Hi All,

I was looking at building a hub dyno from scratch using YourDyno with 2x Keao KAS35 retarders, but I have a few questions about sizing since I have a big gap in horsepower between the engines I will typically run. Here are the cars that I will pretty much exclusively run with some numbers I came up with:

So the questions I have:

1. With the micro sprint, will I have any issues running retarders that big? 
   1. Will the retarders be able to accurately control that load without oscillation or any other problems even though they are so oversized?
   2. Will the load cells be accurate enough? I think I could change the distance between the retarder shaft and load cell and have a different calibration for low horsepower engines, but this isn't ideal.
   3. Will inertia of those two heavy drums be an issue on the lower horsepower engines? Especially if I want to do something like a race simulation and mimic rpm off a datalog? The rotor inertia of each KAS35 is 3.6Kg-m^2.
   4. Would just disabling one of the retarders in software but have them both connected work and help in this case? These are straight axle rear ends so both retarders would spin.
2. For the 410, would these two 3500nm retarders be considered the right size, or should I go smaller? I will mostly be doing a bunch of short pulls in a row, and this is likely the highest horsepower thing that this dyno will ever see.
3. For the late model, sometimes we run weird differentials like some cars have gleason torsen or trackstar differentials, which I am told try to put more power to the wheel with the most load (allegedly). That brings up the question, how does yourdyno decide how much amperage to put to each retarder? Will it try and keep them both at the same RPM or will it try to get consistent torque out of both? I'm going to call this a hypothetical since I don't think the gleason would actually do this, but in the case where the diff puts more power to whichever axle has more load wouldn't you end up getting some weird behavior like overloading one retarder or oscillations between balancing the two retarders?
4. Does anyone have any experience with these Chinese Keao retarders? Is there any significant performance gap to something like a Frenelsa or Klam? Are they just as responsive, or different in any noticeable way?

Lastly relating to powering these retarders I'm considering the YourDyno power supply, but I also looked at Perek and SportDevices. I noticed the latter two brands both have "faster/higher speed" versions of their power supplies, and also fast discharge version of the faster power supplies. I was just wondering, is there any benefit of having faster torque control and fast discharge capacitors on their power supplies? Sportdevices specifically mentions that the advantages are only noticeable on lightweight dynos like hub dynos and less so on things like rolling road, but they don't really elaborate from there. Is the difference significant? Also these power supplies both support control over CAN, is this something yourdyno might consider supporting?

Sorry for the barrage of questions, there is just a lot to learn and I'm excited to get started on building a dyno!

Thank you!

-Spencer