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Cary,
Nice to hear from you again.
Firstly I would have to go over the notes from Ed Anderson for that info - can't exactly remember off the top of my head.
The reason I put those numbers up was, so builders can play with them and do comparisons. However Paul is adamant that the 2" is ideal for Aviation, can't get him to see otherwise.
Yes I remember someone saying you can achieve 120%VE, but that would be packing it in with a high velocity - I sure hope their right, I could do with the extra.
I do have a calculation on runner length, it seems to work alright, but like Tracy said, their ball park figures, I use speed of sound and that varies with altitude - then again doesn't everything.
I will tidy it up and put it up if you wish.
George (down under)
Hi George;
What is the meaning / origin of the value "176.85" in your "Diameter of Inlet" calculation?
You should also try running your calculation with 8000rpm and 120%VE.
SAE900032 has a bunch of useful intake and exhaust info including volumetric efficiency charts versus Pport sizes and intake lengths.
There are other useful SAE papers that Paul posts on the other list periodically.
Cheers
Cary
?
Naturally I take on board all Lynn and Ed say, as they have helped me understand how things work and Ed with the maths to give a ball park figure rather than a WAG, on performance.
So I have condensed the figures Ed gave me a tried to make it as simple as possible to show others - see attached. I hope this helps those willing to look into the maths.
You will notice that the results strongly agree with what Lynn has stated (in general terms). This in turn strongly agrees with what powersport was using i.e. 40mm up to 6,000 rpm and 44mm up to 7,500rpm (checked this with Bill). What Lynn has suggested is 50mm reduced 15% 42.5mm - hello! I've seen that figure before - dia required at 7,200 rpm. I also agree with what Lynn suggests on P-port shapes - I just find round easier to do, so round is probably not optimum, but good enough for some.
Some of the Renesis figures I've increased hp in line with compression increase and rounded off some end result figures.
Hope it helps - it sure helped me.
George ( down under)
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