Piston Travel Distance

[Gus_Mahn]

I remember reading an editorial in a motorcycle magazine about 4 cylinder bike pistons typically travel about 1/5 of the distance in the bore of the odometer reading. I figured I'd ask Grok to do the same calculation for my 2016 5.0 F150: 242,500 miles, 6721 engine hours, 1277 idle hours, stock height tires, and 3.55:1 gears. It said 65,000-66,000 linear miles on each piston (7.3" every stroke). It also figured 629 revolutions per mile, almost 600,000,000 total engine revolutions, and 300,000,000 valve openings/closings on each valve. Each piston has likely traveled about 1/4 of the distance the truck has. I'm hoping to get another 25,000 miles on the pistons of this truck.

 

[fantastic]

Well, that was a fun read.

 

[Allaned]

Isn’t 629 revolutions per mile low?

 

[Rand]

Isn’t 629 revolutions per mile low?

yep maybe ai slop in there.
since the engine isnt doing 629rpm at 60mph...

 

[Gus_Mahn]

Isn’t 629 revolutions per mile low?

Tire revolutions. I misread it. It'd be whatever the tach says at 60 mph. Well under 2000 engine revolutions/mile

 

[RooflessVW]

Not sure why you didn't just do the math yourself. Did you even attempt it?

 

[Gus_Mahn]

Not sure why you didn't just do the math yourself. Did you even attempt it?

No. I used to play with these types of calculations a lot, but at this point in life I fix more stuff than I customize.

 

[CleanSump]

And what do you intend the calculation to be used for beyond curiosity?

 

[97K15004WD]

myself, that's an interesting point of curiosity.

It's for the sake of the question, and the use comes later. You know, like NASA research. And R&D budgets.

OP, thank you for posting that.

 

[dnewton3]

It's an approximation, obviously. There are many things which obscure the true distance the piston travels relative to the odometer. It's a bit disingenuous to calculate an exact travel distance of the piston, but ignore the variability of several other things which play heavily into the numbers:

- tire diameter changes with use; that affects true miles as the tire wears down, it can change the diameter easily by an inch or so
- stroke is different for each engine design (over-square vs under-square) would significantly alter the topic
- engine idle and transmission slip (engine running at a stoplight, for example; sitting in neutral with a manual trans or the TC slip in an automatic)
- and probably the most important ... RPM (because running in 3rd gear at 30mph is a lot different from running in 6th gear at 30 mph)


It's fun to play with math, as long as you don't think you're going to be able to get a true accurate answer out of this topic.


OP - by the way ... your piston does not travel "7.3" every stroke"; that's probably the total distance covered in one full revolution (down and back up). Your statement is wrong semantically.