Q&A Forum
I have build a kart engine dyno utilising an electric trailer brake. The system is geared 8-1 from engine to an axle that contains the rpm trigger wheel and a 30tooth sprocket that drives a 90 tooth sprocket on the brake so the brake is spinning considerable slower than the engine RPM (the brake is also 1/3 speed of the speed of the trigger wheel) The system is electrically controlled and has a manual foot operated lever.
I consistantly get HP reading approxiamtly double of that I know the out put is using either electronic or foot operated method.
I have the right amount of teeth on the trigger wheel in the rpm setup (i even changed to see the results but it just made rpm displayed all wrong)
I have recalibrated the load cell several times and have the correct length.
I feel it has something to do with the torque being mutilplied by the gearng down but cant see what or when to fix it.
Any tips on what setting(s) I have wrong?
Cheers Darrell
Hi, you need to set the Pulses per revolution to the effective number of pulses that YourDyno sees per BRAKE revolution. So if the trigger wheel is not on the brake axle, then do some simple calculation. It sounds like there are 3 x 30 = 90 pulses per brake revolution?
You also need to calculate the gear ratio all the way from the engine to the brake, which sounds like it is 8 * 3 = 24:1.
Thanks Jostein
I did change the pulses to 150 as the 30 to 90 would see the 50 tooth trigger wheel do 3 revolutions per brake revolution however the RPM just ended up wrong
I did play around with gear ratio also but I cant recall trying that AND the gear ratio at the same time which now after clearing my head from the fustrations at the time actually makes sense. I will give it a try
When i changed as suggested the HP reading are reading right. Definatly one of those times when I should have walked away to clear my head, I was so frustrated i overlooked the simple things for a good few hours 🙁