Hacking Hybrids for Greater Fuel Efficiency
26 September 2005
|How MIMA works|
A group of people on Insight Central, an Internet forum focused on the Honda Insight, have initiated a project that provides greater driver control over the activation/charging of the Insight hybrid system: MIMA, or Manual Integrated Motor Assist.
The premise behind MIMA is that (some) humans can do better than the relatively simple automatic hybrid control software in current hybrids at finding the best mix of gasoline to electric drive.
MIMA, which has just finished early beta testing, allows a driver to control the Insight electric motor/generator via a small joystick on the shift lever (or automatically through a programmable system) to activate the assist when the MPG drops to an adjustable set point and to activate the regeneration when the MPG raises to another set point.
The MIMA system modifies the signals from the main engine controller to the electric motor controller, providing the driver with manual or programmatic (as functions of accelerator pedal movement and engine load) control. The MIMA controller may be switched on or off by the driver. When off, the Insight operates exactly as it would without the modification. When activated, the safety, emission control, and fuel conserving features of the Insight remain operational.
Both set points are adjustable in real time as you drive.
At (legal) highway speeds, a MIMA Honda Insight can achieve the nominal EPA fuel economy—or beat it. In the hands of a careful driver it can beat the EPA mpg by a substantial amount.
With the MIMA modification, an additional 15% improvement has been realized, and the system software has a lot of room for improvement, according to Mike Dabrowski, the primary software and hardware developer for MIMA.
Brian Hardegen, this year’s Tour de Sol Monte Carlo mileage rally winner, was driving an early MIMA-modified Honda Insight when he hit 94 mpg on the 150-mile run from Greenfield, Massachusetts to Saratoga Springs, NY.
Some other beta results of MIMA-equipped Insights, as reported on Insight Central:
On a 1,000 mile trip to Washington, DC, the MIMA Insight averaged 100.5 mpg, including driving in the city. Highways speeds ranged between 50–65 mph.
On a steep 10-mile uphill gradient, MIMA delivered 49 mpg versus the usual 35 mpg.
The system is open source, allowing the global laboratory of developers to improve on the software.
It would be very interesting to see how well this concept performs in other types of hybrids and in larger scale testing. Clearly, it’s not for everyone. Many drivers have a hard time doing the rudiments of driving well. But the prospect of being able to deliver that percentage level of improvement at cost of between $425 and $650 could be attractive to a fairly large number of prospects.
And perhaps MIMA, or interface systems similar to it in concept, could mitigate somewhat the tradeoffs toward power over fuel efficiency that we’re seeing in a number of emerging hybrid designs.
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