Company builds 500cc ‘one-stroke’ engine | Hacker News Reader

Company builds 500cc ‘one-stroke’ engine

thedrive.com

142 pointsthrowaway2820364 comments

That's neat.

This is a type of axial engine, a cam engine.[1] People have been trying designs along this line since at least 1926. A recent version was from Axial Vector Engine, which was pushing their stock around 2006 and is now gone.[2]

The problem with this class of designs is that they apply large forces to small parts. The most likely source of trouble is the bearings of those little wheels at the base of each piston. Those have to take the full force of the explosion on each cycle. That doesn't mean it's impossible, but it means it's a long way from the first running engine to one with a long, useful, low-maintenance life.

[1] https://en.wikipedia.org/wiki/Axial_engine

[2] https://web.archive.org/web/20090208215443/http://www.axialv...

also noted, that they don't have that lever like standard pistons do, so torque is an issue.

Torque isn’t an issue if it isn’t pushing a drivetrain, but an inverter generator to charge the electric drivetrain.

That would also lower the forces applied to the piston roller bearings, which should greatly improve reliability.

Yes those tiny new engines (also liquidpiston engine) would make a good range-extender for electric drivetrains, also thinking semi-trucks and big equipment. Wherever you need big torque/power to get going, but once rolling 35hp is enough to keep rolling.

If it's putting out the power you need with good efficiency just gear it for whatever torque you want for the application.

The idea that torque and power represent different qualities out of an engine comes from manufacturers quoting just peak torque and peak power, giving you two different points on the torque and power curve. A complete torque or power curve is much more useful. Either works and which is just a matter of preference as you can just calculate the other from the same data.

In case you’re wondering:

“Now, here's the thing: this motor isn't a one-stroke engine. It has a compression stroke and exhaust stroke, making it a two-stroke cycle. INNengine acknowledges this and has said that it brands the motor as such because people would assume that a two-stroke engine would need to have oil mixed in along with fuel. Most two-strokes do. The company says that the one-stroke name was suggested by an ‘external ICE institution’ and they found it to be ‘catchy,’ so INNengine stuck with it.”

(From close to he bottom of the article)

because people would assume that a two-stroke engine would need to have oil mixed in along with fuel

That suggests most people don't know about 2-stroke diesels, although I suspect much of the older population (at least in North America) have probably heard or been on a vehicle that uses one.

Also plenty of (gasoline) two-stroke engines use oil injection so you don't have to use premix, namely any machine where you'd typically get your fuel straight from the pump like a snowmobile or a dual sport motorcycle, back when those were still two-stroke.

I had a 1983 Yamaha DT-80 (little enduro dirt bike) that had an oil reservoir so you could use pump gas.

Those are pretty nasty for bystanders though.

And there are 4-stroke engines, such as the Stihl 4-mix[0] that use fuel mixed with 2-stroke oil for fuel and lubrication.

0 - https://www.stihl.com/4-mix-engine-lightweight-and-with-good...

> That suggests most people don’t know about 2-stroke diesels

For anyone curious, the Detroit Diesel, aka the Screamin’ Jimmy, is the canonical example of a 2-stroke diesel.

Fun fact: these engines all have a supercharger — which is required to start the engines - but are considered naturally aspirated. GM also made turbo-charged variants (which still had the roots blower for starting) that are properly forced-induction.

A few videos:

Short video demonstrating the distinctive 2-stroke diesel sound: https://youtube.com/shorts/kp5aHCRAORs

These things were kind of prone to running away, with a lots of myth and folklore about catastrophic explosions and death and destruction, so there are a fair number of Youtube videos where people rig these things to run away. This is, without a doubt, on many levels, the best example of the genre: https://youtu.be/bLRF-LRgvJk

In the UK, Foden also made 2-stroke diesels, but they were nowhere near as popular or long-lived as in the US:

https://www.youtube.com/watch?v=5pwhm_xoDiY

What they all have in common is the sound that makes people think it's not a diesel, because the 2-stroke cycle causes them to sound like they're turning twice as fast as a 4-stroke. A 2-stroke at 2000RPM sounds like a 4-stroke at 4000RPM.

My favorite thing about Detroit engines is they designed them to have the supercharger act as almost one of the cycles. Their intake isn't a valve it's actually a port the cylinder opens at the bottom forcing air in and exhaust out.

So, how do they lubricate it?

Like any other engine with a separate oil system.

The same as any other engine that doesn't mix oil into its fuel.

Lubrication in fuel vs lubrication using a separate system and 2-stroke vs 4-stroke are two entirely separate engineering decisions, that are in no way tied to each other. It's just that the most common types of 2-stroke engine use lubricant oil mixed in fuel, and the most common types of 4-stroke engines don't, and so they concepts are thought to be related to each other by most people who don't know much about engines.

