Today I'd like to introduce you to a very
special engine that claims to be a one stroke engine It makes 120 horsepower from only 500 cc
of displacement and it weighs only 35 kilograms it's called INNengine as in "innovation engine"
and it comes from the beautiful city of Granada in Spain and has already been manufactured and
even installed and tested in a Mazda MX-5 In this video we'll take an in-depth look at this engine.
We'll explain how it works and we'll discuss its benefits, drawbacks and its potential and we will
see whether this little thing makes sense or not First up, let's see how this little thing works
and what makes it a one-stroke engine and to understand that we must observe the anatomy. Now
as you can see we have eight pistons in an opposed piston arrangement. We do not have a cylinder head
or a crankshaft. Instead of a crankshaft we have this little complex shaped wavy thing. I'm going
to call it a wavy thing because I don't have an appropriate word for it. Now what happens is that
the Pistons ride on rollers which ride along the surface of the wavy thing. As the combustion force
pushes on the piston the piston pushes on the wavy thing As the rollers go down the slope they force
the wavy thing to rotate. We have two wavy things connected via a common shaft and the forces of
all eight Pistons are transferred through the two wavy things and through the shaft resulting
in a single torque output at both ends of the engine So in theory we can connect a drivetrain
at both ends of this engine and make a very simple well-balanced and lightweight four-wheel drive
vehicle. Now we can connect a drivetrain at both ends because this engine does not have a cylinder
head, cams and valves and as such it does not need a cam-belt or cam-chain at one end of the engine
to be easily accessible and serviceable So how do we allow air in and out of the engine if
we do not have valves? Well, we do it just like conventional two-stroke engines do. We use intake
and exhaust ports that get covered and uncovered by the pistons as the engine operates letting
in air and exhaust out of the engine In the middle between the pistons we also have a fuel
injector and a spark plug which ignites the air-fuel mixture. As combustion pressure builds
it pushes on the pistons sending them outward As the pistons move they uncover the intake and
exhaust ports. Four pistons on one side of the engine deal with intake and four pistons on the
other side of the engine deal with exhaust So how do we prevent exhaust gases from escaping out
through the intake and messing everything up? We do this just like we do it in a traditional
engine, by relying on scavenging, which occurs when both the intake and exhaust valves are open at the
same time. The exhaust port of the INNengine likely gets uncovered first which allows the pressurized
exhaust gases to start escaping out from the combustion chamber. Since they are pressurized they
escape rapidly and they leave a void or vacuum behind them This vacuum is at a lower pressure than the
intake charge outside the combustion chamber which is at atmospheric pressure, which means that the
intake charge rushes into the combustion chamber and fills it with fresh air. The upward sloped part
of the wavy thing then pushes the pistons back up and so they close off the intake and exhaust
ports. Once the ports are closed off compression begins The injector adds fuel and soon we have
a compressed air fuel mixture in the combustion chamber and the process starts once again. The
spark plug fires, combustion occurs, pressure builds the pistons are forced down, they rotate the wavy
thing and torque is generated. So what we have here is a very simple engine without cams or valves
but with direct injection. However because we do not have intake valves we also do not have the
problematic intake valve deposits associated with direct injection only engines which means that we
have the benefits of direct injection without the drawbacks, which is definitely a good thing. However,
if you're a keen observer you might have noticed something in all of this that just doesn't add up. Do
you know what it is? Yeah, it's the one stroke thing This is not a 1 stroke engine. Let's observe. Here
we have combustion. It occurs during the the first stroke We have combustion which then overlaps
with exhaust, and then we have the second stroke beginning which does intake, which then overlaps
with compression. As you can see we need one stroke to do combustion and exhaust and then one more stroke
to do intake and compression. So that is one. Two. Not one. This is a two stroke engine. I really don't
mean to offend anyone but the whole one stroke thing is nonsense because a one stroke engine,
although it could in theory be made, this most certainly is not a one stroke engine and I don't
know of a successful mass-produced one-stroke engine that was ever made and I doubt it will be
made in the near future with current technology Anyways, although INNengine does call their design
officially a "patented one-stroke design" they were pretty honest in a comment response in one of their
videos where they said this: "From a cycle point of view it is certainly a two-stroke engine" So they
admitted it, that's nice. "And the issue with calling it a 2 stroke we found was that people would
instantly assume things like it run with oil in the mixture which it doesn't or that the exhaust
port closes after the intake which again it does not or that it could only deliver so much power. In
the end we found easier calling it something else and we didn't come up with one stroke tag it was
suggested by an external ice institution and we kept it because it sent the right message in terms
of power and to be completely honest because it was catchy. Thanks". So a one stroke it is not. What
it is, is a direct injection two-stroke without all the negatives of a conventional two-stroke
because this engine is not burning any oil The oil is sealed away from the combustion chamber
and I personally find that more impressive than the one stroke word gimmick thing. Now the opposed
piston design is an efficiency advantage for this engine and this is because in a non-opposed
engine we have a combustion chamber above the piston When combustion occurs the energy of
combustion gets transferred onto the piston and turned into motion, useful work, torque. However,
the combustion chamber doesn't really go anywhere It simply absorbs the energy of combustion as
heat. On the other hand, in an opposed design we have pistons both on top and below or if you
will on both sides of the combustion which means that more combustion energy gets to be absorbed,
extracted and turned into useful work or torque which makes opposed designs more efficient than
an equivalent non-opposed engine design A big advantage of the INNengine design is that it can have
a variable compression ratio with a very simple mechanism And this is because the two wavy things,
they are connected to each other however they are not fixed in position in relation to each other.
