Hello everyone and welcome in this video we are talking about Mazda's revolutionary SkyActive-X engine
it's really cool what they're doing with this and the basic approach is they're trying to you know determine
what is the ideal engine and how do we get our internal combustion engine there?
and I think the question will come up. You know why are they spending money and time?
improving the internal combustion engine when the future will probably be electric and they are looking at hybridizing their vehicles
and they are looking at purely electric vehicles. They will be making them in the future
they have said that that is in their plans to do
but that said there are still improvements which can be made to the internal combustion engine
and I think kind of the proof of Mazda's logic with this is that for the past five years
Mazda has had the EPA's highest corporate average fuel economy rating for all manufacturers
and that's without a single hybrid or electric vehicle so their approach is logical. You know they're improving something
they're making it better and they are overall reducing co2 emissions of the automotive world out there
and they're doing it better than pretty much everybody else without hybridizing or electrifying their cars
that's not to say that an electric car can't have better emissions
but the way mazda is doing it is very smart for the time being so before we get started
into, what are the specific changes? They have made to create this ideal engine or work towards this ideal engine
how does this engine work and so the premise of it is something called spark controlled compression ignition?
so it's operating much more similarly to a diesel engine except that it's still using a spark plug
so what you have happening is you have an air fuel mixture?
and you're going to compress that air fuel mixture as much as you can without it igniting you want it to be just
before it's about to ignite from pressure and heat alone and then right when it gets to that point you fire a spark plug
that spark plug creates a pressure wave and as that pressure wave expands outward it forces the rest of that mixture
which is just before self combustion just from heat and pressure the pressure rises just a little bit more and then all of it
simultaneously ignites so similar to a diesel engine
which it gives you a really high temperature and pressure area you spray in that fuel and it immediately ignites
here instead you have air and fuel you wait just
before it's about to ignite fire a spark plug that in the pressure just slightly and then you have all of it combust
simultaneously, so that's the the methodology behind it
but you cannot always run it in this mode, so
in you know the ideal conditions you want to run it with spark controlled compression ignition because the efficiency is greater
but you can't always do that so if you're look at a graph of load versus rpm
there is going to be you know kind of a faded area where it switches from spark controlled compression ignition
to a regular spark ignition engine, so it operates just like any other gasoline engine out there
actually, it'll be running an Atkinson cycle when it's running on spark ignition
but operating like a traditional gasoline engine the spark ignites the flame travels through that air fuel mixture you have combustion occur
so there's kind of this you know shaded area
which where it switches between the two the important thing to keep in mind is that it is always using a spark to control when?
compression occurs, it's not going to have just purely compression ignition
it's always going to be using a spark in order to properly time when that ignition occurs
so now let's get into what are the ideal you know?
what is an ideal engine and how did Mazda work towards that ideal engine?
so an ideal engine has a
super high compression ratio as high as you can make it and mazda previously had the record in a production vehicle with the 14:1
compression ratio for a gasoline engine and in the prototypes which I got to drive
they are running 16:1 so this will be very close to what ends up in the production engine
somewhere around 16:1 is where they found kind of the ideal scenario
and so this will be the highest of any gasoline engine out there. Now, what's the problem with high compression ratios?
They give you more torque
they give you better efficiency, but they lead to engine knock and engine knock destroys engines
but in this case we actually want engine knock occurring at the right time so it's not the same thing
but it's it's very similar so basically they want to control when knock occurs up instead of randomize knock
they want complete combustion of everything surrounding that entire air fuel mixture at the same time and what's cool about
this is they're running a 16:1 compression ratio with 87 octane fuel so regular octane gas
they actually found ideal was with 80 octane, but of course you know in the states 87 octane is the regular fuel
that's available so that's what they're choosing to use but a 16:1 compression ratio would never be paired with the lowest octane fuel
in a different style engine and this one because they want knock to occur not exactly the same thing, but they want that
compression ignition to occur a low octane fuel is desirable
okay, so it has a high compression ratio
that's one thing another thing you want is lean combustion and the
reason why you want lean combustion is lean combustion gives you lower flame temperatures it gives you less nitrous
nitrous oxide emissions, and it gives you less energy lost as heat, so it means it's going to operate more efficiently
and so you know a lot of people say that as you lean out an air fuel ratio it burns hotter
that's not actually true. What happens is if you go if so here
we're looking at a plot of an air fuel ratio here would be a rich air fuel ratio here would be a very lean
14.7:1 that's stoichiometric or the ideal air fuel ratio
which means all of your fuel and air is burned completely so that's going to be
essentially where your peak combustion temperature is and it's also going to be where your peak nitrous oxide emissions are occurring and
as a result that's not really ideal from an emissions standpoint or from a combustion standpoint
because your temperatures are hot and you're producing a lot of bad emissions
so by leaning out that ratio the combustion temperatures start to fall and your nitrous oxide emissions
just completely plummet
and so there's there's a huge benefit if you can run it really lean and the way they do run it lean
there are problems with lean combustion and that is that lean burns slowly, and it burns kind of incomplete
and so they have a very clever method where when that intake valve opens
and the cylinder is pulling down it creates this swirl within the cylinder
and that swirl helps to even out the ratio
and then they also have direct
injection and so they wait as that piston is coming upwards towards the top this has an air fuel ratio about
37:1 which is unheard of in gasoline engines typically you're not going to see much higher than 16:1 something like that
ideally, you know you're floating around that 15:1, so 37:1, 2.5 times the ideal ratio
so as it's coming up
there's a direct injector
and that sprays a little bit of extra fuel which is right beside the spark plug so the area near the spark plug is
