Russian Revolutionary Hybrid car

[Doctor Drivel]

If the battery is depleted somewhat after acceleration the engine provides power to the electric drive motors and to top up the batteries very efficiently as the engine will be running at its most efficient while doing so, unlike a directly mechanically coupled engine to wheels setup via an inefficient and power sapping transmission. Constantly varying the speed of an engine from near zero revs to near maximum is highly inefficient.

A largish car doing 70mph only uses about 20-30% of the power of the engine. Most of the time a car's engines is way oversized and carrying all that surplus weight. The surplus power is for acceleration. Electric drive and kinetic brake recovery using supercapacitors and a decent battery set can mean engines are much smaller. Having range extenders means the engine can be built light, small and optimised to run at its sweet revving spot.

[NT]

An engine with given power rating only produces that power at one engine speed, at other speeds it outputs much less. So a car with a continuously variable drive ratio drive can get significantly more acceleration from a given engine power.

NT

[Dave Plowman (News)]

All this from 40 bhp?

Depends on the design of the engine. But 'your' one will be running at peak revs to develop that 40 bhp. And what it can't do is charge the battery while producing that 40 bhp to power the car along. Regardless of what you think. As usual, you're incapable of doing simple arithmetic.

So this car you're raving about uses super capacitors? Bit of a first for a low priced vehicle.

BTW, you might ponder on why the Prius has had its engine power output increased by 50% over the years. And still has poor (for its size and price) performance on the open road.

[Dave Plowman (News)]

Power is, of course, a function of torque and engine speed. It's the torque which is the important one. The idea of running any internal combustion engine at a steady speed regardless of load is a nonsense.

[grimly4]

I've no doubt you thank your knob on a daily basis.

[grimly4]

If only someone had snipped Drivel Snr.

[dennis]

[NT]

When it comes to acceleration, power output is, not torque.

Depends how literally you take that. Keeping engine at max power output and varying gear ratio gets you a lot more acceleration than a conventional drive system. That's the big advantage of variable gearing.

NT

[Jules Richardson]

The horses in Drivel's head are bigger than everyone else's.

[Andy Champ]

Not just me scratching my head there then.

Yes but... It's unlikely you need max power all the time. Max power is what I'll use for climbing Shap Summit, or more likely one of the passes in the Alps, which has a long climb at high speed - long enough to empty the batteries.

Most of the time the IC engine will be running at a lower, more economical setting. Which is probably wide-open throttle, peak torque until the battery is full - then stopped for a bit. Repeat until journey's end.

Andy

[NT]

Yes, plus with a 40hp engine it'll run flat out more or less whenever you're accelerating in normal driving.

Also I doubt too many small batteries can take a P_in of 30kW, so the engine will run at much reduced speed when recharging too.

NT

[Dave Plowman (News)]

As I said, horribly inefficient.

[Dave Plowman (News)]

Eh? It's the exact reverse.

[Nightjar]

OK, if you prefer, unless the manufacturers have fitted a battery and motor that are disproportionately large for the engine, a vehicle with that little power is going to be horrendously slow.

Actually, I have found a set of specifications for the car, where it is suggested that the engine will be 60bhp, rather than 40bhp. Even that will only get it a 0-62mph of a rather leisurely 12 seconds.

Colin Bignell

[Nightjar]

On 28/01/2012 21:36, Doctor Drivel wrote: ...

I always do. It is usually good for a laugh.

Colin Bignell

[Nightjar]

On 29/01/2012 17:45, Andy Champ wrote: ...

The most economic setting for any IC engine is usually in the range

65%-75% of maximum power.

Colin Bignell

[The Natural Philosopher]

far from true. diesels best at very low power levels 10-20% - unless they are designed not to be of course....

in fact you can design the engine to be best at almost any level, and people do...

because 'full power' is a moveable feast

[The Natural Philosopher]

well its actually both since torque times revs IS power..

[NT]

Lets see with a simple example, of a car doing M mph. Compare Engine at speed S with torque T, so P_out TxS with same engine at speed 2S and torque 0.8T, P_out is now 1.6TxS. In the 2nd scenario, the gear ratio from engine to wheels is a factor of 2 different, so engine torque is only 80% as much, but torque at the wheels is 1.6x as much.

NT

[Nightjar]

So is the term diesel engine, but in the context of this thread, references ought be to the sort that is likely to be fitted into a motor vehicle, not that there has been any suggestion that the Yo-Mobile is going to have a diesel engine. In any case, running at full throttle is not the answer for best economy, so the useful engine output will still be less than the maximum engine power, if they are going for best economy.

Colin Bignell