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- Protege5 2003
I know this would be hideously expensive to do as a one off, and it may be impractical, but at $3.80 a gallon (and rising), one tends to fantasize a bit.
My automatic P5 is mostly driven in the city where it turns in around 22 mpg. Each direction is around 20 minutes and consists of about 20 cycles of cruising up to 35 mph and then braking down to zero. There is about 2-3 mpg loss in the automatic (as compared to what people report for city driving in manuals) and, I'm guessing, something like 10 mpg that could be recovered by regenerative braking. Which got me thinking, how hard would it be to retrofit a car with (electrical) regenerative braking?
Since the P5 is a front wheel drive internal combustion vehicle there isn't much one could do to attach such a system to the front wheels. On the other hand, there is a fair amount of space around the rear wheels, and retrofitting there seems like it could be possible. Braking on just the back wheels isn't ideal but should be ok for average deceleration in traffic conditions. The original brakes are still there for use in more rapid braking or above city speeds. For instance, a narrow "disk like" electric motor could replace the chunk of axle between the bearing and the disk brake. This would have to be braced against the suspension somehow in order to handle the torque needed for braking and acceleration. These two motors do not need to be all that powerful. It isn't necessary to store nearly as much energy as a Prius, just the kinetic energy of the car moving around 35 mph. In other words, don't try for full electric operation, just stop wasting so much energy bouncing the speed up and down. Waves hands - 4 inches across the whole bottom of the trunk should be more than enough for the electronics and batteries (or capacitors) to hold that. The rear wheel motors should actually trim off some of the efficiency loss from the automatic, since they would deliver power directly to those wheels without losing anything in the transmission.
There would probably be some loss in handling, since the weight of the suspended parts in the rear would increase. And maybe some loss in acceleration due to the extra 100 pounds or so of electrical equipment. Maybe, because electric motors tend to provide a lot of torque for their weight, so it's possible the rear axle motors could actually give the car a bit of a boost in acceleration. Think of it as an 80/20 temporary four wheel drive.
For controlling this system there could be a simple variable acceleration dial (only active when the car is running and the parking brake off). Turn it negative to slow, positive to accelerate. The car's computer should be able to deal with this since it is exactly the same as changing the slope of the road, which it can handle now. Safety first - the retrofit wouldn't affect the existing brakes. In fact, touching the brakes (easily detected as there is already a switch for that) would disable the retrofit. Obviously there would have to be an indicator when the (limited) batteries were fully charged, since at that point the retrofit would have to stop braking through the electrical motors to keep from lighting the trunk on fire, and the normal brakes would have to be applied by the driver.
To some extent the retrofit could even be used on the highway. When tweaking the speed up and down slightly twiddle the dial, rather than using the brake and accelerator.
I know, I know, this is not gonna happen. Wish it would. I'd rather spend my money on this sort of mod than than the equivalent amount on gas. Or a heck of a lot more on a different but more fuel efficient car.
My automatic P5 is mostly driven in the city where it turns in around 22 mpg. Each direction is around 20 minutes and consists of about 20 cycles of cruising up to 35 mph and then braking down to zero. There is about 2-3 mpg loss in the automatic (as compared to what people report for city driving in manuals) and, I'm guessing, something like 10 mpg that could be recovered by regenerative braking. Which got me thinking, how hard would it be to retrofit a car with (electrical) regenerative braking?
Since the P5 is a front wheel drive internal combustion vehicle there isn't much one could do to attach such a system to the front wheels. On the other hand, there is a fair amount of space around the rear wheels, and retrofitting there seems like it could be possible. Braking on just the back wheels isn't ideal but should be ok for average deceleration in traffic conditions. The original brakes are still there for use in more rapid braking or above city speeds. For instance, a narrow "disk like" electric motor could replace the chunk of axle between the bearing and the disk brake. This would have to be braced against the suspension somehow in order to handle the torque needed for braking and acceleration. These two motors do not need to be all that powerful. It isn't necessary to store nearly as much energy as a Prius, just the kinetic energy of the car moving around 35 mph. In other words, don't try for full electric operation, just stop wasting so much energy bouncing the speed up and down. Waves hands - 4 inches across the whole bottom of the trunk should be more than enough for the electronics and batteries (or capacitors) to hold that. The rear wheel motors should actually trim off some of the efficiency loss from the automatic, since they would deliver power directly to those wheels without losing anything in the transmission.
There would probably be some loss in handling, since the weight of the suspended parts in the rear would increase. And maybe some loss in acceleration due to the extra 100 pounds or so of electrical equipment. Maybe, because electric motors tend to provide a lot of torque for their weight, so it's possible the rear axle motors could actually give the car a bit of a boost in acceleration. Think of it as an 80/20 temporary four wheel drive.
For controlling this system there could be a simple variable acceleration dial (only active when the car is running and the parking brake off). Turn it negative to slow, positive to accelerate. The car's computer should be able to deal with this since it is exactly the same as changing the slope of the road, which it can handle now. Safety first - the retrofit wouldn't affect the existing brakes. In fact, touching the brakes (easily detected as there is already a switch for that) would disable the retrofit. Obviously there would have to be an indicator when the (limited) batteries were fully charged, since at that point the retrofit would have to stop braking through the electrical motors to keep from lighting the trunk on fire, and the normal brakes would have to be applied by the driver.
To some extent the retrofit could even be used on the highway. When tweaking the speed up and down slightly twiddle the dial, rather than using the brake and accelerator.
I know, I know, this is not gonna happen. Wish it would. I'd rather spend my money on this sort of mod than than the equivalent amount on gas. Or a heck of a lot more on a different but more fuel efficient car.
bling bling!
