dyno horsepower

[630rich]

I was told by a guy who had a dyno at a show that anything other than horsepower at rated 540 is not the true power of your tractor. Is this true? My experience has been that when you really crank it down the power always goes up to a peak, then will kinda fall off a bit. thanks

 

[mEl]

The man is correct, there are calibrated points on the tach scale where the reading is correct, in brief, 1000 rpm for those tractors so equipped, 620 and 540 shaft rpm on a M&W PB400 for instance. HP can be read directly only at those points, HP can be figured at any rpm but a conversion scale is required called a Nomograph, I believe that is the correct term. On that hydraulic PSI and RPM are used to calculate true HP at any given RPM. There is a genuine lack of understanding on that point, The HP gage may read higher at lower rpm but if actually computed by a nomograph it may be substantially lower than indicated. In short, don't believe all the HP claims if the proper use of a dyno is not understood. mEl

 

[GreenIron]

Here we go..A dyno reads oil pressure and rpm"s.It doesn"t care how fast or slow it"s turning. The statement would be correct as far as rated goes.. When you pull a tractor below rated speed you get what is torque rise..Real Power Always a selling point for pulling the plow through the hard spots.You can lug it down for max HP and have bragging rights below rated speed. It just creates another arguement. The problem is as you pull it down how long will it stay cool ?? We can build 3 second dragsters but they"re only good for 1 pass...

 

[Anonymous-0]

I have seen some of those magic dyno readings, there was a green tractor that supposedly had more hp than mine but powered out in 5500 and I'd go on to spin out in 6500, another of my pullers outpowers tractors with a supposed 78 hp with 67 on my dyno, one of us is reading the dyno wrong.

 

[HSE]

Use a dyno that measures torque and RPM (usually a brake style dyno).

Horsepower then can be calulated using HP = Torque * RPM / 5252

If it is an electronic dyno, this function is build in. On my I plumb in sensors and connected to a laptop and it records the measurement so I can plot the load curves using excel.

 

[CLIFF S]

mEL Glad you Explained what We Have Known all this Time!

Cliff S

 

[Big Jugs]

My experience with dynos is that NO TWO will ever read the same, and I will forever stand behind that belief. So, when people talk about what their tractor read on a dyno, I kinda take it light hearted. I don't put a whole lot of faith behind what mine reads either, be it high or low. Just use it to put a load on tractor for tuning.

 

[james rumph]

I have a M&W p-400 dyno.

I had it calibrated and certified , which means the presure gauge is sent out . You can have any presure gauge calibrated , but not all will make certification.

I ended up buying a new gauge as to get the certification ,"wow" was it costly.

There is a formula we use because there isn't to many tractors running at rated rpm so the NE test data at this point goes out the window.

A dyno is a very good tool in the hands of someone that undestands the information he gets from it and applys it correctly.

There is a formuls for getting torque #s after you have gotten max rpm and hp #s. With this you can figure out at what rpm you run out of cam shaft.

I have laughed at some of the post on here about dynos and hp #s. We have found that we can make alot of hp but the torque falls off real fast at a certain point. So in short unless the motor is set up for high rpms , rpms hurt.

At this point i do believe i'm just babbling, never mind me.

Jim

 

[Anonymous-0]

its them cursed long rods with inadequate cam duration.does it everytime

 

[buickanddeere]

HP = torque X RPM / 5252

The dyno measures torque then you calculate HP using rpm.

 

[james rumph]

The dyno measures HP not torque , you have to know the formula to get the torque #s after getting rpm and hp..

There isn't a torque gauge or graph on the dyno, it is hp only.

We apply the formula to get the torque.

 

[Drew]

A dyno DOES measure torque. The HP guage just converts the torque measurement to HP for the given RPM on the guage (IE: 540, 1000RPM, etc)

 

[Drew]

And another variable that I doubt most people think of is weather conditions. I have seen a tractor make a dyno run in March with 45 degree air temp, and a few months later in the summer, 90+ degrees outside, lose 6-7HP...same tractor, same dyno, dyno up to temp. both times.

 

[james rumph]

I'll give you that. The way i read that post lead me to believe he was saying something else.

 

[Anonymous-0]

no two will never read the same is a verry true statement when talking pto dynos . To have a dyno read the same on the same tractor every where in the us . A person would have to calculate elevation dew point barametric pressure etc.

 

[Mel in SW Iowa]

Corrected to STP (Standard Temperature and[barometric] Pressure)conditions.

 

[HSE]

James,

Your M&W dyno is NOT a brake style dyno....It is a hydraulic dyno. BIG DIFFERENCE!!! Hydraulic dynos use a fixed GPM hydraulic pump and a variable flow valve to apply the load. Hydarulic PSI is then mesured and the gauge changes it to horsepower. THE BIG PROBLEM IS THERE IS NO ACCOUNT FOR INTERNATAL PUMP SLIPPAGE. The little calibration disc accounts for some slippage....but how does it know how much the pump is worn?? One way around it is to install a flow meter but that can get a little pricey.

A brake dyno uses a brake pack with a torsion bar and a load cell on it. On most models you can slide the load cell to a particular spot that changes the math to make it read a certain RPM. There is also a setting to measure torque (Oddly enough it is at 12"!) The load cells can either be strain based (electric) or haudraulic based. WEAR ON THE MOVING PARTS DOES NOT EFFECT THE TORQUE, RPM, CALCULATED HP READINGS.

Therefore if you are doing any R&D work you should be using a brake style dyno.

Have a wonderful Thanksgiving!
Brian

 

[james rumph]

All valid points that's why every year the "presure" gauge has to be sent back and re certified by a company who is be licensed by the U.S gov department of weights and scales.

I build automation tooling for a living and i'm very aware of what load cells and brakes are and how they work.

I can't make this dyno anymore accurate so it must be close. I even built a closed cooling system for it so as to keep it at a constant working temp.

Reguardless as long as as you keep tuning off a constant you shold make improvment.