ChadS
12-22-2007 06:51:25
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Re: thread on pulling board in reply to smdv806, 12-21-2007 20:05:23
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Simple, take a M, put it on a dyno, add a digital tach or whatever you got,,, set the dyno at 540, then read the rpm. Do the same for the 400-450. Bout 150-200 rpm difference in the engine speed, no matter how it was tuned, the engine speeds were not the same acording to a tach. Last year, we built a 175 for a 350,,,, I put the engine in a SH chassis, dyno, and it was 47 hp. Took the same engine, dropped it into the 350. The 350 had no live hyd, (removed) dyno hp was 40 hp out of the exact same engine. Rpm was also different, cause the SH ran slower rpm wise then the 350. Its not much of a ratio difference,,, and only an engine tach, and a pto tach will tell what the actual differences would be,, but, there is a difference. Another exapmle of the ratio chages was the 350 utility rated at over 2200 rpm!! Yet, at 2200+ rpm or whatever they are set at,, the pto is slowed down to make the engine speed faster to run a higher rpm, and still not overspeed the pto. if they left the ratio the same speed as the H and ran the engine at 2200, the pto speed will be over 700 pto rpm. quite a difference in pto rpm speed IF they never chaged anything at all. Pullers, well they like to brag on how much power an engine makes by itself,,,, and those readings they take are not rated rpm for a tractor. More like high performance race cars,,, where the spin em til they find what they are looking for. Most cases, 500 engine rpm or more over rated rpm to get the big numbers. Our shop, has always pto dyno tuned engines,,, so no matter what,, the power it puts out is rated rpm for that chassis, and its speced out for 540 pto speed for that model. I keep the tractor in the pulling, cause not all pulling tractors, only see track duty, most do both, work and play and they use the pto! Find a pto tach, an engine tach, and the models mentioned above and do some tests. I did, but you can lead a horse to water, but dont mean, the horse will take a drink. But, we try like heck. Have a good day. ChadS
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