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Old Apr 10, 2013, 10:12 PM
Dean Pappas
central NJ
Joined Feb 2008
6 Posts
Quote:
Originally Posted by Steve Bailey View Post
That all sounds very doable Kevin, thanks. How many exhaust pulses do you think are in the pipe at any given moment? That is what I was talking about when I mentioned there being mutiple increments in header length....if that make any sense. At 14500 rpm there are approximately 240 exhaust pulses per second. I would think there has to be many pressure waves traveling thru the pipe and we just need to get the timing down for one by adjusting the length. Is there a good referance info on pipe dynamics I should read?
Hello Steve.
The answers are one, and the reference you seek is Gordon Jenning's Two Stroke Tuners Handbook. It is long out of print and it can be found on the web in its entirety.

Regards,
Dean Pappas
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Old Apr 10, 2013, 10:51 PM
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doxilia's Avatar
Montreal, Canada
Joined Mar 2008
1,843 Posts
Dean,

although coming from a third party (me), thanks for the reference. I'm sure it will be an interesting read..., just like I remember your pattern column back in the 80's.

Come to think of it, I've been a little puzzled by your comment earlier on Steve. Where does the figure of "240 exhaust pulses/second at 14.5K" come from? If a "pulse" is produced for every combustion cycle, there would be the same number of exhaust pulses as the rpm of the engine - in a 2-stroke. Half that in a 4-stroke. Or maybe I'm not understanding.

David
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Old Apr 11, 2013, 04:00 AM
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Roguedog's Avatar
United States, CA, Norco
Joined Feb 2007
408 Posts
Ahhhh! Simple.

14500 revolutions per minute divided by 60 seconds per minute = 241.667 pulses per second.
or
14500rpm / 60sec = 241.667 pulses or exhausts' or combustion cycles per second.
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Old Apr 11, 2013, 06:12 AM
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doxilia's Avatar
Montreal, Canada
Joined Mar 2008
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I knew there was a reason why I was no mathematician!

Thanks for clarifying that Bryan. If I'd only given it a little more thought, I would have realized we're talking rpm not rps!

I better go back and correct my previous post where frequency is concerned. I guess I can say rpm is the same unit as 60^-1 Hz...

What defies definition is the duration a "moment" represents. It occurred to me that a moment is scale dependent - in some strange nth dimensional way... If you're big, a moment is small; if you're small, a moment is big. Kind of like bushels, fathoms, stones and all those other "mood dependent" units.

Amazing to think that a prop can turn ~250 times in a second. A turbine more than twice that!
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Old Apr 19, 2013, 09:07 AM
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United States, OK, Tulsa
Joined Jan 2010
71 Posts
I too thought the ST X60 were ABC engines until I took another look at mine. It also is a silver head ringed engine. I also have the factory header and pipe all NIB.
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Old Apr 20, 2013, 10:16 AM
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Steve Bailey's Avatar
United States, IN, Mishawaka
Joined Sep 2009
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Hey Computermonkey, do you think you could post some pictures of your engine, header and pipe?
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Old Apr 20, 2013, 08:57 PM
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United States, OK, Tulsa
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Sure thing, here ya go.
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Old Apr 20, 2013, 10:12 PM
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Montreal, Canada
Joined Mar 2008
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For comparison, I thought the following pictures might be of interest. These show the ABC X61 TST (round head) and the X61-K square head with bolt on header. I have a ringed blue head X60 which I think of more as a collectors piece but it would be interesting to compare the performance of the three engines.

David
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