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Discussion Starter #1
How do the newer diesel engines coming out get such good fuel efficiency?

I heard that some functions are turned off when not needed, like the way a thermostat works. Is this correct? If so, could that functionality be added to an older vehicle?

I'd quite like one of these new high mpg cars, but they are either seem to be hatchbacks or not so useful sizes (I'd like a van, MPV or estate), or still expensive (doesn't make sense to spend £10k on a car to me). It would be nice to get this mpg advantage in a more useful vehicle.
 

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ive had over 40 mpg in a vivario and must admit i nearly bought it instead of my t4 I:
 

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How do the newer diesel engines coming out get such good fuel efficiency?

I heard that some functions are turned off when not needed, like the way a thermostat works. Is this correct? If so, could that functionality be added to an older vehicle?

I'd quite like one of these new high mpg cars, but they are either seem to be hatchbacks or not so useful sizes (I'd like a van, MPV or estate), or still expensive (doesn't make sense to spend £10k on a car to me). It would be nice to get this mpg advantage in a more useful vehicle.
I drove a V8 Ford Expedition in the states and it kept fuel economy "low" by shutting off one bank of cylinders when cruising!
 

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i am t4lwb steve
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think thats good
my fiat500 (yes a 500) at 65 on the motorway does over 80 mpg but said that i was slow moving and at 80-90 its down to 65 mpg thats with big wheels and a remap
but i still loke the t4 for the motorway as it feels safer
and yes it cost just over 10k and even with the good fuel consuption thats a lot of fuel to save to make it worth while
oh and most high mpg cars are small and do not look like a brick on wheels weighing in at just about 2 tonnes.I:
i think if a t4 could do over 40mpg we would be lucky and me thinks it would lose even more of its near invisible performanceLOL:LOL:
 

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My wife's 1.4 tdci fiesta never seems to do less than 50mpg round town and 60+ on a run.
The newer bread of diesels are common rail engines. This basically is a slightly different way of getting the fuel to the injectors in a more efficient way. These engines also do things like shut the fuel off completely when you lift off the gas.
 

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I think the real question should be why aren't engines even MORE efficient than they are??

I mean, 50 year old technology is capable of pushing 30mpg +, yet when you think of the advances in car design and the like, having engines that are only capable of an extra 10mpg is pretty poor, to say the least........

In the same time, we've moved from inefficient drums to anti-lock disc brakes, basic carbs to ecu controlled engine management, leaf springs to independant, sometimes even self levelling and computer controlled, suspension, static seat belts to airbags and self-tensioning belts - you name it, it's been MASSIVELY improved...........

Yet making the things burn less of a rapidly decreasing fossil fuel seems to have taken a back seat...........

A cynic might read something into that..............I:
 

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I have had a shade under 45mpg from my van measured over 1200miles.

So 60mpg for a little city car is not that good I don't reckon ?
I'm sure it would pretty easy to achieve plenty more than that if they really put the R&D budget into it ?
 

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Having seen James May testing the actually on sale Honda 'hydrogen fuel cell' car in America it seems that is the way things will be going in a fairly short space of time as the remaining fossil fuels will be needed for industry rather than motive power.

Someone makes the point that engine performance has increased little in comparison with other areas of vehicle technology and I agree entirely; what I have never understood is why the 'reciprocating' engine has survived for over 100 years? You have to say that other technologies if they had been developed would have been a better bet, be that w ankel or turbine.

Spike

(had to put a gap between the 'w' and rest of the word or the software thinks I am saying something naughty!)
 

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Discussion Starter #10 (Edited)
ok, this is what I think I've learnt:

Some early posters site aerodynamics and weight, but...

The commonRail engine has been about since the mid 40's but first used in cars in 1997. It's basically about more control on the injection of fuel - store it up, time a little just before the main injection event.
Adding this to a non common rail would mean accurate ecu timing, replacing the injectors and adding a pressure accumulator - more hassle than it's worth I would guess.
Easier to modify the rear Polo bodywork (now there's an idea....)

nealglover: What do you think lead to such a good mpg there? I take it you look after your van, but do you have any gut feeling on anything in particular that may have helped in particular?

Try Rotary instead of \/\/ankle ;)

I'm reading about the Previa hybrid. Sounds good at £10k, until it works out at 40mpg for mixed driving...
Reading more about the old Previa, they get 20mpg. Similar stuff for the Estima. That then makes me wonder, what causes us to get better values than them? (other than less auto boxes here)

So is that it? Better aerodynamics and commonrail? Both of which aren't of interest to older vehicles?
Heard anything about stuff getting turned off when not in use?

There's a diesel fan and a Prius man having a little fight in my head
 

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Heard anything about stuff getting turned off when not in use?
Some of the v8 mercs and the crysler 300c v8 shut off half of the cylinders when at a constant speed. This is to save fuel.
This only works on big engines. It wouldn't work on a 4 cylinder engine that well. It would feel like it was running as rough as a harley on tick over if it went down to 2 cylinders
 
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