Exhaust manifold design

[entx]

Okay,

I am in the process of designing a set of long tube headers for my car...I am doing this just because I want to take this on...I have an Me back ground and this should be easy for me to figure out...but I am stump as it' been so long since I was in school...I know no excuse...

Obvously with knowing the timing of the cam(int/exh dur, open/closing times, overlap) the mass flow of the gases, temp, press...how would one go about determining the proper tube length for a given diameter...also is there a typical velocity that you want the gases to flow? As most exhaust manifold would be tuned to pulses of the gas flow to prevent interference from adjoining tubes in the collector and to hopefully provide scavaging in the exhaust gases and help introduce fresh intake charge into the cylinder while the valves are overlapped...I have looked hi-lo for some good books on this as well as the SAE book store but there is so much info there it's hard to decipher what you are really looking for...

So hopefully some one on here can point me in the right direction...

 

[GregLocock]

On or other of the search functions will find many relevant threads, on a good day. I'd also suggest you try to type in English - our time is just as valuable as yours.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MikeHalloran]

It >ain't< easy.

Roughly eleven real textbooks have been published on the subject. None are now in print. You might be lucky enough to find one in a library that hasn't purged its "old, worthless" books in a very long time.

One pseudo- technical book is in print, and probably worth buying if you can't find anything else, but don't expect much from it. The title is something like "Scientific Design of Intake and Exhaust Systems" or some such.

It's worth finding the NACA tech note on aircraft mufflers, which is not exactly on point, but good reading for the math and for the experimental techniques.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

This link should get you at a good place to start your search.

http://www.nasa.gov/centers/langley/home/index.html

Like Bill said it ain't easy. As usual, there are conflicting requirements and compromises to be made.



Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[SomptingGuy]

Was this one of the 11?

Theory of Engine Manifold Design: Wave Action Methods for IC Engines (Hardcover)
by D.E. Winterbone, Richard Pearson

 

[MikeHalloran]

No.

The publication date suggests that it should have been available when I was searching for something like it, but I didn't find it then.

Right now, I don't need it. Next week, maybe I'll be able to justify the price.

Thanks.



Mike Halloran
Pembroke Pines, FL, USA

 

[entx]

Thanks so much for the tips on some books and searching through NACA's database..it's always the old books that are the most helpful...and don't get me wrong I know it's not going to be an easy task...I just hoped that it would be a little easier to find reference material on this topic...but this is definitely a good start...

 

[BrianPetersen]

Someone on another board that I am on, ran across this, which might get you started.

http://www.rickwrench.com/bunchofcalculators.html

As for which cylinders get paired ... that's a tough call. It may seem like an inline-four ought to have 1 and 4 paired, and 2 and 3 paired, because those cylinders are 360 degrees apart. But, every single aftermarket 4-into-2-into-1 header set for modern motorcycle engines pairs up 1+2, and 3+4, then joins the pairs.

 

[70AARCUDA]

...the November 1973 issue of HOT ROD Magazine had an article on this subject, "Header Science," pages 114-118, which was also reprinted in their HOT ROD YEARBOOK No. 14.

 

[facty]

Try this book by Blair - plenty of empirical info/design guidlines in Chapt 6:

http://www.sae.org/servlets/productDetail?PROD_TYP=BOOK&PROD_CD=R-186

Most University libraries will have this book as it is very common and relevant to IC engine teaching/research.

Surprising noone else pointed you in this direction!

 

[Junior33]

I will also vouch for Blair's book, very good quality for formulas and empirical evidence.

 

[Rob45]

Facty:
You beat me to it; Dr. Gordon Blair is THE authority on header design, but most especially for racing two-strokes.

As for Brian's observation about motorcycle aftermarket header design:
a) those motorcycle 4-cylinders might not have the same 1-3-4-2 firing order as an automotive 4-cylinder - I don't know; and
b) most of these are designed for selling, and so they'll fit, not so they'll squeeze the last available hp out of an already highly-tuned engine.

 

[Tmoose]

http://www.bentleypublishers.com/product.htm?code=g309

 

[BrianPetersen]

Rob45, firing order on an in-line 4 bike engine is conventional. *Some* of them are designed to look a certain way without regard for anything else, but these days, a lot of them are rather well researched as far as performance goes!

 

[IceStationZebra]

There are only two possible inline 4 cylinder firing orders.
1-2-4-3 and 1-3-4-2
And notice that if you do a 4 into 2 into 1 set-up you still pair the same cylinders together.
ISZ

 

[Lou Scannon]

FYI, 1-2-4-3 and 1-3-4-2 are really the same except reversed, which makes no difference dynamically.
Same with the two six cylinder firing orders, 1-5-3-6-2-4 and 1-4-2-6-3-5.

 

[Dynotech1]

Get in Google and type in avid Vizard. He has written an article that may be of help and you can read it online.

Also there is a book written by Phillip H. Smith that documents his 40 years of research on intake and exhaust systems. I'm sure it's in the library.

I dyno a lot of engines and there is power to be gained from a "good" exhaust system. To determine a "good" system you'll need to put your engine on a dyno. Every engine builder will tell you the same thing. I have seen a torque increase of 96 lb/ft below peak torque on a 406 SB Chevy just by increasing the collector length 18 inches. The same engine lost power when the collector length was increased 8 inches.

Ron

 

[VaBeachZ]

The Nov '73 issue of Hot Rod 70AARCuda suggests is alot better to understand than the latest Pit Stop answer in Sept 2007 issue.

2007 article is great for the math person, but for the quick decision person, the '73 article is quick reference.

Just my 2 cts,

Everett#2390

 

[70AARCUDA]

...VaBeachZ--"Thanks" for the kind words! I'm glad to hear that people still remember my old HOT ROD article(s).

 

[VaBeachZ]

You're welcome. I saved the article from 1973.

Everett#2390