The current generation of the 1.6-liter turbocharged V6 found in Formula 1 cars is without doubt the most advanced combustion engine available today. Only four manufacturers participated in its development, having invested huge funds in it, and although Honda is leaving racing after 21 years, its engineers are already looking for ways to apply existing racing developments in production cars.
And motorcycles, of course. Do not forget that with the external similarity of cars and F1 cars, the engines on the latter in terms of operating modes are more reminiscent of motorcycle engines – these are highly accelerated, high-speed units, from each cubic centimeter of the working volume of which the maximum possible power is removed. And at least one of the technologies used in the newest generation of F1 engines will find its way into production motorcycles in the very near future.
Volga car engine as a close relative
We are talking about the technology of the so-called pre-chamber ignition, or jet ignition, but our compatriots know it primarily from the unusual series of engines for the Volga car, which, by an incredible coincidence, very much resembled Honda engines. This story was overgrown with moss, since it took place in the 70s, and in Soviet technical terminology, all this beauty was called “prechamber-flare ignition”… True, half a century ago, our ancestors could not cope with the quality issues of a serial product, and engines for the Volga with prechamber-torch ignition were notorious among the people, and at the first opportunity they were changed to a more traditional one. But the meaning of this technology is that such an engine runs on an incredibly lean mixture and at high compression ratios, has extreme economy and efficiency of fuel combustion, and now, when the Formula 1 regulation limits fuel consumption, the technology has been re-implemented, already on a modern technological base. …
What’s the point? The fact that the theoretical maximum combustion efficiency is achieved when using a stoichiometric mixture – 14.7 parts of air to 1 part of gasoline. However, most engines run on a much richer mixture (that is, containing more fuel), which keeps the CPG temperature lower for a variety of reasons, and the likelihood of knocking is significantly reduced. Detonation is one of the main enemies of the engine, since it literally destroys it with powerful blows to pistons, rings, valves, sometimes knocking out candles or breaking partitions between annular grooves, not to mention burned out or punctured pistons.
Detonation arises not so much from the poor mixture as from the high compression ratio, but the leaner mixture has to be compressed more for its effective ignition. That is, the poorer (and more efficient) the mixture, the worse it ignites from a spark, the higher the compression ratio required for its effective combustion, but the higher the likelihood of its detonation. The solution is precisely the technology of jet ignition: in modern Formula 1 engines, the spark plug is not installed in the cylinder, but in a small chamber separate from the combustion chamber. This pre-chamber is filled with a small amount of very rich mixture, which is easily ignited without much compression, and then the slowly burning mixture is injected into the main combustion chamber, which contains a much leaner mixture, and ignites it. This happens at a compression ratio at which the probability of detonation is low, and as a result, the engine runs on the most energy-efficient mixture and burns fuel as efficiently as possible, while delivering maximum power.
In the case of F1, the implementation of prechamber-flare ignition is complicated by the fact that in the engine design, the regulations allow only one nozzle per cylinder, which leads to difficulties with filling the cylinder with a lean mixture, and the prechamber with a rich one. However, this is not a problem on production bikes, and Honda has created the system described in the new patent applications that uses two injectors per cylinder.
The first nozzle is completely ordinary, supplying fuel to the intake tract directly under the throttle valve, then it enters through the intake valve as on any modern gasoline engine. But the second nozzle is installed in a small preliminary chamber (prechamber) above the main combustion chamber. A spark plug is also installed there, and between the chambers there is a rotating damper driven by a timing chain that separates the pre-chamber from the main chamber.
This is where Honda’s design differs from F1 technology. A rotary flap is essentially a tube with a carefully calculated hole pattern so that it performs a variety of different functions in different phases of rotation.
Its main part, which is at the same time the top of the central part of the main combustion chamber, has a large window on one side. It opens into the combustion chamber during the exhaust and intake strokes, allowing the pre-chamber to be purged of combustion products and filled with a fresh portion of the lean mixture.
At the compression stroke, the tubular damper closes the window into the combustion chamber with a solid part and turns to the prechamber with the window, and to the nozzle (which, of course, cannot be placed directly in the prechamber) with a small hole. The nozzle through it injects fuel into the flap, which enters the pre-chamber through a large window.
At the moment of the outbreak, the large window of the tubular damper is at the top, the damper tube itself, together with the prechamber, is filled with a rich mixture, and a group of small holes on the side of the damper opposite from the main window looks directly into the combustion chamber. The spark ignites the rich mixture in the antechamber, and the flame front, expanding, spreads in the form of jets (torches) through small holes and ignites the lean mixture in the main combustion chamber.
Such a scheme of work, as we have already mentioned, has found its modern embodiment in Formula 1 cars. However, Soichiro Honda himself also oversaw the development of the CVCC system (composite vortex ignition) in the early 70s of the last century, and it was embodied in the Honda Civic model 70s. However, a carburetor and a small additional valve were used there to control the flow of the rich mixture into the pre-chamber. Then CVCC made it possible to bypass the 1975 exhaust cleanliness restrictions without the use of a catalytic converter, which competitors had to resort to.
The new patent application does not disclose which models the system can be installed on, but the illustrations show the completely recognizable next-generation FireBlade, suggesting that the technology’s primary application will be high-performance racing bikes.
Well, it is quite logical and understandable, especially since even more stringent economic norms are not far off, which may require working on a stoichiometric mixture of any new motorcycles.