Turbo Engines are NOT more efficient than big N/A
Discussion
As nicely demonstrated by Audi's new A8 3.0T
http://www.autoblog.com/2012/05/08/2013-audi-a8-3-...
the 4.2 V8 get's the same fuel economy on the combined US test cycle and provides more power.
This brings me to the conclusion all this talk of "downsizing" to smaller capacity turbo engines is just marketing hyperbole.
A turbo artificially increases the displacement so that 3.0T is actually behaving like a larger engine. The only way to save fuel is to keep the revs so low that the turbo is not used and therefore negating the point of it.
I hope this becomes obvious when the 1.0 turbo focus starts selling.
http://www.autoblog.com/2012/05/08/2013-audi-a8-3-...
the 4.2 V8 get's the same fuel economy on the combined US test cycle and provides more power.
This brings me to the conclusion all this talk of "downsizing" to smaller capacity turbo engines is just marketing hyperbole.
A turbo artificially increases the displacement so that 3.0T is actually behaving like a larger engine. The only way to save fuel is to keep the revs so low that the turbo is not used and therefore negating the point of it.
I hope this becomes obvious when the 1.0 turbo focus starts selling.
How much has the car weight changed? Weight will affect duty and therefore ecconomy. Has the drive cycle changed? Could totally change the duty cycle and ecconomy. Is the engine meeting different emissions targets? Some emissions technology hurts fuel ecconomy.
Totally unfair story comparing new and old like that in such an out of context way. Anyway effecient in this context probably means lower c02. That does not always mean better MPG.
Totally unfair story comparing new and old like that in such an out of context way. Anyway effecient in this context probably means lower c02. That does not always mean better MPG.
jimbobsimmonds said:
Wouldn't that N/A usually run on a higher compression ration effect economy?
We need some experts here...
I would hazard a guess at this being largely an irrelevance. An NA engine might be 10:1 and a turbo at 9:1 geometrically, but running 1.0 bar of boost (effectively twice the capacity) will still push the cylinder pressures well beyond the NA engine.We need some experts here...
In this particular case, I would say the supercharger is sapping power. Turbo's are more efficient.
Edited by Kozy on Wednesday 9th May 15:15
Vocal Minority said:
doogz said:
All this proves is that this turbocharged engine, is as efficient as that V8 engine. Nothing more.
Spot on that man. You need more than one case to be conclusive. I know we like our big engines on here, me included, though this just feels like aversion to change.
jbi said:
should probably have stated "forced induction" engines
The method of forced induction playes a big part though, superchargers tend to make more low end grunt in the lower revs and not provide the same top end HP that turbo's make. I'd hazzard a guess that the same block with a turbo instead of a supercharger would be more economical in the emissions tests, yet develop noticably more top end power.And while a supercharged 3.0 may have the same top end HP as a N/A 4.2, i doubt the 4.2 would stand a chance in a dragrace, torque is where it's at.
I've been driving a Renault 1.2 T a lot recently and it basically feels like a tax dodge engine. It's got the power of a 1.6 normally aspirated engine, but it's also got the fuel consumption to match it. Even mincing around it just about crests over 40 to the gallon, normal driving sees mid thirties and if you give it death then it'll drop as far as high twenties. The only real advantage of it over a normally aspirated engine is that it has excellent mid range torque, but then you pay for it with the boost threshold meaning that it's completely gutless if, say, you coast up to a roundabout at idle in 2nd gear and give it the beans.
Having said that, it depends on the specific engine. If it's not been afflicted by too much cost cutting then the components should be specced to handle a bit of heat, and it should be able to do more than just NEDC loads and speeds without chucking in loads of fuel for component protection, in which case you've got the magic combination of a small, light engine with low friction for normal driving mated up to the performance of a much bigger engine when needed.
Having said that, it depends on the specific engine. If it's not been afflicted by too much cost cutting then the components should be specced to handle a bit of heat, and it should be able to do more than just NEDC loads and speeds without chucking in loads of fuel for component protection, in which case you've got the magic combination of a small, light engine with low friction for normal driving mated up to the performance of a much bigger engine when needed.
Vitorio said:
The method of forced induction playes a big part though, superchargers tend to make more low end grunt in the lower revs and not provide the same top end HP that turbo's make. I'd hazzard a guess that the same block with a turbo instead of a supercharger would be more economical in the emissions tests, yet develop noticably more top end power.
And while a supercharged 3.0 may have the same top end HP as a N/A 4.2, i doubt the 4.2 would stand a chance in a dragrace, torque is where it's at.
But conversely, in a barge a 4.2 offers a far more relaxed mid end comfortable crusing experience than a smaller turbo charged engine off boost. 'orses for courses and all that.And while a supercharged 3.0 may have the same top end HP as a N/A 4.2, i doubt the 4.2 would stand a chance in a dragrace, torque is where it's at.
drivin_me_nuts said:
But conversely, in a barge a 4.2 offers a far more relaxed mid end comfortable crusing experience than a smaller turbo charged engine off boost. 'orses for courses and all that.
Very true, a big slightly lazy V8 is going to be the better cruiser, i was just contradicting the claim that Turbo-ed engines are less efficient, because in terms of mpg/HP, a 3.0T would do better then a 3.0SC, if only because of the characteristics of a turbo engine and the method of emission testing.An audi A8 needs an 8-cilinder really, keep the 3.0T for the A6 and all that
A ever "it depends". A well designed FI engine will use less fuel at cruise because it's effectively a smaller engine until you put your foot down. I'm pretty damn sure a new 328i 2.0 turbo will get better MPG than the old 3.0 6 in almost all situations (that'd be a good test PH - new 328i vs N52 E90 330i).
The thing is, any car with the same shape and weight, and the same wheel properties, at a specific speed, will need the same amount of power, (at the wheels,) to move it. (How it goes about making the power is the interesting bit.
Now, the 4.4l V8 version of a car won't be much different in real mpg at a constant speed on the motorway to the 3 litre straight six. The six will be working a bit harder, but may well have a lighter duty gearbox, for instance.
The real way that car makers can make their cars do more mpg in the real world are, and always have been:
Reduce rolling resistance.
Reduce weight.
Make the car more aerodynamic.
However, all of that is completely useless if the operator is driving like a tool.
Now, the 4.4l V8 version of a car won't be much different in real mpg at a constant speed on the motorway to the 3 litre straight six. The six will be working a bit harder, but may well have a lighter duty gearbox, for instance.
The real way that car makers can make their cars do more mpg in the real world are, and always have been:
Reduce rolling resistance.
Reduce weight.
Make the car more aerodynamic.
However, all of that is completely useless if the operator is driving like a tool.
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