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Old 05-05-2000, 01:22 PM   #1
Catfish
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Member#: 1322
Join Date: Apr 2000
Location: Silicon Valley
Vehicle:
2000 2.5RS Sedan
72 Datsun 240Z

Question Aren't Header's supposed to be equal length??

I've seen several pics of the Borla headers, and from my limited view, it appears they are of unequal length. Is it just me or is this the case?




I've always thought the reason for headers was to create equal length primaries for improved exhaust flow and scavenging. If one side is longer than the other, how is this possible?

I just don't get it, can someone please enlighten me?

Dave
'00 2.5RS Sedan
'72 Datsun 240Z w/ equal length headers
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Old 05-05-2000, 01:49 PM   #2
8Complex

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Post

Maybe the long side is exactly 1.25 liters larger in volume? Nope, definetly not. Look at the left side of that... they are definetly different lengths, by far. They do look much more free-flowing then stock though, I must admit.
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Old 05-05-2000, 02:30 PM   #3
jhuang76
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Royal Blue Pearl

Lightbulb

Here is what KK posted in the "backfire" post which turned out not to be backfiring but rather, a "poof" sound.

Guys...the reason why the exhaust are making "poof" sounds when pedals are let go..
this because the headers aren't equal length..when gas pedal released, the right hand side exhaust mainfold's gas hit the gas on the left...therefore "poof" it sounds...
this is no big deal...

So I guess if you made the headers all the same length, then you wouldn't get the "poof" problem.
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Old 05-05-2000, 03:04 PM   #4
Catfish
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72 Datsun 240Z

Post

I guess I'm not seeing things then. It sure seems strange to me, that someone would put forth effort to build something that isn't right. What's even stranger, is that it's a big name company with a reputation and resources to do a good job, and it's totally screwed up. Shame on them for passing that off as a header. How in the world can unequal lengths be of a benefit? The stock system may be restrictive, but at least it makes some sense.

Besides, for $450+shipping, I can build my own custom headers, that are properly bent and sized. There are many race shops that build custom headers all the time, and should be able to produce a real nice set. It doesn't seem like the Subaru should be very difficult anyway, especially since it's a flat 4. You should see the headers on my straight 6 in the Datsun 240Z. Now that's a tricky bit of bending and welding. Just by looking at it, you can tell some actual thought went into it.



Dave
'00 2.5RS Sedan
'72 Datsun 240Z (w/ "real" headers)
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Old 05-05-2000, 03:36 PM   #5
AaronB
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Wink

Either a lot of thought, or those were the pieces they had leftover from a different project

I thought there was a vendor that made equal length headers for our car...although maybe I am getting confused again
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Old 05-05-2000, 06:25 PM   #6
cOz
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Dark Green

Post

What you guys are looking for is here www.racebreed.com/sti03a.htm (click on air flow) They are made by sims I think. I suppose if you put in a lagacy 2.2t crossmember you could use them on the RS. Well anyway its well worth a look racebreeds site rocks anyway.

cOz

Oh yeah a turbo to plug them into probably would also help!

[This message has been edited by cOz (edited May 05, 2000).]

[This message has been edited by cOz (edited May 05, 2000).]
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Old 05-05-2000, 06:31 PM   #7
Joel Gat, 1.8L
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Post

Hello,

Folks, there are two ways of designing good headers. Equal length and tuned length. Tuned length headers are designed so that the exhaust pulses reach the junction point at the right time to help with scavenging. The whole point to equal length is that you get cylinders on one bank firing, then the other bank, then the first bank, etc. You get pulses of exhaust running down the headers and they reach the junction one after the other, so the vacuum behind each high pressure pulse pulls the next pulse faster. With tuned length, you get the exact same effect except for the first couple rotations of the engine (ie during startup).

Of course, tuned length are better for a specific range of rpms, while equal length are better for a huge range of rpms. The problem with a flat-four engine design is that equal length headers would have to come to a meet either in the middle (tranny in the way), or on the side. On the side means one side must have very long header tubes. The other side will have shorter ones, OR will have to have a huge spaghetti mess of tubes to give it the length.

Joel
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Old 05-05-2000, 06:48 PM   #8
Ver.III
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Thumbs up

Hey, that turbo header is like the one I have except mine is made by Maxim.
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