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Interesting comparison...OMC /HD Rod and Piston

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PhilSch

Regular Contributor
I was scraping gaskets off my Johnson parts and happened to look up at a Top Fuel Harley rod and piston hanging on my shop wall. I chuckled because of the size difference which prompted me to lay it next to the OMC piston on the table for a photo. The TFHD motor is 186 cubic inch, 1000 horsepower on 97-100% nitromethane. 0-100 mph in 1.3 seconds. 0-230 in 6.2 seconds.
 

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How many revolutions does the HARLY crankshaft turn during a run down the strip for 1.3 seconds.-----How many turns would the OMC crankshaft make at full throttle during 1000 hrs ?
 
racerone said:
How many revolutions does the HARLY crankshaft turn during a run down the strip for 1.3 seconds.-----How many turns would the OMC crankshaft make at full throttle during 1000 hrs ?
Click to expand...

I've not done the math to see how many total revolutions it makes during the quarter mile but engine is only spinning about 4800 RPM at 230 miles an hour. A good competitive elapsed time is in the low 6-second range. The motors are naturally aspirated, mechanical injection. They are torque monsters; making that kind of power at such a low RPM. Because of the torque the biggest challenge is just hooking the tire up. A fine balance the power and clutch slip are needed. If you put too much slip in the clutch along with a little bit too much fuel the fire goes out because Nitro needs a load to keep burning. For example if you have a puddle of nitro and put a match in it it will not ignite. On the other hand if you took a drop of nitro and hit it with a hammer it would explode.
 
Racerone,

You piqued my curiosity so I pulled up one of my good runs from 2008...the max rpm was 4800 but the average for the 6.2 second run was only 4600. That's 61 revs per second so the crank turns 378 times to get from start to finish.
 
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