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Automobile turbo(super)chargers may provide a clue about efficiency too. They certainly do allow smaller engines to produce a lot more power, so the power to weight ratio will be better than a larger normally aspirated engine of equal output, but I'm not aware of any car companies claiming that turbocharging improves fuel economy.
Ford claims they are able to use higher compression from the turbo. This does improve fuel economy.
Yes. It's new...Ford calls it EcoBoost. Should be available on their 2013 models.
Quote from: Geezer on 16/09/2009 16:19:27Yes. It's new...Ford calls it EcoBoost. Should be available on their 2013 models.From I've (quickly) found on the web, it looks like Ford are only going to get a 2mpg improvement of vehicles of ~18mpg(US). By 2013! - I despair!I can see that the technology has real advantages over the older injection techniques, especially when combined with high boost.I still expect hybrids (allowing peak the engine to operate in its peak efficiency range for much longer) to continue outstrip this slight mod.BTW - how much horsepower does a high pressure fuel injection system eat up?The cylinder cooling effect of DI just doesn't make sense to me. What also doesn't make sense is that engines running lean get hotter (even when compared to stoichiometric) - I think it might be to do with a slower flame-front speed relative to rate of expansion.Anyway, my thought is if the engine is at part-load then the turbo is going to have to be bypassed or the cylinder walls will get too hot - putting the engine back into standard non-boosted configuration for much of the time.
If the mixture is rich, some of the fuel is not oxidised, so it acts as a coolant then gets ejected out the exhaust.
This lean-burn ability by the necessity of the limits of physics, and the chemistry of combustion as it applies to a current gasoline engine must be limited to light load and lower RPM conditions. A "top" speed cut-off point is required since leaner gasoline fuel mixtures burn slower and for power to be produced combustion must be "complete" by the time the exhaust valve opens.