2-stroke engines often go into handheld tools or dirt bikes that can't explode when you turn it upside down (at least, immediately), and since it eliminates the oiling system, premix is often chosen for these.

2-stroke engines also have great power densities (at the cost of fuel efficiency), which means those two often go hand-in-hand.

2-stroke engines also have great power densities (at the cost of fuel efficiency), which means those two often go hand-in-hand.

Large, or perhaps huge would be a better adjective, 2-stroke diesels are extremely efficient, better than 2-stroke gasoline, 4-stroke gasoline, and 4-stroke diesels:

https://en.wikipedia.org/wiki/Brake-specific_fuel_consumptio...

actually a two stroke, 2 opposing pistons in a common cylinder cycling through compression stroke-combustion-power stroke. no connecting rod to bend or break, and large cams replacing the crankshaft

https://www.thedrive.com/uploads/2023/07/14/innengine-1.gif?...

[Now, here's the thing: this motor isn't a one-stroke engine. It has a compression stroke and exhaust stroke, making it a two-stroke cycle. INNengine acknowledges this and has said that it brands the motor as such because people would assume that a two-stroke engine would need to have oil mixed in along with fuel.]

the goal seems to be a hybrid ehicle that places more duty reliance on electric propulsion, but keeping the long range capabilities of petrol fuel in a combustion-over-electric design.

[adndm] this is 120HP in 500cc displacement, which is superbike engine stuff

Indeed. My old bike had 1400cc and was rated at only 94 hp.

'old' may have something to do with it here, engine tech has seen all kinds of improvements over the last two decades resulting in tiny engines with ridiculous levels of output while still having reasonable life span. A pretty common small car engine that has .9 L displacement and a turbo yields 105 HP, that's 120 HP/L, vs 67 HP/L for your bike. A few years ago I had a 660 CC 4 cylinder engine in a car that did 67 HP so that's about 100 HP/L.

This engine is pretty clever, it avoids one nasty problem of swashplate drives and their cousins: the piston travel is only half here of what it would be otherwise. But there is a lot of extra complexity.

We should probably call a spade a spade here. This is a 2-stroke motor. In today's powersports world it's normal for a factory 650cc motor to be putting out over 135HP. It's not impressive in terms of the performance to engine size and, as I mentioned in another comment, this engine will be extremely weak on the torque side of the equation which will make those ponies virtually useless.

That's fair, for a two stroke it isn't substantially better than what's out there. As for weak on the torque, for a generator that may not matter all that much. What I'm more curious about is the powerband, in other words how wide the RPM range is over which it produces max power. If that range is wide it might be a very useful engine (because you can simply couple it with an appropriate gearbox for torque), if it is very narrow then it really only will work well as a generator producing high frequency AC.

That's one reason why specialty generator engines tend to run with very sharp cams on the camshafts: they only need to work in a very narrow RPM range and opening them earlier or later is just going to waste fuel so for maximum efficiency you want the valves to be open just long enough to take in enough air or to exhaust the expended fuel/air mixture.

edit: apparently this engine also has a super charger, which isn't quite 'atmospheric'.

The Ariel Atom V8 did ~160hp/liter in a 3L NA engine.

I'm sure its pretty high strung, but its also older and more "conventional" than exotic supercar engines.

The Atom is an absolute beast.

There are 1.9L/1900cc turbo diesel engines rated at 95hp - funny to think about

why I feel like this would put pressure on one side of cylinder block due to non-linear force against bottom wave-plate and cause wear and tear?

Agreed.

Also, how does it get started? Seems like the only force pushing the piston against the axial cam is the fuel explosion. (Perhaps extra springs to retract the piston for intake?)

> Also, how does it get started? Seems like the only force pushing the piston against the axial cam is the fuel explosion. (Perhaps extra springs to retract the piston for intake?)

In lieu of combustion you still have the air spring rebound from the compression... (at least until the exhaust opens)

Presumably an electric starter, much like a traditional engine - only it’ll turn the driver shaft instead of a cam shaft.

> this is 120HP in 500cc displacement, which is superbike engine stuff

HP-wise, maybe. But the reality is this is not a performant engine you'll see replacing high performance 2 or 4 stroke motors anytime soon.

First is that the company has lied a lot in their marketing. They imply that the motor is naturally aspirated and then show a car, with said plant running a very obvious supercharger. They also lie about the motor type - there is no viable 1-stroke motor and there likely never will be based on the laws that govern our planet. They even admit to their own lie in the name of marketing (a non-oil burning 2-stroke is not a 1-stroke by default).

The real reason this motor will not touch a comparable superbike cc-to-cc is that this motor has no claimed torque specs. It really doesn't matter at all if they're able to put out 120HP in 500cc if it has low torque. And we know it has low torque based on the fact that this motor has no crankshaft, and therefore the mechanical advantage that adds.

