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The Tesla Model S


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HOLA441
The point is that you have to supply the energy, i.e. fuel in some shape or form, for the 12k miles whether you supply it directly to the wheels over the 12k miles or store it in batteries for the 12k miles during the period when the generator is running.

Battery cars almost certianly will make sense but a battery car which has to lug around a power station is just stupid.

The power station is sub 50kg so not much to lug around. Add 5 gallons of fuel at 20kg and your looking at a range of 300miles on the generator. Another 20kg of fuel and it becomes 600 miles.

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HOLA442
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HOLA443
OK

What car can do 45mpg at 90mph? It seems optimistic. Something like a BMW 320d might manage 35-40mpg.

20% efficiency is too low. 25-30% is more like it for a modern petrol engine.

LWD's numbers seem far more realistic. Also confirmed by the facts that no 30hp car that can do 90mph has ever been produced and that Chevrolet use a larger generator in the Volt.

If the 320d can do 35-40mpg at 90mph then ther should be no problem in building a car to do quite a lot better. The 320d is big and heavy. A sensible design to do the same thing would be half the weight and two thirsd of the frontal area. That would mean designed by engineers rather than marketing people of course.

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HOLA444
well if someone could give us accurate figures for mpg at 70-80-90mph we can work it out.

I run 2 typical cars - a 2.0turbo petrol (golf) and a 1.9turbo diesel Saab.

I use cruise most of the time on the motorway and accelerate using the button, not the pedal (you can do that with forced induction !). I also plan ahead and tend not to dab my brakes all the time as I look ahead for hazards so don't need to brake or accelerate that often and don't hold up faster traffic if I have my dawdling head on.

70 mph

Golf 40mpg

Saab 62mpg

80mph

Golf 33mpg

Saab 54mpg

90 mph

Golf 28.29mpg

Saab 48/49mpg.

with cruise on over a decent distance. Neither of those cars are economy specials - the Saab's the 150 hp one, same as in Alfas, Vauxhalls and FIATs - it's gruff, but it's torquey and will outdrag a 2.0tdi VW in a Passat or A4 or the 150hp 2.0 diesel E46 BMW 3 series through the gears once it's got traction ... not that I could advocate such childish games, obviously..... the Golf is a GTI

0-60 times are 7 seconds (Golf) and just under 9 (Saab). Top speeds are 142 (Golf) and 125 (indicated 136 as tested :) ) in the Saab. A Prius is a total waste of time in my book.

The Saab has averaged, in all traffic conditions, including around town a bit and one rushed (100mph) plus wherever possible journey - 49.2mpg over the last 2,400 miles (I checked it last night off the OBC, which is relatively accurate).

The Golf has an average over the last 2,000 miles (since its last service) of 33.2mpg - in all conditions.

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HOLA445
BHP and mpg are equivalent in the same engine. (Not quite as efficiency varies with rpm etc but it isn’t a bad estimate.)

I don’t know what BHP we need to get a car to 90mph but I can work it out using its mpg when at that speed.

if you definitely know what bhp it takes then let us know

Anyway, the whole point was that you don’t need a 150BHP engine to give you the performance of a 150BHP engine. You only need a 40BHP engine strapped to a generator, the batteries/capacitor provide the excess energy when accelerating.

You miss the point. If you need a 150BHP engine to allow for the maximum power output which you may require but only use an average of say 30BHP your total fuel burn will be ralated to youre average BHP not your peak BHP. OK, the 150BHP engine will be at peak efficency for less of the time than your 40BHP engine but the extra whight and efficiency loss of the hybrid system are going to cause a lot of losses, neber mind costs.

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HOLA446
I don't really suppose that it would be difficult to build one but at what price and what sort of lifespan would you get? The bike boys could enlighten us, I'm sure.

i am pretty sure that engine is sub 50kg and more than 50HP

http://en.wikipedia.org/wiki/1KR-FE

it is a normal engine so i guess with some maintenance is expected to hit 100k miles

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HOLA447
You miss the point. If you need a 150BHP engine to allow for the maximum power output which you may require but only use an average of say 30BHP your total fuel burn will be ralated to youre average BHP not your peak BHP. OK, the 150BHP engine will be at peak efficency for less of the time than your 40BHP engine but the extra whight and efficiency loss of the hybrid system are going to cause a lot of losses, neber mind costs.

