Don't forget the VE on  PP engine can be over 100%!

On 6/1/07, Ed Anderson <eanderson@carolina.rr.com> wrote:

Remember that the 13B is supposedly an 80 CID engine.  In reality it acts
like a 160 CID 4 cylinder 4 stroke or a 80 CID 2 stoke power-wise.  Now this
is assuming a 100% Ve for induction efficiency, any restrictions and your
air flow is, of course, less.

So for a 160 CID 4 cylinder air flow CFM = CID*RPM/(2*1728) = 160 *6000
/(2*1728) = 277.77 CFM

Now if you can turn 7500 rpm (say with a Renesis and the 2.85 gear box) you
would have

Air Flow = 160 *7500 * (2*1728) =  347 CFM  and if in an automobile and
winding to 9000 rpm you would get

Air Flow = 160 * 9000 * (2 *1728) =  416 CFM but still short of an all-out
V8 - sorry!  If you want more airflow then forced induction or  nitrous
oxide injection is the only way I know got get that kind  power.  With
nitrous oxide of course you don't need to increase the airflow because the
nitrous oxide gas is providing the extra oxygen needed during the combustion
process..

Concerning air velocity through your throttle body

For a 3" dia TB flowing 278 CFM here is what I get using my Excel
Spreadsheet.

Your TB area is pi*(dia/2)^2 = 7.068 sq inch = 7.068/144 = .049087 sq ft

Flow rate = Velocity * Area = (ft/min)*(ft^2) = (ft^3/min), so solving for
velocity = Flow Rate/Area

Velocity = flow rate (ft^3/min)/Area (ft^2) = 277(ft^3/min)/(.049087(ft^2))
= 5663.369 ft/min velocity through TB

Converting to feet/sec = 5663.369(ft/min)/60(sec/min)  = 94.389 ft/sec
converting that to MPH = 94.389(ft/sec)*3600(sec/hour) /5280(ft/mile)  =
64.35 Miles/hour MPH for air velocity through your TB at 6000 rpm.  I could
have screwed up the math along the way, but that's what I get.

So I get 64.35 mph air velocity through your 3 " TB - a rather stiff breeze
{:>).  So its important to minimize pressure drops and drag in your inlet -
but, keep in mind its just one part of  the total 3 component system  -
induction/engine/exhaust - that determines your through put.  You can have
the best inlet money and theory can buy, but if you engine and/or exhaust
can not support that flow, then you won't get it.



Ed



----- Original Message -----
From: "Bill Bradburry" <bbradburry@allvantage.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Friday, June 01, 2007 8:16 AM
Subject: [FlyRotary] Intake CFM air flow


> Thanks Bob and Ed.
>
> I would appreciate the pictures, Bob.
>
> Ed, I expected a much higher flow.  I thought that it would be in the
> neighborhood of 600-800 CFM!  I guess I have been spending too much > time
> reading the carburetor adds for V8s....
> I think that the 278 CFM would translate to an air velocity of about > 48.25
> MPH going through my 3 inch throttle body.  That seems like a gentle
> breeze!  Maybe I am spending too much time trying to remove > restrictions
> to the air flow in the inlet??  :<)
>
> Bill B
>
>
>
> Subject:
> Re: [FlyRotary] Intake CFM air flow
> From:
> Bob White <rlwhite@comcast.net>
> Date:
> Thu, 31 May 2007 18:48:02 -0600
>
> Hi Bill,
>
> I built a can around it out of aluminum.  The can clamped on at the
> same place as the filter and it was about 6" dia or maybe a little
> larger.  I then made a fiberglass air inlet that sealed to the can with
> a strip of red silicon engine baffle.  I was hoping to generate some
> ram air pressure, but didn't get a chance to measure it to see how good
> it worked.  I'll take some pictures next time I get to the airport.
>
> Bob W.
>
>
>> Subject:
>> Re: [FlyRotary] Intake CFM air flow
>> From:
>> "Ed Anderson" <eanderson@carolina.rr.com>
>> Date:
>> Thu, 31 May 2007 19:22:24 -0400
>>
>>
>> Bill, at 6000 rpm the airflow is 277 CFM assuming 100% Ve.  Here is a
>> formula
>> for calculating airflow for the rotary.
>>
>> Air Flow (CFM) = (40 cubic inches per face)*2(number rotors) * 3(faces
>> per rotor)*rpm of rotors(=  E shaft rpm/3) /1728 (conversion to CF) =
>> 40*2*3 *(6000/3)/1728 = 240*2000/1728 = 277.77 CFM
>>
>> Or simplifying Air Flow (CFM) = 80*RPM/1728 = 277.77 CFM air flow at >> 6000
>> rpm for a 2 rotor.
>>
>> Ed
>
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