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Thanks Bill,
I'm transposing off a larger document which was done piecemeal over a period of time, for my own benefit and you picked me up on some transference typo's. I've amended the attached copy.
Your right it's saying how much air you need and how fast that air will get there (speed now included). Perhaps I shouldn't have labeled it Tuned. The rule of thumb has been between 18 -21" for tuned manifold length ( from what I understand) and this supports that theory. How much the reflected wave affects the speed is still beyond me, at this point in time, however it you think of the variables as Tracy suggested your going to get confused, I know I do. This approach just gives a rough start point - it works for me however I do find the outcomes interesting, when you do some comparisons on variables.
George (down under)
George,
Why is the Renesis horsepower lower than the standard at 7500 and higher
than the standard at 7200? It also is higher at the lower rpm??
Regards the tuned length. I thought the idea was to get a reflected wave to
bounce from one inlet to the other just as it was closing. If I understand
what you have said, your calculation is how long a tube it would require to
hold one charge of air??
Bill B
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of George Lendich
Sent: Tuesday, March 30, 2010 1:10 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: P-Port performance
Cary,
Ed came to the rescue (once again) and reminded me that was a conversion of
inlet speed of 120.58 mph to seconds a minute. I adjusted the attached info
sheet, to reflect this information).
The maths isn't a problem, however Ed has a knack of knowing how to approach
and work through a problem, whereas most of us wouldn't bother. This must be
how the engineers do it to get to a start point.
I don't know of anyone needing to go to 8,000 rpm and if they did they might
need another ratio reduction drive, in that case they might need a slightly
larger inlet. However greater VE would need to be driven by a greater inlet
velocity and a bigger inlet has a reduced velocity, but I'm sure 120% VE is
achievable in the racing game and much higher rpm, much as I would love to
see it at our rpm. Then again I would love to be proven wrong. Perhaps with
the higher peak inlet speed Tracy indicated was available. We won't know
until we get mare data, perhaps from bill, down the track.
Knowing how you love to dabble in things, ( nothing wrong with that) I
included a calculation for inlet tube length, in this latest attachment -
mind you their only ball park figures, but to me it gives a rough start
point and an understanding of the processes involved.
Hope that helps.
I do have some figures on exhaust speed if your interested.
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
--
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