headers:what difference

[Hauntd ca3]

The 2" outlet is on purpose. I planned to make a well under the car to fit in a 2.50" Hooker Aerochamber muffler right after the collector outlet so that the exhaust exits into the muffler with about .5" overlap and can expand and cool with a little bit of a exhaust reversion dam created from the difference in pipe diameter. The exhaust velocity will drop so I will just run 2.5" back to a 2.5" straight through style muffler... preferably a Buddy Club ProSpec, since I've installed them on another car and it sounded quite nice. Problem is all packed mufflers will tend to deteriorate and the sound quality will drop over time, unless it's packing some serious packing. Also with the Hooker Aerochamber muffler installed under the car might increase interior noise.

I also would have considered a 2" SMSP Catalytic Converter overlapping into the Hooker or the 2" collector overlapping into a 2.5" SMSP Cat.
The concern between those two options is that having a proper sized cat may help it flow better past the screen/mesh... where as the wrong size can just screw up everything I'm trying to do. The placement of the cat closer to the engine is partly because I remember reading that hotter gases help the cat work better... not sure if that's true or not.

Note that the large increase in exhaust pipe diameter after the header goes against the view that the exhaust and header should be tuned together to reach a Optimal Exhaust Velocity of 240-260 FPS at a given rpm. I'm settling on the idea that I can get away with just getting the velocity I need from the header and everything else after the header should flow enough CFM to not cause any back pressure.



A word of caution when following the lengths of aftermarket headers IE: DC SPORTS, PACESETTER, LIGHTSPEED, is that they have to be built to fit the stock mounting points or risk losing customers, they are not built with a specific engine build in mind. It's not to say that the stock header lengths are not a good place to start, but it's a fair bet that production cost will mean they are shorter then they should be.



just do a photobucket account and post the links they generate for you.

havnt heard of those aerochamber thingees before.
are they a hollow resonator of some sort?
i think 2 1/2 is bout as big as you'd want without having to go to bigger cams and head work, you'd prob lose hp on a stock motor with an exhaust that size.
i fyou can pull the muffler to bits, repack it with stainless steel wool.
lasts for years but is a touch louder than fiberglass packed ones.
the cat will work better if its closer to the motor but only if you dont cane the crap out the motor.
you do that and the mesh in the cat will melt from getting to hot.
talk to the manufacturer of the cat to find out optimal posi.
i fyou run to big an exhaust, you can go back wards and actually create backpressure.
if you let the gas expand to quickly, it cools to fast and becomes more dense creating a sort of moving gas plug.
get some of that exhaust wrap tape and wrap it right back to the collector or a bit past it.
if you can keep the gas as hot as poss for as long as poss the gas moves faster and reduces bp.
my headers are none of those brands you mentioned.
the company that makes them duz quite a bit of research on he headers it produces so are prob a comprmise between power and torque.
and i had to lose my a/c to get them in
i found they work brilliantly, no drop off in power right to the limiter.
it just keeps pulling then limiter
so i think i have it spot on wit the combo i have

[A20A1]

I agree that the exhaust systems should maintain exhaust velocity till it's out the tail pipe and that 2.00"-2.25" is pretty much optimal for most people on the site without major mods, but I'm trying something different.

I'm testing:
1) Collector venturies
2) (Engine / Engine Exhaust CFM to Exhaust System CFM) based "0" Back Pressure System post I read a while back
3) Interior noise and exhaust sound differences with chambered muffler installed under mid section of the car rather then at the back.

Usually you would test those things individually against a baseline but it's too much work at the moment.

I need the jump in pipe cross section size to allow for a relatively strong and long suction wave A.K.A Scavenging Wave a few inches after 61". This way the header collector is the starting point of that negative wave, where as having the collector connect to a regular exhaust system with no cross sectional change till the muffler or tailpipe, will IMO ruin the tuning I put into the header. I also don't want there to be too little a change in cross section after the header from connecting the collector to a 2" or 2.25" exhaust, because I will end up with a long but weaker return pulse/suction wave. The 2.5" muffler inlet is plenty big, where as running an open header is too big and I risk losing the benefits of a longer return pulse/suction wave even if a shorter suction wave is stronger... and since 2.5" is the inlet size I might as well maintain that and run 2.5" outlet.

[Hauntd ca3]

from what i understand bout tuning lengths, just working on the speed of sound at which the pressure waves travel at i think, could be wrong
the pressure waves change direction at every change in pipe diameter.
so you'd get a pressure wave travelling backwards and forwards up the primary pipe, the idea from what i pick up is to have the length so that at the desired revs the reversion wave thats come back up from the collector gets to the exhaust port just as the valve is opening, that way the pressure wave is just turning to head backout the primary towards the collector as the new one is meeting it helping it drag the exhaust gas out. if am right , you'd try and match all the pressure waves up so that they do that same thing all the way along the whole exhaust.
but i dont know the science behind the gaseous side of the equation .

[A20A1]

Yup, the positive pressure wave starts at the valves and pushes gasses in the same direction, while gas will flow in the opposite direction of a negative suction wave created when the positive wave reaches the first change in diameter and travels up the pipe towards the valves.

[Hauntd ca3]

heres a quick pic of my headers.
nice, simple design that works well

[b20a86lude]

so wat or who makes headers and does the h22 fit gud