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“Inside-out Wankel” rotary engine delivers 5X the power of a diesel

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51–60 of 211 posts

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#51
post #3

My understanding is that everyone acknowledges that rotary engines are great, bt in comparison to piston based engines they have far shorter longevity.

If we lived in a world of rotaries and BMW came out with the S85 we'd say that piston engines were emotive and fun but too unreliable for mainstream use. When we refer to rotary engines we mostly talk about two generations of one engine from one manufacturer used in sports cars that were designed before emissions targets changed.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#53

I'm surprised the air intake isn't more aerodynamic, more like a fan blade to compress the air into the engine? Could this engine be fitted inside the rear wheel to save space and weight as well?

Actually mounting an engine inside a wheel increases "unsprung weight" which is bad for handling. But putting such small engines near the wheels (but still on the body so the suspension can do its job) that could indeed improve cargo space. Pushing the engine weight outward toward the wheels would also make the vehicle harder to rotate, which is bad for track cars and go carts, but good for passenger and freight vehicles.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#54
post #36

Earlier quoted context omitted.

That's a really good idea. Mazda is doing something that I think is fairly novel, which is almost exactly what you've described. They've scaled down the rotary engine from their RX cars to a single-rotor and put it into their new EV (almost tucked into the front wheel well,) and letting it act as a 70ish horsepower generator for the otherwise battery-powered car to extend range.

Mazda really seems like the only company innovating in the ICE space (this, wankel rotary engines, skyactive engines) and their cars look damn good these days too. On top of that, they make fun cars. With buttons and knobs on the dash! I'm glad they're still around doing their thing.

Agreed, but there's also Koenigsegg, which has managed to eliminate the need for cams, and complete heads from ICEs, replacing them with their 'freevalve' tech (which basically replaces the timing chain with computers so that instead of having one or two modes that a camshaft can opt into, you can precisely dial in bespoke timings for every RPM, or every RPM and speed, or ever RPM / speed / gear combination. They've also practically reinvented the transmission to invent a new transmission that eliminates moving gearsets and gives you a dual-clutchish transmission with a 6 speed manual AND a 9 speed automatic in the same device.

IIRC, the Freevalve tech is like a 30% efficiency hack for any ICE you put it on, and it's a part of how Koenigsegg are managing to squeeze 600 brake horsepower out of just a 2L, 3-cylinder engine.

Wesley Kagan reimplemented their freevalve technology on his Mazda Miata, and it's probably the coolest hobby automotive project I've seen in years. https://www.youtube.com/watch?v=E9KJ_f7REGw

Here's a really cool explainer on the transmission - https://www.youtube.com/watch?v=Hvb6J96KiSM

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#55
post #42
post #30

Earlier quoted context omitted.

A Traxxas 5407 TRX 3.3 engine used in RC cars makes 1.42 horsepower, weighs 305 grams, and fits in the palm of your hand. This is 1hp per 0.46 pounds of engine weight, nearly three times better than the camry engine. Granted an RC engine runs on a mixture of fuel and nitromethane, and doesn't have any reasonable durability compare to a Camry engine. But it also only costs $200.

You can't just make the Traxxas 18x bigger and get linear performance improvement. Trying to compare power/weight between engines with radically different weight constraints is silly.

If you had 18 such engines it would get you precisely 18x the performance, at precisely 18x the weight.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#56

I'm surprised the air intake isn't more aerodynamic, more like a fan blade to compress the air into the engine? Could this engine be fitted inside the rear wheel to save space and weight as well?

You want the unsprung mass to be as low as possible. As in you want the wheels to be much lighter than the rest of the car for a smooth ride. The wheels should bounce around but the rest shouldn't. Newtons law and all.

Putting engines in wheels causes a very rough ride. Even if the engine is light you're still likely creating an order of magnitude more unsprung mass. That's an order of magnitude rougher ride.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#57
post #14

Ok, so they're "shooting for" a performance of 1hp per 1.57 lbs of engine weight. A Toyota Camry engine produces 1hp for every 1.41 lbs of engine weight. It produces 1ft-lb of torque for every 1.94 pounds of engine weight, compared to 1.58 for the Camry. How is this revolutionary motor being outdone by a mid-range sedan engine?

Their target market is the military - which has plenty of kerosene / jet / diesel fuels as part of its standard supply chain. The Camry engine will only run on gasoline - which the military neither carries, nor wants to.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#58
post #36

I'm surprised the air intake isn't more aerodynamic, more like a fan blade to compress the air into the engine? Could this engine be fitted inside the rear wheel to save space and weight as well?

That's a really good idea. Mazda is doing something that I think is fairly novel, which is almost exactly what you've described. They've scaled down the rotary engine from their RX cars to a single-rotor and put it into their new EV (almost tucked into the front wheel well,) and letting it act as a 70ish horsepower generator for the otherwise battery-powered car to extend range.

This was done by BMW for the i3 with REX (range extender) equipped models. To be classified as an EV the gas tank range can’t be greater than battery range. This led to a 2ish gallon tank.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#59
post #36

Earlier quoted context omitted.

That's a really good idea. Mazda is doing something that I think is fairly novel, which is almost exactly what you've described. They've scaled down the rotary engine from their RX cars to a single-rotor and put it into their new EV (almost tucked into the front wheel well,) and letting it act as a 70ish horsepower generator for the otherwise battery-powered car to extend range.

Mazda really seems like the only company innovating in the ICE space (this, wankel rotary engines, skyactive engines) and their cars look damn good these days too. On top of that, they make fun cars. With buttons and knobs on the dash! I'm glad they're still around doing their thing.

Nissan released cars with variable compression engine.

Re: “Inside-out Wankel” rotary engine delivers 5X the power of a diesel

#60
A commodity chainsaw (Stihl ms660) returns 1.4kg per kw from 2 stroke fuel. Before any performance tuning takes place.

That’s at about a quarter of the size of this. I bet there’s efficiencies to be had if it were scaled up.

I’m just not sure this is the game changing breakthrough the article’s tone suggests.

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