Q&A Forum
I'm very familar with that thread.
Your hubdyno results are only good for your own dyno comparison! As you stated " it's only a tool " comparing with other dyno's seems very mmm........ ??????
Who's dyno reading is right or wrong ?
Quote from that thread link you posted " one in particular example sticks out like a sore thumb " Rover 2.0 turbo 242Fwhp /252hp - 3.97% " there is no way in hell it only loses 3.97% powertrain losses from the flywheel back to the driveshafts coupled up to a hub_dyno. You seriously have to question this. Drivetrain losses are greater than some people think. I haven't yet proven it but in due course. I need more input from these quoted figures."
PLEASE EXPLAIN THE LOSSES HERE ?
To answer this unexplained phenomena that occurred on you hub_dyno with i can't explian why your findings was a 3.97% powertrain losses ???? I'm still at a loss ?
Anyway keep dyno'ing
we already discussed here:
Give us some power losses numerical figures for these Honda Civic EG you have been tuning and testeing?
Q1 -Year of the Honda Civic EG ?
Q2 -Engine BHp of the Honda Civic EG ?
Q3 - FWDH_Hp of the Honda Civic EG measured on your hub_dynamometer?
Q4 -What gearbox/differential is used on this Honda Civic EG ?
id say, if too much power affect to drivetrain loosses, it Would be measured on dyno, It's like when i dynoed 2 cars that had some problems with brakes, i tuned many of these cars (Civic EGs) and i know already drivetrain loosses when any car has a specified engine/gearbox, anyway there is minimal difference between engines/gearbox, 2 of these cars had brake problems then i noticed was Reading too high drivetrain losses, after we get rotors spin freely, got the right losses. im pretty sure, if a gearbox get more losses by load, heat, it would be measured perfectly.
So what are the RIGHT engine power loses percentage % engine to front/rear wheel vehicles (and 4WD vehicles) drivetrain losses for chassis_dynamometer and hub_dynamometer ?
id say, if too much power affect to drivetrain loosses, it Would be measured on dyno, It's like when i dynoed 2 cars that had some problems with brakes, i tuned many of these cars (Civic EGs) and i know already drivetrain loosses when any car has a specified engine/gearbox, anyway there is minimal difference between engines/gearbox, 2 of these cars had brake problems then i noticed was Reading too high drivetrain losses, after we get rotors spin freely, got the right losses. im pretty sure, if a gearbox get more losses by load, heat, it would be measured perfectly.
Hi Jostein.
The calculation you describe is what I would expect. When i talk about speed, I am saying that the losses are related to the roller speed. Greater speed = greater power loss.
The tire loss and loaded losses are exactly the algorithms I'm asking about. Tire losses are probably related to tr active effort, weight of the vehicle and "flex" of the tire.
Dev
@dev, you are not correct on the calculation.
The dyno measures the retardation loss much like an inertia dyno in reverse. YourDyno knows the MOI and measures the deceleration and from there calculates the torque required to slow the rollers down like that retardation curve. This negative torque curve is added across to the positive torque curve (i.e. the torque loss at each RPM is added to the torque at each corresponding RPM at ramp up), and the result is the engine torque curve. Same for HP. It does not use speed or anything like that, it just measures the torque at every RPM.
The losses that are not accounted for are:
- Additional drive train losses due to the extra load under power. This is typically larger for higher hp cars. Loss at coasting, which is what we measure, is not the same as the loss at full power. High performance cars have gear box and diff cooling for a good reason...
- Tire to roller loss. This can be significant (the tires get hot...) and again is typically higher for higher hp cars. Loss is higher at smaller diameter rollers.
Complicated field. If anyone has algorithms to use to account for these losses, let me know!
it's used a lot in SPain maha, a lot of slippage problems.. in Germany , some of shops strap it down the car using engine support modified!
Have a look at some Maha dyno graphs, they are have a nice model.
i guess so just doesnt have nothing to do with power increase as i said, there are other factors or i'd say even important problems on roller dynos by tires
Yes with Hub dyno you will not see that much difference. On car that starts off at 230bhp and then goes to 450 bhp - it's quite a lot of difference.
i'd say in acceleration yes, not in desaceleration , but talking in numbers, how many hp? or percentage Will be noticed on dyno? i already said what i see in my dyno above.
yes, that's why i said maybe i have a bit advantage by using hub dyno, ive seen some ppl having a lot of drivetrain looses by using drag slicks!
It does increase with power, more thrust loading on helical gears etc.
But, the biggest increase in loss is through tire flex. Especially when you are running 500bhp through a narrow 225 tire on twin rollers - the heat generated is immense.
"lanzada 3" : a turbo RWD car..nothing special, just i think it's very important to get always same drivetrain looses readings.