less lean than the area of the rest of the cylinder so about 29:1 right beside the spark plug and then
37:1 on the other areas the reason they do that is to help for that
spark controlled ignition to occur so the spark controlled ignition occurs
then it starts to expand out and it forces the rest of this to combust
simultaneously so very cool what they've done. Now this is actually a
supercharged engine
so there's a supercharger on it Mazda calls it a lean
supercharger and the reason why they call it a lean supercharger is because it's not to improve performance it can
improve performance a bit and they do use it slightly for that
but the real reason why it's on there is to control the amount of air going into the engine
they want to be able to produce these super lean
conditions where you have that air fuel ratio of 37:1 and that means a ton of air needs to get packed in there
and so that's why they use the supercharger and the benefit of running this lean combustion as mentioned
you've got less energy lost as heat from those lower combustion temperatures. You've got less nitrous oxide emissions and
because you have extra air in there that extra air heats up during combustion and that basically multiplies the effect of
increasing the pressure within the combustion chamber so you're improving the efficiency without necessarily using more fuel so it's a very clever
method of getting super efficient combustion, okay, let's move on to our third ideal scenario
which is instant combustion basically with an internal combustion engine you want that combustion to occur
completely at up dead center all at once no delay whatsoever and so with a gasoline engine
you have a spark that fires, and then the combustion travels outward from that spark
and eventually burns up everything in there with the diesel engine it's much more instantaneous. It's much faster
you spray in the fuel and immediately everything burns, so as you can see the in a diesel engine
you've burned up everything when the piston hasn't moved down all that much from top dead center versus in a gasoline engine
that piston is going to move down significantly more before all of the ar and fuel has been burned
so why isn't that ideal?
well think about it this combustion is what's pushing your piston down,
so if it combust at the very top that means it's going to be pushing your piston down the entire time if it's combusting
towards the bottom that means it doesn't have much time that it's going to be pushing that piston down
so it's not doing as much useful work so with SPCCI. It's much similar to diesel ignition
you have that spark fire, and then instantly everything else around it combusts
so it's a much quicker combustion than a gasoline engine that improves efficiency and that also improves torque
very cool to have
so our final thing is combustion timing and as mentioned you want complete combustion to occur at top dead center
and you want that combustion to occur at top dead center so timing is the really tricky part here,
which is what you know initially, why they chose to use a spark plug to control the compression ignition
so what's super clever about this engine,
they have a pressure sensor on the top dead center, so it's not actually a spark in the top center
the spark is a little bit offset
just like the fuel injector
and they've got a pressure center up up top there and that pressure sensor is
monitoring the pressure inside of this combustion chamber
and so if you look at pressure here on our vertical axis and the time you know basically our crank angle on our
horizontal axis so where is that piston right here from here to here?
it's during the compression stroke, so that's the time from the compression stroke
this is the time for the power stroke, and then right here this green line
we have dead center, so your spark fires during that compression stroke
and you can see that that causes the pressure to rise so that little bubble of
you know combustion that's occurring is going to cause the pressure inside the cylinder to rise and you want that pressure to rise to the
self ignition temperature of the air fuel mixture
so once it reaches that self ignition temperature and pressure then all of a sudden the rest of the cylinder combusts
and you have a big peak in pressure, so you want that peak and pressure to occur?
basically immediately after top dead center so that you get all the useful work out of it
you don't want it to be delayed. You know way after top Center, then you're not getting as much useful work and
so the way that they control this what happens with if you have different humidity, different air temperature, different engine load, different rpm,
things like that there's all kinds of variables that will cause how long it takes this spark to reach the self ignition temperature
for that combustion pressure to get high enough for the rest of the compression mix
to combust and so that timing is what's super-sensitive basically
you know all kinds of ambient conditions are changing this so that's what this pressure sensor is monitoring
it's saying how long is it taking for the spark to fire and then compression ignition to occur and if it's taking a long time?
it'll advance the timing and if it's taking a shorter amount of time
it'll push that timing back and so that way it's always using this pressure sensor to optimize that this
big peak right here in pressure is occurring right after top dead center
so you get the maximum amount of performance and efficiency out of the engine.
Very cool what they're doing all four of these are really exciting kind of methods of having this
approaching towards the ideal internal combustion engine, so what are their results you know what is all this done
well the SkyActiv-G engine was class-leading that's their previous
gasoline internal combustion engine was already class-leading in fuel economy, and they have increased its fuel economy by 20%
and almost just as exciting if not more exciting than that is that it now operates
efficiently at a much wider load range and a much wider rpm range, so what does that mean?
well you can be on the gas more and it can also use shorter gearing or more aggressive
gearing so that you're at higher rpms, and you can get that response without
sacrificing fuel economy so that's what's really cool about this engine you can be at higher rpms and higher engine loads than you would traditionally
be at and still be more efficient
so that's it's it's really cool that it's going to be an engine that will have a lively characteristic
I did get to drive it which was pretty exciting and
you know it's not a super powerful engine the prototype that I drove was about 190 horsepower
but you know you have you can have more aggressive gearing with it, and you get response out of it
so it leads for an engine that has characteristics that make it fun to drive
i'm sure you could tune it for you know different horsepowers
but ultimately the idea behind it was to make this ultra efficient internal combustion engine, but it also doesn't sacrifice
you know the boredom that could be associated with a highly fuel economy highly engineered vehicle purely for fuel economy
so thank you all for watching, and if you have any questions or comments feel free to leave them below.