Author Topic: port mapping old school  (Read 1630 times)

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Offline 1manband

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Re: port mapping old school
« Reply #40 on: May 23, 2015, 09:43:20 am »
angle-area gives a much clearer idea of what is going on in comparison to just degrees alone.

what using angle-area alone does lack is the "time" portion, of time-area.  without it, it still becomes a form of albeit more informed guesswork.

....with the recommended angle areas, when the corresponding T-A values were found, they were roughly 75% less than lower range limit recommended for time-area given in the graph.

(even with a mean port area one and a half times larger than stock, it yielded a T-A of 0.0000385........while the lower rec limit stood at 0.00011......in the example motor)



 
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Offline 1manband

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Re: port mapping old school
« Reply #41 on: May 27, 2015, 07:41:58 pm »
Jonsereds 52

ANGLE AREAS recommended vs. stock
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Offline 1manband

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Re: port mapping old school
« Reply #42 on: May 28, 2015, 04:37:14 pm »
at this point, there are many paths to go on, in the long run there's still time to change the road you're on?

1.  get the blue dots to match on top of the green dots.....to the macdizzy flavor.
2.  bring each of the blue dots up a bit to get more of a stock flavor style goodness.
3.  bring the intake up a notch or so closer to the exhaust to resemble the mac style pattern.
4.  discount all of this
5. etc.......

this is not a porting thread.......so i don't give a frog what is chosen.  pros/cons and should/not's for each.  just wanted to show some folks some details on these old school methods.

the time it takes to do this is worthwhile, imo to give a closer look at whats going on.  imagine that about 5 motors could be machined and ported to equal the time it takes to work through all of this.

for motors 65cc and up would guess that the T-A numbers and A-A numbers would fall somewhere within the graph by the GJ method.  this motor was a bit too tiny to hit....the only reason i had to end up just using A-A numbers.

the stock 35 year old jreds 52 50cc (and variants) has a bmep that rivals today's lower end saws:
2.3 kW
peak kW power at 8500 rpm
max rev at 11400

hope it helps
-joe


edits: clarity





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Offline aclarke

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Re: port mapping old school
« Reply #43 on: May 28, 2015, 10:19:56 pm »
Excellent thread.  Glad someone finally shed some light on chainsaw port time area requirements vs the bike motors.  Thks. 

Primus fan?  Les Claypool is my all time favorite bass player/character!! 

Offline 1manband

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Re: port mapping old school
« Reply #44 on: May 29, 2015, 06:32:41 am »
caught a show a little bit ago. will catch yet another when he gets back from tour in europe.  then he is west coast.  go see.  nothing like it.
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Offline aclarke

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Re: port mapping old school
« Reply #45 on: May 29, 2015, 09:41:19 am »
How does piston speed In a short stroke motor effect time area requirements?  Seems like in general, the short stroke saw motors turn higher rpm than their square bore/stroke bike counterparts so slower piston speed may not play into the difference in the T/A graphs?

Offline aclarke

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Re: port mapping old school
« Reply #46 on: May 29, 2015, 11:02:35 am »
Smaller saw motors 32mm stroke are about 1000fpm slower piston speed Than a 54x54 bike motor at max rpm.  Less on the big saw motors 43mm stroke

Offline 1manband

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Re: port mapping old school
« Reply #47 on: May 29, 2015, 04:46:07 pm »
How does piston speed In a short stroke motor effect time area requirements?  Seems like in general, the short stroke saw motors turn higher rpm than their square bore/stroke bike counterparts so slower piston speed may not play into the difference in the T/A graphs?

think that what you are referring to, may be behind what is happening to cause the little motors results being outside of GJ's graph.  the graph is fine......but the angle areas just don't match up with the sloping T-A lines for tiny motors.  so it seems to be a 'time" issue.

looking at this whole thing just with math.

T-A values needed, increase with rpm.  for a given rpm, as you say a short stroke piston motors piston travels less distance than a longer stroke piston per degree of crank angle.  that is a definite difference.  Bill Grumpy Jenkins wrote a whole engine building book based on just that.

the angle areas do not depend on rpm....just port open durations in degrees.  so it is not that.  the mean port areas also depend on just degrees.  not that.

the T-A calc depends on rpm.  the only part that involves a time element.  the calc itself is not whats wrong.  the slopes for the T-A lines and ranges were chosen by GJ based on the motors he had data for at the time which the graph came to be.  the T-A graph slopes for smaller motors i am wagering would be quite different.  would take a boatload of different small motor measurements on a boatload of motors to try to draw in a replacement slope angle that would work.  and this is just guessing at even that.
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Offline aclarke

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Re: port mapping old school
« Reply #48 on: May 29, 2015, 05:41:38 pm »
Makes sense knowing the sample data that was used to design the T/A  charts was from motors that were relatively square.

Is there a list of what motors were used to come up with the T/A charts? (requirements)   

Offline 1manband

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Re: port mapping old school
« Reply #49 on: May 30, 2015, 05:22:56 pm »
Makes sense knowing the sample data that was used to design the T/A  charts was from motors that were relatively square.

Is there a list of what motors were used to come up with the T/A charts? (requirements)

yamaha tr5 racer was the bike:  http://www.barhopperchallenge.com/2012/01/a-1972-yamaha-tr3-eats-everything-in-its-way-at-track-day/

looks like the yamaha engineers Naitoh & Nomura who got this whole time-area thing going......gordon jennings and also gordon blair ALL got some inspiration from the same bike above.

gordon blair's bike beat a yamaha factory 'works' bike in a GP race in 1971.  yamaha promply hired blair to design motors in 1972. http://profblairandassociates.com/GPB_Tribute.html   

a string of 13 daytona 200's was won by yamaha. 

jennings used the Naitoh and Namura T-A results to put together the missing link needed for his graph:  http://www.bridgestonemotorcycle.com/documents/aspirin_takers6.pdf
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