Hello, everyone and welcome. In this video
we're going to be talking about Skyactiv-X, Mazda's revolutionary new engine which they say they're going to be implementing in the year
2019 as a part of their overall vision looking out towards the year 2030 which they are calling "Sustainable Zoom-Zoom 2030"
(I'm not making that up.)
That's the ridiculous name that they came up with but anyways the name is silly the technology is not the technology is very cool, so
The engine basically is running HCCI - "Homogeneous Charge Compression Ignition"
and this is kind of the holy grail of
gasoline engines because it's the best of both worlds
when comparing a gasoline and a diesel engine. So a quick overview of how this works I do have a separate video
Explaining HCCI engines, but what Mazda's doing is a bit different so a gasoline engine has a homogeneous charge meaning
you've got air and fuel mixed in there
and you ignite that air and fuel with a spark
A diesel engine controls ignition by when it injects fuel so your using compression ultimately to ignite it
You inject in that fuel and the temperature and pressure is hot enough that that fuel ignites as it's sprayed into the cylinder
now homogeneous charge compression ignition
engines have that mixture of air and fuel already in there of gasoline and as it's compressing that pressure from
Compression is what ignites that Air & Fuel mixture
Now as you can imagine
timing is going to be more challenging with this because you can't control timing with a spark or when you inject fuel it's
Simply based on the temperature inside of this chamber when that temperature reaches the point that it can ignite everything everything ignites
you know mix with that pressure and so
The the challenge is of course controlling that internal temperature so you can use EGR to regulate it, there's different methods
You can use valve timing
In order to regulate the temperature within there and make sure you have good timing to be able to use this feature
So the biggest challenge with HCCI engines is of course controlling that internal temperature and making sure you have the range
where
HCCI is possible if it's too cold you run into ignition problems, cold starts are a great example
If it gets too hot you start to have engine knock unpredictable timing and you don't want that to occur either
Now Mazda said "Wait a minute." You know we don't have to have this all-or-nothing engine. How do we fix this range?
Well, you throw in a spark plug
So you kind of go back to the old way of just a traditional gasoline engine
And that's how they solve this issue of you know for example a cold start if you have super cold ambient temperatures
Which aren't conducive to having this HCCI function running if you're really high load high RPM
You can use a spark ignition
To you know make sure that your timing is perfect
When you're cruising down the highway when you have Low load scenarios
And you want ultimate efficiency you can switch into this HCCI mode
Where now you have you know a much more efficient Mazda says that it's twenty to thirty percent more fuel efficient than their current
Skyactiv Gasoline engines so a huge efficiency improvement
You know when they're able to run this method this method of combustion
Now this is basically. What we know
And over here is more speculation on my part because Mazda hasn't released all that much information about this engine
So take it with a grain of salt
But it's kind of cool to think about the ways that they're going to be controlling this engine some of this stuff
We do know some of it
We don't know kind of works through it
But basically when this engine is running in a gasoline mode
What I would imagine they're doing is lowering the effective compression ratio. So when you're running the engine on compression ignition
You want a higher compression ratio to be able to ignite that air/ fuel mixture
Now they haven't released what the compression ratio is there's some sources out there saying it's 18:1
Mazda doesn't have it directly stated, but let's just assume
It's 18:1
When it's running in this HCCI mode in the gasoline mode where you're using a spark to ignite it
You're going to lower the effective compression ratio by opening up that intake valve during the compression stroke
And this is what they do with their current Skyactiv engines
It's called the Atkinson cycle, and so it allows you to have a lower compression ratio
And then a higher expansion ratio which is an efficient way to run it
but of course if you had for example an 18:1 compression ratio
You would have knock and pre ignition problems and so in order to mitigate those issues
You lower the effective compression ratio by leaving that intake valve open during compression
And then have less air and fuel overall to combust
And you're also going to run at a richer or stoichiometric air fuel ratio and Mazda has announced that these engines will be supercharged
So you're kind of going to get the best of both worlds
Where you can have power when you really want it
And then you can be super efficient when you don't need that power and run it into this homogeneous charge compression ignition mode
Now one of the benefits of this compression ignition
Method is that you're able to run Super Lean air/fuel ratios
Leaner than you otherwise
could run and ignite with a spark. A spark wouldn't be enough to ignite it you need these higher temperatures and higher pressures from
Compression in order to ignite that Air fuel ratio and so this allows them to run
You know this is what gives you that major boost in efficiency
You're running super lean you've got a high compression ratio and overall you're going to get a twenty to thirty percent more
Fuel-efficient engine as a result. Now Mazda stated there are two major challenges
with this type of engine
The first is this range as we talked about earlier and the way they really address that is with a spark plug
but that introduces the second issue, which is how do you switch between spark and
Compression ignition and have that be seamless and smooth
and they haven't really said how they've done this but they have stated that there is this method of
How this engine can run where you use the spark plug to control compression
And I'm guessing that that is part of how they're addressing this seamless
Switch between when they're running it on spark vs. when they're running it on compression
So how this works is this kind of intermediary mode is when you're compressing that air / fuel mixture
The spark is going to start the combustion
So you're going to have you know a somewhat richer air / fuel mixture that can have a spark ignite it
The spark's going to start the ignition
And then that flame front is going to start to expand out. So as that flame propagation is expanding Outward
It's going to be increasing the pressure in the entire cylinder. As you increase pressure
In the entire cylinder you increase the temperature as well
And so all of the rest of the cylinder reaches a pressure in the temperature at which everything simultaneously
combusts and so the spark plug is
controlling the timing of compression-ignition
SPCCI. So that's where SPCCI comes from. Ah-ha!
and I believe that that's probably something to do with their switch between
Using compression to ignite versus using a spark to ignite it
So thank you guys for watching and if you have any questions or comments feel free to leave them below