say you have two headers for a given motor, one has longer primaries and the second has short primaries. Say the long one is 20" and the short one is 8". What will the performance characteristics be like for them?

-Shing

 

Same diameter? They 20" should have more top end hp, and a higher torque peak. The 8" pipe will have more torque at a lower RPM, and less hp at the top end, I think. Don't quote me on that though!

 

I am thinking... does it work like the intake? ie the way the length on intake runner effect the power range... if so I think you'd be right... hmm how some no one makes "variable" length exhaust manifolds?

 

for the same given pipe diameter, longer primaries usually have better low end torque but less high end breathing ability. And the shorter primaries will have better high end breathing power but less low end torque. It has to do w/ the resonance effect. Each combination of diameters and lenghts will resonate at a different rpm. It also has to do w/ the scavanging effects and design of the header. ie... for V8s, 4-into-1 designs are different than tri-Y designs. it similar to the longer piping in the cai. But a better way of looking at it would be the contrast between two large *** Solex 50mm DCOEs compared to two smaller SU carbs on a 4 cylinder. The SUs will have nice low end punch but run out of breath up high. The Solex carbs will have nothing down low but will rev the car until it blows itself up.

 

Long primaries result in tuning at lower rpms. Shorter primaries tune to higher rpms. BUT, diameter plays a huge affect as well. A header with 1-7/8" diam, 20" long primaries will actually tune to roughly the same rpm compared to another with 1.5" diam, 12" primaries.

The collector diameter and physical connection of the primaries also plays a large role...typically, you want the collector to be slightly smaller than the rest of the exhaust system (collector is small but then opens up slightly at the header outlet), but it really depends on the car.

The best header for a VTEC motor with lots of cam timing overlap will have step transitions in the primaries, wherein the tubing steps abruptly from smaller tubing (at the head) to slightly larger tubing (at the collector). This impedes reverse flow during the overlap period (acts as a check valve) and also weakens the reflected shock wave from shoving exhaust gas back into the port at certain rpms. The placement of the steps is also important but I don't know the specifics.

[Edited by Keven97SE on 08-28-2000 at 10:55 AM]

 

this actually isn't for the CRX... it's for the 'Stang.

The headers are 1.625"(diamter I assume). They are the same diameter but one's long and the other is short...

<img src="http://www.macprod.com/macstore/images/tf3895.JPG">

vs

<img src="http://www.macprod.com/macstore/images/TF3845.jpg">

The nice thing about the Long tubes is that I can connect it to the h-pipe and just run a dual exhaust.
<img src="http://www.macprod.com/macstore/images/TF3800.jpg">

This would eleminate the cat, but they make h-pipes with cats or I can just weld two in there.

Does this help in trying to answer the question?

-Shing

 

mustangworld or corral and see what those V6 guys run. I hear you can just bolt on the V8 dual exhaust and gain some nice hp.

 

Dammit, I can't believe they make headers and stuff for friggin V6 Mustangs but nothing for the Maxima...

Those shorty headers I believe are really too short to be effective. You remove the restrictions from the factory manifolds (smooth, good transitions, etc), but you don't get tuning benefits because the primaries are too short (want to tune to too high rpm to work well with the mild V6 cams). I'd think the long primary headers would be the ones you'd want. Check out the Mustang sites for feedback, though.

 

Stuff is too new unfortunately... I think she's be one of the first to try. Although I have a feeling it would make lots of power. First off, if we ran the long tubes and h-pipe, we get ride of the pre cats and main cats. I don't mind lose the pres, but the main ones I am concerned about. So figure we weld in a some generic high(er) flow cats to fix that... any how, what Iam getting at is this set up is supposed to be goot fo 20-30hp at the wheels, this is including a cold air. That mean mean assuming similar drive train lose, maybe a little higher, we are looking at close to 180hp at the wheels on her auto stang. Get aluminum drive shafts, I bet we could see another 3-5hp. 185 for that auto wouldn't be too bad. Get an electronic shift kit to speed up the shifts, I suspect that that stang could knock on 14's, given the fact that 1) it's RWD so will get better launchs, and two, it's RWD and will give better traction.

Hmmmmmmm, then there is the Vortec.

-Shing

 

Good luck Shing! Remember when those guys on Stang.net were talking smack about imports? Well, it turns out that the fastest V6 stang on the board is a 97 V6 5-spd, SC'd with a lot of other mods as well. He was running a 14.6! Rustangs are just plain slow, unless you get a Cobra.

 

They do make headers for the 4th gen. The question is are they worth the extra $$ over a Y pipe. If we only knew that one could buy headers overseas .



Stuff is too new unfortunately... I think she's be one of the first to try. Although I have a feeling it would make lots of power. First off, if we ran the long tubes and h-pipe, we get ride of the pre cats and main cats. I don't mind lose the pres, but the main ones I am concerned about. So figure we weld in a some generic high(er) flow cats to fix that... any how, what Iam getting at is this set up is supposed to be goot fo 20-30hp at the wheels, this is including a cold air. That mean mean assuming similar drive train lose, maybe a little higher, we are looking at close to 180hp at the wheels on her auto stang. Get aluminum drive shafts, I bet we could see another 3-5hp. 185 for that auto wouldn't be too bad. Get an electronic shift kit to speed up the shifts, I suspect that that stang could knock on 14's, given the fact that 1) it's RWD so will get better launchs, and two, it's RWD and will give better traction.

Hmmmmmmm, then there is the Vortec.

-Shing [/QUOTE]

 

Boy Ari, you really pulled this one up from the dregs.......

Emax did buy the Header/Y-pipe combo from down under. There was almost no gain for a N/A car, just as predicted by many.....