Maserati’s new mid-engined monster has dropped to some of the world’s motoring press, and driving impressions are filtering in nice and slow. I didn’t pay much attention to the MC20 teasers, but driving impressions have me sitting up at attention. Beyond how cool the new car seems, the new Nettuno engine has really caught my interest – especially the new combustion technology called “dual combustion” – which uses two spark plugs and two fuel injectors per cylinder.
After brushing up on the origins of the “all new” (but not really) 90 degree V6 from Maserati with Bozi Tatarevic’s excellent breakdown for Road & Track on the parts it shares with the Ferrari F154 V8 and Alfa Romeo V6, I perused through some press photos of the Nettuno engine and its technology. I do agree with Bozi that uses a good bit of parts sharing and the “100% Maserati” claim feels a little fast and loose with the truth. The engine’s heads, however, are truly unique to the Maserati, and that’s the most important part of making an engine click.
So what is dual combustion? Well, it’s a form of pre-combustion technology, which doesn’t sound much simpler. But it isn’t too bad to understand in the abstract.
Normally, most engines do all of their combustion in the, well, combustion chamber, which is basically the cylinders of the engine. Internal combustion nerds, I know that explanation isn’t totally thorough, but bear with me. Once the piston is at its highest point in the cylinder (top dead center) the volume of the space between the top of the piston and the cylinder head is the actual combustion chamber. In that volume, air and fuel mix around and get ignited by a spark plug, causing an explosion that forces the piston back down. Repeat that hundreds or thousands of times per minute, and you make some power. Most of you might have already known that.
Dual combustion takes that combustion chamber volume and adds an extra semi-combustion chamber called a pre-combustion chamber. You see, a big challenge about engine design is making the fuel and air mix thoroughly. The more vigorously mixed it is, the more power and efficiency is available from the explosions. The pre-combustion chamber does the kind job of doing that extra mixing, creating what’s called a homogenous charge, nerdspeak for a well-mixed fuel mixture.
Now, how does that relate to ’70s Honda tech? Honda’s version of this concept was called CVCC: Compound Vortex Controlled Combustion. Honda’s system is much less complex, but perhaps more ingenious. It also used a pre-combustion chamber, but instead of injecting extra fuel, it uses a normal carburetor and draws fuel from it. Instead of cavernous air passages, it uses a simple little pocket chamber for the fuel-air mixture to get mixed up. The one and only spark plug was positioned in the chamber, and combustion was sparked from there, and the fuel-air mixture was metered with a lil’ baby valve. Cute!
Honda (and everyone else) uses the pre-combustion technology to make big power out of 1.6-liter turbo V6 engines in Formula 1. Over 800 horsepower was generated alone from the turbo V6, which is hard to even grasp from a Ford Fiesta ST sized engine. In a way, this means that CVCC lives in the highest tier of racing in the world.
Not really, but I will certainly contend that it spiritually does!
The Maserati interpretation of the technology is newer and closer to Formula 1 than Honda’s old system, but the idea is similar. Even then, it’s still uniquely Maserati. Thanks to this fascinating diagram from Maserati itself, we can see the details of the system. I marked the important stuff out for easy viewing! We can see that the pre-injector is positioned outside of the cylinder, like a port injector, but it has a complex cavern of air passages and pockets where it delivers fuel. These small caverns are the pre-combustion chamber. It’s hard to parse out in the diagram, but the air passages curl around the cylinder and deliver the mixture evenly through the cylinder, while the two spark plugs are next to each other in nearly the same place.
Maserati even claims that the pre-combustion system can be bypassed when unnecessary, which is a cool bit of engineering, and the reason for the second spark plug. It seems that one or both of the spark plugs work at any given time, and the pre-combustion spark plug has an extended electrode. It’s super freaky engineering, and almost looks like a modified twin-spark style ignition system.
50 years of advancement and mass adoption of the technology in Formula 1 engines since the 2014 regulation change have resulted in the Maserati system. It is truly the first road car application of the technology as a power generating device and makes the MC20 a fascinating sports car proposition. Extremely cool stuff is going on at a company that has felt dormant for over a decade, and I hope to see some more of my colleagues driving the MC20 soon.
