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Comment by digitalzombie | Hacker News Reader

Did they fix the reliability and oil consumption for Rotary? The rx8 ate a lot of oil cause the oil lubricating it evaporates. Also the Rx7 rubber hoses tends to wear down over time.

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.

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Mazda rotary engines are designed with oil injection to lubricate the seals - they are designed to consume oil.

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.

Reputedly, if you own an RX-7 or RX-8, you should spin the engine up to 9k revs at least once every trip... lest carbon deposits build up and wreak havoc.

I can't imagine a technology like this is that well suited to constant and relatively low power delivery.

Not entirely accurate. The 5th and 6th ports don't open up until 3800 and ideally you want to slightly redline it for a few seconds, but you definitely want to at least open up those ports. You can also get away with not doing it for a while, but you shouldn't.

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.

Rotary engines make good constant speed engines because the intake and exhaust ports can be tuned for that constant running.

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.

> While the rotary did won Le Man 24 hr endurance race, it is still plagues with problem.

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.

Rotary engines still have a lot of potential as range extenders for EVs.

Why haven't there been any diesel-electric hybrids yet? It seems like the perfect application for a small, 2-4 cylinder efficient diesel driving a light and compact neodymium generator. Trains and ships and submarines have been using diesel-electric hybrid power for over 100 years now [1] , so it blows my mind that this technology is still considered novel / new / and isn't totally refined yet.

1. http://en.m.wikipedia.org/wiki/Diesel_locomotive#First_funct...

One thing to consider is that with so few moving parts, the engine could be made of ceramic and use the fuel and exhaust gases for lubrication directly. I saw a documentary about it in the 90s and remember a guy holding a ceramic piston and discussing it but never heard anything else about it.

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.

Do you know the state of the art for ceramic engines?

IIRC, it wasn't feasible to make large parts with available sintering tech.

This rotary engine being smaller, perhaps its feasible to use ceramics.

fwiw the article linked from the article talks about oil, no word on reliability:

"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."

As someone familiar with Mazda's (incomplete) Wankel, that sentence reads more like marketing speak and is nearly meaningless.

Something about this design smells to me but I can't quite pinpoint it yet.

You are right to be skeptical. We've been down this road of lots of promises for new technology before. If there was an problem with the design the company isn't letting us know. Maybe its durability? Torque? repairability?

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?

These guys have been around since 2005, if I'm not mistaken. So I dunno if I'd call them new.

Agreed, but I think for me it's that the apex seals were always the weak point in the Wankel design. So the apex seals are moved to the case, but what material advancements have made them more robust and resistant to wear and leaking?

Apex seals were eventually solved by Mazda, though. You can still kill the apex seals through neglect, but to be fair you can do that to piston rings and valves as well.

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