DYNO

[MASSEY/AC]

I had my tractor dyno the other day.I was wondering why at 1500 RPM I had 60 hp but at 1200 RPM I had 78 hp? The dyno was a M & W pto. What I cant understand is why I have more hp at 1200 RPM ? Is this just how the dyno works. which HP number should I use? Also 78hp to me seems too much but 60 hp is what i was thinking it would be.
 

[Dblair]

the hp is figured at pto speed probably 535 anything more or less is figured with the chart using the pressure and speed to figure hp . if that's what you did then you have a really powerful machine at 1200 rpm.
 

[north puller]

The M&W dyno is not correct for any speed other than 540 on the pto. Reason is the dyno actually measures torque, and gives HP numbers assuming that you are turning 540 on the pto. Anything faster than 540 will give you lower than real HP numbers, and anything slower than 540 will give you higher than real HP numbers. What the dyno did tell you is that 1200 (engine) rpm is your peek torque rpm range.
 

[bgreer]

Uh...aren't M&W dynos hyraulic pump based so you are technical measure hydraulic pressure??
 

[tempola]

so if I showed 34 HP,,.....with the engine turning 2450,.....I should have dynoed to at 1650 factory setting for my tractor.........wonder what the actual HP would be?


evidently I overspeeded the dyno also.


AT.
 

[DAVE Thompson jr]

Put your tractor on the dyno set the rpms at stock. Let the engine warm up and crank the dyno until it gets to 540 and then look what hp the guage says that is what you have. You dont need the power at the begining of the track you need it at the end. My Farm and Field tractor will hold 64 hp right at 300 or so rpms. Adjust you fuel screw and see what it does why it is getting a load. Just my opinion A friend of mine and I bought a MW dyno a few years ago and it solves tuning while gong down the track.
 

[Eldo case]

Your actual horsepower {no mater what engine speed was when you started} is pulled down to 540rpm on the pto.
 

[Gary H.]

If you check any chart about all tractors have a different RATED pto speed. Best to go by the chart. Rated pto speed is what you need to go by. Just my 2 cents worth.
 

[VicS]

You guys are all right about MW dyno's. When I worked as a Moline mechanic back in the 60's, we had a A & W dyno. It had a oil cooled brake with water around it to cool it. The difference was that there was a bar sticking out the back with a load cell. The bar was marked from like 50 rpm at the outer end to 5000 about 2 inches from the middle. You could turn it clock wise or counter clock wise. So if we were checking a MM U with M5 blocks and had revved it up to 1800 and wanted to check it at 1600 we set the load cell to 620 and when we had pulled it to 620 the gauge read hp at that rpm. If you wanted to see hp at 800 rpm you would set it at 310. If you wanted to see the hp of say a 4020 at 3000 you would see what the pto speed was at 3000 and set the load cell there. It was a lot more versatile than a M & W. and went to 500 hp. Just a rant Vic
 

[JDGnut]

The new digital dynos will calculate the HP at the different RPM's do you don't have to go to the slide ruler.. It sure makes it easier to use..
 

[bgreer]

VicS,

That is what mine is too (A&W)... I always set the load cell at the 12" mark (to read foot pounds of torque). I got a pressure transducer to read the load cell pressure (which is ft lbs torque) and I also tapped into the RPM pickup sensor and I feed these two signals into a laptop so I can data log the runs so you dont have to load it more than 30 seconds to keep things from getting too hot. By reading true torque and RPM and then calculating the horsepower allows you to throw away the idea of holding it at 540 and lets you map the power band of the complete RPM range of engine. When I run turbo diesels on it I use a pressure dump valve because I never could back the valves off fast enough from killing the engine when the turbo boost dropped off.
 

[JDGnut]

I'm guessing you have an older A&W dyno.. I think the newer ones will do this.. I've been fight the software on mine, and haven't had time to get it working... but I'd be interested to do that to my old M & W dyno.. I just can't get enough water to my dyno..
Bryan
 

[bgreer]

Its a P375...not sure when it made. I built my own data acquistion system to connect it to laptop and the wrote my own software to collect it. That way it is my fault if it dont work lol... It would be tough to do a M&W dyno. To do it correctly you really need to put a hydraulic flow meter in with the circuit before the pressure load valve. That would be about the only way to compensate for internal hydraulic slippage that you need to account for if your doing any testing that you really want any true accuracy. I always laugh when guys get their little cardboard wheel out and try to calibrate their M&W dyno. Maybe they used majical hydraulic pumps that never internal wear any. M&W are good for breaking in engines or exercising old tractors....but they're not ideal for research projects.
 

[Thad]

Andy we read it at 540 pto speed. He just pulled it down to pto speed then read it. Thad
 

[tempola]

Thanks for clearing that up and dynoing my tractor Thad!

AT