Honda Normally Aspirated B22 Exhaust Header Pipe Lenght?? Disscuss

[ordengineering]

I want to discuss about exhaust header length for normally aspirated motor,

my motor was 2.2L, 86mmx95mm 15:1 cr, pro 3 camshaft (310ish adv duration, 270ish @ 1mm duration) and individual runner carbed 50mm twin weber with ventury 48mm.
some of those Honda guys out there, he was Don Flores from DFE give me a rule of thumb for building header with 45mm inside diameter pipe.. I made the primarry length 70cm / 27.5 inch..

those motor was run madly
It made brutal power 308whp @ 8400rpm, peak tq @ 7.600rpm… even my driver cant handle it. It spin everywhere from 1st-3rd gear…. On mt 24.5x9.5

but I know my dastek dyno was a lot inflated…. I guess it was only 260-270whp in sae..


I plan to built another header for this motor.
Now I’ve seen that so many race header fabricator using shorter length about 45-50cm (I just guessing the lenght by viewing the picture on Honda-Tech.com), they were such as Bisimoto, RMF, etc.

And RMF design with shorter header like that promising lot more HP than the old (long primarry) version.

Is that true that the shorter primarry made more power than the long primarry?
But if I see the header picture, it was only 45-50cm length. Based on rule of thumb (such as graham bell, jim mcfarland) calculation, that kinda length with big camshaft like pro 3 (270ish 1mm exhaust duration) would make power above 10.000rpm.

I plan to built another header for my 2.2L motor but I don’t have any clue about how is the best length for my setup. and I hope anybody here that have a bit similar setup with me feel free to tell me about their 2.2L motor header sizing (inside diameter and length). And with an explanation about the correct length sizing formula.


Please teach me more guru…


Regards


Odie Rachmat

 

[willeng]

What is the application of the engine & what fuel are you using?

 

[patprimmer]

Primary pipe length and cam timing determines the rpm where the maximum benefit from pulse tuning occurs. It does not really change the magnitude of the pulse, just the timing. Diameter of the pipe affects the total exhaust flow. The collector and the secondary pipes also have an influence, but it gets to complicated to cover here and eventually gets down to trial and error with a particular combination. Some race teams even have different exhausts for different tracks.

If you use the google site search you will find various previous threads on this topic.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[Cargeke]

I second what Pat says. To elaborate a little bit, the pipe diameter plays a critical role in the velocity of the exhaust gas charge. Too big a pipe leads to low exhaust velocities, killing the scavenging effects you're trying to get with headers in the first place. To understand the basics, search for "organ pipe tuning".

 

[silverbullet8686]

Honda B22 motor? That isn't a factory block nor do any of the bore or stroke numbers match any of the B series or H22 specs.

There is so much to pipe design, and there is no such thing as the best exhaust since different people setup their engines for different uses (peak HP numbers, wider range for road racing, etc). Read some of the stuff about fluids mechanics and pipe flow on engineering toolbox.

 

[patprimmer]

SB

I never saw him call it B22. I think it is an over bored and stroked B20. Aftermarket blocks will certainly support those bore and stroke sizes. I do agree the language in the OP leaves a lot to be desired and to my mind undermines credibility.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers