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Chapter 5: RPM Input Options
Option 4- Manual Ratio Entry-
If DYNertia3 knows the drive ratio between the engine and the dyno it can calculate actual engine RPM from the dyno
RPM (as measured by its sensor). This option will require you to know the drive ratio being used, this is usually not
practical for a chassis dyno as tyre size, roller size, gear box and final drive ratio must all be known and calculated. If
testing engines without gearboxes (e.g. kart) then this is a very good option.
e.g. For an engine dyno: Ratio = Number of dyno flywheel gear teeth divided by number of teeth on engine drive gear.
Ensure the “Use Default RPM/Speed System” is selected as the RPM source.
Manually enter a ratio into ‘User Ratio’ or any of the 8 ‘Compute Ratio’ fields, then press
Enter key.
You can enter data for other gears also if you want to do testing in multiple gears (up to 8). We recommend you use
“Compute Ratio 3” for 3rd gear etc.
Ensure you select the correct set ratio in the ‘Record Settings’ panel for “Current Ratio”, choose “User” if you have used
the ‘User Ratio’ field (or any of the 8 ratios if these were used).
Option 5- Manual RPM to Speed Entry-
If DYNertia3 knows the speed the vehicle does at a certain engine RPM then on a chassis dyno it can then calculate
engine RPM from the dyno speed (as measured by its sensor).
Manually enter an RPM and speed separated by a “=” sign, enter into ‘User Ratio’ or any of the 8 ‘Compute Ratio’ fields,
then press Enter key. The example above was used as this vehicle does 1550RPM at 100kph in 5
th
gear.
You can enter data for other gears also if you want to do testing in multiple gears (up to 8). We recommend you use
“Compute Ratio 5” for 5th gear etc.
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