|
|
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
--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
|
|