How to calculate header pipe length

In summary, the author is looking for information on header design and suggests looking into books with titles such as "Tuning and Engineering of Turbocharged and Supercharged Engines" or "High Speed Engineering: A Comprehensive Guide to Turbine Design." The author also suggests checking Amazon.com for automotive books with "tuning" in the title.
  • #1
SpencerC
2
0
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, that's 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
There have GOT to be standard tables for such losses...engineers must use that kind of stuff all the time...
 
  • #4
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
gmax137 said:
Check Amazon dot com for automotive books with "tuning" in the title. A Graham Bell's books are classics...

seconded
 
  • #6
Thanks a lot for the info guys. That really helped a lot.
 

1. How do you determine the proper length for a header pipe?

The length of a header pipe is determined by calculating the acoustical length, which takes into account the frequency of the sound, the speed of sound, and the cross-sectional area of the pipe.

2. What is the formula for calculating the acoustical length of a header pipe?

The formula for calculating the acoustical length of a header pipe is L = (c/2f) x A, where L is the length of the pipe, c is the speed of sound, f is the frequency of the sound, and A is the cross-sectional area of the pipe.

3. How do you measure the cross-sectional area of a header pipe?

The cross-sectional area of a header pipe can be measured by taking the diameter of the pipe and plugging it into the formula A = πr^2, where A is the area and r is the radius of the pipe.

4. Can the length of a header pipe be too long?

Yes, the length of a header pipe can be too long. If the pipe is too long, it can cause back pressure and decrease the performance of the engine.

5. Are there any other factors to consider when calculating header pipe length?

Yes, other factors to consider include the material of the pipe, the number of bends and curves in the pipe, and the location of the pipe in relation to other parts of the engine. These factors can affect the speed of sound and therefore the acoustical length of the pipe.

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