Boingers

Gary Derian gderian at cyberdrive.net
Thu May 7 12:13:22 GMT 1998


All this talk about balance and efficiency has little meaning.
Reciprocating motion is not necessarily wastful.  When one piston slows
down, another is speeding up.  The net result is a flywheel.  A rotating
radial engine would be impractical and offer no benefits.  Piston inertia is
useful in counteracting gas pressure forces and actually reducing bearing
loads.

A Wankle engine's displacement, say the Mazda 1.3 liter, is really mis
measured.  For every crankshaft revolution, a 4 stroke piston engine pumps
1/2 its measured displacement.  A Wankle pumps all of it.  To compare the
two directly, the Wankle engine's displacement must be doubled.  But even
that doesn't matter.  The important parameters of an engine are Specific
Fuel Consumption, Specific Weight, Cost, Emissions and Longevity.
Displacement is only an artificial measure used by racing organizations to
equalize classes (doesn't work very well) and governments (not USA) to
assess taxes.

Wankles are great for high power per size, no valves to get in the way of
flow, lots of rpm (don't forget the rotor rpm is geared up 3x) but as
Raymond pointed out, by the time a whole car is built, there is not much
advantage.

Gary Derian <gderian at cybergate.net>

From: Robert Humphris <r.humphris at indigo-avs.com>


>The point with the Wankel is that it is a 1.3, where as a Camaro is
>what, 3 times that displacement? Yet they have similar performance.  Add
>that to the weight of the engine, which does add to the performance of
>the car ( less weight = better power to weight ratio, and better
>handling as the car ceases to be engine heavy, so you start getting
>easier moments of force on the car ).
>Lets compare like for like, I guarentee that if you added sufficent
>number of rotors to take the displacement to that of the Camaro, fuel
>injected it, you would be unable to out drag it.  Then if you take the
>same displacement as the Saturn ( What is one of these we don't have
>that model over here in the UK ) and put it in a similar weight car,
>that the engine would be just as lively, and the performance would be as
>good if not better as the weight would be less.
>
>Two stroke direct injection engines?  We will see what they are like
>when they are mass produced.
>
>Rob Humphris
>>
>>I'm not talking about specialized racing applications, or even how many
>>people it takes to pick it up.  I understand that the power/weight ratio
>>is better than a four-stroke piston engine.  I'm talking about what sells
>>cars.  Go down to your favorite Mazda dealer and drive one.  Yah, it's
>>pretty fast and gets decent mileage.  Now, go to a Chevy dealer and hop
>>into a Camaro Z28.  It'll blow the doors of the RX7, and the mileage
>>still isn't that bad.  Now, go hop into a Saturn twin cam.  Much better
>>mileage and not too shabby on the performance.
>>
>>My point is that the mileage/performance balance isn't significently (if
>>at all) better than the other cars you can buy off the lot.  If I have to
>>swap an engine, I might appreciate that it is lighter.  When I'm driving,
>>I appreciate the performance of the car as a whole.
>>
>>There are some directly injected two-stroke engines on the drawing
>>boards.  I don't have the exact figures, but I would be willing to bet
>>(if I were a betting man) that the power/weight ratio of these
>>two-strokers will be similar to the Wankyl.  They won't, however, suffer
>>from the wierd-shaped combustion chamber and longevity of the Wankyl.
>>
>>




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