Efficient Rotary Engine Lands Million-Dollar Darpa Contract
popularmechanics.com
popularmechanics.com
While the rotary did won Le Man 24 hr endurance race, it is still plagues with problem. These problems isn't because Pistons are better but because Pistons had tons of time refining it. Rotary so far have been neglected and it seems like EV/battery technology will be the future while hybrid is just an intermediate step between oil and electric.
Another interesting engine that GM tried was Turbine, jet engine for cars. It sound like a vacuum cleaner.
Rotaries, properly cared for, are a reliable engine with fantastic power delivery and small size. It's a shame they are plagued with high fuel consumption which limits their usefulness in anything but sports and racing applications.
If you read the article this is not a conventional wankel rotary - the rotor design looks like a wankel housing, so it's flipped around.
I can't imagine a technology like this is that well suited to constant and relatively low power delivery.
on a pre-89 that (factory) redline is at 7k, 8k on 89-. RX8s you have to hit 9k.
This does make it hard not to speed in an RX7, especially if you've done a little bit of work to it - not so much in the RX8.
They're also ideal for alternative fuels like natural gas because the combustion chamber is in a different location to the intake/compression, which makes it easier to limit uncontrolled ignition (detonation). And the oil injection makes them suitable for adding specific lubricants to the intake charge.
On the topic of giving engines a good dose of WOT and revs, all modern direct injection cars need this as the loss of port injection means that the intake runners and valves are no longer given a constrant stream of fuel to clean them. As some exhaust gases enter the intake runners when valves overlap, over time this leads to massive carbon buildup in the intake side. Google some pictures of Audi engines with carbon deposits - makes your eyes water.
So if you have a modern direct-injection petrol injection make sure you give it a good 'italian tune up' on frequent occasions as well.
"Where the rotor holds the seals in a normal Wankel, the housing does that job in the X1 engine. This allows significant reduction in oil consumption over a regular rotary motor."
http://www.popularmechanics.com/cars/a8174/liquidpistons-hyp...
Something about this design smells to me but I can't quite pinpoint it yet.
Reminds me of the "orbital engine" out of australia last century that had some challenges it couldn't overcome. There are lots of other attempts to make different engines.
http://en.wikipedia.org/wiki/Orbital_engine
Alternative engines are always interesting though, and who knows?
1. http://en.m.wikipedia.org/wiki/Diesel_locomotive#First_funct...
I believe the carbon residue acted like graphite. The hardness of the components was so much higher than metal that it was like comparing the lifetime of ceramic bearings like silicon nitride (Si3N4) to metal bearings.
IIRC, it wasn't feasible to make large parts with available sintering tech.
This rotary engine being smaller, perhaps its feasible to use ceramics.
Well, they were given dispensation to run 170kg lighter than any other car in the class (830kg v. 1000kg). It's likely that that made the deciding difference in their win.
Also, it's worthwhile remembering a lot of the fuel efficiency problems with rotaries are avoided by running at a constant, relatively low RPM. For a generator motor, they make a hell of a lot of sense. Sealing the chamber is also a lot easier at a constant RPM, which should help with oil consumption and reliability.
This runs on Diesel, and advertises a low-temperature exhaust; can someone who knows more tell me if diesel's need hot exhaust for emissions reduction? I know that they tend to use EGR for NOx, but every car with a diesel I've seen still has a catalytic converter to do something.
But they will have a shorter overall lifespan. That large moving inner chamber and the outer chamber walls around it will wear down, and when they fail you replace a significant amount of that combustion chamber (or just junk the entire motor).
It's a neat application of the technology, and particularly in contexts where either the motor is going to run for long periods at a specific speed or not be used all the time, it could make a great option for power generation.
The reliability of the engine itself is way misunderstood. They aren't more or less reliable than any other engine (okay, they're way more reliable than Subaru engines...).
The problems are with heat and lubrication. The early RX8s had a flawed design. 2nd and 3rd Gen RX7s had problems with their OMPs and terrible electrical problems. 2nd gens have really weak alternators stock. Turbos usually fail before engines do.
Honestly the engine itself is awesome. Yes, if you lose a seal it will screw your engine (but usually the housings & rotors are salvageable). Piston engines throw rods and screw your whole car. If you bypass the OMP and run premix and actually do proper maintenance on your car, they will last. My 10AE has over 110k miles on it and has not blown up yet -- probably has another another 40k on it before it'll be ready for a rebuild. I still am on the stock OMP (it's an S4).
They're really cool motors, I'm in that boat with you. How they work means forced-induction doesn't necessarily impact engine life the same way FI on piston/crankshaft motors. That the piston motor is just going to last longer not needing or before it needs major restoration.
A mildly interesting point is that heat isn't an easily mitigated factor, unless we're talking the exact use cases in the OP article -- generators, which run in a very controlled RPM band. Same when we talk about UAV engines or other electricity-generation applications. So, you can engineer the motor to be efficient at those rotation speeds WRT heat management and fuel efficiency.
1: https://books.google.de/books?id=IB2lMFqTTl8C&pg=PA117&lpg=P...
That's really low. I don't think I've ever bought a car with only 110k miles on it...
I had a toyota land cruiser with 365,000km on rebuilt engine and 800,000 km on the body though.
Where do you live that 110k miles is low mileage? How many miles is a lot to you? How/why are people driving that much?
That's largely because of the need to salt roads in the canadian winters - yearly, excessive exposure to salt water drastically limits the possible lifetime of a car. The further away from cold weather requiring salted roadways you get, the longer cars last.
I'm really curious where the parent lives that people are investing so much in the longevity of a vehicle. By the time they get to 300,000 km even if they aren't rusty they are usually 20 years old and things like drivetrain start to go and the vehicle is not worth the cost to keep up the required maintenance.
Now to be fair, SoCal has a rather unique and essential car culture, so this is probably an outlier as far as "most" cities go.
Not all places use salt, and even then if you get your car washed and underbody cleaned it should help the longevity of the car.
Older cars, you keep them relatively clean and knock your boots before getting in so that the salt doesn't grind your carpets away, and replace things as they start to fail. A lot of older cars will just keep on chugging along.
The 10AE year was 1988...
Are Subaru engines really unreliable? I was under the impression that as long as you kept the power output under about 300 wheel horsepower that the entire drivetrain is pretty reliable.
But you're mostly right. They will last if you leave the car 100% stock. Just don't modify them. Ever.
How on earth do you get a 400lb diesel engine that ONLY produces 40HP. First, when comparing engines for power production, you should really talk about kW production capability, not HP. Engine's HP is only half the story, you also have to talk about it's torque.
I know rotary engines are a cool technology, but something about this smells like BS.
[1]http://www.popularmechanics.com/cars/a8174/liquidpistons-hyp...
Edit: citation added
and 40 hp is 29.8kW. they're both measures of power. you don't need to know the torque to make the conversion.
https://en.wikipedia.org/wiki/Wankel_engine
Originally invented and patented way back in 1929.