kei car "hybrid"

[Kwik]

take 1 japanese KEI car with 4WD and rear engined.


-660cc, supercharged 4wd.

disconnect prop shaft going to the front and add a mid sized electric motor, small amount of lithium batteries and some form of electronic speed controller to control it.

when you drive around with petrol engine the front wheels drive the electric motor charging the batteries, when you want an extra bit of horse power for overtaking or showing off.

no need to plug it into a wall and you could call it a hybrid?

would it work?

[majic79]

One possible flaw....

was there a 4wd kei car?

[Relentless Rob]

One possible flaw....

was there a 4wd kei car?

Something like the Subaru Vivio would do it, but the weight of the motor and space the batteries would take up would make it practically useless.

How about getting hold of a Subaru Justy replacing the four wheel drive box with a Suzuki Swift fwd one and using the rear diff' with a motor mounted in the the old prop' tunnel under the car? That way you could put a battery pack in the spare wheel well (or cut the well and boot floor out and mount a rack of batteries) so it would take up the same room as an LPG kit.

Rip a generator apart and put the business end on the engine. Once you've built up momentum you can put the car in neutral and use the engine to generate electricity to keep the motor running. With the batteries as back up or a silent running mode.

[Kwik]

the subaru sambar was a supercharged 4wd kei van with 5 speed...

im only thinking about using enough batteries for a boost, for a short period of time like 20 seconds. so the battery packs wouldnt be too big.

i was thinking motor in the prop shaft tunnel and batteries under the seats? or a thin set of lithium batteries under the floor? there will be room somewhere.

i just dont know if the motor powering a second axle would work whilst your already moving...

[Relentless Rob]

Centrifical or actuated clutch so the motor doesn't cause drag. Either that or use the motor to charge the cells.

Kei-Kers (engine or motor assisted drive) instead of a Hybrid (motor, motor assisted or engine drive)?

You may as well keep the four wheel drive and have a chain and sprocket on the prop'shaft so the motor assists the engine instead of two separate systems.

[Kwik]

i just thought that getting rid of the heavy prop shaft would save weight, these kei cars aren't powerful so saving weight is crucial, besides you dont need 4wd in such a weak car, it only has it (subaru sambar) for light off roading for farming in japan. as it wont be use for farming the 4wd wont be needed so why not eliminate the propshaft, add motor etc and minimise the weight gain...

[Renrut]

Several fundamental points missing here.

Lets start with conservation of energy. You can't create or or destroy energy, you can only convert it. However there is no 100% perfect conversion (mostly due to heating and friction things) so every time you convert energy from one form to another you WILL lose a little bit. How much depends on the process. Internal combustion engines do chemical energy to mechanical (kinetic) energy and are about 60% efficient at the very best. More typically for car type engines they're about 40% at the peak efficiency point.

Electric motors are (electricity to kinetic energy) about 60% efficient but can be a lot better in specialist applications (up to about 90% iirc). But the power drive electronics will be 98% at best, same for any battery charging functions. Then you have to take account that your generator will be only 60% to 90% efficient as its a variant of an electric motor. So very roughly electric motor driven off car engine via batteries will be ~0.4*0.6*0.98*0.98*0.6 = 0.138 = 13.8%. Now if your car engine never operates near its efficicieny peak then you could see some major improvements. This is what things like the new VX Ampera and the Jag CX75 play on. The other trick they and other hybrids use is they stop the ICE ever running at maximum potential acceleration and throttle response to curb its thirst and use the electric motor to give the instant throttle response.

Next point weight. Weigh a prop shaft for a kei car. Weigh a 12V car battery. There might not be much difference. Weigh a resonable power electric motor. It will be much more unless its extremely hi-tech.

Best method I can see is either do away with the mechanical drive altogether and run the motor in steady state at peak efficiency to keep a battery buffer charged for the electric motor(s) to run off. This system can work and very well btw - it's what many very large ships use http://en.wikipedia.org/wiki/Diesel-electric_transmission
But you need a very efficient motor generator for this to make sense.

