Equal length headers? myth or truth... - Tilted Forum Project Discussion Community

animal909 · 10-12-2004, 02:54 AM

anyone care to expand?

merkerguitars · 10-12-2004, 07:48 AM

Well they do create horse power by helping an engine breath better...what else did you want to know about them?

Scooby · 10-12-2004, 08:04 AM

I think he wants to know, if it's better, if the pipes of a header are equal in lenght or not.

My friend and I were compareing two different headers on ours civics. We both have the same cars (Civic SiR). We both have the same mods. CAI, stainless 60 cm exhaust from header till rear muffler, just headers are different. My friend's car also has strange voice. Like subaru impreza (i'm not kidding). He also has 5 HP more on dyno. We were wondering where this 5 HP are coming from. We did't find anything obvious. At last we decided to mesure headers lenght. The second and the third pipe of his header were longer for about 2 mm.

I'm not 100% that this is the reason for aditional 5 HP but mybe it is.

BadNick · 10-12-2004, 08:09 AM

There was an interesting comparison test of headers in a recent issue of HotRod Magazine comparing engines running open headers, then into full exhaust, with and without collectors, with and without collector extensions. I don't specifically recall this article dealing with equal length vs non but that would be something I'd look for at the magazine's website. Here's a link that I saved that also mentions header issues: http://www.vetteguru.com/mods/headers/

waltert · 10-12-2004, 08:38 AM

about you SIR
each engine from the factory will have slightly different power characteristics. do you have the same wheels and tires, etc(will make a difference on an inertial dyno)? was it dynoed at the same place on the same day? most dynos arent really all that accurate anyway.

burnsstainless.com also has a highly detailed article on the principles of header construction.

unequal primaries will basically cause an individual cylinders horsepower characteristics to be different from its neighbors. think about how often you see a car with intake runners that vary in length from cylinders 1-4. I have never seen one.

Scooby · 10-12-2004, 08:46 AM

You mybe right. I said i'm not 100%.

What about sound? Can difference in lenghts make different sound?

I read somewhere that subaru impreza has original header with different lenghts. And because of that it has such a unique sound.

animal909 · 10-12-2004, 12:52 PM

well on my maxima forums everyone is enamored by the hotshot and catman headers which are equal length. But on my friends bimmer forums, which btw are a lot more powerful than my maxima, say that equal length is a myth when creating more horsepower.

mighty mouse · 10-12-2004, 08:11 PM

Its true! Equal length headers when properly tuned to the engine will make more peak power.

However, and its a big however. In a car that needs to move around the rev range(like a street engine) unequal length headers can actually produce better acceleration as they tend to "spread" the power envelope.

Basically, unless you have a dire need for that one or two horses, don't worry about it. If you are really after that last enth degree tune the headers to the intake and ram that shiat home.

Exhaust tuning can actually produce more negative pressure at the intake valve than the piston moving down the bore on its own......very very interesting stuff really.

10-12-2004, 02:54 AM	#1 (permalink)
animal909 Crazy	Equal length headers? myth or truth... anyone care to expand?

10-12-2004, 07:48 AM	#2 (permalink)
merkerguitars Buffering......... Location: Wisconsin...	Well they do create horse power by helping an engine breath better...what else did you want to know about them? __________________ Donate now! Ask me How! Please use the search function it is your friend. Look at my mustang please feel free to comment! http://www.tfproject.org/tfp/showthread.php?t=26985

10-12-2004, 08:04 AM	#3 (permalink)
Scooby Upright Location: Ljubjana, Slovenia, Europe	I think he wants to know, if it's better, if the pipes of a header are equal in lenght or not. My friend and I were compareing two different headers on ours civics. We both have the same cars (Civic SiR). We both have the same mods. CAI, stainless 60 cm exhaust from header till rear muffler, just headers are different. My friend's car also has strange voice. Like subaru impreza (i'm not kidding). He also has 5 HP more on dyno. We were wondering where this 5 HP are coming from. We did't find anything obvious. At last we decided to mesure headers lenght. The second and the third pipe of his header were longer for about 2 mm. I'm not 100% that this is the reason for aditional 5 HP but mybe it is. __________________ "Pedal To The Metal!"

10-12-2004, 08:46 AM	#6 (permalink)
Scooby Upright Location: Ljubjana, Slovenia, Europe	You mybe right. I said i'm not 100%. What about sound? Can difference in lenghts make different sound? I read somewhere that subaru impreza has original header with different lenghts. And because of that it has such a unique sound. __________________ "Pedal To The Metal!"

10-12-2004, 08:09 AM	#4 (permalink)
BadNick Riding the Ocean Spray Location: S.E. PA in U Sofa	There was an interesting comparison test of headers in a recent issue of HotRod Magazine comparing engines running open headers, then into full exhaust, with and without collectors, with and without collector extensions. I don't specifically recall this article dealing with equal length vs non but that would be something I'd look for at the magazine's website. Here's a link that I saved that also mentions header issues: http://www.vetteguru.com/mods/headers/

10-12-2004, 08:38 AM	#5 (permalink)
waltert Insane	about you SIR each engine from the factory will have slightly different power characteristics. do you have the same wheels and tires, etc(will make a difference on an inertial dyno)? was it dynoed at the same place on the same day? most dynos arent really all that accurate anyway. burnsstainless.com also has a highly detailed article on the principles of header construction. unequal primaries will basically cause an individual cylinders horsepower characteristics to be different from its neighbors. think about how often you see a car with intake runners that vary in length from cylinders 1-4. I have never seen one.

10-12-2004, 12:52 PM	#7 (permalink)
animal909 Crazy	well on my maxima forums everyone is enamored by the hotshot and catman headers which are equal length. But on my friends bimmer forums, which btw are a lot more powerful than my maxima, say that equal length is a myth when creating more horsepower.

10-12-2004, 08:11 PM	#8 (permalink)
mighty mouse Crazy	Its true! Equal length headers when properly tuned to the engine will make more peak power. However, and its a big however. In a car that needs to move around the rev range(like a street engine) unequal length headers can actually produce better acceleration as they tend to "spread" the power envelope. Basically, unless you have a dire need for that one or two horses, don't worry about it. If you are really after that last enth degree tune the headers to the intake and ram that shiat home. Exhaust tuning can actually produce more negative pressure at the intake valve than the piston moving down the bore on its own......very very interesting stuff really.