Thread: Max piston speed/acceleration?

I get that stronger bolts are better, but I'm looking for some quantitative explanations, so that I can start doing some math on my long term project (NA 3.6L M104. After the LD28(T))

I was doing a loose reference to something that I had read that you posted some time back. I can not remember specific of what you had posted. I found your comments clear and concise on the matter. I had also read a long time ago about a fellow that was snaping cranks around the 8k mark, could never find that thread to reference it in the tread that had your comments in it. I do admit, I kinda take your word as gospel....

Quote: Originally Posted by PanzerAce but really, what determines how fast you can spin your engine without destroying anything (assuming everything is built right out of quality parts). From what I read, mainly the rod bolts. Piston speed up and down the bore involves piston slap as the thrusts on the conrod go to and fro as the rod goes around the circular path of the crank, but that's a matter of accellerated wear, not explosive...

Quote: Originally Posted by PanzerAce So...I would put this in an engine specific sub forum, but I suspect it's something that every one could use, so it's here instead. I'm wondering how people come up with their engine's redline. I see on other forums that people talk about mean piston speed, max piston speed, or sometimes max piston acceleration, and always with a pre-set number as a maximum; but really, what determines...

http://forum.grumpysperformance.com/...+redline#p1170 an engines red-line is the rpm limit where the stress is approaching the strength limitations of the weaker components in your engine, in most cases that's the rod bolts, rods, or a valve train control issues, on most engines. on most American V8 engines that's reached at about 4000 fpm (feet per minute) in piston speed, with high quality forged components and a solid lifter...

There are tons of variables, but I'm going to toss out some references for mean piston speed... low speed diesels ~8.5 m/s for marine and electric power generation application smedium speed diesels ~11 m/s for trains or trucks high speed diesel ~14 m/s for automobile engines medium speed petrol ~16 m/s for automobile engines high speed petrol ~20-25 m/s for sport automobile engines or motorcycles competition Some extreme examples are...

'As high as 8000' huh? As I recall, someone with good knowledge on the subject said if you are breaking cranks on the tail end, look at how you're fastening your flywheel bolts!