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Tractor Dyno thoughts

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Hello Yourdyno people 😉

I have an old Eggers Tractor trailer dyno with the Yourdyno controller kit on. Dyno has an ARB M300 eddy current retarder setup at 192V (3200Watt). It runs well so far (y). But i could could use some thoughts on the PID setup of this. I cant seem to get rid of all oscillations. I have followed guide on this site. 

Start: Raise P until unstable Rpm and I+D at zero. I can raise P to about 2.00 then i start to get oscillations. These only come a low engine Rpm <1200Rpm. Over 1200Rpm = stable. If i need stable at low Rpm then P needs to be under 0,5. 

Rpm is way off with only P. Again i Raise I untill system is unstable, then lower factor a bit. I have same issues here. Low Rpm needs a very low I factor. 

Low PI factors are not the real issue here. Its that ill need to make a dyno test Quick cause retarder heats op very fast, and then has low braking power. The smoothening factor in settings does nothing visual soo far i can see. So P and I at aprox 1.5 then i get fast reactions on Rpm control but unstable at low rpm. Low P+I then very slow response where i need test time at min 3 minutes (2200->1200rpm) if Rpm actual and real must match. Does any of you have any dyno sheets you could upload here so i can see how stable your Rpm control is for your retarder setup? I have attached a typical Measurement. Does any of you have some thoughts on this, or on my setup? 

Also i see a lot of you is asking on where you can buy retarders. well i am considering buying a new 4300Nm from frenelsa cause mine is getting to small for new tractors. So if anyone could be intrested in a fully working ARB, Austria Retarder Bau model M300 retarder then you can contact me. I dont have any specs on this other than max brake Torque is aprox 2600Nm and is setup to 192V.

Cheers - M




Posted : 04/08/2018 6:32 pm
Posts: 1400
Member Admin


Which power supply do you have? 

Here are a few things to consider. 

  1. You can go for Brake sweep. For sweeps it is not necessary that the RPM follows a certain RPM curve, it just needs to be a smooth sweep through the RPM range. Brake sweep is by nature stable. There is a new (beta) version available now it has a few improvements to the brake sweep function (sweep up and down are supported, plus static brake percentage start),  http://www.yourdyno.com/YourDynoInstaller_3.01.69.msi.
  2. Also for RPM sweep, do not worry too much that the RPM follows exactly the curve. The readings come from the actual RPM and brake force (plus acceleration), not from the RPM sweep curve
  3. It looks like your engine/brake/power supply combo has different sensitivity at different RPMs. This is not uncommon. The engine is probably much less punchy at 1200 RPM compared to when at full power. If you want to stay with RPM sweep, you have two choices: You either go for the lowest setting necessary for the whole sweep to be stable. Or you can use the Advanced PID setup for this. If you have a set of parameters that work at low RPM and a different set that work on some higher RPM, then  you can calculate what the multiplication factor needs to be. You can make a curve of multiplication factors (but dont make it too complicated). Start for example at 1200 RPM and set the optimum parameters for this RPM and the multiplication factor there to 1. Then for some higher RPM set the multiplication factor to 0.5 or 0.25 or whatever you need. 
  4. A sweep will typically need lower PID parameters than a steady state. So even if Kp of 2 makes it stable at 1200 RPM, this starting point is probably too high for a sweep. This is another reason why a brake sweep is simple. You just need the parameters to be right for that one static starting RPM.


Posted : 04/08/2018 7:55 pm
Posts: 46

For power supply i am using skpc200-440 and skch28/12. Mounted just like specified on yourdynos website.

Yesterday i got time for another test. I got the PID settings better adjusted for fine curves for Rpm sweep function.
I also did try brake sweep like you said. I myst say that this function works very well for tractor testing. It is giving me very stable torque curves!.
In the start of brake sweep it is slowly raising brake power. It is taking a while before i starts to load the engine. So somehow setting brakeload faster in the start would be prefereable. I usually setup the brake sweep from 2200rpm to 1400rpm. But the load is also causing very fast rpm drop on engine below aprox 1700rpm. This causes the engine to almost stall before engine load is zero even though i set stop rpm to 1400. iItried to lower sweep rate. This causes, so far i can see, a far longer start load time, but a better control at low rpm, without engine stall.

I have attached a measurement of same tractor with rpm sweep (blue lines) and brake sweep (red lines). These two measurements aren't fully idendical. What is causing this? Is moment of inertia from retarder used in both? I am using a value of 4,6 kg*m^2. The brake sweep shows a little higher value at high and low rpm than the rpm sweep. 

Also the brake sweep can somethimes make some curls at measurement start (2200-2300rpm). This is not a big issue but can these be removed? I think making a latency on logging just like rpm sweep will do the trick.

Another question- I an using a 1000kg load cell. Do any of you have a good way of calibrating this? i have used a specified weight of 60kg directly on loadcell to calibrate. The weight was weighted very precise. Wouldnt it be preferreble to have a much higher load, like 50% of loadcell capacity? As far as i can read loadcells arent fully lineær. Does anyone have input or good ideas?
It isnt easy to find a precise 500kg weight and mount this on loadcell. And in case i need retarder upgrade soon then a 2000kg loadcell will be needed.

Cheers  😉 


Rpmsweep vs brakesweep

Posted : 07/08/2018 8:28 am
Posts: 350

Can i ask a silly question ?

Why are you ramping downwards from high rpm down to  low rpm ? 

