Originally Posted By: jrustles
Um, no. What you said is false.
No, it's not.
Originally Posted By: jrustles
A rotor consists of three distinct working chambers, and they all
work simultaneously.
A three cylinder engine consists of three pistons and cylinders, all working simultaneously thanks to the crankshaft, exactly like a rotary engine. There's no difference.
Originally Posted By: jrustles
The displacement of a Wankel is the
swept volume of
one of those chambers. That's how Wankel displacement works. Period. The industry has spoken.
I'm not sure why you're stating that so pointedly, nobody's going to argue that. You'll understand in a minute.
Originally Posted By: jrustles
A rotary engine will not displace more than the swept volume of one of the chambers for any given 'charge'. It physically cannot do that, however, it CAN conduct the strokes simultaneously.
Once again, a piston engine is also conducting all of its strokes simultaneously, exactly like a rotary. It just uses more parts to do exactly the same thing.
Originally Posted By: jrustles
Some people experience great and terrible anal anguish at the fact that with one sweeping motion (one tumble) of the rotor, it accomplishes three strokes
simultaneouly and spins the output shaft (eccentric shaft) once, 360 degrees. Conversely, a piston 4 stroke can only accomplish one stroke in 180 degrees. The piston engine
must waste 540 degrees of output shaft rotation (crankshaft) JUST PUMPING the other three cycles before it can make power again.
A rotor has four distinct and equally spaced strokes per rotor lobe, just like a piston engine has four equally spaced strokes per cylinder. The only, THE ONLY difference is how the engine couples those strokes to the crankshaft. A rotary engine makes things look very smooth but is very hard to follow because so much is going on with just one rotor, whereas a piston engine makes things far more simple because everything is broken down per cylinder.
Originally Posted By: jrustles
The ability to simultaneously conduct the strokes of the Otto cycle is in and of itself volumetric efficiency. You can't say "hey no fair" and punish it for doing so. That's not how it works. That's the very nature of the engine. Swept volume in one tumble, in one chamber is how Wankel displacement is determined.
Statement in bold = absolutely WRONG. Volumetric Efficiency (VE) is the efficiency with which an engine fills it's "chamber" on the intake stroke. The torque curve of an engine is closely related to a "Volumetric Efficiency Curve" since torque output is relative to how much air you can get into the engine on each intake stroke (varies slightly with ignition timing, A/F ratio, etc.). More air in, higher VE, more torque. FYI, most street car engines have no more than about 90% VE.
Originally Posted By: jrustles
Motorsport clubs may feel the need to level the playing field for the piston guys, and governments for taxes. That's fine and sometimes necessary to maintain competition.
IMO the Japanese government has the closest 'equivalency' rating at 1.5x piston displacement, because the rotary engine needs 1080 degrees to complete all cycles, on all faces of one rotor, whereas a piston engine needs 720 degrees for one cylinder to do so.
Your statement in bold agrees 100% with what I'm saying, and also highlights the KEY point here:
- A 650cc rotor displaces 650cc per intake event.
- A rotor has one intake event per crankshaft revolution.
- A two rotor Wankel has two rotors, each with one intake event per crankshaft revolution.
- A two rotor Wankel has two 650cc intake events per crankshaft revolution.
- A two rotor Wankel displaces 1300cc per crankshaft revolution.
- A two rotor Wankel displaces 2600cc per every two crankshaft revolutions.
- A 2.6L V6 displaces 2600cc per every two crankshaft revolutions, just like a two rotor Wankel.
Huh. Turns out those Motorsport and Government guys are smarter than you thought.
Originally Posted By: jrustles
Should 2 stroke engines be considered double their displacement, just to be fair to the 4 stroke piston which has to waste 540 degrees of output shaft rotation just pumping?
Nope. 2 stroke engines work completely differently to four stroke engines and can't be related without far more complex study. A rotary, on the other hand, is a good ol' four stroke just like any piston engine.
Originally Posted By: jrustles
Wankels are really in a class of their own, and people get mad about it for some reason.
Wonder why (Skip to 10 minutes for the fun )
That video proves nothing, and if you pay attention the rotary in that car is a THREE rotor... or equivalent to a 3.9L nine cylinder engine.
I think the reason people get frustrated is because many rotary supporters are assuming that what Mazda claims as displacement is actually true. It's not, and a rotary engine doesn't bend or break any laws of physics. It's Brake Specific Fuel Consumption (BSFC) isn't much different than other car engines, which means it's burning roughly the same amount of fuel and consuming about the same amount of air per horsepower generated as other engines. It's performing the same mundane four stroke routine as piston engines are.
Forget everything you've read and heard so far and look at a video of a rotary functioning. THINK about what's happening as the rotor is turning and you'll see what I've said cannot be argued. That IS how a rotary engine works, and that IS how it's displacement is determined. No racing handicaps or government regulatory quotes required, just the mechanics of an ordinary, yet admittedly cool looking, air pump.