So if you wanted LOADS more power then you hook the Kei engine up to a generator, store the energy in some power buffer (ultra caps or batteries up to you) and drive the wheels with much higher power electric motors. You won't be using full power all the time and the little kei generator will slowly recharge them when not in use.

[majic79]

Internal combustion engines do chemical energy to mechanical (kinetic) energy and are about 60% efficient at the very best. More typically for car type engines they're about 40% at the peak efficiency point.

Ok, can we just clear up a point - IC engines are around 12-25% efficient - the most efficient being turbo-diesels, most petrol engines hover around 15% efficiency and turbocharged direct injection petrols climb to the heady heights of 18% efficiency.

Efficiency is calculated on the calorific value of the fuel (ie, the energy stored in the fuel going into the engine) and the useful work energy (rotational power at the flywheel) taken out. The best gas turbine (mechanical drive) is about 32% efficient and it only climbs if you extract waste heat through a boiler to generate some steam and use that steam (ie, Combined Heat and Power or CHP power stations, popular in europe but not so much UK)

It's amazing how much heat is wasted and thrown out of the exhaust of a car engine.

[Neil Davies]

extract waste heat through a boiler to generate some steam and use that steam (ie, Combined Heat and Power or CHP power stations, popular in europe but not so much UK)

It's amazing how much heat is wasted and thrown out of the exhaust of a car engine.

How about runing the exhaust manifold through a water jacket, along with the water from the radiator and using the heat generated to generate elecricity for an auxilliary electric motor?

[majic79]

The water needs to convert to steam and be under pressure - copper pipe under the lagging around the exhaust manifold might do it, temps are certainly high enough around there, but more than a foot to eighteen inches away and you'll have extracted as much heat as you're likely to get out.

There are some small enough steam turbines out there for this kind of thing and could be hooked up for direct drive, could make an interesting petrol/steam hybrid that way..... just think of the water you'd have to carry in addition to fuel, but with a suitable condenser on the back you might be able to recover some so it's not a total loss system...

[Renrut]

Internal combustion engines do chemical energy to mechanical (kinetic) energy and are about 60% efficient at the very best. More typically for car type engines they're about 40% at the peak efficiency point.

Ok, can we just clear up a point - IC engines are around 12-25% efficient - the most efficient being turbo-diesels, most petrol engines hover around 15% efficiency and turbocharged direct injection petrols climb to the heady heights of 18% efficiency.

Efficiency is calculated on the calorific value of the fuel (ie, the energy stored in the fuel going into the engine) and the useful work energy (rotational power at the flywheel) taken out. The best gas turbine (mechanical drive) is about 32% efficient and it only climbs if you extract waste heat through a boiler to generate some steam and use that steam (ie, Combined Heat and Power or CHP power stations, popular in europe but not so much UK)

It's amazing how much heat is wasted and thrown out of the exhaust of a car engine.

Yes the 60% figure was over optimistic for ic engines but...

*cough*

http://www.gizmag.com/go/3263/

" at maximum economy the engine exceeds 50% thermal efficiency. "

*cough cough*
http://www.google.co.uk/url?url=http://en.wikipedia.org/wiki/Internal_combustion_engine%23Energy_efficiency&rct=j&q=efficiency+internal+combustion+engine&usg=AFQjCNEXh2oXi3I1nc_QEg3t9xtLa5Jovw&sa=X&ei=ESWZT_7pCYij8gOs1KCOBg&sqi=2&ved=0CDgQygQwAA

Turbo'd engines "average efficiency of about 18%-20%".

The numbers were to make a point of the having to take whole drivetrain into account and the relative differences - energy store to motive force.

WRT petrol engines don't some of new proposed CI/DI ones also throttle using the valves plus rely on HCCI and therefore get to diesel efficiency levels?

On the plus side this says I should fit turbos to my jag if I want to be more green