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From: Nick Finnigan on 19 May 2010 15:25 GT wrote: >> Firstly, it will be necessary to define what is meant by "efficient". > > This was already defined - MPG, or miles per gallon. How far the vehicle can > be driven on 1 gallon of fuel. mpg is a poor measure of efficiency when comparing engines that run on fuels of quite different densities (e.g. diesel v petrol v LPG v ethanol). That is why TPTB introduced g/km of CO2 for tax bands. For engines with the same aspiration and power, CO2 emissions using different fuels are quite similar.
From: GT on 20 May 2010 04:59 "Nick Finnigan" <nix(a)genie.co.uk> wrote in message news:ht1dum$skm$1(a)news.eternal-september.org... > GT wrote: >>> Firstly, it will be necessary to define what is meant by "efficient". >> >> This was already defined - MPG, or miles per gallon. How far the vehicle >> can be driven on 1 gallon of fuel. > > mpg is a poor measure of efficiency when comparing engines that run on > fuels of quite different densities (e.g. diesel v petrol v LPG v ethanol). > That is why TPTB introduced g/km of CO2 for tax bands. > > For engines with the same aspiration and power, CO2 emissions using > different fuels are quite similar. Comparing CO2 output from 2 different hydrocarbons doesn't compare efficiencies, it simply indicates how much carbon there was in the CH compound. That is a measure of emmisions and a clever way of taxing the motor vehicle. To compare efficiency between 2 hydrocarbon burning devices, we have to examine how much hydrocarbon source is used to generate a fixed amount of power. MPG is such a measurement. Some might argue that the figures are skewed by different vehicle weights, but I would counter that the entire vehicle is being assessed, not just the engine.
From: boltar2003 on 20 May 2010 07:54 On 19 May 2010 16:16:29 GMT Adrian <toomany2cvs(a)gmail.com> wrote: >boltar2003(a)boltar.world gurgled happily, sounding much like they were >saying: > >>>Bloater seems to think this is somehow relevant to lean burn petrols. > >> Because a lean burn engine basically gets rid of throttling losses so >> is more efficient at lower rpm when the throttle would otherwise be >> partially closed. > >ITYM "diesel". Lean-burn petrol is still throttled in the usual way - No they're not. Thats the whole point you numpty. B2003
From: Adrian on 20 May 2010 12:33 boltar2003(a)boltar.world gurgled happily, sounding much like they were saying: >>>>Bloater seems to think this is somehow relevant to lean burn petrols. >>> Because a lean burn engine basically gets rid of throttling losses so >>> is more efficient at lower rpm when the throttle would otherwise be >>> partially closed. >>ITYM "diesel". Lean-burn petrol is still throttled in the usual way - > No they're not. Thats the whole point you numpty. So - do tell us - how DOES it work?
From: Nick Finnigan on 20 May 2010 13:20
GT wrote: > > Comparing CO2 output from 2 different hydrocarbons doesn't compare > efficiencies, it simply indicates how much carbon there was in the CH > compound. That is a measure of emmisions and a clever way of taxing the > motor vehicle. To compare efficiency between 2 hydrocarbon burning devices, > we have to examine how much hydrocarbon source is used to generate a fixed > amount of power. 'how much' is measured by mass, or energy. MPG is such a measurement. No, it isn't. |