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The issue here is that, in most cases, while engine downsizing tends to provide some decrease in emissions, fuel consumption isn't all that much better. If you

The issue here is that, in most cases, while engine downsizing tends to provide some decrease in emissions, fuel consumption isn't all that much better. If you look at the Fiat 0.9 Twinair 2 cyclinder engine real world consumption is somewhere between 35 and 40MPG despite a manufacturer claimed 68MPG. You cannot have a car with less than 80BHP either, it would be undriveable. In comparison, the VW EA888 2.0 turbo petrol engine (in the Golf GTI, Golf R, etc) has the same real-world consumption (because I drive one), yet can produce up to 300BHP at the top of the rev range if and when you need it. The reason for this is that the engine produces so much power and torque in the low-mid rev range compared to the 0.9 Twinair, the same rate of acceleration is possible without having to work the engine at all. It's not until you put the car into Race mode and use full open throttle that consumption drops below 30MPG to the mid 20s. What's more, in the case of automatic transmissions, gear ratios and software can be made to work the engine at low RPMs 99% of the time to decrease fuel consumption. This isn't possible with the 0.9 Twinair engine because it produces too little power at low revs.

pjc50 9y ago
> You cannot have a car with less than 80BHP either, it would be undriveable Why say things like this, which are so easily contradicted? I used to drive a Peugeot 306 1.4 with a 75BHP engine that was perfectly adequate. I'm sure that people like big heavy cars that accelerate quickly, but it's worth questioning how much you actually "need" one.
- pistonhead 9y ago
  Because I also drive a VW Up! with a 59BHP engine (1.0 N/A) and I think the engine is too weak for the car. The issue isn't the peak power, but the torque curve. Small, naturally aspirated engines have very poor torque curves, which means that you really have to rev the engine to get the rated power from it. In real driving, where you're between 2,000 and 4,000RPM most of the time, the engine only makes at most 40BHP (peak torque of a meagre 80lb-ft doesn't come in until 3,500RPM). This is fine for driving in built up areas, but it's really bad when you need to accelerate up-hill on an on-ramp to join a motorway or build up speed on dual carriageways where there are roundabouts every mile.
- eeekz 9y ago
  Cars have gotten a fair bit heftier since the days of the 306, largely due to advances in safety (crumple zones, airbags etc). Would you be willing to trade all that for better emissions?
reallydontask 9y ago
My GF's VW Up! with a beefy 59 BHP is perfectly driveable. Sure, I do find myself shifting more than on my car and it won't push past 100 mph but it can comfortably do 80 mph on the motorway. It also gets about 60 mpg on regular use ( best i've measured is 70 mpg, beating VW's figures, IIRC; Mostly A roads and motorway within the speed limit)

pjc50 9y ago

> You cannot have a car with less than 80BHP either, it would be undriveable Why say things like this, which are so easily contradicted? I used to drive a Peugeot 306 1.4 with a 75BHP engine that was perfectly adequate. I'm sure that people like big heavy cars that accelerate quickly, but it's worth questioning how much you actually "need" one.

pistonhead 9y ago
Because I also drive a VW Up! with a 59BHP engine (1.0 N/A) and I think the engine is too weak for the car. The issue isn't the peak power, but the torque curve. Small, naturally aspirated engines have very poor torque curves, which means that you really have to rev the engine to get the rated power from it. In real driving, where you're between 2,000 and 4,000RPM most of the time, the engine only makes at most 40BHP (peak torque of a meagre 80lb-ft doesn't come in until 3,500RPM). This is fine for driving in built up areas, but it's really bad when you need to accelerate up-hill on an on-ramp to join a motorway or build up speed on dual carriageways where there are roundabouts every mile.
eeekz 9y ago
Cars have gotten a fair bit heftier since the days of the 306, largely due to advances in safety (crumple zones, airbags etc). Would you be willing to trade all that for better emissions?

reallydontask 9y ago

My GF's VW Up! with a beefy 59 BHP is perfectly driveable. Sure, I do find myself shifting more than on my car and it won't push past 100 mph but it can comfortably do 80 mph on the motorway. It also gets about 60 mpg on regular use ( best i've measured is 70 mpg, beating VW's figures, IIRC; Mostly A roads and motorway within the speed limit)