Advanced Two-Strokes To Power Formula 1’s Future?

The question on everyone’s lips: Will MotoGP follow?

Grand Prix motorcycle roadracing
Will Grand Prix motorcycle roadracing return to the glory days of 500cc two-strokes? Not so fast. The two-stroke engine that Formula 1 is reportedly considering would be a modern marvel, “very efficient and very emissions-friendly.”Gold & Goose

In a shock announcement, Formula 1’s Chief Technical Officer Pat Symonds said, “At F1, this is what we are engaged in at the moment. I’m very keen on it being a two-stroke.” Symonds was speaking at the MIA Energy-Efficient Motorsport Conference held earlier this month in Birmingham, England.

F1 faces two big problems—one immediate, the other longer-term. Immediately, racing fans find little excitement in the muffled sound that filters through the turbochargers on the current field of hybrid V-6 engines slated to power the field until 2024–’25. In the longer term, if racing is to survive, it must deflect opposition from environmentalists who strongly oppose burning any fossil fuel for less than the most urgent of reasons.

Symonds characterized modern forms of two-stroke engines by saying, “Much more efficient, great sound from the exhaust, and a lot of the problems with the old two-strokes are just not relevant anymore.”

So before you imagine the great racing circuits of the world once more resounding to the pop-pop, pa-pop ding! of Honda NSR500s and Yamaha YZR500s, with the wind carrying the scent of burned castor oil, consider Symonds’ next sentence: “Direct injection, pressure charging, and new ignition systems have all allowed new forms of two-stroke engines to be very efficient and very emissions-friendly. I think there’s a good future for them.”

The two-stroke engines that powered all Grand Prix motorcycle classes from 1975–2002 drew fuel-air mixture from carburetors into their crankcases. Pressure from the descending pistons drove that mixture into the cylinders, where about 30 percent of it was lost out the exhaust ports during the cylinder-filling process. That built-in high UHC emission spelled the end for street-legal two-strokes in the US in the 1980s.

Yet in other respects, two-strokes had advantages:

  1. Very low emissions of nitrogen oxides (NOx) owing to natural charge dilution by exhaust from the previous cycle
  2. Small size and low weight per horsepower
  3. Lack of the pumping loss that makes four-stroke operation on low part throttle so inefficient
  4. Lack of the four-stroke’s complex and expensive valve train

From the mid-1980s to early ’90s, nearly every major automaker ran a two-stroke evaluation program, based upon the ability of direct cylinder fuel injection (DFI) to eliminate high UHC emissions during cylinder filling. I counted 19 such programs then, but in the end, all makers decided to “keep to the well-trodden path” because 1) they understood four-strokes better and 2) no one could predict what the EPA or other national emissions authorities would require next.

I believe Symonds’ remarks referred in part to the highly efficient opposed-piston—two pistons in each cylinder—two-strokes being developed by Achates Power of San Diego, California. The first point to make about such an engine is that the usual heat loss through the cylinder heads of traditional engines is completely eliminated. The second is that, being two-stroke, its combustion can be of the recently developed “cool” variety that generates very little NOx; its formation has a temperature threshold. A four-stroke of equal displacement, power, and rpm must have combustion that is twice as intense as that of a two-stroke.

Achates Power
More economical to produce? More efficient to run? Achates Power opposed-piston two-stroke powerplant eliminates the cylinder head and valve train of a conventional engine. Achates claims its design “fits all vehicle platforms.” Motorcycles too?Achates Power

Cool combustion includes such varieties as lean-burn, HCCI, and the more recently announced Reactivity Controlled Compression Ignition (RCCI). The cooler combustion can be made, the less heat is lost to coolant and exhaust. Recently developed combustion systems give promise of greater economy than diesel, but without its problems of NOx, need for particulate filtration, etc.

Symonds also said, “The opposed-piston engine is very much coming back and already in road-car form at around 50 percent efficiency.”

It was then noted that such an efficient engine, operating on synthesized fuel made by combining hydrogen with carbon from atmospheric carbon dioxide, could be greener than electric. It was suggested that such carbon-neutral fuel could also in future propel the aircraft that transport the teams.

Technology, which again and again shows its power to change our lives, has seldom been a matter of scheduled breakthroughs.

It is interesting to note that just after World War II, when the turbojet engine’s high fuel consumption would have required aircraft flying New York to London to refuel at Gander, Newfoundland, Napier’s Nomad two-stroke turbocharged diesel, driving conventional propellers, was expected to be efficient enough to make the flight direct and unrefueled.

Symonds also said, “The internal-combustion engine has a long future. A future that’s longer than a lot of politicians realize because politicians are hanging everything on electric vehicles.”

Technology, which again and again shows its power to change our lives, has seldom been a matter of scheduled breakthroughs. No one can predict what comes next or in which directions it will lead us.