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A Christmas Present

Yes, I have to admit it – the holidays are upon us. And, to provide a bit of entertainment, I thought I’d present you with one of my hare-brained inventions of long ago. To explain it, I have to tell a little story, so I must ask you to bear with me.


Jean-Pierre Jabouille in the Renault RS01

It begins in the mid-sixties, when it was decided to change the formula for F1 cars from 1.5 liters to 3.0 liters. This came at a time when two or three of the engine manufacturers had just invested huge sums in fiendishly complicated little engines that they thought would outperform the rest. And so the FIA threw the manufacturers a bone: an allowed alternative to the big 3.0 liters was a 1.5 liter supercharged engine.

This was actually no compensation at all. At the time, no supercharged 1.5 could hope to match the power of a 3.0 liter and so the provision was ignored for ten years. But over those years the science of turbo-charging developed and, in 1977, Renault entered a turbo-charged 1.5 liter car. It was fast but unreliable at first but, as the engineers solved the heat problems of turbos, it became clear that such an engine could produce far more power than any 3.0 liter. The turbo era of the eighties dawned.

But, if I may take you back to the time of that rule change in the sixties, a wild idea had been born in my imagination. I read an article in a motoring magazine that considered the alternative specification that had crept into the regulations and pointed out that, if one could supercharge a 1.5 two-stroke, it would produce phenomenal amounts of power. Theoretically, such an engine would be an almost unlimited power source; what a pity that it was impossible to supercharge a two-stroke.

“Is it?” thought I. One sees the problem immediately: no valves. Without valves, any pressure built up by a supercharger would force the mixture straight through the combustion chamber and probably cause a nice little explosion in the exhaust system. But what if you added valves? Ordinary valves won’t do, of course – the ports in a two-stroke are in the sides of the cylinders and any valves would stick out and get wiped off promptly by the piston. But there are other types of valve that don’t need to protrude into the combustion chamber; rotary valves, for instance. And one could time the opening of the valves so that the exhaust closed just as the inlet opened.

Now, anyone who knows anything about engines also knows that rotary valves are more trouble than they’re worth. They have tremendous problems with sealing – finding a material that will stand up to the heat and wear implicit in seating such a valve would be enormously difficult. The valve would have to rotate at astronomical speeds to keep up with the high revs of our theoretical engine. It was probably beyond the technology of the time to seal such valves effectively. But today, it might just be possible. Certainly the Mazda engineers have solved similar problems on the rotary engine that bankrupted NSU in the sixties.

So I maintain that it’s not impossible to supercharge a two-stroke engine. And, if my memory serves me correctly, the article I read suggested that power output of such an engine would exceed 700 bhp. With that sort of power, it would have dominated F1 for a decade at least.

If it had ever managed to finish any races, of course. Merry Christmas everyone!

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