Chainsaw Repair

tool (file is just above the graph picture)
&
graph

.......attached the program again.  previous posted file would not open. 

1.  first download and save the file onto computer.
2.  find file.
3.  right click with mouse, then select 'extract all'...........should open to allow typing in numbers.

....added a graph

file below.

50cc stock porting

TA conditions where it runs out of air at 11400 rpm.......(stock referenced info from magnus' site).

I started doing a modification for more square ports, but I've been a bit lazy working on that I'm afraid! 

I still wonder how much these port relationships hold without a pipe.  The pipe effect is so dominant that all porting becomes an exercise in optimizing the pipe, and near as I could tell all the work being discussed was about piped bike engines.  I'm not convinced that the optimum ratios of intake//exhaust/transfer time area would be the same without a pipe. 

I started doing a modification for more square ports, but I've been a bit lazy working on that I'm afraid! 

I still wonder how much these port relationships hold without a pipe.  The pipe effect is so dominant that all porting becomes an exercise in optimizing the pipe, and near as I could tell all the work being discussed was about piped bike engines.  I'm not convinced that the optimum ratios of intake//exhaust/transfer time area would be the same without a pipe.

Chris, I do have a program that will account for rectangles w/rounded corners shape already.  Thing is, it adds about a thousand rows to the program, this will make the program way too big to post.  It also becomes very time consuming to take the required motor measurements.  You are welcome to it, let me know.

This thread, is about the Jenning's method of time*area.  Keeping in that theme, I presented it in that regard, along with his recommendations for the port time*area ranges.  My point being that I did not want to put a “spin” on his work, but to present it using his information as he originally had done, in case anyone would travel down that road in the future.

Agree with the point that he was writing about piped motors.  After him, Blair also wrote about piped motors.  I don't see that being a stumbling/stopping point to using time*areas at all.

….much like using degrees, nowhere have I seen written that you “have” to set the exhaust port at 190 duration.  Easy to scale down the range for what you want.  Time*area is just a tool, an accurate beneficial tool, but still just a tool.

FWIW, the stock motor example above is dead nuts on Blair's recommendations, for all but the intake port, if that helps.  Blair's work is another can of worms to unravel however.