erm, it isnt?
Just a note to all here.....as stated above....we are talking about efficient :y
QuoteJust a note to all here.....as stated above....we are talking about efficient :y
that's me knackered then :(
Just a note to all here.....as stated above....we are talking about efficient :y
| Opening the inlet valve | |
| Earlier | Later |
| More power at higher rpm | Less power |
| More overlap with exhaust valve | More torque at lower rpm |
| Lower flexibility | Better emissions! |
| Poorer response at low rpm |
| Closing the inlet valve | |
| Earlier | Later |
| Less power | More power at higher rpm |
| Higher compression ratio at low rpm | Compression ratio improves with higher rpm |
| Better torque | max. torque in higher rpm band |
| More flexible engine |
| Opening the exhaust valve | |
| Earlier | Later |
| Less pumping losses, bit more power | More pumping losses,less power |
| Hotter outlet valve | More complete combustion, less emissions |
| More chance of pre-ignition | Lower exhaust temperature! |
| Closing the exhaust valve | |
| Earlier | Later |
| Less overlap with inlet valve | Part of intake mixture goes straight into exhaust at lower rpm (engine is "Off cam") |
| More flexible engine at low rpm | More high end power |
| Less power at higher rpm | Less flexible engine at low rpm |
| More torque at low rpm | Low torque at lower rpm |
| Improved emissions |
Quoteerm, it isnt?
Well actually its mpg is not bad at all.....
The answer is already above....highlighted!Ah, I think we posted at same time!
So I guess so!
The answer is its the petrol engine setup that gives it the efficiency!Added to that, surely all the battery charging is seriously going to hurt economy anyway, thus raising emissions in reality (even though not raising on the standard tests)?
The Prius does not have an Otto cycle engine, it has something closer to the Atkinson cycle with valve timing etc skewed towards max efficiency as per the highlighted fields above.
Trouble is that such an engine is rather horrible to drive so they have to bolt an electric motor setup on it to make it useable and over come its poor standard operating conditions.
The choice of cycle also explains why its shite on a track for economy as your now operating in the upper revs where it has no go!
QuoteThe answer is its the petrol engine setup that gives it the efficiency!Added to that, surely all the battery charging is seriously going to hurt economy anyway, thus raising emissions in reality (even though not raising on the standard tests)?
The Prius does not have an Otto cycle engine, it has something closer to the Atkinson cycle with valve timing etc skewed towards max efficiency as per the highlighted fields above.
Trouble is that such an engine is rather horrible to drive so they have to bolt an electric motor setup on it to make it useable and over come its poor standard operating conditions.
The choice of cycle also explains why its shite on a track for economy as your now operating in the upper revs where it has no go!
I real world, is it that much more efficient (purely on day to day mpg) than a similar sized car (Focus/Astra)?QuoteQuoteThe answer is its the petrol engine setup that gives it the efficiency!Added to that, surely all the battery charging is seriously going to hurt economy anyway, thus raising emissions in reality (even though not raising on the standard tests)?
The Prius does not have an Otto cycle engine, it has something closer to the Atkinson cycle with valve timing etc skewed towards max efficiency as per the highlighted fields above.
Trouble is that such an engine is rather horrible to drive so they have to bolt an electric motor setup on it to make it useable and over come its poor standard operating conditions.
The choice of cycle also explains why its shite on a track for economy as your now operating in the upper revs where it has no go!
Battery charges at 'opportune' moments...i.e. when cruising and to a lesser extent, under braking (regenerative). Clearly that spent enegry for charging is recovere when the motor is running (round town and accelerating).
But, as stated, we are discussing the reason behind the efficiency here.....rather hoped somebody might pick straight up on it following the engine threads but, it still highlights the theory and consequences of operating at one extreme of valve timing! :y
QuoteI real world, is it that much more efficient (purely on day to day mpg) than a similar sized car (Focus/Astra)?QuoteQuoteThe answer is its the petrol engine setup that gives it the efficiency!Added to that, surely all the battery charging is seriously going to hurt economy anyway, thus raising emissions in reality (even though not raising on the standard tests)?
The Prius does not have an Otto cycle engine, it has something closer to the Atkinson cycle with valve timing etc skewed towards max efficiency as per the highlighted fields above.
Trouble is that such an engine is rather horrible to drive so they have to bolt an electric motor setup on it to make it useable and over come its poor standard operating conditions.
The choice of cycle also explains why its shite on a track for economy as your now operating in the upper revs where it has no go!
Battery charges at 'opportune' moments...i.e. when cruising and to a lesser extent, under braking (regenerative). Clearly that spent enegry for charging is recovere when the motor is running (round town and accelerating).
But, as stated, we are discussing the reason behind the efficiency here.....rather hoped somebody might pick straight up on it following the engine threads but, it still highlights the theory and consequences of operating at one extreme of valve timing! :y
I did, but only because you prompted me, so I went and looked over the timings :-[QuoteQuoteThe answer is its the petrol engine setup that gives it the efficiency!Added to that, surely all the battery charging is seriously going to hurt economy anyway, thus raising emissions in reality (even though not raising on the standard tests)?
The Prius does not have an Otto cycle engine, it has something closer to the Atkinson cycle with valve timing etc skewed towards max efficiency as per the highlighted fields above.
Trouble is that such an engine is rather horrible to drive so they have to bolt an electric motor setup on it to make it useable and over come its poor standard operating conditions.
The choice of cycle also explains why its shite on a track for economy as your now operating in the upper revs where it has no go!
Battery charges at 'opportune' moments...i.e. when cruising and to a lesser extent, under braking (regenerative). Clearly that spent enegry for charging is recovere when the motor is running (round town and accelerating).
But, as stated, we are discussing the reason behind the efficiency here.....rather hoped somebody might pick straight up on it following the engine threads but, it still highlights the theory and consequences of operating at one extreme of valve timing! :y
Yes because the engine can be optimised for efficiency!Real world, Prius is around mid 40s. I would have thought that a 1.4 Focus/Astra should be achieving near that anyway without lugging all that heavy metal about?
QuoteYes because the engine can be optimised for efficiency!Real world, Prius is around mid 40s. I would have thought that a 1.4 Focus/Astra should be achieving near that anyway without lugging all that heavy metal about?
I know our loan Rover 414 we had for ages a while ago managed high 30s day to day.
Real world, Prius is around mid 40s. I would have thought that a 1.4 Focus/Astra should be achieving near that anyway without lugging all that heavy metal about?