Quote:
Originally Posted by CanAutM3
I found a major flaw in the analysis just after reading the first sentence.
You cannot take the reading of a chassis dyno to establish optimal shift points. Even more error when using a roller dyno (the 4 wheel dyno used by MT makes it even worse). The shape of the power/torque curves is altered due to losses (mostly tires rolling losses) and inertial impacts.
You should redo the exercise using the official power/torque chart published by BMW.
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I tend to agree. If the dyno alters the shape of the torque curve, it can effect the shift point prediction. As I don't have access to the raw data or corrections, I've run the study with a second data point. Enter
Sport Auto. I've grabbed the data and calculated the torque at the wheels. I prefer to use this data over OEM supplied curves as they have incorporated drivetrain losses. EDIT: The data below includes the drivetrain losses of the car as well as the drag of the Maha dyno. It appears that it will be exceedingly difficult to separate torque transfer losses and dyno drag, so I'll include both the dyno-influenced wheel torque and a another group of plots to show the flywheel torque. The three dyno-influenced plots below will predict LOW shift points due to the shape of the torque curve incorporating dyno drag. When I post the group of plots based on the flywheel torque curve, that data will predict HIGH shift points since no losses are incorporated.
In reality, the optimal shift points will fall somewhere in the middle.
Same three graphs as before
- All gears
- Gears 2-4
- Optimal shift points
A quick review of the Sport Auto data suggests that the two gearboxes are about equal regarding max torque at the wheels. As you work your way up in speed, they trade max torque back and forth (blue boxes show speed ranges in which the 6MT gearing produces higher values).