Engine size vs number of pistons?

[jeffmorris]

I was watching a video of Bugatti Chiron being built in the factory. They said that the car has a 8L W16 engine. I know that Cadillac had a 8.2L V8 engine. I know that heavy-duty trucks in USA usually have 6-cylinder engines that are twice as big as engines in cars. Does a W16 engine have smaller pistons and/or stroke than a V8 engine of similar size? Does a truck engine have bigger pistons and/or stroke?

[fredjacksonsan]

Yes to both of your questions… A high revving Formula One engine has really small pistons, heavy duty truck has larger pistons. It has to do with generating horsepower versus torque, and also the reciprocating mass of each of those pistons.

Back in the day the Jeep 4.0 had more horsepower than V-8s of it's time. .667 of a liter per cylinder, and it had a relatively low rpm limit of 5,000 rpm. HP fell off like crazy after about 4500-4800 rpm.

The Bugatti is .5L per cylinder and has a higher redline, I did not find the limit with my searches, but did see the quote that it "produces linear power between 2000 and 6000 rpm". Didn't see any bore or stroke info; apparently Bugatti ain't telling.

Some shipborn diesel powerplants have enormous pistons several feet across. Low low max rpm on those, I think some are around 600-800 rpm.