## 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.

Resources:

Most of this went over my head. Couldn't Honda just beef up the software to achieve MIMA-like economy?

Could they? Sure. Whether they will or not—and whether they would allow drivers to have direct control as the MIMA solution allows—is a different question.

In one sense, the MIMA hack is similar to the performance modifications made by driver/enthusiasts to their stock cars over the years. The difference here is that instead of a mechanical engine modification to deliver more horsepower than the stock car provides, MIMA is a software and hardware modification that allows the hybrid driver to deliver better fuel economy than the standard car provides.

Why wouldn't they beef up their software then? Seems to me like 100 mpg would be quite an advertising pitch.

The tradeoff with MIMA is most likely battery life, and Honda Insight battery life is already pretty minimal as compared to every other hybrid.

It seems to me that Honda/Toyota etc. should program a couple of settings for their hybrids and allow the user to chose. You could have a power setting and a fuel efficiency setting which would both utilize the battery assist for different goals. They could be configurable by the dealership or better yet by a switch or by the onboard screen that Priuses have etc.

There may not be a tradeoff in battery life, unless the maximum discharge setpoint of the battery is being overided. The driver, unlike today's cars, can anticipate the driving conditions in the future. So for example, if there is a stop sign ahead, the driver could over-ride recharging of the battery with the ICE, to allow more energy to be stored from regenerative braking. I envisage with a car like the current Prius, software could be developed where standard route profiles are stored on a computer, for example driving from home to work. The profile would be analysed to determine opportunities to optimize regenerative braking and maximize electricity use along the route. Later, when the driver sets off to drive a stored optimized route, the car uses odometer readings to determine the best hybrid setup to use based on current conditions and optimized route parameters such as battery charge.

For example, Attila Vass has written a software program for monitoring hybrid parameters on the current 2004+ Prius, see; http://www.vassfamily.net/ToyotaPrius/CAN/cindex.html

Hi I am the developer of the MIMA system.
With the MIMA system, users are finding that the charge at will ability, presents many opertunities to recharge the batteries, so they have been able to keep the State Of Charge (SOC) within a narrower band than the stock battery management system, so the depth of the discharge cycles can be lower than on the stock system.In the PIMA mode(Programmable IMA mode), careful choice of the charge setpoint relative to the assist setpoint, allows charging assist control via the throttle. An IMA "dead band" where no charging or assist is allowed, can be set between say 95-120MPG.Once the MPG rises above 120 MPG, the charging will begin, as the MPG raises to higher numbers, the charging gets stronger, until the max is reached.The same with assist, as the MPG drops below the 95MPG point assist begins, and gets stronger as the MPG drops.
If the automakers provided a programming connector and information about their internal serial control protocal, this type of Manual/Programmable user control could be developed for most of the hybrid cars of today. Will they? Unlikely, but the advantages based on early data would seem to make this type of low cost modification a no brainer.I hope to see a MIMAlike option on my next Hybrid, but for now we need to use MIMA to demonstrate that a HHI (Hybrid Human Interface) that includes manual and programmable automatic control of the gas electric mix can improve MPG on even the most efficient hybrid on the market.
Mike

I just purchased a Honda "INSIGHT" 2006 Model, and even before being Broke-in it is averaging 57.1 mpg !! I plan to install some new flex-high density Solar Cells on the roof to charge the battery pack and force the electric motor to be activated up to possibly 25mph in city conjested driving. I will look on this site for additional info on the MIMA development,
Thanks for this great WEB site,
Wally B.

I just purchased a 2006 New Honda "INSIGHT" and want to learn more about the installation of the Mima Joy stick.

Has anyone installed thin film amorphous solar cells on the hood and roof of their Insight to increase charging? If so, what has the affect been on MPG? Please specify vehicle location.

Thanks!

Bob D.

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