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Chrysler Hybrid-Electric Cars of the 1990s: Dodge Intrepid ESX

Evan Boberg, in his book Common Sense Not Required: My Career With Chrysler, wrote that none of the hybrid vehicles described here lived up to the specifications given by Chrysler.

The Intrepid was Chrysler's first attempt to exceed 80 mpg without losing space or acceleration. The total project cost $3 million to make, and Chrysler estimated that, if produced, the ESX would cost $80,000. Most of the cost was from the exotic materials and electronic components.

The engine was derived from a series hybrid-drive propulsion system meant to use 40% of gasoline's potential energy (the typical car only uses 15% of gasoline's potential energy). The car was powered by three engines. The first was a VM Motori S.p.A. 1.8-liter three-cylinder, turbocharged diesel, whose energy was diverted to an 180-pound, 300-volt battery and two oil-cooled electric wheel motors. The electric motors were also part of the regenerative braking system, where energy normally lost through the disc brakes recharged the motors.

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The rear suspension, where the two 100-hp electric motors were located, was the semi-trailing arm type with coil-strut shocks. Panels were made of ultrathin-gauge aluminum, cutting the weight by 600 lb.. The controls for parking, reverse, and forward were located on the windshield wiper knob. The styling was incorporated in the 1998 Intrepid production car.

Evan Boberg wrote that the Intrepid ESX was actually a rush job, set up as a show car late in the game; they decided to use a series hybrid because it would be faster to set up, though a real production car would not have that architecture. "[We were] building what we knew was obsolete hardware ... We made up impressive fuel economy numbers (lies) that were slightly based on our simulation." Press rides were made with the car on full-battery, he wrote; "the controls to charge the batteries had not yet been developed," and cited real fuel mileage, based on simulations, at around 30 mpg. Through the ESX development, though, Mr. Boberg said that the company was indeed working on a real high-efficiency vehicle program, and "were getting close to the government's goal of 80 mpg." This would be the ESX-3.

Specs: Dodge Intrepid ESX hybrid-electric car, 1997

  • Vehicle: rear-engine, rear wheel drive, hybrid propulsion, 5 passenger,
    4-door sedan
  • Engine types: I-3 SOHC diesel, 2 valves/cylinder, with 2 electric wheel
  • Regenerative braking (brakes acted as generators to recapture energy and
    converted it to electricity)
  • Power: 75 bhp diesel + 2 x 100 hp electric motors = 275 bhp
  • Torque: 135 lb-ft @ 2400 rpm
  • Fully electric power steering
  • Acceleration: 0-60 in 15 seconds (this was decreased in 1998 to around
    9 seconds)
  • Transmission: none
  • Wheelbase: 113.0 in
  • 600 Bolder Technologies spiral-wound lead-acid batteries producing 300
    volts DC (180 lb), stored under the hood
  • Length: 195.0 in
  • Curb weight: 2880 lb
  • Estimated 55 mpg
  • Low emissions - below Tier 1
Specs: Dodge hybrid, 1998

  • Same as above, except:
    • Engine types: I-3 SOHC diesel, 2 valves/cylinder, with 2 electric wheel
    • Power: 80 bhp diesel + 2 x 100 hp electric motors = 280 bhp
    • Torque: 135 lb-ft @ 2400 rpm
    • Acceleration (0-60): 9 sec (for 3.2-liter)
    • Curb weight: 2880 lb
Dodge Intrepid ESX2

The second run was the ESX2, with a more modest goal of 70 mpg. Chrysler called it a "mybrid" (mild hybrid) because its reliance on electrical power was not highly dependent on the battery. This system contained two motors that worked in parallel: a 1.5 liter, 74-bhp direct-injection Volkswagen diesel and a 20-bhp AC induction electric motor. Coupled with the powertrains were a 5-speed electronically shifted manual transmission, a nickel-metal hydride battery pack, and controlling equipment which included components from the Patriot hybrid race-car program.

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The main power came from the diesel engine. The electric motor charged the batteries, added to the acceleration, and powered the reverse gear.

Evan Boberg wrote that the car did indeed meet a simulation of 70 mpg, if one made uncalled-for assumptions, including lighter weight than was practical (2,000 lb - the ESX3 actually weighed in at 2,250), better aerodynamics than any five-person car ever built, and extremely low rolling resistance tires. The diesel engine would also have had to be smaller than any available at the time. Many of the components were supplied by Delphi. In the end, he wrote that the car would likely have made similar numbers had it done without the motor.

To cut down on cost and weight, Chrysler fitted the car with a cheap, unpainted thermoplastic body attached to an aluminum frame. The shape had low aerodynamic drag. Inside, trim was constructed of carbon-fiber and seats were constructed from tube frame. The final projected cost was claimed to be only $15,000 more than a regular Intrepid, or about $37,000; though this may not have worked out if it had been approved.

Intrepid ESX-3

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The ESX3 was reported as costing only about $7,500 more than a comparable gasoline-powered car, down from a $15,000 premium with the ESX2, and $60,000 with the ESX - if it had been approved for production.

The ESX3's mild hybrid electric powertrain combined a diesel engine, electric motor, and lithium-ion battery to achieve a claimed 72 miles per gallon (3.3 liters/100 km). An electro-mechanical automatic transmission (EMAT) provided the fuel efficiency of a manual transmission with the convenience of an automatic (this technology's origins are unclear.)

The lightweight body used injection-molded thermoplastic technology that cut weight and cost (Chrysler was working on other projects to use this kind of material, including the Plymouth Pronto). The ESX3 weighs 2,250 pounds (1020 kg) while meeting all federal safety standards.

Rethinking the car's electronic and electrical systems cut several pounds from the weight of electronics while providing an ergonomic system of controls and indicators, high-performance audio and video systems, and a state-of-the-art telematics package.

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Some elements were incorporated into other vehicles. The Dodge Durango hybrid had 20% higher mileage, though it mainly used General Motors/BMW technology (an electric motor setup within the automatic transmission). A thermoplastic hardtop would be used on the Jeep® Wrangler for the 2001 model year, while EMAT transmission technology was being developed for future production vehicles - never to actually be produced by Chrysler, though planned for minivans and Rams.

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