Oh I don’t expect a 40BHP generator hybrid to be 4x as efficient as a 160BHP car. But it can be 20-30% more efficient mpg when running off the generator.

The whole idea of a series hybrid is to have an electric car but get around the very expensive batteries and range problem.

Hopefully if you have a range of say 50 miles on the battery then most trips you are doing on the batteries but for the longer trips you can use the generator.

You could make the generator detachable if you like but I don’t think 50-75kg for a generator plus fuel is going to impact the efficiency much at all. But it does give you lots of range.

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HOLA448
@90mph

Golf 28.29mpg

Saab 48/49mpg.

48.5 mpg at 90mph

1.85 Gallons an hour

82 kWh an hour

20.5 kW power to maintain 90mph. (assuming the engine is 25% efficient at 90mph)

so a 23kw or 30HP (taking into account 10% loss) generator could maintain that car at 90mph.

Real world example.

So a series hybrid would only really need a 30HP engine in it to hit 90mph constant.

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HOLA449
Given the quality of the fit and finish it's fairly priced. You need to compare it to a high spec BMW or Merc, not some dreary ford.

Easy comparison :

5-series... great motorway mile eater, comfortable all day, bit of a waste of time round town but if that's all you're ever going to do with it you've bought the wrong car in the first place. Expensive to run, but hey, if you can afford one new you probably don't really give a damn about that. Quite flash in the eyes of certain people.

Tesla Model S... a sort of 5-series for use around town, futile for longer trips thanks to hopeless one-way range due to lack of charging infrastructure, and absolutely embarrasing radius of operations (in reality, probably around 100 miles). Cheap to run, but hey, if you can afford one new you probably don't really give a damn about that. Very flash in the eyes of certain people.

Okay, so I'm not the sort who'll ever spend a lot of money on a car (bikes, on the other hand...), but I genuinely cannot see the point in a big, mile-eating, semi-luxury saloon that you couldn't seriously use for even moderately long journeys. Driving down to the West Country for the weekend? Best spend the money you've saved on petrol pottering around town on a second hand Mondeo for the occasion then...

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HOLA4410
So a series hybrid would only really need a 30HP engine in it to hit 90mph constant.

agreed, but it has to get there and not be lethally slow in ordinary traffic - that requires more power and ruins economy....

if you use a Prius to keep up with traffic, it's very easy to get less than 30mpg :)

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HOLA4411
agreed, but it has to get there and not be lethally slow in ordinary traffic - that requires more power and ruins economy....

if you use a Prius to keep up with traffic, it's very easy to get less than 30mpg :)

You don’t need more than 30HP generator ever on a series hybrid.

The electric motors could be 150HP and when they draw more than 30HP the power comes from the batteries and the generator.

However when they draw say 15HP the other 15HP can be charging the batteries for when you need to draw from the batteries. If your stuck in traffic the generators 30HP can be diverted fully to charge the battery.

the prius is a piece of crap petrol car with a battery stuck on. so not really a fair comparison.

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HOLA4412
You don’t need more than 30HP generator ever on a series hybrid.

The electric motors could be 150HP and when they draw more than 30HP the power comes from the batteries and the generator.

However when they draw say 15HP the other 15HP can be charging the batteries for when you need to draw from the batteries. If your stuck in traffic the generators 30HP can be diverted fully to charge the battery.

the prius is a piece of crap petrol car with a battery stuck on. so not really a fair comparison.

driving style is massively important

on the usual long distance trip we do - 200 miles, give or take

me - time 3 hours - fuel economy - 55mpg

her - time nearer 4 hours - fuel economy under 50mpg......

needless to say she only drives when I am over the limit or absolutely knackered.

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HOLA4413
driving style is massively important

on the usual long distance trip we do - 200 miles, give or take

me - time 3 hours - fuel economy - 55mpg

her - time nearer 4 hours - fuel economy under 50mpg......

needless to say she only drives when I am over the limit or absolutely knackered.

That seems to be the a which a lot of people are totaly unaware of. You see so many posts on motoring blogs to the effect that 'car X claims 45MPG for the combined cycle but I only get 38MPG, what is wrong, how am I being cheated?'

They simpley don't raelise that different people drive in differnt ways or indeed the same person drives in different ways at different times. I'd bet in fact that a persons average fuel consumption would bear a close relationship to their consumption of brake pads.

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