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1987 Toyota MR2 Mk1 Electric Conversion Project Car


									                                                              May 30, 2009 lmu

    1987 Toyota MR2 Mk1 Electric Conversion
                 Project Car
                   PEVA Owner: Lee Underkofler

My electric vehicle (EV) project is the conversion of a MR2 Mk1 Toyota sports
car to electric drive. Two pictures of the vehicle purchased to be converted
are shown. It is a small two seat car that is light weight (~2250 lbs) and has
a published aerodynamic drag figure (Cd) of 0.31– 0.34 and CdA of 5.80. The
MR2 is a mid-engine rear wheel drive configuration which I believe is an ideal
choice for electric power conversion. I looked for a couple of years to find
this particular MR2 which has a „targa top‟ and no energy wasting power
steering, power windows, power mirrors and such. The gas motor had a loud
rod bearing “knock” which allowed me to purchase it for an economical(?)

I was able to obtain a three-phase AC motor and drive unit from a General
Motors 1997 S-10EV pickup for this conversion. Two photos of this motor
and drive are shown.
   Photo 1 is a right side/rear view of the 85 kW (114 hp) induction motor
which is attached to the reduction drive unit shown the lower right (drive
mostly hidden). This motor is liquid cooled; the green caps cover the
connections for the coolant. The orange cable and connector at the top of
the motor is the input for the high voltage AC. The black object on the rear
of the motor is an „encoder‟ that originates two low level analog AC signals
electrically 90 degrees apart to allow monitoring the speed and direction of
the motor.
       *[As I write this, the encoder from my S-10EV motor has been installed
on an EV-1 motor that is on it‟s way to England to run in the „Isle of Man
Clean Air‟ motorcycle race June 12, 2009.]
   Photo 2, taken from the left side of the motor, results in a better
perspective of the gear reduction and differential drive unit into which the
electric motor is bolted. It also clearly shows the high voltage cable end
connector that plugs into the S-10EV inverter. The plan is to mount the motor
and gear reduction/differential unit in the place the original transaxle
occupied. The CV-joints on the half shafts driving the rear wheels will mate
directly to output shafts on the left and right sides of the drive unit. There
will be no transmission or clutch; only a single speed gear reduction from the
motor to the axles. The motor and the attached gear box weighs ~150 lbs;
considerably less than the original gas motor and transaxle! Of course,
battery weight will more than make up for the difference…

My current effort on the MR2 project is determining the approach I want to
take for the motor inverter/controller. At the moment I am considering three
possible ways to proceed:
                                                              May 30, 2009 lmu

   1) Do a “lobotomy” on the original large and heavy S-10EV pickup
   inverter replacing the logic and control circuitry with a much simpler
   „brain‟ for motor control only…

   2) Purchase a custom inverter offered to me by the team that built the
   EV-1 powered electric „Isle of Man Clean Air‟ race motorcycle…

   3) Further investigate the possible use and purchase of a MES-DEA vector
      control AC motor drive…

The MR2 chassis will require much work and repair. At the least, it needs
ball joints front and rear, shocks, brakes, bearings, new front bumper,
possibly new springs, and ?? Mounts for the motor and reduction drive will
have to be fabricated and welded into place. Likewise, the inverter will need
to be mounted and cooling systems for both the motor and inverter will
require design and fabrication. When a decision is made on batteries, the
battery containers will also require design and fabrication, etc., etc.

To be continued….the progression of a project in process.

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