Dyno results

mark20

Member
We had the dyno out on the weekend playing around. Dyno'd all the tractors but one farmall h that rev's 3000rpm ,the guy used 740 PTO rpm. The tractor made 97 horse at the 740. I assumed it was 540. My farmall m was 80 horses at 540. Is there any way to figure out what the horse power on the h would be at the 540 mark and is the 740 accurate. Also I'm looking for some dyno parts, I need the big round paper gragh that tells you the hourespower
 
I think it is accurate enough. If you had
reved the H on up to 1000 rpm pto.
Wouldn't it have been right. All you had
to do was pulled the H to 540. And you
would have known.
 
Only real way to do it would be to put more load on till it was 540, then you'll know exactly what it was, anything else is just a guess, but if say it made the same torque at both 740 and 540 it would make 70 hp at 540 rpm.
 
(quoted from post at 17:04:28 05/08/16) We had the dyno out on the weekend playing around. Dyno'd all the tractors but one farmall h that rev's 3000rpm ,the guy used 740 PTO rpm. The tractor made 97 horse at the 740. I assumed it was 540. My farmall m was 80 horses at 540. Is there any way to figure out what the horse power on the h would be at the 540 mark and is the 740 accurate. Also I'm looking for some dyno parts, I need the big round paper gragh that tells you the hourespower

The dyno measures torque and RPM. HP is [u:e90bc73dd0]calculated[/u:e90bc73dd0] using the equation: HP = (Torque (ft-lb) x RPM) / 5252. The "big round paper graph" is simply this equation in graph form. To obtain a torque reading, the dyno is used to place a load on the tractor with the tractor at full throttle.

For the Farmall H: The dyno would have measured 688.4 ft-lbs torque and 740 RPM. Plugging the values into the equation yields 97 HP.

For the Farmal M: The dyno would have measured 778.1 ft-lbs torque and 540 RPM. Plugging the values into the equation yields 80 HP.

To your questions: To determine the HP of the H at 540 RPM, the tractor would need to be tested at 540 RPM. Since this tractor has been modified to run at a higher speed it may develop significantly less torque when loaded to the 540 RPM level. I suspect that is the reason for testing at 740 RPM.

Yes, the HP measurement at 740 RPM is accurate as long as the above equation is used, with the values of 688.4 ft-lbs and 740 RPM. That is to say the "big round round paper graph" must be based on 740 RPM, for this power measurement. If the graph is simply a look up chart based on 540 RPM then [u:e90bc73dd0]no[/u:e90bc73dd0], it is not accurate.

As a follow on question: what if the 97 HP of the farmal H was based on 540 RPM instead of the actual RPM of 740? 97 HP at 540 RPM would mean the dyno would have measured a torque output of 943.4 ft-lbs. Actually, the tractor was able to output this torque level at 740 RPM which would be 132.9 HP.
 
So we're only really guessing on the hp of the H. We need to re-dyno to get the real HP at 540. We were trying to compare apples to apples but once we found out that it was tested 740 and mine at 540, it's hard to compare. They both pull really good, so that's all it matters, the rest is driving skills
 
(quoted from post at 09:00:08 05/09/16) So we're only really guessing on the hp of the H. We need to re-dyno to get the real HP at 540. We were trying to compare apples to apples but once we found out that it was tested 740 and mine at 540, it's hard to compare. They both pull really good, so that's all it matters, the rest is driving skills

You do not have apples to apples tractors. The H is modified to make it's HP at a higher RPM than originally manfactured; you should not use the same RPM point to compare with another tractor that makes it's power at a lower RPM. If the question is which tractor has the most HP; you need to re-test to determine the Maximum HP of each tractor. In that case you may find the H makes Max HP at 985 PTO RPM and the M makes Max HP at 358 PTO RPM. With this information the driver can determine the RPM range needed during the pull to utilize the HP built into the engine.
 
mark I assume you are using M&W P-400B dyno. It is what I have and book to go along with it. First the M. Rated engine speed under load is 1450 RPM and PTO speed of 550 RPM. If you measured it at 540 RPM PTO this give you motor speed of 1424 RPM. This gives you 295 ft lb of torque at this RPM. On the H how did you come up with the HP at 740 RPM without the paper wheel? The H is rated at 1650 RPM under load and 550 RPM on the PTO at that speed. 3000 RPM would give you 1000 PTO RPM. 740 PTO RPM would give you 2220 RPM of the motor. If you did measure 97 HP at that RPM this would give you 229 ft lb at 2220. You should read directly off the dyno at 1000 PTO RPM on the gauge if you turn your motor up to 3000 RPM. Just pull the H down to 535 PTO RPM and read directly off dyno gauge will give you the HP there. Lynn
 
The dyno's not mine, a buddy was good and brought and ran it so we could test on it, he said the paper gauge was in rough shape so I thought I would try to find one for him. I was going by what he said, I just thought you always tested at 540 or 1000. I didn't even think about 750. So why is it better to test the H with 3000 motor rpm at 750 PTO rpm, that's sorta new to me. Mine was tested at 2200 motor rpm at 540pto rpm
 
The dyno's not mine, a buddy was good and brought and ran it so we could test on it, he said the paper gauge was in rough shape so I thought I would try to find one for him. I was going by what he said, I just thought you always tested at 540 or 1000. I didn't even think about 750. So why is it better to test the H with 3000 motor rpm at 750 PTO rpm, that's sorta new to me. Mine was tested at 2200 motor rpm at 540pto rpm
 

You should ask your buddy why he tested the H at 740 PTO RPM....I am thinking he had good reason.

You stated the H had been modified to run up to 3000 RPM. For non-modified tractors typically, the best power is produced around the rated PTO speeds 540 or 1000. Since the H had been modified to run at higher speed typically, one would expect the best power to be produced at a speed above the rated PTO speed. In this scenario, testing the H at 540 PTO RPM would have placed it at a disadvantage, since there should more power available at a higher PTO/engine speed.
 

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