Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

newatlas.com

Post reply on HN
Print view View original

71–80 of 211 posts

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

#71

Post by Syonyk »

someweirdperson wrote: post #66
Syonyk wrote: post #50

Earlier quoted context omitted.

If it's an aviation engine, it'd better be able to!

Multiple thousand at max power? Typically, overhaul at 2000 hours. And maximum continous power isn't usually full load.

It really depends on the engine, but almost all the general aviation engines you'll find (Lycoming and Continental 4s, and the smaller 6s) are rated for continuous operation at full power, and if they're flown regularly, will typically make well past the 2000-3000 hour TBO (which is a recommendation/expectation, not a legal requirement, though I believe some of the small diesels can't be operated past it).

Our flying club engines in the 172s typically make at least 3000, if not 3500 hours, and I think some of the overhauls at that point have been a "Well... it's still perfectly fine... but..." thing where the board was just starting to get uncomfortable with the hours on it.

And, yes, they spend a lot of time making less than rated power, because of density altitude, but they're still rated for full power operation, and since there's basically no wear going on with an engine in operation (almost all the wear is during starting), there's no real difference there.

It's not until you get into the really large engines where "maximum continuous" is a different thing from "takeoff power." The turbocharged 500s are about the smallest I know of with that sort of rating, and even then I don't think it's all of them. Most of the big radials have that limit, though. If you find a smaller plane with that sort of limit, it's either a possible resonance issue between the engine and prop, or a noise regulation for certification.

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

#73

Post by pas »

aidenn0 wrote: post #64
syrrim wrote: post #55

Earlier quoted context omitted.

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

And precisely 1/18 the MTBF

but it fails gracefully, right? (only one engine fails at a time)

it's like RAID, great until the RAID card itself fails

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

#74

Post by astral303 »

mywittyname wrote: post #10

A non-turbo diesel is an interesting choice of competitor. The big selling point of the Kohler motor is that it's almost silent - even the valve train is belt-driven to reduce noise. Not sure a rotary engine screaming at 6500RPM is comparable here to a diesel with a peak torque at 2000 and peak power at 3600. > LiquidPiston has been working on these X-engines for nearly 20 years now, I'm guessing they will never actu…

rotary engines do not really scream at peak power... this is why Mazda has plans to use rotary at peak power to generate electricity for their hybrid EVs.

re 20 years to make a new engine point, compare investment $ in traditional ICE across the car industry vs investment $ into rotary or other alternative engines (the former is order of magnitudes more)

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

#75

Post by ghostpepper »

kube-system wrote: post #47
Syonyk wrote: post #37

Earlier quoted context omitted.

> How is this revolutionary motor being outdone by a mid-range sedan engine? Go ask your Camry engine to make 100% rated power indefinitely, and see how long it holds up. That's the difference. A typical car engine is designed to make 30-50hp sustained, and occasionally generate more power for reasonably short periods of time. An aviation engine, generator engine, or any sort of "industrial" engine is going to be abl…

IIRC some automakers do test automotive engines at 100% duty cycle (in a test stand configuration). And more than a few automotive engines are used in slightly modified variants for marine and aviation applications. As I understand, the reason a typical car engine can’t sit at 100% duty cycle isn’t the engine itself, but usually the cooling and oiling configuration. Examples: https://youtu.be/GNPB3RtHN2M https://www.…

The first time I learned you can increase, sometimes significantly, the performance of a car by upgrading the oil cooler blew my mind a little bit, but of course in hindsight it makes perfect sense.

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

#76

Post by Syonyk »

kube-system wrote: post #47
Syonyk wrote: post #37

Earlier quoted context omitted.

> How is this revolutionary motor being outdone by a mid-range sedan engine? Go ask your Camry engine to make 100% rated power indefinitely, and see how long it holds up. That's the difference. A typical car engine is designed to make 30-50hp sustained, and occasionally generate more power for reasonably short periods of time. An aviation engine, generator engine, or any sort of "industrial" engine is going to be abl…

IIRC some automakers do test automotive engines at 100% duty cycle (in a test stand configuration). And more than a few automotive engines are used in slightly modified variants for marine and aviation applications. As I understand, the reason a typical car engine can’t sit at 100% duty cycle isn’t the engine itself, but usually the cooling and oiling configuration. Examples: https://youtu.be/GNPB3RtHN2M https://www.…

I'm aware of some auto engine conversions - the 13Bs out of the RX-7s and related could do it, the older Subaru engines (EA81) would do it, but they're just a small aircraft engine in a car, design-wise...

Looking over the Viking engines, I don't think it's fair to call those "automotive engines," because my read of the description of what they do means they're pulling it apart and replacing an awful lot of pieces. They claim they're "based on" the latest Honda engines, and once you're starting to change the cylinder bore offset, custom hone the cylinders, replace your pistons and conrods, etc, it's no longer a car engine.

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

#77

Post by ww520 »

shadycuz wrote: post #21
causi wrote: 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?

The engine is the size of a push mower. > XTS-210 is about the size of a basketball, weighs in at 19 kg (42 lb), and displaces 210 cc. So you are talking about a 26HP lawn mower. While the Camry might make more power at its normal size. It would not if you scaled it down to the size of a basketball. I'm guessing it would make 1-3HP at that size.

The Camry engine has 4-6 cylinders for its size. A single cylinder is not much bigger than a basket ball.

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

#78

Post by elihu »

Kind of weird article that doesn't talk about either the main benefits or design hurdles. The advantage of the LiquidPiston design is that at the time of ignition, the combustion chamber is a roughly round shape, as opposed to a traditional rotary where it's a long crescent. This should theoretically improve the emissions and fuel economy to be more like piston engines.

I don't think Liquid Piston was talking about a 2-stroke version before. That's news to me, and it seems like it would throw out the efficiency/emissions benefits in exchange for more power. Maybe the author of the article was confused and this isn't actually a 2-stroke design?

The main design hurdle has been longevity. Their prototypes in the past only work for a short time and wear out. That's probably just a matter of doing the necessary R&D to figure out the best alloys to make the engine out, and the best ways to lubricate everything. It's not clear from the article if this new version has this solved so it can last a normal amount of time or not.

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

#80

Post by 93po »

aidenn0 wrote: post #64
syrrim wrote: post #55

Earlier quoted context omitted.

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

And precisely 1/18 the MTBF

In a way, sure. Often when a car engine fails people just replace it. If you were to replace all 18 when the first one failed, the same way you would with a regular car engine, it's not 1/18 the MTBF. And if it was just 1 failing prematurely and you replaced only that one, you also see that same dynamic with car engines when a single component of it fails that's worth fixing.
Post reply on HN