>>
    >> I am stuck on 1 7/8 [ID] runners. Sames as the Lemans engine.
    >> Why reinvent the wheel. I know it rolls :)
    >>
    >> Paul Lamar ...No rotor no motor.
    >>
    > *****
    > Hi Paul,
    > I can't find my torque/power figures for the LeMans engine; what rpm
    > was it getting max figures at?
    > I'm thinking 1.75 in runners might suit our rpm better.
    > Ta, Dave McC
    >
    > There is a big difference in the port area.
    > 1.75 OD is is really 1.625 ID. Area is 2.07 square inches.
    > 2 inches OD is 1.875 ID. Area is 2.76 square inches.
    > My guess is HP would be less than 200.
    >
    > Here are the Lemans curves.
    > --
    > Paul Lamar ...No rotor no motor.
    >

   Paul

   Are you sure about that 1 7/8" figure? A drawing and test results I
   received from the engineer that actually designed the Leman's
   manifold shows
   the ID at 50mm. or 1.968 inches or 20 square centimeters. His report was
   done at on 2-22-1989.

   Max power is about 664 PS at 9,000 rpm. This four rotor engine
   slightly pre
   dated the wining Lemans engine but I can't imagine Mazda decreasing the
   manifold size diameter and getting more power out of the next version
   engine.


   DougFir

   I would like to have a copy of that report Doug if it is in English.

   1.968" - 1.875" is .093 or 93 thousands. We could go to .035 wall SS
   tube
   which has an ID of 1.91 or only 1.968" - 1.91" or .058'"or 58 thousands
   difference. I got it as close as I could at the time.

   Burns Stainless now offers 2-1/8" OD .065" wall
   6061 same center line radius so that would give us 2" ID. Perhaps
   its worth a try. We would wind up with a little less support for
   the apex seal as it passes over the intake P-port.

   We got about 243 HP with a Weber 58 mm carb at 7000 RPM and they
   got 295 HP with a slide throttle at 7000 RPM. The p-port engine
   with two 48 MM (1.889") Mikunis might do better than the Weber as there
   is less obstruction in the runners however the throats are smaller.

   It remains to be seen what HP we will get with our slide throttle.
   We are about to find out as Mark Suspinski should have his engine
   running this coming week end.
   --
   Paul Lamar ...No rotor no motor.

   Guys,

   I'm with Dave on the smaller runners -- 1.75" ID, 44 mm.

   I'll take the better torque below 6000 rpm with the smaller runners.
   Think about how you fly your plane. You want your torque peak to be
   below your cruise rpm, so that when you push in the throttle, your
   power comes up quickly.

   If your torque peak is above your cruise rpm, pushing in that
   throttle is going to feel pretty lame. You might as well forget
   about controlling pitch attitude with power -- like in a power-on
   approach for example.

   Anyway, the Lemans engine was tuned for peak power at 8500 rpm. With
   2.85 reduction gearing your limit is going to be about 7500, which
   gives just over 2600 prop rpm.

   If you compare volumetric flow between 8500 rpm and 7500 rpm, you
   see that it is 88 percent of the higher rpm. So since the 1.75" ID
   has 87 percent of the area of the larger tube, it should be just right.

   This will give plenty of power. My turbo chart spreadsheet shows 253
   hp at 7500 rpm, assuming a VE of just 1.1.

   Pick up a couple of those 44 Mikunis for a couple of hundred bucks,
   a needle valve for maybe $50 and you're in business.

   Regards,

   Gordon.


Not true Gordon. HP is what airplanes fly on. It is not like a car.
Forget all you know about car engines. Your computer model is flawed.

HP is torque TIMES RPM.

You want max torque at cruise RPM because that is where the best
BSFC is.

Your making a big mistake as your BSFC will also be worse.
The Lemans engines was designed for minimum fuel burn
because the rules stated one had only so much fuel to run
the race on.

As I said before an intake manifold is an aerodynamic device with
aerodynamic drag. Power is consumed by the engine to pump the air
in. It is a trade off with organ pipe effects. If you want the best
BSFC you want to minimize the aerodynamic drag in your intake manifold
and you therefore you want to minimize the air velocity in the intake
manifold and maximize the cross sectional area to skin area ratio.

Smaller pipes work in cars at low RPM because the intake air velocity
is much lower and the organ pipe effects dominate. Mazda spent big
bucks tuning the Lemans engine and nobody has got more power or less
fuel burn.

The velocity in an intake manifold can be as high as Mach .4 or higher.

Paul Lamar ...No rotor no motor.

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