I recently came across several compact car conversions on YouTube where the stock engine was replaced with a 670cc V Twin Predator engine via a centrifugal clutch. The result is essentially a large go cart. A subcompact car is able to reach modest highway speeds on level ground - with 40-50 seconds required to get up to speed.
Adding a drive motor in a parallel hybrid configuration to significantly boost torque would not be terribly difficult. This configuration can provide several benefits. First, the vehicle can be driven by the motor, the engine, or BOTH. The battery capacity required is modest, and this relatively small battery system could fit in the engine compartment. The engine could power the vehicle on level ground up to modest highway speeds with the motor available for torque boosts as required for more rapid acceleration and/or hill climbing. Furthermore, the motor can be configured to act as a generator to charge the battery(*).
Cost for parts for the drive system would be on the order of $5000-7000. The main benefits in my mind are the ability to eliminate fuel consumption on short trips, and the ability to maintain the vehicle indefinitely with relatively trivial maintenance (small engine maintenance is straightforward and the EV drive components are highly reliable). Also, such a conversion has the potential to show impressive fuel economy in highway driving as the engine would have near wide open throttle during operation (most of the time).
NOTE: A Honda engine with similar performance costs about 2X the Predator. I would go with the Honda in this case. If it were 3X or 4X, then I might stick with the cheaper engine. But the Honda is worth the extra $ in this case.
VIDEO This video is part of a series describing an EV conversion of a Geo Metro.
The specs for the motor used in this conversion are very similar to the motor I had in mind. The motor is DC and uses a 72v battery pack. The rated current of the motor I had in mind is 200 amps, and it can sustain 400 amps for one minute before overheating. Notice the conversion mounted the motor to the transaxle after REMOVING the clutch. The gears can be shifted without using a clutch in this setup. Also important, the superior torque profile of the electric motor makes it possible to not have to shift at all under most conditions. For example, in city driving the vehicle here is normally kept in 3rd gear at all times. The vehicle can also be started from rest in any gear including 5th gear. However, shifting can be done where appropriate or desired. For example, 1st gear might be appropriate when starting from rest up a hill.
(*)Many DC motors will operate as a generator without modifications. I'll try to give the reader an idea of how this works. Assume a DC motor with a permanent magnet rotor. When a voltage is applied to the motor windings that surround the rotor, then a magnetic field generated around the windings interacts with the magnetic field around the rotor. The resulting force generates a torque on the rotor causing it to rotate. However, the rotation of the rotor generates a voltage in the windings that OPPOSES the applied voltage. This is why motors often draw VERY high current when first starting from rest. But as the motor speeds up, then this voltage generated by the motor works to reduce the current from the battery. Now imagine the car is cruising on level ground at maximum rated motor rpm (which is roughly 3000 rpm for the motor I am looking at). However, as the car begins climbing a hill, then naturally the car will slow down. Well, this reduces the rotor RPM. Therefore, the voltage generated in the windings that opposes the battery voltage will go down in direct proportion. The result is the NET voltage applied by the battery goes up. In effect, the electric current moving through the windings also goes up, and the result is MORE torque generated on the rotor. Voila, the car climbs the hill. Of course, this requires more energy from the battery. Now, if we try to climb a ridiculously steep hill, then the current demands can be too high. So, we use the transmission to change the gear ratio which increases torque to the wheels.
NOTE: The vehicle in the video used lead acid batteries. This explains the significant voltage drop on acceleration. Voltage goes from 72v down to well below 60v on higher motor power demands. The voltage drop would not be nearly so significant with a lithium-based battery. Therefore, the current would also not go nearly so high for the same power.
In summary, this would NOT be a performance vehicle. But it could be reliable, efficient, and easily maintained. If someone went the extra mile on the conversion, then engine exhaust heat could be used to heat water circulated through the stock heater core. Air conditioning could be provided with a window a/c unit powered by a 72v inverter on the battery (at least that's how I would go about it).
Adding a drive motor in a parallel hybrid configuration to significantly boost torque would not be terribly difficult. This configuration can provide several benefits. First, the vehicle can be driven by the motor, the engine, or BOTH. The battery capacity required is modest, and this relatively small battery system could fit in the engine compartment. The engine could power the vehicle on level ground up to modest highway speeds with the motor available for torque boosts as required for more rapid acceleration and/or hill climbing. Furthermore, the motor can be configured to act as a generator to charge the battery(*).
Cost for parts for the drive system would be on the order of $5000-7000. The main benefits in my mind are the ability to eliminate fuel consumption on short trips, and the ability to maintain the vehicle indefinitely with relatively trivial maintenance (small engine maintenance is straightforward and the EV drive components are highly reliable). Also, such a conversion has the potential to show impressive fuel economy in highway driving as the engine would have near wide open throttle during operation (most of the time).
NOTE: A Honda engine with similar performance costs about 2X the Predator. I would go with the Honda in this case. If it were 3X or 4X, then I might stick with the cheaper engine. But the Honda is worth the extra $ in this case.
VIDEO This video is part of a series describing an EV conversion of a Geo Metro.
The specs for the motor used in this conversion are very similar to the motor I had in mind. The motor is DC and uses a 72v battery pack. The rated current of the motor I had in mind is 200 amps, and it can sustain 400 amps for one minute before overheating. Notice the conversion mounted the motor to the transaxle after REMOVING the clutch. The gears can be shifted without using a clutch in this setup. Also important, the superior torque profile of the electric motor makes it possible to not have to shift at all under most conditions. For example, in city driving the vehicle here is normally kept in 3rd gear at all times. The vehicle can also be started from rest in any gear including 5th gear. However, shifting can be done where appropriate or desired. For example, 1st gear might be appropriate when starting from rest up a hill.
(*)Many DC motors will operate as a generator without modifications. I'll try to give the reader an idea of how this works. Assume a DC motor with a permanent magnet rotor. When a voltage is applied to the motor windings that surround the rotor, then a magnetic field generated around the windings interacts with the magnetic field around the rotor. The resulting force generates a torque on the rotor causing it to rotate. However, the rotation of the rotor generates a voltage in the windings that OPPOSES the applied voltage. This is why motors often draw VERY high current when first starting from rest. But as the motor speeds up, then this voltage generated by the motor works to reduce the current from the battery. Now imagine the car is cruising on level ground at maximum rated motor rpm (which is roughly 3000 rpm for the motor I am looking at). However, as the car begins climbing a hill, then naturally the car will slow down. Well, this reduces the rotor RPM. Therefore, the voltage generated in the windings that opposes the battery voltage will go down in direct proportion. The result is the NET voltage applied by the battery goes up. In effect, the electric current moving through the windings also goes up, and the result is MORE torque generated on the rotor. Voila, the car climbs the hill. Of course, this requires more energy from the battery. Now, if we try to climb a ridiculously steep hill, then the current demands can be too high. So, we use the transmission to change the gear ratio which increases torque to the wheels.
NOTE: The vehicle in the video used lead acid batteries. This explains the significant voltage drop on acceleration. Voltage goes from 72v down to well below 60v on higher motor power demands. The voltage drop would not be nearly so significant with a lithium-based battery. Therefore, the current would also not go nearly so high for the same power.
In summary, this would NOT be a performance vehicle. But it could be reliable, efficient, and easily maintained. If someone went the extra mile on the conversion, then engine exhaust heat could be used to heat water circulated through the stock heater core. Air conditioning could be provided with a window a/c unit powered by a 72v inverter on the battery (at least that's how I would go about it).
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