“Basically it achieves that by persuading enough fuel-air mixture into cylinders and burning it efficiently enough at the highest possible crankshaft speed. At that moment, from what John told us, with the latest cylinder heads and larger exhaust pipes and recently introduced taper intake trumpets (plain cylindrical for most of their length), it still doesn’t reach peak power at 10,750rpm, proving that it isn’t breathing that restricts but the mechanical limits of the unit.”
“The normal working range is between 8500 and 10,500rpm. An electronic ignition cut-out is fitted which nominally stops the engine being revved beyond about 10,600rpm. Firstly because even these relatively sophisticated rev-limiters gradually lower the limit during their life, and secondly a rev-limiter cut-out switch is provided because a few hundred more rpm can be allowed to the driver desperate for that little bit extra. Drivers do go to 11,000rpm, but it isn’t recommended.
“At that speed, at the bottom of one of the eight pistons’ stroke, it is stationary. It has to be accelerated from that brief rest to near-enough 75mph in 1¼in, then slowed down again in the same distance. And it has to do that each way every three-thousandth of a second. The acceleration involved is around 230g.”
So, how long between rebuilds?
Back in the days where truly tiny independent teams were still common in Formula 1, this varied a lot. McLaren tended to rebuild engines after 600 miles – or one weekend, practice and race.
Showing the remarkable evolution of the DFV, Nicholson said: “When it first came out in 1967, we were probably getting 1000 miles out of them. OK, we were running to 10,000rpm then, but they were producing say 420 to 440hp. Now they’re running to 11,000rpm, really, and that extra is not good for them.”
As providers and maintainers of race-worthy engines, Nicholson Ltd’s job primarily was not to measure the wear of each part, but to avoid the results of a crucial breakage.
“Pistons get replaced every 1000 miles,” Nicholson said. “They won’t do two race weekends. If you had a failure because of a piston, which in turn broke the engine – even a secondhand one that cost £4000 – that would have bought you a set of pistons for every race in the season, so it isn’t worth economising here.”