Does a hybrid make sense for motorway miles?

unrealrocks said:
Hybrids actually spend...
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Thanks, I put the 'AFAIK' in there hoping to be corrected.

From an engineering perspective (it seems to me, again arguments welcome) the only way a hybrid could do better than ICE on the motorway is if it's more efficient to go petrol engine -> alternator -> (battery, maybe) -> electric motor than petrol engine -> gearbox etc.. Obviously this works very well for trains, AFAIK they use diesel powerplants to drive electric motors, so maybe the same is true of cars.
 
That is the most efficient way since you only need a capacitor and a tiny engine, no heavy batteries. In normal hybrids it's the weight that's the problem.
 
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joeyjojo said:
Thanks, I put the 'AFAIK' in there hoping to be corrected.

From an engineering perspective (it seems to me, again arguments welcome) the only way a hybrid could do better than ICE on the motorway is if it's more efficient to go petrol engine -> alternator -> (battery, maybe) -> electric motor than petrol engine -> gearbox etc.. Obviously this works very well for trains, AFAIK they use diesel powerplants to drive electric motors, so maybe the same is true of cars.
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My understanding is that the power to charge the battery comes from energy otherwise not used to drive the wheels, so for example - a car on a motorway run never stays at the exact same acceleration level constantly, so as you let off slightly, travel down hills or slow for traffic ahead this is how energy is put into the batteries. Also there may well be an element of added drag constantly to charge the batteries - don't think it is definitively documented as I'm sure someone far smarter than me has figured this out and is now property of Toyota and the likes!

Certainly from my experience, if you drain the batteries before hitting a motorway, accelerate up-to 70mph and within a few minutes the batteries will then be partially charged again. Maybe a bit of both is happening!
 
Nasher said:
That is the most efficient way since you only need a capacitor and a tiny engine, no heavy batteries. In normal hybrids it's the weight that's the problem.
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The Prius battery weighs around 45KG, around half the weight of a person. It makes little difference in the economy of a 1.5 tonne car.
 
unrealrocks said:
You are far oversimplifying what the hybrid drivetrain is doing, on a regular hybrid it isn't a case of either 'electric' or 'petrol', a high proportion of the time it is using the electric motor to facilitate the petrol motor to increase economy. My Auris will only run in electric only to 50mph, and accelerate at any rate to 32mph - however still manages 60mpg on a motorway journey ... somehow I don't think that is just the 1.8 petrol ;)

PHEVs are far better in all situations - but then the huge difference in cost does time into it.

IMO motorway use only the hybrid is still entirely an option, yes diesel is in its sweet spot for this usage - but hybrids are still entirely competitive as my experience of my last ~40k miles in my hybrid has shown :)
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So at 70+ on a motorway whats happening, does the petrol and electric work together or is it a case of run battery down, then petrol kicks in to charge it?
 
unrealrocks said:
The Prius battery weighs around 45KG, around half the weight of a person. It makes little difference in the economy of a 1.5 tonne car.
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Plus the weight of the motors etc. If it was a regular petrol car it wouldn't be anywhere near 1.5 tons, which is pretty heavy for a car that size.
 
Nasher said:
Plus the weight of the motors etc. If it was a regular petrol car it wouldn't be anywhere near 1.5 tons, which is pretty heavy for a car that size.
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If you scroll back up the thread if we take the Auris as an example (its one of the few cars I know of that comes in Petrol, Diesel and Hybrid), 1435KG for the 1.6 diesel vs 1420KG for the hybrid, 1350KG for the 1.6 CVT petrol to be comparible. So in-fact the 'whole system' only comes with a 70KG weight penalty, hardly going to cost more than a couple of mpg, if even that!
 
Nasher said:
That is the most efficient way since you only need a capacitor and a tiny engine, no heavy batteries. In normal hybrids it's the weight that's the problem.
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Its really not. The weight penalty just isn't relevant, a Prius weighs the same as a diesel golf. It doesn't have a turbo, a big engine, DPF, iron manifold, intercooler etc etc. Especially now if you consider urea tanks.... and SCR.

