Power reading too low
- Worn out engine
- Poor quality fuel
- Faulty engine control – error codes active
- High intake air temperature
- Run too short for turbocharger to spool up
- False advertising on performance parts power gain
- Moment of inertia calibration too low
- SETTINGS / Roller / Connected inertia
- PROJECT / Eng. inertia
- PROJECT / DT. inertia
- Power transfer efficiency corrections too low
- SETTINGS / General / Loss from load factor
- PROJECT / DT loss factor
- Improper load cell calibration
- Coastdown losses not measured or not calculated
Power reading too high
- Vehicle left in gear on coastdown losses measurement or brake pedal pressed on coastdown
- Faulty engine control – turbocharger pressure too high
- Moment of inertia calibration too high
- Power transfer efficiency corrections too high
- Improper load cell calibration
- Internal loss model for dyno or rollers set too high
Inconsistent power reading
- Faulty engine control
- Engine control corrections kicking in due to high temperatures or knocking
- Boost pressure reduction
- Ignition angle retardation
- Wheel slippage or wheel losing contact with one of the twin rollers
- Leak in the intake air system with supercharger / turbocharger
Different power readings on different gears
- Incorrect or skipped engine moment of inertia correction in PROJECT / Eng. inertia
- Different gearbox efficiency in different gears. Some gearboxes have direct 1:1 drive in 4th or 5th gear, where the efficiency is higher than in other gears.
Power correct, incorrect torque
- Incorrect engine-roller speed ratio
- Too much tire slip on rollers
Test setup effects on turbo engines
Turbocharged engine power output is strongly linked to variables other than only throttle opening.
- Temperature – with not efficient enough vehicle cooling (or even despite big blowing fan in the dyno room) intercooler will heat up and ECU will reduce power output below expected.
- Time – turbocharger needs time with opened throttle to spool up and enable the engine to generate expected power / torque. On the other hand, with time temperature goes up, and power output can be reduced by ECU. Optimal run time is often required to get maximum power reading from vehicle.
How to select optimal acceleration rate (run time)? Try different acceleration rates on the same car, see the difference in curves, gather experience. Try 250RPM/s, 500RPM/s, 750RPM/s engine acceleration rates. With too high acceleration rate, turbocharger may not fully spool up before you pass the peak torque position, and you’ll not get expected torque. With too low acceleration rate, the intercooler will be overheated when you reach peak power position and the power output will already be reduced by ECU. Somewhere in the middle there will be a sweet spot where you will get full peak torque and full peak power. With insufficient cooling system in your dyno cell, it may be impossible to get the expected measurement results in a single run.
Today something broke, dyno was reading fine yesterday
- Put some other cars that you measured earlier to eliminate possibility that it’s the today’s car that’s acting up
- Check speed sensor readings – sensor may get loose and move away from the toothed wheel. Wiring may fail.
- Check load cells readings – wiring may fail from vibration. Compare loadCell_n_value channel with torqueController_n_output. If the absorber is working and the load cell reading is not correlated to the output control signal, something is wrong with the load cell or wiring.
- If the software is not showing any result in ANALYZE, check:
- Display range selection
- If you have engine speed reading
- If you have ambient conditions readings for power correction
- Use the dyno math description and check which data you have and at which point it’s missing. That may give a clue what is missing along the way.