That's interesting because some sources claim that gasoline with 10% ethanol hurts fuel economy. The MPG numbers you posted are high. I don't think(and I may be wrong) that gasoline with ethanol really hurts mpg with the I2. I've used blends with and without and can not detect any differences.
Ethanol burns faster than petrol, in practical application that results in more power but less torque and as a result you have to work an engine harder, resulting in reduced fuel economy. This is showing up in super cars tuned to run on bio-ethanol which manufacturers are betting on as the future of super cars once oil becomes to scarce and expensive to be a practical fuel source.
However the reason it's 10% is not just because of the problems sustaining a ethanol supply but also to minimise the effect on burn efficiency and therefor on fuel economy.
In addition remember that the whole point of a hybrid is that an electric flywheel motor adds supplemental torque to a small, low torque engine so you don't have to work it so hard and as a result it keeps the problem of reduced torque to an absolute minimum, so more power should result in slightly better economy at higher speeds and under acceleration.
Ethanol burns faster than petrol, in practical application that results in more power but less torque and as a result you have to work an engine harder, resulting in reduced fuel economy. This is showing up in super cars tuned to run on bio-ethanol which manufacturers are betting on as the future of super cars once oil becomes to scarce and expensive to be a practical fuel source.
However the reason it's 10% is not just because of the problems sustaining a ethanol supply but also to minimise the effect on burn efficiency and therefor on fuel economy.
In addition remember that the whole point of a hybrid is that an electric flywheel motor adds supplemental torque to a small, low torque engine so you don't have to work it so hard and as a result it keeps the problem of reduced torque to an absolute minimum, so more power should result in slightly better economy at higher speeds and under acceleration.
So in other words the Insight with its IMA electric motor, supplying additional torque, offsets the drop in torque by using 10% ethanol in the ICE.
What is offsetting the drop in torque is going to be extra throttle, which results in either more IMA usage or higher RPM, essentially more fuel usage.
More power, less torque? Doesn't really make much sense, power is a function of torque and speed, you lose both with ethanol. With the same octane rating the fuels should be burning at a rate close enough to the same. With pure ethanol(not a gasoline mix), I think the burn rate is actually slower considering that, even though it has less total energy content per volume, it has a higher octane than gasoline. Ethanol at very high levels, above 75% causes issues with low vapor pressure when operating below about -10f/-23c to where some E85 flex fuel cars have block heaters standard and recommendations to use them in the winter to prevent starting problems due to slower ignition which becomes worse with lower temperature causing low vapor pressure. If I recall correctly, I think I've seen the E85 pumps labeled at 105 octane, pure ethanol is somewhere around 120 but it allows for less octane increasing additives to be put into the fuel so a lower octane for the gasoline portion can be used with more ethanol content in the mix.
I'm not looking forward to the Minnesota corn lobby pushing for 20% ethanol, which causes a 7.7% performance/fuel economy drop over pure gasoline due to less energy available in the fuel.
What is offsetting the drop in torque is going to be extra throttle, which results in either more IMA usage or higher RPM, essentially more fuel usage.
More power, less torque? Doesn't really make much sense, power is a function of torque and speed, you lose both with ethanol. With the same octane rating the fuels should be burning at a rate close enough to the same. With pure ethanol(not a gasoline mix), I think the burn rate is actually slower considering that, even though it has less total energy content per volume, it has a higher octane than gasoline. Ethanol at very high levels, above 75% causes issues with low vapor pressure when operating below about -10f/-23c to where some E85 flex fuel cars have block heaters standard and recommendations to use them in the winter to prevent starting problems due to slower ignition which becomes worse with lower temperature causing low vapor pressure. If I recall correctly, I think I've seen the E85 pumps labeled at 105 octane, pure ethanol is somewhere around 120 but it allows for less octane increasing additives to be put into the fuel so a lower octane for the gasoline portion can be used with more ethanol content in the mix.
I'm not looking forward to the Minnesota corn lobby pushing for 20% ethanol, which causes a 7.7% performance/fuel economy drop over pure gasoline due to less energy available in the fuel.
Actually power is an expression of torque multiplied by rotational speed and rotational speed is directly impacted by (amongst other things) burn speed. Are you sure your not getting confused by the drop in power that resulted when the fuel used in the IndyCar Series changed from methanol to ethanol?
Whatever the reason may be, I, Cobb and I'm sure others are getting good fuel economy(significantly above the EPA's numbers) using gasoline with 10% ethanol. Up by me, gasoline containing 10% ethanol is on average 15 cents(or around 5%) less per gallon. As long as the drop in fuel economy is equal or less than that it shouldn't matter.
Although it may exist, I can't notice any drop in fuel economy with the I2; using gas with the ethanol blend. With other vehicles, I do notice a slight drop in MPG.
So in other words the Insight with its IMA electric motor, supplying additional torque, offsets the drop in torque by using 10% ethanol in the ICE.
Yes, more low end torque means you don't have to work the engine as hard, you don't have to press the throttle so far open or push the engine to higher revs, to get it moving. On the other hand once moving and especially around the mid - high rev range "power" becomes a little more important, so more mid range - high range power should help, not hinder fuel economy.
So I'd expect the impact on fuel economy to be far smaller with a hybrid than with a conventional car and even potentially result in a very small improvement.
Took off the snow tires, Temps went up to around 50 degrees over the past few days, and mileage is up to 53 on the display, so I am at about 51. Hope it stays warm!
Took off the snow tires, Temps went up to around 50 degrees over the past few days, and mileage is up to 53 on the display, so I am at about 51. Hope it stays warm!
Did you get a chance to test which had the biggest impact on economy, tires or the weather conditions?
Last edited by nliwilson; 02-17-2011 at 08:43 PM.
Reason: removed anomalous or
I was running the defroster without the a/c on but the front windshield would fog up a bit, so I turned the driver front vents up at the window and it cleared the windshield. Temps starting to get back to the low 40's and mileage finally starting to creep back from 41-42. Just hit 46 today.
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