This is because both of them rest on angled grooves and moving the wavy things along the
angled grooves changes their position in relation to each other. So for example if we
allow both pistons to meet at top dead center and the wavy things in this position then
we're going to get our maximum compression ratio which is let's say 12 to 1. Now if we rotate the
other wavy thing but we keep the opposed piston at top dead center, in the same position, but we get
the piston on the other side, we get it a bit down the bore, this gives us a reduced compression
ratio, which is let's say 9 to 1. Now what we can do is that in theory we could combine this with a
turbocharger and have a low compression and high boost at high RPM for a very high power output
but at low RPM we still have high compression for improved efficiency and responsiveness off boost.
And all of this with a very simple mechanical arrangement But wait, there's more! The in engine
actually has perfect primary and secondary engine balance out of the box. as you can see we have an
opposed piston arrangement which means that the primary piston forces. they cancel each other
out. The pistons move in and out together and also as you have probably noticed we do not have a
connecting rod, which means we also have a perfect secondary balance. Now if you want to know more
about primary and secondary engine balance I have links in the description and in the video corner,
I am not explaining primary and secondary balance again So if it has direct injection without direct
injection problems and variable compression and perfect balance then we must ask the obvious
question. If it's so good then why aren't we using it? Well the logic of this statement "If it
were good we would be using it already" is flawed And that's because I'm sure that long ago
somebody on foot told somebody who wanted to ride a horse "if horses were so good we would already
be riding them" and then somebody on a horse told Carl Benz "well if your cars were so good we
would already be driving cars" and then somebody in a car told to somebody pitching an airplane
"if airplanes were so good we would all already be flying through the sky". Things tend to not
exist and not be used before at some point they start existing and become used. Most of the things
we today own and take for granted and that have made our lives much easier were seen as weird
or stupid idea at some point in the past "A bird in the hand is worth two in the bush" is a nice
proverb but if we stuck to it at all times then we would also be stuck in the Stone Age smashing
stones against each other. Risks have to be taken and experiments have to be made and different
things have to be tried if progress is to be made Another very important reason why most novel
engine designs either fail or have limited success is because the conventional rod and piston
design has a century of development behind it That makes it very much immune to replacement. It is
very hard to compete against 100 years of research and development. I'm sure that if we spent the
past century developing the scotch yoke or the INNengine or whatever, and then if somebody came today
and pitched the rod and piston conventional design as something novel many people would probably
comment "Ah that's so stupid that's never going to work" All that being said the conventional engine
design has one big advantage over the INNengine and that advantage is torque. That's because
the crankshaft may be heavy and take up a lot of space as it's rotating but the crankshaft is
also essentially one big lever and this lever then magnifies the forces generated by combustion
acting on the crankshaft. So we have a very healthy torque output from conventional engines even at
low RPM. But if you observe the INNengine you will see that there is no significant leverage
anywhere. Instead we have this Merry-Go-Round arrangement where pistons act on little
slopes. We do have eight pistons so we have a lot of tiny little torque bursts so this
should accumulate into a big single torque output for the entire engine and indeed on their website
INNengine claims that their 500 cc engine outputs 150 Newton Meters of torque which is impressive.
But what we do not know is where in the rev range this peak torque occurs? However based on simple
physics and observation my suspicion is that peak torque occurs very high in rev range and that low
RPM torque is disappointing. To understand why all we have to do is observe a single cylinder 600cc
motorcycle engine in comparison to a four-cylinder 600cc motorcycle engine. In the single cylinder
we have one big lever and one big piston so each power stroke creates a pretty significant burst
of torque which is why we have good torque even at low RPM. In the four cylinder we have tiny little
levers and tiny little pistons which means that we get a lot of tiny little torque bursts and we
have to accumulate or stack up a lot of these tiny bursts to generate some meaningful torque.
