Weird curves  

Member Customer

I’m a newbie and need some advices.


At first, thank you Jostein. Nice piece of work. I’m very happy with it.

But now I’m struggling. Please can someone look at my files?



My Problem:

Some runs put out smooth curves (Test3_2) and I can repeat the result. A run after something is wrong. There are peaks in the drawing and also in the retardation(Test 3_3,3_4). What happens at this point?

And on other runs I have oscillation(Test2_1,2_2). I think I found a good PID setup (0.30,0.15,0). Or have I not?


I tested an other car before and the power output looks accurate. On this car not. It should be more than 300HP.


An other problem is the RPM. On manual brake mode I have problem to hold the set RPM. On power sweep is also a drift in higher RPM. I drive in the limiter before I reach the set RPM. Without load the RPM matches perfect.

I reading about tyre deflection. Can this be the reason?




My Equipment:

AVL Eddy current dyno from the 70’s

Twin roller 320mm, not heavy, not linked

Sportdevices PWS3.2, analog in

Testcar, Renault Clio 2L Turbo



thanks in advance


Posted : 21/03/2020 6:03 pm
Member Admin

Hi there.

Send me a raw log file and your configuration (backup options to file) to . I will take a look!

Posted : 21/03/2020 6:14 pm
Member Admin


I looked at the files. You have noise on the RPM signal that needs to be sorted. If you turn off the curve filtering and watch the RPM vs time you will see it.

What setup do you have on the RPM side? Are you following the guidelines here: . What kind of trigger wheel do you have?


Posted : 21/03/2020 11:44 pm
Member Customer


Now I can see it. I need to switch off the graph noise filter and not only the rpm filter
I have made a 60 tooth trigger wheel. I saw your wheel specs too late. So, my slot width of the trigger wheel is not in your dimension description.

Can you see the problem here?

I put it on bolts of the eddy brake side flange. The air gap around the wheel is 0.5mm.
The sensor I use is the one you sending out with the blue box.

I need to check the sensor mount. But its pretty solid.

Also thinking about "thermal expansion" of the components.



This post was modified 1 week ago by Reto Nietlispach
Posted : 22/03/2020 1:33 pm
Member Admin

1mm gap is fine. The spec is up to 2mm, but go for a bit less. 

Yes, the noise can come from the trigger wheel. Have a new one machined per the specs and you should be fine!

Posted : 22/03/2020 8:39 pm
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