Hello, and welcome to PowerDrift, this is Simplified, where we take complicated automotive
ideas and break them down into something simple. This is a series of videos and if you've never
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One of the most common questions we get for Simplified is, what are engine formats like
and what do they mean for you.
And today, let's break them down and let me warn you, this is a really complicated topic,
so my job is to keep it as simple as possible, so let's begin with single-cylinder engines.
Most of us use single-cylinder engines anyway, and they are the most common format when it
comes to petrol engines that go into motorcycles.
And the reason for that is they're simple to make because there's just one piston, one
conrod, one crank, one set of valves, a cam or two and that's basically the entire engine.
The problem with the single-cylinder engine is that because the piston moves up and down,
and remember, this is accelerating up and then decelerating to a stop at the top, which
is what we call the top dead centre, then it accelerates again and then decelerates
to a stop at the bottom again, this acceleration and deceleration process basically causes
what we perceive as vibration and that's why single-cylinder engines can't become too large.
So in the world today, if you look at the KTM 690s, or the Husqvarna 701s, those 650cc
engines are roughly the largest singles that money can buy and the reason why manufacturers
are scared or don't want to build engines bigger than that is because the vibration
becomes more and more difficult to handle.
One way to handle vibration is of course to add a counterbalancer, but remember, the counterbalancer
also takes away power from the engine, so there is a finite limit to how much you can
counterbalance an engine and that's why you have twin-cylinder engines.
Now in theory, when you have twin-cylinder engines, obviously you have two cylinders,
two pistons, two conrods, and all of that is connected to one crank, you can use these
pistons movements against each other to cancel some of this vibration out,
but how is this done?
Now if you think about the crank on the engine, it's obviously rotating, right?
Each rotation is counted in degrees, so it's a 360-degree crank as it were and for a four
stroke cycle to complete, it needs 720 degrees of rotation because the crank has to rotate
two times over.
It's that number which is used to give you what is called the firing order, which determines
when the sparkplug will fire and that is a crucial part of how an engine feels to ride.
Some of the oldest twins used to have pistons that would go up and down together, when the
two pistons go up, one of them fires and on the next cycle, the other one fires.
This is a format which is a very old school format, which has since evolved, and today
you get a lot of parallel twins, which is the same as an inline twin, there's no difference
between the two formats, you get parallel twins, which fire their engines at 270 degrees apart.
The fun part about 270-degree firing orders is that that's what a V-twin, especially a
90-degree V-twin, what Ducati specialists at, that's what they use as their firing order
for twin-cylinder engines and the surprise is that when you take an inline parallel twin,
and you put it in a 270-degree firing order, it actually sounds like a V-twin.
So what you hear of an engine, the vibration that you feel is largely a function of how
many pistons does it have and what firing order is it using.
Now in that sense, if you think about it, an engineer designing the engine has a very
flexible system in front of him, you don't see this flexibility because you see the finished
product, but if I were to start designing an engine today, and let's say it's a parallel
twin, I have a choice of what firing order would I like to use, I have a choice of how
much weight would I like to put in the crank, a heavy crank versus light crank will completely
change the character of the engine, I can choose compression ratios.
So if I wanted an unstressed engine, I might do something reasonable like 7/8/9:1 as compression,
if I wanted a high performance engine, and remember, higher compression ratios also return
better fuel economy, then I would go to something much higher like 12.5/13:1, right, so this
is a very flexible system, which engineers all over the world, who work for manufacturers
used to create engines that talk to what the brand represents.
As platform engineering progresses, manufacturers are now able to make engines that do multiple
roles with small changes primarily to ignition timing and fueling, that create dramatically
different riding experiences.
Now when you want to make more power from an engine, then you need more cylinders, or
you need more displacement, so let's assume that our parallel twin is at a cap, we don't
want to grow this any further, then you'd simply add a third cylinder to the engine.
Again, with the three-cylinder engine, you can play around with the firing order, most
of them are pretty even, so they'd fire 1-2-3 or 1-3-2, but it basically doesn't make any
difference to the character of the engine, but because it has three cylinders, there
is some native vibration to this engine which needs to be controlled.
When it is controlled well, we perceive it as character when it is not controlled well,
we say that engine vibrates a lot and I wish they'd done more work.
One of the smoothest engine formats, and that's why it's so popular is obviously the inline-four
obviously what that means is there are four cylinders in a row and again, an engineer
can play around with how he wants the pistons to be moving up and down what the firing order
is to create all kinds of variation.
So the crossplane crank that Yamaha's so famous for, it's basically a trick with the firing
order that ensures that this feeling of connection between what the rear wheel is doing and what
your throttle hand is doing is very strong and comes natively, one of the reasons is
the fire order that they've chosen.
Other inline-fours can use a very smooth, even firing order, which produces that smooth
humming sound that we so love about inline- fours but remember, again, this is a flexible
system, this is what the engineer chose to make
in a race application where they want maximum performance, that may not be the most optimal
firing order and obviously, the latest in the series is obviously a V-4, I say the latest,
because they've appeared on the scene the latest and their adoption is increasing now.
So a V-4 is essentially two V-twins added together and it produces a remarkable engine because
it's much smaller than an inline four, if you play with the firing order, you can create
the same feeling as an inline four, but most manufacturers don't actually want to do that.
In the case of Ducati again, they built a V4 that actually sounds like a twin because
the firing order was designed like that, whereas Aprilia has a much more even firing order
and it sounds more or less what like the MotoGP's bikes sound like today.
In fact, an RSV with a nice exhaust going down the racetrack, it actually sounds like
a MotoGP bike going fast and it's an incredible, incredible sound and what I would like to
tell you is that all of this knowledge is nice, but what is most important is how does
it feel when you ride the motorcycle and this is why I continue to say it to you, you ask
us questions about what motorcycle you should buy, our answers are usually, this is what
these are about, but you need to test ride and decide because what feels good to you
is a very personal feeling and it's very hard for us as testers to identify exactly what
makes you tick.
So in sum, I would say ignore the engine format when you're buying a motorcycle outside of
trying to get a sense of what this motorcycle will feel like.
Ride the motorcycle with an open mind, see what you like and what you don't like and
pick the motorcycle that makes your heart sing.
Thank you so much for watching, this is Simplified, this is PowerDrift.
If you'd like us to discuss this in more detail or you'd like something else on Simplified,
all you have to do is leave us a comment and we'll get right on it and obviously, I will
now invite you to hit the four buttons that all of us love to hit subscribe, the bell
notification icon, like and share.
Thank you so much for watching.