Exhaust Header design

[GV260]

I'v been looking into the various types of exhaust headers that are available and was wondering if anyone categorically knows what is the best shape, primary length and diameter? My application is for a race L28 with triple 45's. Any recommendations for off the shelf headers? Some examples are below

 

http://www.hmheaders.com.au/index.php?q=46.html

http://www.stahlheaders.com/Frame%20New%20RR.htm

[NZeder]

Those hmheaders look too short for a race engine the stahlheaders are very very good but they cost a lot of coin.

[Roberto]

http://www.thezstore.com/page/TZS/CTGY/PEC01

 

I like the MSA 6-1 headers.  They are tuned length and I have read many good reviews about them.  They are on my wish list !!

[stevo_gj]

If anyone has access to material concerning the design of exhaust headers (and indeed design of any engine components) such as engineering textbooks, I would be really keen to hear about them.

 

..at UQ the only way to learn automotive stuff is to join the FSAE team which I tried but found to be far too time consuming.

[NZeder]

I recall seeing somewhere that the L6 engine should have 28-29" primaries and then run a twin system for a total length of 72" after that you can join the twin into a single - 72" ends up just before the diff I think. That was from an old Datsun race book I think.

[Zedman240®]

I have a "Scientific Design of Exhaust and Intake Systems" book which goes into very fine detail on everything. A bit exy but a good read. This is the book that in several chapters explains that 6 cylinder engines should have two seperate systems for cylinders 1-3 and 4-6.

ISBN 0-8376-0309-9

[ozconnection]

I have a "Scientific Design of Exhaust and Intake Systems" book which goes into very fine detail on everything. A bit exy but a good read. This is the book that in several chapters explains that 6 cylinder engines should have two seperate systems for cylinders 1-3 and 4-6.

ISBN 0-8376-0309-9

 

I read the same thing.....fascinating. Dudes in the US run twin exhaust systems, look on youtube to see and hear them. I'm thinking about doing this the next time I need to work on the exhaust.

 

SWR in Sydney worked on headers for exactly this application. They can give you advice as to what's best for your combination. Tell Stuart Wilkins that Mark with the 280C sent you, he might give you a bit of a discount!! (mates rates!)

 

Cheers. 

[maddos]

Any idea what MSA would charge for shipping?

[ozconnection]

Any idea what MSA would charge for shipping?

 

They're not cheap......try ebay US or import monster.

[tbscobraZ]

Dimitri is right its to do with exhaust pulses same theory behind a twin scroll turbo where they have a divider and hence why they perform better but there is no doubt the MSA ones are awesome and give great performance.

[maddos]

Think I'll get a shipping qoute off them

[stevo_gj]

Did you ever get the shipping quote? I'm currently deciding on headers for my own L28 with 45s.

[d3c0y]

MSA headers have a compromise in their design because the have to clear the steering knuckle/shaft on a LHD car. "How to modify your Nissan & Datsun OHC Engine" has a whole chapter on it.

 

It says a header with 32" long, 1-3/4" diameter primary pipes is often the best for a 2.8L or larger 6 cylinder, Shorter primaries enhance high-RPM power. Use a 6-2-1 collector configuration with 1,2,3 and 4,5,6 emptying into 2-1/4" or 2-1/2" secondaries that are 72" long.

[Six_Shooter]

There is no one correct answer to this.

 

There is no magic primary length or type of design that is "best".

 

Sure one design might work best on one engine used in one application, but not for a similar or same engine in another application.

 

General rules are, equal length headers generally created a "peakier" power range, where as unequal length will help create a broader power band.

 

One engine might like longer primaries than another, one might like a dual system, another might like a single, some might like a stepped primary...

 

The only way to truly find the "best" for your application is to try several different sets.

 

Barring the ability to do that, an educated guess would likely get you what you want.

 

grapeaperacing.com used to have a great article on exhaust design and theory, but seems to have removed it.