13/08/2026
You can get hold of one of these race-used Cosworth CA2010 pistons along with the connecting rod from the Memorabilia section of our on-line shop (see link in comments). Here's some of the tech details contained within these pistons...
The Cosworth CA2010 engine was a development of the CA, a 20,000 rpm engine which was designed and built for the 2006 Formula 1 season for use by Williams. When the CA2010 was introduced four years later, the rules mandated a maximum speed of 18,000 rpm, but engine life had increased almost threefold, so there was no let up in the pursuit of reliability.
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One of the most stressed parts in the engine was the piston, and itโs not hard to see why. At these speeds the piston was subjected to accelerations of over 10,000 G. Force is mass multiplied by acceleration, so reducing piston mass was a critical step to reducing the forces that the piston was exposed to.
The piston design represented the culmination of years of hard work to reduce mass, and the CA2010 piston hit the scales at just 215 g. Considering that the material had to be an aluminium alloy as mandated by the F1 technical regulations, this was a remarkable achievement.
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A lot of the weight saving came from the unique shape of the piston. Alex Hitzinger, who was the chief engineer in charge of the design of the CA engine, commented on how the undercrown shape of the piston evolved: โWe came up with this design philosophy (dog bone shapes, extremely stiff, hollow structures) through a design study we did for a very thin walled investment cast titanium piston.
"We never made one, because titanium got banned as a piston material before we could try it, but we learned a lot through that exercise and the result was the a piston that was capable of revving to 20,000 rpm.โ
Looking at the undercrown, the shape looked like a fairly conventional boxed and bridged design. However, there were a number of clever design features that were optimised through an extensive period of FEA (finite element analysis).
One of these features was the vertical drillings at each corner of the central box section that carried the pin bores. These drillings were actually slightly angled inwards, and were there purely for mass reduction.
The area underneath the buttresses was waisted down, and there was no material underneath the spars of the box section. These features couldnโt be generated from forging and so have had to be machined out.
In fact, the entire undercrown had to be extensively machined to remove any surface defects that might have been left over from the forging process.
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The design of the crown was carefully shaped to match the corresponding geometry of the combustion chamber in the cylinder head. The crown shape consisted of a diamond-shaped central flat section which actually wasnโt flat.
Although difficult to see in photos, the crown of the piston was very slightly domed, which at TDC created a small flat bowl into which the spark plug would initiate the combustion of the air and fuel mixture.
The crown included a pair of very shallow pockets for clearance to the inlet valves and another pair for the exhaust valves. Any sharp edges had to be carefully blended away to reduce the chances of pre-ignition.
One of the obstacles that had to be overcome was stopping the crown from melting, hence each piston was cooled by six oil sq**rt jets. The contact with hot oil resulted in the staining that could be seen on the undercrown after extended periods of running.
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One of the most notable features of the piston was the tight packaging of the ring grooves, which were moved upwards as much as possible. Like most F1 pistons of this era, the sealing of the cylinder bore wall was accomplished with just one compression ring along with an oil control ring.
The height of the compression ring groove was incredibly small at just over 0.63mm. Inside this groove were small horizontal ports that fed combustion gas into the back of the groove and thus helped force the ring out towards the bore.
Likewise, the oil control ring groove was also very narrow at 1.5 mm height, and it contained ports that allowed oil to drain from within the groove to the underside of the piston.
Between the two ring grooves was whatโs known as an accumulator groove. This was a vee shaped groove that created a volume of gas below the compression ring. This then helped to maintain the differential pressure across the ring that was required for effective sealing.
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The skirt of the piston was very short, just enough to minimise rocking of the piston in the bore. The coating on the skirt was DLC (diamond like carbon), which had been introduced in 2004 on the forerunner to the CA engine, the TJ. Cosworth estimated that the coating was worth around 4 bhp on the TJ, thanks to the coatingโs ability to reduce friction.
The profile of the skirt was a complex shape that featured both barreling and ovality. This shape had been optimised through FEA and dyno testing to ensure that the skirt matched the shape of the cylinder bore when the piston was distorted from loading and thermal expansion.
