[bluedino]

> Inline-sixes also tend to have more low-end torque as their balanced design allows for a longer stroke, which promotes low-rev performance.

Automotive myths that won't die. 'Stroke' doesn't make more low end power than bore, displacement is displacement.

[theodric]

Longer stroke provides a greater lever arm on the crankshaft, allowing the same combustion force to generate more torque during the power stroke. What's your counter-argument?

[bluedino]

That sounds fantastic but it means nothing in practice. It's like something you'd hear in a "Engineering Explained" video, but with no real-world application. There's so much more that goes into an engine that it doesn't matter.

Again, it's a myth.

Similarly, there was always the debate over rod length (in the same displacement engines). You use the same crankshaft but the piston has the wrist pin located higher. The longer rod was always supposed to make "more torque" because of the angle but that ended up not being the case.

You can verify this buy putting engines together with different bores and strokes that are roughly equal displacements, and with the same heads/cam on them, they will make identical power. Picture something like a 3.50" bore and 4.00" stroke, and vice versa. Look up someone like Richard Holdener on YouTube for actual data. Displacement is displacement, it doesn't really matter how you make it.

Bore is what would make you more power after a certain point, anyway. You get more surface area to fit larger valves, etc. But again, using the same heads (that aren't shrouding the smaller bores), either combination of bore/stroke will make the same power throughout the rev range.

Then you get into things like piston speed and all that but none of that matters unless you're talking about a race engine. And when you are, they'll just rebuild it more often so they don't care how long it lasts.

Here's another read:

https://rehermorrison.com/tech-talk-53-big-bore-or-long-stro...

[Brian_K_White]

Luxuriously incorrect. When you go, at least you go all the way.

"Leverage is leverage."

Short stroke is exactly the same as being in a high gear at all times.

[bluedino]

Nope. As I said, you can build two engines with different bore and stroke, but the same displacement, and they will make mirror images in the power curve.

If it was such and advantage, wouldn't all performance engines have much longer stroke?

The newest Corvette ZR1 makes 1064hp from a 4.1 inch bore and 3.1 stroke. How much power are they leaving on the table by not making it a larger stroke than bore like many inline 6's? (Hint: inline sixes don't have larger stroke than bore for "torque")

Any change in power from a larger stroke is due to the larger displacement. It goes up with a percentage of the increase. Nothing to do with the leverage of the longer stroke.

By the way if you work the math out on that, it's not significant. And there are many other things that go into the losses of and engine turning. It's such a useless micro optimization, like speeding up a function that takes two seconds to run by shortening it by only a couple instructions.