That is awesome amount of torque , what diesel engine is in the tractor?



Posted : 14/08/2018 1:44 pm
Posts: 46

Its not a silly question - i have actually also asked myself that. I do it because ALL agricultural dynamometers (Eggers, Froment etc.) do it this way. Tractors are made for work ie- 100% engine load at all times, and keep engine rpm where highest powerlevel are. The speed within agri is always determined with transmission ratio. Most tractors sold today comes with infinity variable transmission to keep engine rpm where max power is archieved.

But i have actually thought of trying from low rpm to high once i get time. What are your thoughts on doing it this way instead?

This test is just from a little baby tractor 😉 - 6,8 liters diesel, CR with VGT and EGR. Aprox year 2014 i think.

Posted : 14/08/2018 7:48 pm
Posts: 1400
Member Admin

Hi MadsWP, 

Nice curves :-).

Yes, the MOI will impact the brake sweep vs RPM sweep. If it is slightly off, the you will get different results when the engine is accelerating at a different rate. Also, if the engine itself may have a somewhat different response when it accelerates fast vs slow, so even with the MOI perfect, you may not get exactly identical results. 

To remove any parts of the curve you can save it and open it in a text editor and delete the beginning or end. Check out in the results vs time window what time frame you want to remove, and do this in the text file, then open it again in YourDyno. 

About calibrating the sensor. Check out the latest video I put out,  https://www.youtube.com/watch?v=Oq0ruw0zpC4. I use a long bar to extend the load arm length. The trick is that you can extend the load arm and put a load far from the load cell. You enter this distance to the weight (not the load cell) in the load arm length in the calibration window. This works great for big cells like what you have. You need to add the weight of the bar, and do some quick calculations on its effect on the weighs out where the rest of the weight is. 


Posted : 14/08/2018 9:38 pm
MadsWP reacted
Posts: 46

That was a really nice way to calibrate load cell!

Jostein, The brake sweep function works very well. I dynoed 3 tractors today. But i have a small issue with this. In options of brake sweep i have to choose at least 1400rpm for brake switch off, otherwise the brake will stall the engine. I feels like there is some latency when reaching the aimed brake switch off rpm and the actual unload rpm. Yourdyno will stop logging at 1400 rpm as choosen for brake switch off, but will continue to load engine to idle (800rpm) or lower and then engine will stall.

What can i do to make a brake sweep down to 1000rpm (turn off brake immediately, when aimed rpm is reached)?

Posted : 15/08/2018 6:44 pm
Posts: 1400
Member Admin

Hi MadsWP, I will check that, the brake should indeed turn off immediately at the specified end RPM.

Posted : 17/08/2018 9:42 pm
Posts: 1400
Member Admin

Hi MadsWP, you can download the latest version, version 3.01.73. Here the unfiltered (immediate) RPM is used to turn off the brake, rather than the filtered version. 

With low noise reduction settings this difference should not be very noticeable. In any case make sure the noise reduction setting is not higher than necessary. 

Posted : 19/08/2018 2:56 pm
Posts: 46

Thank you for great support! I will report back when i get a another tractor dynoed  😉 

Posted : 19/08/2018 4:14 pm
Posts: 46

Had another tractor dynoed today. Brake sweep off rpm works perfectly as should now. But logging it not stopping at brake sweep off rpm. I need to turn this off manually.

Posted : 21/08/2018 3:23 pm
Posts: 46

I also suddenly have many connections dropouts. Every time yourdyno disconnects then brake will be activated and load engine so it stalls sometimes. Dropouts tend to come more often when retarder is rotating. Can my retarder or power supply make some electrical noise and be the cause? 

I have a 10 meter usb cable between laptop and yourdyno. Can this be the cause? i have just updated fw with the one on forum for connections dropouts to see if this helps. 

Posted : 21/08/2018 4:52 pm
Posts: 362
Dyno Wizard

What quality is the USB cable.
Iv had trouble with a 8M chinese one going from engine bay into cabin for tuning a link ecu with. That would pick up the ignition nose and get drop outs.
Got a quality shielded one made up and got rid of my problems. Wasnt cheap tho with the shielded cable alone costing $11 per M.

If you wanted to change to wire free connection to Yourdyno you could set it up like I have mine setup.
Have a seperate computer just for controlling the dyno.
Have VNC server installed on it and it hooked into the workshops wifi network.
Then on my laptop have VNC viewer. Which lets me remote control the dyno computer over wifi anywhere Iv got wifi on my laptop.

Posted : 22/08/2018 2:23 am
Jostein reacted
Posts: 46

Do you have a link where you bought the usb cable?. I checked ebay an local shops. All cable looks like cheap china cables. Even the expenssive ones. when plugging in the 10m cable in usb3 port then yourdyno cant get detected. So think cable must be replaced. ubs 2.0 works, but with connection issues sometimes. 

Its a good idea with wireless. But my setup is mobile. So it will be a bit overkill to mount a laptop on trailer for wireless. But a raspberry pi with web interface of yourdyno could be awesome i think  🙃 

Posted : 22/08/2018 1:40 pm
Posts: 362
Dyno Wizard

Wasnt bought online.
Got the cable from my local cable supplier (cables nz)
Then got the USB ends from local electronics store (jaycar).

Thats a intresting idea with a R Pi.
Would be lacking a bit in the processing power but youd just get it to send you the csv at the end of the run and let the laptop handle all that client side.

Posted : 22/08/2018 10:35 pm
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