Q&A Forum
Hello community
I have yourdyno kit on my tractordyno. Dyno has recently been fully restored with new frenelsa 4200Nm retarder include new 1500kg loadcell.
When measuring power it now tends to read power relative low on first run. Power then rises a bit on second run, and again on third run. After aprox 5 dyno runs i get consistant power measurements, where each measurement is within +-1 hp, and grapfs looks similar to each measurement. Have any of you seen this issue before?
I am very careful of making sure engine coolant temp, transmission oil temp etc is at working temperature before starting measurement. only thing i can think of is that my loadcell measurement is very dependant on its temperature, as it gets heaten op a bit by heat from retarder after a few runs. does any of you have any inputs on issue?
Regards
M
Are you sure that the whole system is up to temp on the first few runs? What about motor oil?
To check your idea on the load cell, put the calibration load back on after 5 runs and see if it shows the same as when cold.
There are load cells that are temperature compensated that you can try if this indeed is caused by the load cell.
Engine oil temp is also within spec. issue has definitely come after upgrade. I will try applying a little heat on loadcell to see if anything is changing.
Can you, Jostein or anyone else, recommend a specific loadcell with temp compensation?
Wouldnt retarder tempture have more of an effect?
With mine it grabs harder once its gotten hot vs when its cold.
As in I could do a run with retarder cold and car would output 500HP going though RPM range at 340rpm per sec.
Then heat up the retarder with a 20 sec steedy state hold.
Do another run now car will be 520hp and go though RPM range at 300rpm per sec.
I dont see why retarder temp should have influence on measurement. a hot retarder would just need higher voltage for same braking torque. the force measured by loadcell would still be the same.
When measuring tractors its done by starting measurement from max rpm, and force engine down to idle rpm. The run time is the same, as i use rpm sweep. Can issue be Rpm sensor, or noise i someway?