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kenOfYugen

Mean Piston Speed [1] is a good indicator of engine longevity.

~16 m/s for automobile engines

~25 m/s for Formula one engines

~26.5 m/s for Koenigsegg’s 2.0-Liter

[1] https://en.wikipedia.org/wiki/Mean_piston_speed

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Interesting that they use the mean of the absolute value instead of root-mean-square as in other sinusoidal applications (63.7% of the peak value vs. 70.7% for RMS).

RMS has all sorts of interesting properties, being directly proportional to effects that result from the square of the quantity being measured such as force on the connecting rods or acceleration of the piston, but mean piston speed is easier to calculate from familiar quantities to an automotive engineer like stroke and RPM. I wonder if engine longevity is actually proportional to mean piston speed or RPM, it would be easy to mistake the 7% difference given all the confounding factors...

If they're only different by a constant factor, then both have the same interesting properties and neither is much more difficult to calculate than the other -- at least for sinusoids.

If something is proportional to one, it's naturally proportional to the other.

Almost anyone on this website could answer better than me for this, was always weak in math, but I believe they differ by a constant factor for a sine, but for a more complex waveform they will not (well, the amount they vary by would be different for each waveform).

It's true that the factor between RMS vs peak-to-peak is different for e.g. a sine vs a sawtooth wave, but for other waveforms its still a constant (just a different one), and for this engine it should be just about a sine wave anyway.

Circular motion about a crank produces a precise sinusoidal waveform.

And Formula 1 engines are only meant to last hours (yes really, most engines don't even last one season), albeit at ridiculously high stress levels.

If we extrapolate from this, where high performance drag cars typically last minutes (20 years ago they only lasted seconds), that would mean this engine might only be good for a couple of hours of driving around the track. Assuming this is true (I am not saying it is), this engine would be pretty worthless for anything other than being a collector's item or being used for 1 or 2 races before it had to be retired.

and F1 tires only last a few laps. it’s all designed in. the F1 engines don’t expire in a few races because they can’t build them more robust, they expire in a few races because the rules require them to last that long. they could last all season (yes, with same performance) if they were required to do so.

Indeed. Back in the days they used to weld the cylinder heads to the engine block before qualifying, so they could run it that bit harder to get that extra bit of performance. Obviously not something that increases the lifespan of the engine...

Similarly in current F1, they know quite well how much life they have of the engine, and how much life a quali lap takes from the engine compared to a calm outlap.

If the regulations mandated a single engine per season they could do it, though they'd mostly just turn everything down.

I'd be surprised that they could build tires to go on for 22 GPs with the same performances, but who knows. The goal was raw speed when there were multiple manufacturers. The only year with a rule to forbid tyre changes during a race was 2005. Maybe you remember that Indianapolis GP with only 6 cars racing because thr banking destroyed the tires of the other manufacturer (which won all the other GPs.)

7 races per engine including Saturday practice and qualifying. It's about 5 hours per weekend times 7. 35 hours, which a commuter car does in about 10 days.

> yes really, most engines don't even last one season

"Even" one season? If they last more than one race it means they didn't push it hard enough so it makes sense that the engine last just marginally more than the race.

The new rules set the limit at 3 engines per season, which is 21 races plus testing. So it's a balancing act, but you definitely need to reuse the engine for more than 1 race.

And for those not in the know, a F1 race is ~305km, and they have do two days of practice plus qualifying in a race weekend using the engines they have (same engine for qualifying as for racing). There's some more detail in this[1] article, where they point out the Mercedes F1 engine did over 3000 miles (~4900km) during pre-season testing without issues (most in race-like conditions).

That said, from my impression it is usually the turbo or the hybrid systems that break down, it's rare for the actual engine block to be the issue barring specific production issues.

[1]: https://autoweek.com/article/formula-one/mercedes-f1-engine-...

F1 regulates the maximum number of engines a season (to 3 currently). So they have to last ~7 races.

Edit: old numbers updated

Koenigsegg Gemera use their direct drive system, with only one gear. So the engine will only see max revs when you're traveling at top speed, which will probably be quite rare since it's 400 km/h (249 mph).

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