Exhaust/Collector length & size?

[phangster]

Hey guys!
i need to helpppp in finding out how to calculate the length, diameter of the primary exhaust, collector of the primary into the secondary exhaust, blah blah... by the way, it's a 600cc YZF-R6R...
are the any exhaust person out there who can help me? thanks a million!

Cheers

[scooter2131]

from what I understand 1 3/8 primaries are pretty common. 1 1/4 primaries may help you w/ low end torque a little but will be more restrictive at higher rpms. You usually want to step up a size or two each time you collect depending on what size collectors are available and what your muffler inlet size is. Here's a pretty comprehensive summary of header design:

http://www.burnsstainless.com/TechArticles/Theory/theory.html

Let me know if you have any other questions and stay open minded to what other have to say, this was my first time designing our exhaust.

[Matt N]

Our testing this year wasn't as perfect as I would have liked it to, but it did reveal that 1 1/4 primaries don't have to be worse.

Oh - and they didn't boost torque where we would have predicted either ...

Matthew

[phangster]

hey there...
just got a few questions...
1)shouldn't the diameter of the primary hearders follow the size of the exhaust ports?
2)for the length of the primary pipes, do you take into consideration the length from the exhaust VALVES to the ports?
3)when you say step up a size of the outlet of the collector, is there a calculation for it or its just an estimation? say i have a 1.5" tailpipe, from the secondary collector, the dia should not be more than 1.5"?
4)do you know how or what formula to use when calculating the lengths of the pipes?(4-2-1) eg.the primary hearder, secondary pipes and the tail pipe. wish i could lay my hands on the X-design thingy!

thanks so much!

[Sam Zimmerman]

My opinion (for what it is worth)

It seems to me that the primaries should be the same size as the exhaust ports or you may set up a standing wave between the exhaust valve and the exhaust port, minimizing your scavenging effect.

The exhaust wave has to travel from the valve to the collector and back, so I would take the whole distance into account. In addition, the effective length will be 3-4 inches beyond the actual length of the primaries.

Blair, Heisler, Winterbone, and many web-sites have formulas for calculating header length.

[John Bucknell]

I'm with Matt, they work - just not like the equations tell you. Almost so far into a black art that cut and try seems to work best - using the bike dimensions as a starting point.

[Matt N]

phangster-

1) theoretically yes, in practice no. The header I built this year has a size reduction, and the motor makes killer power and torque. Nuff said.

2) Yes.

3) There are calcs for this but basically, at our power levels a 1 3/4" tailpipe is what you want. Split the difference from your primaries to your tailpipe to determine your secondary size - probably 1 1/2 or 1 5/8.

4) this is where the black magic comes in. You could have an overall runner length of 18 with 12 primaries and 6 secondaries, or 14 primaries and 4 secondaries, etc...

I assume you are talking about Burns' x-design program. I called them, immediately mentioned FSAE, and was hooked up with a guy (don't remember the name) who told me 90% of their design parameters, within 5 mins, for only the cost of an intelligent conversation. Very helpful, you might consider calling them.

One major thing - I think the most important tuning principle to keep in mind is that the engine is a complete system. Hence your exhaust should be designed alongside your intake manifold. Its the overall combination that counts.

One other thing - take care of the little details. I've seen designs where hours and hours were spent narrowing down the parameters to come up with the ultimate design, and then the fabrication (especially collectors) ends up super ugly, not only aesthetically but mainly flow-wise. Spend some time looking into collector science (or ultimately, build a mule header and test) if you are serious about building a top-notch header.

John-

I wish I was going to comp this year, so I could discuss manifolding (especially exhaust) ... next year ...

Matthew

[John Bucknell]

Matthew

Good points on the collector details. They're called merge collectors for a reason....

I'll be here next year with any luck. Maybe even with my new street-legal (including AC & stereo) FSAE-inspired two-seater I'm building.

[Matt N]

John, whats the powertrain? Any pics? Vehicle mass?

I'm beginning to pencil down a full bodied super sized FSAE type "street" car myself ... thinking Hayabusa and 80" wheelbase...

Matthew

[John Bucknell]

Matt,

Actually, I've been noodling on building an exotic forever - well not exactly, just since I've been involved with FSAE http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif. Then I moved to michigan, and I could only ride my sportbike six months out of the year (and dropped it three times in the last two years during track days). So ten years on, I finally have the means (modestly) as well as the ability. Due to the aforementioned modest means - I'm adapting a production car to leverage that whole economy of scale thing so I can have an exotic-like daily driver with heat, defrost, windshield wipers, and power windows instead of building a Yamaha 0x99-11 replicar
http://ash-institute.web.infoseek.co.jp/ash_personal/photo_car/yamaha_ox99-11_frqtr.jpg
with hover/sucker power ground effects and all terrain racing capabilities like if I had unlimited resources. I'll post pics of that particular design some time http://fsae.com/groupee_common/emoticons/icon_smile.gif

As for the powertrain, that would be telling - but does SRT4 mean anything to you? How about Stage 3R and HOM? http://fsae.com/groupee_common/emoticons/icon_razz.gif

[syoung]

Bodywork? Windshield? Windows? Why?
Ariel (http://www.arielmotor.co.uk). http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[John Bucknell]

Maybe you island-dwellers haven't seen the crystalline form - but it's called snow around here....

Oh yeah, I'll have a better installed power to weight than the Atom as well http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Matt N]

You're crazy to drive that in the snow. You don't happen to have an SRT4 winter beater around? How bout its humble origin, the turbo K car? I'm sure I could find your car a dry garage, if you need it to be safe over the winter...

Matthew

[John Bucknell]

Actually, i'm able to dial down the boost via a handy rotary dial on the dash - so snow should be no worse than any other exotic http://fsae.com/groupee_common/emoticons/icon_smile.gif

My summer beater is/will be a 310 bhp 1985 GLH....