Wow, somehow all of my text got wiped out when I uploaded pics, and I can't edit posts, so I'll rush through it.

I picked up the DIY engine dyno after talking to a buddy. He had recently sold his chassis dyno and was considering building a DIY Hub dyno as a replacement.
I wanted to take a shot at doing a small scaled down version, so I started on a hydraulic torque arm dyno capable of around 50 horsepower.
The max budget was just $500, but I managed to finish it for $400.

The concept is simple. The engine drives a hydraulic gear pump, that is mounted inside of a spinning cradle supported by pillow bearings.
Fluid is draw out of a 5 gallon propane tank, circulated through the pump, and dumped back into the tank.
A needle valve at the pump exit is used to close off the fluid return and build pressure, making the pump harder to turn.
The pump and cradle themselves begin to rotate. Attached to the pump is a 12" torque arm (center to center) with a load cell on the end. 1 lb at the end of a 1 ft torque arm = 1 ft-lb.

Everything is arduino controlled. An electronic load cell, Bosch BME280 for SAE J1349 correction, AEM wideband, and a 24x GM crank sensor for RPM.
At the start of a run, the Bosch sensor captures weather data, and I calculate a correction factor from it. I lock in the correction, and then sensor data gets captured by the arduino until the end of the run.
RPM, load cell readings, and wideband data are all captured together, forced as serial data to the laptop, and its all graphed out for me in halfway professional looking graphs.

I built the dyno to test various design concepts and ideas, fuel types, and tuning strategies.
I've tested ultra cheap conventional oil vs expensive synthetic race oil vs cheap conventional with additives. I've tested 87 vs 93 vs Race gas (on an engine that only requires 87), and spark plug types/heat ranges.
I'm not sure where I'll go from there, but I have a few ideas in mind.

 

Cool stuff Joe! Your mind is always at work... I wish they would drop the restriction on you...

 

That's really cool!

 

damn dude that rips!

 

I've been working on automated load control that'll use a stepper to control the pressure valve, which controls the rate of RPM increase.
Hoping for a 300 RPM/sec rate. It'll make power measurements much more consistent.

Eventually I'll scale up to a larger 100 horsepower version. My main holdup right now is the noise. My current neighbors aren't too thrilled with the noise level I usually produce.
20 horsepower 8000 RPM single cylinder engine with an open header pipe is pretty damn loud.
I'm working on having a new house built right now as well, which will make it even harder to get any major work done.

 

One thing I noticed, as I have messed with hydraulic stuff before, is heat buildup in the hydraulic fluid. Is the reservoir large enough to dissipate the heat accumulated during a run? Or you might want to put a cooler in the return line.

 

The fluid gets to about 110* or so after a dozen runs. Heat hasn't been an issue yet.
A full dyno pull only moves about a 1-2 gallons of fluid out of the 5-gallon tank.
I think it would have to recirculate in full a few times before there were any real heat issues.

 

Oh OK! Just something that came to mind. I know you're up on things pretty well, and had it figured out, but I thought, you never know....
Looks like it's under control! Take it easy!