Hofmann Dynatest 112
i am starting a new thread,as the old topic was a bit off topic and maybe this helps to others with the same dyno.
So,the dyno is a Hofmann Dynatest 112 with an eddy brake (Frenelsa F16-160 EL 96V).
The frame was repainted and all bearings replaced with new units. The rollers are in a good condition.
I was able to use the original power supply for the brake with some help in this forum.
Yourdyno works well,i am now playing with the PID settings of the brake. When i run a brake sweep, for example 2000-5000-2000 to calibrate the inertia,I experienced some overshooting. So the PID activates when the engine reach 2000 rpm but overshoots to 2500-2700 and then it recovers nicely to 2000. I had to set the time at 2000 to around 7s to stabilise the rpm. Then sweep to 5000 in 7s,the brake turns off completely,so the inertia is big enough to keep the rpm/s. Reaching 5000 the brake turn on,overshoot to 5700 and stabilises at 5000. Again,the hold time needs to be set at least to 7s. Going down looks faster to me,best would be to make a video of the run. I tried to get up and down power as close as possible,but i am sure the measurement is still not right. It was always crossing lines, no two paralell lines as on youtube video.
Made a power run after that,went pretty smooth,again in inertia mode,brake was only used to hold at 2000 rpm. I think the inertia is still not right,the difference between WHP and HP looks to big to me. It was 94 at the crank and only 65 at the wheels. Car is a Fiat X1/9 1.6 turbo,but the turbo was disabled for the calibration to have a smoother torque characteristics. The drivetrain is just like an FWD transverse engine.
Ok,i checked again the video of MOI, i forgot to turn off horsepower correction for frictional losses. I need to do a run again.
You should use one continuous RPM curve that first stays flat at 2000 for some seconds to stabilize, then goes up to 5000 stays there for 1 sec or so then goes down to 2000. No need for 2 different curves.
And yes indeed frictional losses need to be turned off.
You can try to increase the PID parameters a bit, that will make it lock faster. You can increase until you see oscillations either in the beginning or during the run, then you need to dial back a bit again. You may want to increase the Ki first, as this sets how fast the regulator reached 0 error.
maybe i was not clear,i had one rpm curve: 2000-5000-2000. I let 7s to stabilise on each rpm. I think the main issue is,the car is weak without turbo and the brake is at 0% when going from 2000 to 5000,then brake kicks in. I may try 3rd gear to put more torque in the measurement,hopefully in this case the brake will be on during the run.
Overall,i am very happy with the Yourdyno system,i need to learn how to use and set it properly.
Please let us know the Parameters. I have to test exactly the same Dyno in the Future. At the Moment my Yourdyno Box is connected to my Engine Dyno for Test.
Have you converted the Triggerwheel, or do you use the original part ?
i use the stock trigger wheel,it has 100 tooth,with a hall sensor. I was worriing abouth the tooth width,but it works just fine.
I use only one rpm sensor,on the roller connected to the brake.
A PWM to DC converter was needed to have 0-10v linear output. This output is now connected to the blue box (the AC-DC converter). It has a few wires on the top,one of them is the 0-10v signal,the other is the ground. Other parts of the original controller is now not used. I have a remote control in my setup,which was previously fitted by the last owner. It controls now the lift up and down only. I hope this can be controller lated by yourdyno.
Just let me know what info do you need.
I use also a conversion like Yourdyno at the Moment. A Friend has build it 12 Years ago. It runs very properly.
My Plan is to use the 0-5Volt analog output from Yourdyno and convert it to 0-10 Volts. The most important thing is the right calibration of the PID parameters.
how much power can your Hofmann handle? Acc. to my measurements,the inertia is around 11kg/m2. Acc. to the calculation excel spreadsheet,it is big enough to handle 300kw itself without the brake.
I do Power Runs only in Inertia mode, because my rollers are polished from exessive use. 300-350 Kw should be possible (i do no big Turbos)
Yes,i expected something similar. My fear was when i brought the dyno,that acc. to factory papers,it is only good for 200kw in steady state and power run mode as well. I think the original software was not smart enough to calculate with inertia and brake power.
Do you know what it the light inside the control box for? Does it have an important function? In mine it is not operated. As far i understood the circuit,it is running on DC voltage already.
The light will give you a feel how many Voltage is going to your Brake. (More Voltage is brighter light) You can also klick the switch on the DC Box and give the Voltage with the Poti by Hand for testing the Brake or the circuit to the Brake.
This was what was my thinking. But having a direct feedback from yourdyno about the brake %,the light is useless,or at least it can be disabled.
i made finally a power run,but there is a mismatch of the RPM. I calibraded yourdyno at 4000rpm,reading engine rpm form the ECU software.
Started a brake sweep from 2000 to 5000,in the ECU log i see it holds rpm at 2500 and ends at 5900. Is the ratio lower than required?
Maybe to much Pulses per Revolution from the Triggerwheel with the very small teeth? Or a little bit Wheelspin on the Rollers?