Hi,

As you say, this dyno uses the formula Pressure x Flow (rpm) = Horsepower.

You can definitely use YourDyno for this application. Here is what you do: 

1) Pressure sensor is connected in place of the load cell. Very likely you can use the one you have, otherwise a suitable one costs $50 or so. The sensor needs to be of a wheatstone bridge type with analog signal out. 

2) For calibration you need two points, one point with no pressure (very easy obviously) and one point representing a known horsepower at a known RPM. Take the horsepower and calculate what torque that means at the prop shaft. Enter 100 cm (or 12 in) in the load arm length and enter the Newtons (lbs) you have calculated that the engine outputs at max. Run the engine to the max and press "Load calibrate". Save and do a run and see if you get the power you expect, otherwise adjust the calibration and try again. 

A somewhat more controlled way is to apply a known pressure. Then convert that into Newtons or lbs and press "Load calibrate". 

Actually I have wanted to add this functionality to the software, but have not have access to a suitable test bench. Let me know if you want to buy a YourDyno and I can add the native software support for pressure sensors, and you can test it out for me in a month or two. Until then you can follow the procedure above.

Cheers,
Jostein

I would be willing to do some testing for you. The gauges I have are all mechanical and it doesn't have a formula for direct horsepower it has a chart that shows what the pressure should be for a given rpm on each specific engine these numbers were gathered my actually running the engine when new and recording the numbers. I have run formulas and they rarely line up with the rated horsepower of the engines. This is why i want to add a system like yours to it so i can get confirmed hp numbers. It seems to me the only way to confirm the accuracy of the reading off the pressure senser would be to have a load sensor tied in as a second load cell so you can compare the 2 hp reading or do 2 runs 1 with each sensor and compare the readings. I would be interested in buying you system with a load cell then adding the pressure when you have it ready. Can that be done with a firmware update? Could I add the pressure sensor as an AUX input until then  so I can record the pressure during my runs? I seams to me that with a pressure sensor setup the difficult part would be the initial calibration because without an actual flow meter you would have to manually enter that number and the accuracy of what you input would determine the accuracy of you hp readings. 

It is definitely more accurate to use a load cell. It measures the actual torque. The biggest inaccuracy of the pressure x flow method is the flow. The pump is spec'ed for a certain flow per revolution, but it varies with pressure, temperature, viscosity of the oil, wear of the pump, etc. So while it is good enough in many instances for comparative runs, it is not so good for absolute measurements. 

Can you mount a load cell? If so, then great, no need to even measure the pressure. I did not understand why you would still want to measure the pressure too?

YourDyno has the option of two load cells, so electrically, yes, you can connect a load cell and a pressure sensor, but the software does not support it directly. Let me know what you want to do, and maybe there is an easy way.

Anyway, if you can mount a load cell you are good to go!

I believe I can build a bracket to mount a load cell. I was thinking of a pressure sensor as an aux input so I would have a more accurate reading than my mechanical gauge to compare to the chart that I have just for my own curiosity. 

Yes, using a  load cell is better.

You can connect the pressure sensor to an aux input if you run it through a conditioning circuit that converts the signal from the sensor to a 0V-5V signal. Use for example this one: 

http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=73&products_id=199

Could you point me to a pressure sensor that would handle 5000 psi?

Hi,

Here is one with amplifier built in (for connection to aux):  https://www.digikey.com/product-detail/en/te-connectivity-measurement-specialties/M7139-05KPG-500000/223-1618-ND/5277353

Here is an analog one for connection to the load cell input:  https://www.digikey.com/product-detail/en/te-connectivity-measurement-specialties/89-05KS-4R/223-1505-5-ND/5277618

You can search around, there are many other options.

Cheers

Is it possible to use one of the Aux inputs for the "load cell" feature, pressure transducers are much more available with a 0-5v, 0-10v, .5-4.5v and 4-20 mA outputs.  And will you be adding the field for a pressure sensor in place of a load cell?  If we could input flow at 2 given RPM's and a min and max scaled pressure, it would be enough to calculate the braking horsepower.

I'm about to build my dyno, but it would be much easier to use a pressure transducer than try to fabricate an assembly to hold a pump and allow it to torque on a load cell.  Especially when the pump is capable of 150+HP, they are very large and heavy at that point.

You can use a pressure sensor in place of a load cell (whetstond bridge type). You just need to be able to calibrate it with a known pressure and convert that to a known torque, then you enter 1m length of arm and the calibration weight to be Torque (Nm) / 1(m) / 9.81Kg/N. 

You can also use an 0-5V Aux input, this will essentially read torque. Then you need to use math channels to convert this into Power. The Max Power/Torque functionality will not work then, but you get the curves like normal