tank before, 250.3 miles, just over 9.4 gallons, 26.6 mpg
i drove REALLY fast that tank......
Fuel economy and iAWD - let the fun begin!
I wouldn't be surprised if the AWD/FWD switch exists to pass the emission tests. The EU procedure for measuring the city/urban/combined emissions and corresponding EURO1/2/3/4/5/6 category is as unreal as possible. First they take the car, and run it on completely flat and perfect surface to measure the resistances from turning wheels, air, etc. - so they accelerate the car and measure how far it goes when the engine gets turned off. From that point on, the car is completely static. The actual measurement does not measure the fuel consumption, but rather CO2 production. The car is kept in a hall with temp between 20-30C, lights, radio, AC etc turned off. Since AWD is an on/off feature, I assume, that it is turned off as well. Then there is a fixed procedure saying steps like: engage 1st gear, push the pedal 20%, wait 10 seconds etc etc to simulate driving while a probe in the exhaust measures CO2 emissions. From that, the fuel consumption is calculated based on some weird formulas.
If only front wheels are turning on the dyno, than disengaging the AWD could actually save some fuel (in lab of course), since the engine has less work to do (remember, the vehicle is static at this phase).
Since the "eco tax" is paid based on the CO2 emissions, then every manufacturer (at least in EU) is forced to make these as low as possible and the manufacturers cheat in every way possible(example: when measuring the distance the vehicle travels passively from a given speed, they will overinflate the tires so that the rolling resistance is minimized, even tough this is dangerous in real world). Also, you cannot sell a new vehicle if it doesn't meet a certain emissions category. I think that currently, EURO4 vehicles cannot be sold anymore in EU.
If only front wheels are turning on the dyno, than disengaging the AWD could actually save some fuel (in lab of course), since the engine has less work to do (remember, the vehicle is static at this phase).
Since the "eco tax" is paid based on the CO2 emissions, then every manufacturer (at least in EU) is forced to make these as low as possible and the manufacturers cheat in every way possible(example: when measuring the distance the vehicle travels passively from a given speed, they will overinflate the tires so that the rolling resistance is minimized, even tough this is dangerous in real world). Also, you cannot sell a new vehicle if it doesn't meet a certain emissions category. I think that currently, EURO4 vehicles cannot be sold anymore in EU.
Mechanical components wear, clutches wear and fail. Me thinks the On/Off button is simply to prolong the sealed unit's life expectancy. Why wear out the thing when you really don't need to? It's not re-buildable or serviceable.KiwiME wrote:The main thing to understand is that the clutch is operated by a mechanical servo that amplifies the magnetic attraction provided by the 0-2.8 amp control current. The servo (a cam plate with ball rollers) relies on the speed difference across the clutch to provide power to squeeze the plates together. If the front/rear axle gearing is the same (and it normally is) then there must be some other speed difference present due to either slippage at the front or cornering (from the Ackermann effect) in order to activate the clutch.
Manual could read as follows...
AWD switch position: Snow, Rain, Twisties: ON; all other times: OFF
Ron
2010 Kizashi GTS, CVT, iAWD (3/10 build date)
2011 SX4 Premium Hatch, CVT, iAWD (12/10 build date)
2018 Mazda CX-5 iAWD Touring
2014 Wrangler JKUW (GONE, traded
)
1991 Samurai, 5-Speed, EFI, Soft-Top (
sold)
2010 Kizashi GTS, CVT, iAWD (3/10 build date)
2011 SX4 Premium Hatch, CVT, iAWD (12/10 build date)
2018 Mazda CX-5 iAWD Touring
2014 Wrangler JKUW (GONE, traded
) 1991 Samurai, 5-Speed, EFI, Soft-Top (
sold)Have a look in your owner's manual - I'll bet a beer that it says you must disconnect the driveshaft if you put the car on a FWD dyno or otherwise spin-up either axle alone, such as when towing. The reason is that the actuator cam inside multi-plate clutch does have a slight drag even when the excitation current is off (eg. AWD off.) If there is a large speed difference between the front and rear axles there is a chance that the clutch may suddenly engage.
I don't see a reason why you couldn't tow the FWD model.
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Knightstruth
- Posts: 215
- Joined: Tue Jun 04, 2013 10:22 pm
I know it is always advised to use a flatbed for awd. I'm not sure if it makes a difference if the car is in fwd mode.
It won't matter. When the ignition is off, the AWD car is mechanically in the same condition as ignition "on" and in "2WD." There would be no excitation current to the AWD clutch but a major speed difference between axles could result in nasty surprise as it can still engage suddenly. Frankly, it's a weakness of using a fairly simple AWD clutch design.
No reason why the FWD car couldn't be towed providing the transmission gets proper lubrication with the engine not running. If it say's you can't tow it, then that will be the reason. Edit: oops, obviously it could be towed on the back wheels
No reason why the FWD car couldn't be towed providing the transmission gets proper lubrication with the engine not running. If it say's you can't tow it, then that will be the reason. Edit: oops, obviously it could be towed on the back wheels
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Knightstruth
- Posts: 215
- Joined: Tue Jun 04, 2013 10:22 pm
What I would like to see going forward is that car reviews start seperating AWD and non AWD. Its seems to me many reviewers seem to make AWD as a minor feature and review it as such. Should an AWD Kizashi/Legacy really be put up against a camry/accord? Having AWD in the base four engine will result in slower accelartion and lower fuel economy. IMHO AWD midsize should have their own category.