Direct drive is the most efficient, energy is like a bar of soap, the more you handle it the less you end up with.

Hybridisation of a petrol engine typically allows the electric motor to deal with acceleration such that the engine can move from the typicall Otto cycle to a Miller/Atkinson and hence get more out of the fuel.
 
arfoll said:
Of course it's not just petrol or electric, but same time you can't keep the eletric going for long at all on 1.3kw/h so my guess is it's not used much at all. And considering you can't charge it beside regen braking, I simply don't believe it's helping you much on the motorway. The cost of motorway is not acceleration it's keeping a constant speed going. Over any time, the speeding up on the sliproad is a pretty irrelevant. In my experience - like you - deceleration on motorway charges the battery nicely but power transfer is far from perfect and realistically you accelerate again on petrol otherwise you'd see the battery depleted immediately so I really don't think you gain much unless you keep rolling down a hill ;-)



I'd argue they're worst. You may only have a light battery, I have a 150kg+ one and that's not counting motor in the gearbox etc... A friend can get 60mpg on the same trip on the motorway on a mk7 golf 2.0TDI, I can get 45/50 depending on my avg speed. The one thing you can notice is on light acceleration my GTE will try keep constant RPM and just use electric to accelerate, this works nicely and may help a little.



It's not bad, but the prius drivetrain really is a very efficient petrol engine and it's not bad on the motorway but even toyota claim you can get 10mpg better with their own diesel and it's not in the best diesels out there imho. I love my hybrid, but to me it's simply not the ultimate motorway machine.
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Wasnt the prius worse round the track in terms of mpgz vs an m5 on top gear?
 
Having driven many hybrids I can say without doubt, hybrids are for town driving and some extra urban but definitely not motorway.

Motorway driving is definitely the domain of the diesel auto.

320d or C220 are the 2 best diesel motorway mile munchers imho. BMW has the edge on fuel economy and the mercedes on premium feel and comfort.

The best Hybrid I drove was the BMW 330e but even that only managed 60mph before the petrol engine took over.

X5 Managed around 50mph

Prius is a shocking car and the most painful way to achieve 50+ MPG ever, hateful thing to drive.

Lexus 220H is marginally better but still not in the same league as the BMW hybrids.
 
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Dr Who said:
Prius is a shocking car and the most painful way to achieve 50+ MPG ever, hateful thing to drive.

Lexus 220H is marginally better but still not in the same league as the BMW hybrids.
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You realise the CT200h is actually based on the same 'New MC' platform as the Prius (and most other Toyotas) - only with a much shorter wheelbase and the same drivetrain? I'm very surprised you actually preferred the CT given it generally gets fairly slammed compared to the Prius!

Comparing these to cars costing ~£8k more new seems a bit academic, yes a car more expensive is generally nicer. But as Fox has said the 3 series and C class are far from the 'best', there are some far more expensive options which are FAR superior to these.

The BMW Hybrid as arfoll mentioned is both much newer, hilariously expensive (almost twice the cost of a Prius!) and not driven entirely by economy - it has really brisk acceleration and certainly BMW seem to be looking to market them as alternative propositions to their higher performance diesels, hence it being named as a 330e, not 320e. Again we aren't comparing apples to apples however!
 
Jonnycoupe said:
Its not really a hybrid though, its a plugin so has a separate energy source o the fuel you put in.

The best is a Range Rover Hybrid :p
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Shame its a diesel really :p I can imagine a V8 Hybrid Range Rover would be the ultimate, using the hybrid tech in more of a performance manner than eco manner - ala P1/918 :D
 
My current company car is a 65 plate Lexus 300h F-Sport (with Mark Levinson). I drive 14 miles a day mixture of urban/back roads 95% of the time.

If I'm really careful I achieved my best last month of 36mpg (around 400 miles to the tank). The first month I had it I achieved 26mpg until I realised that keeping it in sport mode wasn't very efficient.

Compared to my e46 330i my best mpg on the same route was around 23mpg.

Not sure why the Lexus is not getting more love as I find the interior and overall quality a joy of a place to be in?
 
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