Hybrids do well on gasoline because they have efficient undersized engines combined with light weight and excellent aerodynamics. This retrofit wouldn't change any of those things so I doubt it would have the claimed mpg benefit on a long drive. With a big battery pack, I could see it boosting MPG in city driving but it doesn't have gearing to use the motors at high speeds like highway driving. The big battery pack hurts city driving because you need to accelerate and decelerate that added mass.
It reminds me of similar retrofits that might be comparable and easier:
1) Replace the alternator (or AC) with a small 6-10hp motor. This is like a DIY version of the Honda IMA. I think GM was promoting something like this. You're limited by the power a belt can transmit, but it does go through the transmission and allows easy stop/start of the engine (ex: at a traffic light).
2) Remove the rear drive-shaft from a 4WD like a truck and attach a motor to the differential. This is also somewhat easy and a truck is better equipped for carrying batteries. There was a Jeep design that did this. Stay in "4wd" without applying power to the motor and it's like a front wheel drive. The downside is that the motor isn't geared so it's only good for one speed range (perhaps low end torque).
Unfortunately, both designs are just mild hybrids. To really go far enough with the motor you need lots of batteries. For example, the 80lb NiMH pack in my Insight can barely go a few miles. Regen makes sense but you lose a surprising amount of energy charging/discharging. I get the best gas mileage trying not to use the hybrid systems (even in city driving).
Hybrids do well on gasoline because they have efficient undersized engines combined with light weight and excellent aerodynamics. This retrofit wouldn't change any of those things so I doubt it would have the claimed mpg benefit on a long drive. With a big battery pack, I could see it boosting MPG in city driving but it doesn't have gearing to use the motors at high speeds like highway driving. The big battery pack hurts city driving because you need to accelerate and decelerate that added mass.
It reminds me of similar retrofits that might be comparable and easier:
1) Replace the alternator (or AC) with a small 6-10hp motor. This is like a DIY version of the Honda IMA. I think GM was promoting something like this. You're limited by the power a belt can transmit, but it does go through the transmission and allows easy stop/start of the engine (ex: at a traffic light).
2) Remove the rear drive-shaft from a 4WD like a truck and attach a motor to the differential. This is also somewhat easy and a truck is better equipped for carrying batteries. There was a Jeep design that did this. Stay in "4wd" without applying power to the motor and it's like a front wheel drive. The downside is that the motor isn't geared so it's only good for one speed range (perhaps low end torque).
Unfortunately, both designs are just mild hybrids. To really go far enough with the motor you need lots of batteries. For example, the 80lb NiMH pack in my Insight can barely go a few miles. Regen makes sense but you lose a surprising amount of energy charging/discharging. I get the best gas mileage trying not to use the hybrid systems (even in city driving).