Here is your formula ( you wanted it !!!):
you must at the very least consider exhaust gas temp, speed of energy
wave, exhaust duration and rpm. Some formulas calculate a long pipe length
because they are based on a different energy wave.
Waves resonate in the pipe. Retarded ignition, timing and conditions
increase exhaust gas temps, which cause the energy wave to travel faster. as
a result the formulas make certain assumptions, that may not be valid for
every engine combination.
L= 1380 x ex ,divided by rpm. this results in a very long
header. works well with large diameter stepped headers
L = 950 x ex divided by rpm. this results in a shorter header
because it is factored against a different pulse.
Where:
L = header length in inches
ex = 180 plus cam's exhaust valves opening BBDC
rpm = rpm in the middle of the power band.
I am sure there are other books with this inf.. I use the V- twin tuners
handbook. it has three sections, race math, reference tables, and conversion
factors. Any motorcycle shop that deals with Biker's Choice can order it.
Also most of the race math can be done on the Accelerator 3 program, which
also allows you to "build a motor" and get a accurate estimate of torque and
horsepower. (I can play all day on it){but no exhaust functions}
Dale "chief" Thomas
OFOS racing.
-----Original Message-----
From: Dick J <lsr_man@yahoo.com>
To: Thomas E. Bryant <saltracer@awwwsome.com>; Dale & Evelyn Thomas
<bikerschoice@worldnet.att.net>
Cc: FastmetalBDF@aol.com <FastmetalBDF@aol.com>;
landspeedracer@email.msn.com <landspeedracer@email.msn.com>;
dferguso@ebmail.gdeb.com <dferguso@ebmail.gdeb.com>; dhaller@techline.com
<dhaller@techline.com>; land-speed@autox.team.net
<land-speed@autox.team.net>
Date: Wednesday, January 05, 2000 5:59 PM
Subject: Re: Exhaust Extraction --- it's exhausting
>
>
>--- "Thomas E. Bryant" <saltracer@awwwsome.com>
>wrote:
>>
>> There is a formula for header lengths that has
>> been used for years
>
>
>I couldn't find it searching the archives. Maybe
>I just searched wrong. Do you have the formula
>handy by any chance? thanks
>
>=====
>Dick J
>in east Texas
>ECTA #72 FX/GMR
>Talk to your friends online with Yahoo! Messenger.
>http://im.yahoo.com
>
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