I currently have 650, 800 and 850cc 2-stroke motors today that have similar HP-to-cc today compared to the 120HP they've claimed from 500cc. The difference is that all these motors have the torque required for driving performance.

While I would love to see something bridge the gap of small heavy 4-stroke vs light oil burning 2-stroke this is, unfortunately, not it.

this is 120HP in 500cc displacement, which is superbike engine stuff

The real question you should be asking when you see suspiciously high power densities is "for how long?"

A car and a truck engine can have the same HP rating, but the former is not going to last very long producing that power continuously, while the latter is essentially designed to spend most of its time at full power.

They admit it's two stroke, but they use that name because they have no oil in fuel and "it's cool".

It's small, lightweight, perfectly balanced but has low torque so it's not a best fit for cars. Would be great for generator.

Considering the negative associations with two-strokes (noise and emissions) it makes sense to try and distance themselves from it if it does not have these properties.

Would be great for generator.

That was my first thought too -- this design seems simpler and correspondingly less prone to failure than most engines, which would make it well suited for emergency use.

They're pretty explicitly marketing it as a "range extender" for hybrid electric vehicles. In the mockups in the article it seems like they don't have a traditional gearbox, so it sure looks like they're intending to suggest running it as a straight-up electrical generator even when mounted in a car. Neat application of the concept. Diesel locomotives have worked this way for a long time.

Here's a great deep dive into the engine, explaining the pros and cons: Yes it's simpler and more compact, but the lack of crank shaft means that it doesn't benefit from the lever effect of the shaft so it doesn't have as much torque.

https://youtu.be/9I0_3qFmPUM

Then it’s perfect for a hybrid vehicle that uses electric when torque is needed

Decent video analysing the claims they make and pointing out some problems with their claims - including the fact that the Mazda has a supercharger installed. https://www.youtube.com/watch?v=9I0_3qFmPUM

While the actual method of connection between pistons and the lobed plates seems new, opposed piston engines have been around for a long time, so I'm not sure this is quite as new as the article appears to make out [1]. I instantly thought "deltic"!

[1] - https://en.wikipedia.org/wiki/Opposed-piston_engine

That's a variation on the swash plate drive:

https://en.wikipedia.org/wiki/Swashplate

I like theirs better than an actual swash plate because you can pull all kinds of timing tricks by shaping the lobes just so, and it looks easier to lubricate.

120 HP is 88kW. You could shrink this considerably & still have a very nice range extender. (Edited: proper conversion)

Many cars use only 20kw to go highway speeds, imagine if this could shrink to 1/8th its current size.

That conversion is the wrong way around. 120 HP is roughly 88 kW. The point still stands, of course. If it indeed can be shrunk further while remaining efficient.

What kind of conversion efficiency would you expect from a range extender, like 90% or so?

Converting shaft to electrical energy should be 90%+ efficient, yeah.

This is about the efficiency we should expect from modern EVs making traction power (with some better, some worse), and the efficiency backwards has some nuance about torque vs power, but generally generation is using the same principles & systems in similar configurations.

If anything, I think efficiency should be higher for comparable-ish systems, since a range extender can tune for an incredibly narrow power-band where-as EV electric motors have a range of rpm they have to operate across.

Something to notice in the line drawing: The rear is powered by an electric motor. I assume that's to get it moving in the first place before there's enough momentum for this engine to keep it going.

I would assume so, yes. This is exactly how regular motors get started, unless you have one of those old-timy cranks you had to manually turn to get the motor running

They tend to be near the engine, and not the opposite end of the vehicle, though. The electric motor is right beside the passenger-side rear wheel.

Would make a great boat engine for smaller leasure crafts and sail boats.

Immediately Installs It in a Miata

https://yt.artemislena.eu/watch?v=-evhsWLWlkY [video]

Would this be good in a bike? Would it likely be more power than say my R1?

I don't think it'd be very good.

It has no torque on the low end so you'd have to set idle really high to get useful low range performance.

This type of engine is great for its intended application though: A steady-state range extender/generator.

Now, at higher revs, it might be pretty sweet.

Yep, you’d have to run it at high RPM, like a rotary.

It's like a two-stroke diesel, but with spark plugs.

I wonder if this would be a good engine for an airplane?

In theory, yes. But especially the single engine aircrafts are very set on old but reliable engine design, for reasons.

In terms of power curves and power to weight, absolutely. But I would be really unhappy taking off in a plane that uses a cam engine. Those are not historically known for their great reliability.

Man, a smaller version of these would be awesome in motorcycles and scooters. Wonder what the MPGs are….

Is thermal efficiency mentionned? The Aston Aerospace strokeless engine is 60%.

The simplicity! Kudos to the designers.

of COURSE they put it in a miata. :)

looks like the dynacam, whatever happened to that?

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