How to calculate header pipe length

1. Oct 13, 2008

SpencerC

Hey guys n gals, Looking for a little help here. I am looking to build an equal length header for my truck and was wondering how to calculate the losses through the amount of 45, 60, 90 and 180deg bends for 1.5 sch.40 pipe. Now, for clarity, I do NOT mean equal centerline length, thats easy enough.

In the picture is an idea of what I am talking about. From right to left the first pipe would seem to have less friction loss than 3 or 4.

Explain it all, This curious mind likes to learn :) Thanks in advance.

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2. Oct 14, 2008

Naty1

There have GOT to be standard tables for such losses....engineers must use that kind of stuff all the time....

3. Oct 14, 2008

Naty1

4. Oct 14, 2008

gmax137

I'm not so sure that the equal length approach is intended to give equal losses, it may be more important that the volumes be equal.

Just to make up a few numbers, a header pipe exhausting a one-liter cylinder running at 5000 rpm is going to pass about 80 cubic foot per minute (for a four stroke). If this pipe is about two feet long the pressure drop in the pipe is only a fraction of a psi (about 0.2). This is small relative to the pressure in the cylinder when the exhaust valve opens.

Header design is all about the pressure waves or pulses which take place due to the periodic stroking of the exhaust valve. There are a number of excellent textbooks out there that go into this in great detail. Commercial software such as that identified above is typically based on steady-flow solutions which are of no help in this instance. Headers are designed using (1) well established thumbrules,(2) extensive testing, and (3) maybe some sophisticated computational fluid dynamics (CFD). The price tag on those kinds of programs make the 700 GbPound price of the steady state piping program look cheeep.

Check Amazon dot com for automotive books with "tuning" in the title. A Graham Bell's books are classics, but there are many others.

5. Oct 14, 2008

minger

seconded

6. Oct 14, 2008

SpencerC

Thanks alot for the info guys. That really helped a lot.