Cosworth Says It Made a 250 HP Naturally-Aspirated Three Cylinder and It's Emissions Compliant

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Legendary engine builder Cosworth’s job was to design the Aston Martin Valkyrie’s 1,000 horsepower V12, which had to be naturally-aspirated and emissions compliant. But designing a big V12 takes a while, so to get things going it made a three-cylinder test engine, and that ended up making 250 HP with no turbo.

Bruce Wood, managing director for Cosworth, spoke with Henry Catchpole of Carfection, to explain how it all came to be. Basically, it would have taken more than a year to build a full V12, but Cosworth threw together basically one quarter of the new engine to test its basic design:

Let’s start off with the fact, this didn’t actually start as a V12. Because the first ones you tested were three cylinder. Is that right?

That’s right, absolutely. We know that to go from a blank screen to having the first running engine was going to be of the order of 12 or 13 months. And because of the sort of conflict of needing to meet emissions, and needing to deliver such a high power per liter, we knew there was a really big challenger there. What we did not want to do was wait 13 months to prove to ourselves that we had met that challenge.

So we took a four-cylinder engine that we already had, and we designed and manufactured a three-cylinder cylinder head for that, that was an absolute replica of three cylinders of the Valkyrie design. And we were able to get that up and running within about five months.

So from the start of the program, we had a three-cylinder engine, which was an absolute quarter of the Valkyrie, because we have four catalylists, so each catalyst serves three cylinders, so by running a three-cylinder engine we were able to replicate every part of a genuine quarter of the finished article.

That is to say within five or six months of starting the program, we were able to say, ‘yes, we’re going to be able to deliver emissions and performance.’

So that three-cylinder delivered both 250 horsepower and an emissions pass, effectively.

Wood says that the whole thing gave them “a little bit of breathing space,” just so nobody on the team would have to go back to the drawing board.

What I really want to know is what, exactly, this three-cylinder looks like, sounds like, and whether or not it would fit into other production cars. Friend of Jalopnik Manny Suazo didn’t waste time putting that thought to pixels:


For a little context, Ford makes a 1.5-liter three-cylinder for the new Fiesta ST and it only makes 197 HP, and it’s turbocharged. Assuming that the Cosworth three is roughly the same size (one quarter of the Valkyrie’s 6.5 liters is about a 1.6), that is amazingly efficient for a naturally-aspirated engine.

I need one, and I need one bad.