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Tractor Pulling Discussion Forum

pto dyno question

Author  [Modern View]
clampdaddy

07-19-2013 12:09:11
166.137.191.36



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Changing the primary reduction gears on a Deere changes the engine to tranny ratio so I was wondering, will it have an affect on horsepower numbers when its hooked to the dyno?




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north puller

07-20-2013 09:22:15
207.219.69.198



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 Re: pto dyno question in reply to clampdaddy, 07-19-2013 12:09:11  
Some people don't get this, so i will try and explain in simple terms.

I will use a farmall example, just because i know them.

With a little bit of work, a farmall m engine could go into a 560 or viva versa.

A super m makes 47 hp at a rated engine speed of 1450 rpm. If you wind it up, it will make 53-55 hp at 1800 engine rpm.

now a 560 tractor is set up so that the engine turns 1800 rpm to get 540 pto. If you put the super m engine into the 560 tractor and put it on the dyno, the engine would turn faster (1800) to get a 540 pto speed, and you would read 53 hp on the dyno.

Put that engine back into the super m tractor and put it on the dyno, and it would turn 1450 to give you 540 pto and read 47 hp on the dyno.

You are basically doing the same thing. You are changing the engine rpm in relation to the pto rpm.since in the tractor world hp is measured based on pto rpm, changing the engine input speed will give you a different hp reading.

If you were to use a pony brake belt pulley dyno, you would see no difference on your John Deere because the pulley speed doesn't change with the gearing change.

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showcrop

07-19-2013 17:15:13
75.67.231.80



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 Re: pto dyno question in reply to clampdaddy, 07-19-2013 12:09:11  
Most dyno's you have to input the rpms so yes the reading would change.



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Roger in Iowa

07-19-2013 13:29:17
166.182.3.144



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 Re: pto dyno question in reply to clampdaddy, 07-19-2013 12:09:11  
Engine will still make the same HP, just the dyno reads differently.

What brand of dyno?



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clampdaddy

07-19-2013 13:52:51
166.137.191.23



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 Re: pto dyno question in reply to Roger in Iowa, 07-19-2013 13:29:17  
Quoting Removed, click Modern View to see

No dyno in particular, just curious if it would show a horsepower change even though the engine is still the same.



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buickanddeere

07-19-2013 16:31:50
216.183.153.246



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 Re: pto dyno question in reply to clampdaddy, 07-19-2013 13:52:51  
If it did tractors would have a 1HP engine and lots of gears to pull a 40ft chisel plough.



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north puller

07-19-2013 12:59:58
207.219.69.169



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 Re: pto dyno question in reply to clampdaddy, 07-19-2013 12:09:11  
If it is a transmission driven pto, then yes. If you slow down the transmission by 10% (and therefore the pto by 10%) for example, then you will have to turn the motor 10% faster to get your "rated" 540 pto speed. You will end up reading whatever horse power the engine makes at this new rpm.



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