Hello everyone and welcome
beside me is the Mercedes AMG GLC 63
and probably some other letters and numbers that I'm forgetting and it has Mercedes
latest generation of their multi spark ignition
So this is a twin turbo four-litre v8
Engine and one of the really cool things about it is that the unique ignition system is designed to fire the spark plugs
Five times during the power stroke. So five spark firings during that single power stroke
This is an update from their previous generation, which fired that spark plug four times and all of that happens within one millisecond
What why would you fire the spark plug five times? Well, the idea is actually to improve low end combustion
So it's not for creating power instead. It's used for when you're at light load
so when you're not too heavy on the throttle and that low rpms
and they do this to improve combustion efficiency and combustion consistency
now if only there was some sort of tool that I could use to better explain this
(snaps three times)
Here we are, well, what do you know now?
Now, that effect was either really stupid and didn't work very well or it looked kind of cool
On that second snap of the fingers either way. I'm gonna leave it in the video
Because I don't want to retake the shot
So let's talk about why you might want to do this at low loads
it's ideal to start running, you know a leaner mixture than at higher loads
you don't have to worry about knock as much with low load so you can get away with leaner mixtures and as a result you
Can get better efficiency if you can use less air to the amount of fuel that you're using
So fourteen point seven to one is stoichiometric. That's your ideal air fuel ratio. That's by mass
So fourteen point seven parts air one part fueled by mass anything greater than fourteen point seven to one will be considered lean
Now when you have a lean mixture, one of the challenges is that you have inconsistent
Combustion and the reason for this is because you have different pockets with varying air/fuel ratios
throughout that mixture
And so when you try to ignite it
You're hoping that you have a good air fuel mixture
Near this spark plug so that you can start ignition and then have that flame spread out and combust all of the air and fuel
The challenge however, is that because you don't what the air/fuel ratio is going to be near the spark plug,
It's challenging to predict how consistent combustion is going to be now research has shown that if you fire that
spark plug more times for that single power stroke
You're going to increase the energy here at the spark plug and as a result
You're going to start within a larger flame kernel initially
So here's just using a single spark and then the you know exaggerated here, but it's going to be a larger flame kernel
Which research has shown that if you do that if you fire that spark plug multiple times
You have a larger energy around there. You have that larger flame kernel which initially starts combustion. You have a greater probability
Ultimately of starting combustion faster and so as a result you get more consistent combustion and you get faster combustion
So the papers that I read looking into multi spark ignitions
Were seeing that you could get fairly consistent combustion with a single spark with air/fuel ratios as high as twenty to one
but if you're using a multi spark ignition
You could use air/fuel ratios a little bit higher about twenty one point five to twenty three to one and still have equally consistent
Combustion as just firing a single spark plug at twenty to one
So you have a higher probability of ignition starting you have a four percent shorter ignition delay
Once that flame starts to spread from when the spark plug fires you have six percent faster
Combustion and all of this results in a five percent improvement in efficiency
now engineers are always looking for any little way to improve efficiency and
it's the cumulative effort of all of those different methods that ultimately leads to an efficient engine
and Mercedes claims that this spark strategy alone is able to provide two percent better fuel economy
And then in combination with direct injection
Injecting at twenty nine hundred psi, they're able to improve fuel economy by four percent
I also read a study looking at a Ferrari v8 engine employing a similar strategy and they found that depending on in the engine
region, you know the load and the rpm they were able to see brake specific fuel consumption improvements as high as 4.5%
In other words making the exact same amount of power using 4.5% less fuel. Of course
Feel free to leave any questions or comments you have below. Thanks for watching