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Ok, so not really. But it can be useful. I've slowly been learning the math behind motor design and operation as part of a long slow mini-motor design plan. I've started taking the math and making a 'motor sim' out of it. Those in the know have access to FAR better apps than this basic air pump sim, but hey, it's a start, right? :p



http://www.x386.net/TTR/tech/cgi-bin/motorsim.cgi



It's gawdawful slow 'cause it's running on a 386. Expect to wait a min or two for it to come up.



Red is up to 70% volumetric efficiency, Yellow is up to 100%, Green is over 100% up to 115% VE. Unported stock engines are typically around or below 70% VE out of the crate, and it varries across the rev range based on carb, intake length, etc. (I'll eventually model that info too...)



The graph goes gray when the sim looses accuracy because of valve flow estimates, or valve flow velocity (based on cam lift as well as valve setup) speed estimates. Don't use the gray area for estimating. : )



Safe piston speeds are noted, and you can see when you exceed a conservative safe speed for a cast piston as the chart text changes.



As I learn more, I'll add to the model.



Note - This thing is so horribly simple you can't expect anything near reality out of it. :p
 
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It's not to terribly off on a stock 124SE. It does read low compared to my dynos but for the information you put in that's pretty good. About a 10-15% error is all for stock at peak hp rpm. With high performance, error goes up but everything is different when you start talking modification. On a few other engines it looks closer as well. Even on the 124SE stock engine taking drivetrain efficiency up to 90% takes away a lot of the error. Very cool Kurlon.
 
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Joeybags919 said:
Yeah that is pretty accurate

on my 124 se

before porting on pump gas was a little more it was more like 10.4 I think

after porting and pump gas it was 12.8

so some race fuel and it should be pretty close


What are the specs on your engine (cam, carb, ignition, etc)? What dyno were you using?
 

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cyclerider57 said:
What are the specs on your engine (cam, carb, ignition, etc)? What dyno were you using?




that seems pretty low considering you were doing 16 with the old style SE head, right?



whats the difference between the older style SEs and the new ones?
 
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DynoJet is the number one motorcycle dyno. Mustang is pretty big as well.



Stock isn't close to 16 I know that much. Mine stock was 13 the first time I put it on the DynoJet before I started playing with intake lengths. That was with a PE28 carb. It was 12 with a 24mm carb. Those were done on pump gas with Two Bros Perimeter Frame pipe.



I've been told the new vs old SE head is just a slight port change around the valve guide.



Mine is now pushing 17.5hp and 9ft-lbs of torque but I've done a lot to the head. The rest of the engine hasn't been touched since I first built it.
 

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"Dyno jet" that was it..

yours stock was 13 .. thats pretty impressive!!

I don't know, I think anything over 16 hp is retarded for dirt .. it's only a ten inch tire.



I should have mine back on the dyno in a couple weeks so I'll let you guys know the #'s
 
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