knowing all the measurements, seeing dynos for each, and comparing across headers. Likewise, a set of headers with really smooth transitions into a nice collector will make a big difference.

I know there was quite a buzz for a while over the momentum headers, which, I believe, were shorties, but I think the folks boasting the best gains also had a port and polished IM, larger TB's, etc. so it wasn't simply a matter of bolting short vs long tube headers on, re-tuning, and calling it a day -- there was considerable tweaking on the intake side as well.

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