And this is why a typical four-cylinder 600cc motorcycle engine usually has pretty weak low RPM
performance, weak low RPM torque, and generates peak torque usually very high in the rev range. Now you
can imagine what that torque curve will look like if we have eight pistons and absolutely minuscule
little levers in a 500cc package. And this brings us to my gripe with the INNengine. I honestly
feel like this is a very creative, very interesting design It also feels like there's genuine passion
behind the project and I think there's potential even big potential for this engine in certain
fields. However I also feel that the engine is being presented as something that it is not. The
most obvious example of this is the installation of the engine and the driving around with the
Mazda MX-5. We are shown footage of the engine in the car, someone working on the engine and then
the car driving around. And at the end of the video we are given some specs: 500cc, 120 horsepower,
35 kilograms, 40 centimeters. Very impressive And then in the description we are told this: "With
just 35 kilograms and 500 cc our patented one stroke engine was able to move push the Mazda with
ease thanks to the 120 horsepower delivered at atmospheric pressure, no turbo, just pure power in
a 40 centimeter package. Okay, no turbo, atmospheric pressure, sure, I would believe that, if there
wasn't this big old centrifugal supercharger right there in the engine bay feeding compressed
air into the engine. It doesn't matter if it's a turbo or a supercharger, it is forced induction
and it is certainly not atmospheric pressure Of course there's no official explanation for this,
but I think it's pretty obvious that the engine struggled with the car without the help of forced
induction. And a conventional 500cc engine could easily make 120 horsepower with the help
of a forced induction device a supercharger So it really doesn't feel like the engine has any
more power potential than a conventional engine And the other issue I have with the video is
that we are never shown footage of the car at full throttle acceleration, not to mention from a
standstill. The stock 1.6 engine present in the NA and NB Mazda MX-5 makes anywhere, I believe from
116 to 136 horsepower, depending on the market and the generation. Although it's not the
fastest car in the world we still have pretty healthy acceleration from a standstill and
that's because we have a healthy torque at low RPM As we already explained however we never really
see any sort of powerful acceleration any sort of footage of full throttle acceleration from the
INNengine so we really don't know what kind of torque and where does this engine generate even
with a supercharger. The other issue I have is of course all the one stroke stuff but what's even
sillier is that on their website they take this even further, and they claim that their engine
and I quote "has twice as many power strokes per cylinder than a two-stroke engine and four
times that of a four-stroke one" In another part they also add how "Our combustion chamber
has two combustion events per revolution" All of this is very much misleading and that's
because they're comparing a four-cylinder eight piston engine against one cylinder one piston
conventional four-stroke and two-stroke engines Once we equalize the number of cylinders the
nonsensical nature of this argument becomes very obvious The INNengine fires every 180
degrees of rotation that's absolutely the same firing interval as a conventional four-cylinder
four-stroke engine. Yes in the in engine we have combustion in two combustion chambers occurring
simultaneously, we definitely do not have two combustion events in one combustion chamber. I have
no idea how they came up with it that? Seems like they're counting the whole engine as one single
combustion chamber? Which really doesn't make sense But what's important is that we still have one
power stroke, one burst of torque every 180 degrees of engine rotation, the same as a conventional
four-stroke four cylinder. And also what we must not forget is that here we have eight
pistons in the INNengine and that is the piston ring friction equivalent of a conventional V8.
So it's very possible that the efficiency gains from the opposed piston design are negated by the
very high amount of piston ring friction Another slightly silly claim INNengine makes is with their
other engine which they call the Rex-B and this is basically just half of their opposed piston design.
We have one wavy thing and only four pistons and although they call this a one-stroke engine as
well this really is just a conventional two-stroke engine pre-mix and all. And this engine makes
22.7 horsepower from 125 CC of displacement and INNengine claims that this is twice the power
delivery of a conventional two-stroke This is not true. There are many conventional two-stroke
engines with 125 CC of displacement that may make more power than this. I personally owned and
rode one. It was a 125 CC engine in my Yamaha TZR125, it was a two-stroke engine and it made 28
horsepower, more than the INNengine. However that engine certainly did not weigh 5 kilos like the
INNengine, and personally this is what I would focus on promoting: The very low weight and the compact
nature of the INNengine rather than all the one stroke stuff. But what's nice is that INNengine is
very objective and realistic in the application section of their website. Here the one stroke
argument is gone and we see that the engine is meant to be a range extender. It's also great for
light aircraft and drones because it's very small and very lightweight. It's also great in Maritime
power generation applications to make electricity for boats and to power hydraulic equipment on
yachts and stuff like that. Again it's very small and very compact. And also because the engine
can be installed right side up or upside down doesn't matter, it is going to work equally well, so
it's going to keep running even if the boat capiszed and you can do any sort of flying maneuvers
for any length of time with your aircraft with this engine installed. And there's also plans for
a bunch of hydrogen stuff. So when we see all of this it becomes very obvious that the engine
isn't meant to replace the conventional design It's simply meant to be a contender in certain
applications and this then makes the one stroke stuff and the installation in the Mazda MX-5 look
like a little more than attention grabbers and publicity stunts, and personally I feel like really
there's no need to misrepresent this engine as having more strokes or being more powerful and
capable than a conventional design because it probably isn't and doing this takes away from
the credibility of the engine and takes away from the true benefits which are simplicity,
very low weight and a very compact design
