Just a quick question. I have been wondering how the flex fuel cars adjust to the fuels. Can the vehicles adjust for premium use as far as making use of the available octane? Or are they just prepared to enrich the mixture for the use of E85? The reason I ask is because a friend has a new 2011 Chevy HHR 2.2 VVT and I wonder if he would get better power out of premium like my old 2.4 HHR did since it required premium. I assume it probably would not adjust itself to the premium but I wonder if anyone has more info?
Flexfuel / Octane question
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Flex fuel cars have a sensor in the fuel line that can determine, on-the-fly, the ethanol percentage. That's how they can manage to run on anything from pure E-85, to a 50/50 mix of E-85 and E-10, down to straight gasoline. The earliest ones I remember (mid/late 90s Chrysler flex-fuel cars) used an optical sensor that measured the index or refraction of the fuel to determine how much alcohol it contained, not sure if that's the same sensor technology still being used or not.
Flex fuel cars carry injectors large enough to deliver much more fuel than required for pure gasoline or E-10, and then the computer can crank up the injection pulse width to put in more fuel when E-85 is in the lines. They also no doubt alter timing to take advantage of the higher inherent octane of ethanol, but then most all cars do that via the knock sensor. Basically, all engines with a knock sensor run as much timing advance as they can without knocking on any fuel, regardless of ethanol content.
Flex fuel cars carry injectors large enough to deliver much more fuel than required for pure gasoline or E-10, and then the computer can crank up the injection pulse width to put in more fuel when E-85 is in the lines. They also no doubt alter timing to take advantage of the higher inherent octane of ethanol, but then most all cars do that via the knock sensor. Basically, all engines with a knock sensor run as much timing advance as they can without knocking on any fuel, regardless of ethanol content.
The Ecotec 2.2 in the HHR shows gains for both TQ and Hp when comparing E10 to E85 numbers. Something must be changing in the ECM, timing... Not sure if premium to regular would yield the same or similar results but would be interesting to find out.
2.2 on E10
155 Hp
150 Tq
2.2 on E85
161 Hp
158 Tq
2.2 on E10
155 Hp
150 Tq
2.2 on E85
161 Hp
158 Tq
Yeah that is exactly what I was wondering. I know if you run a car tuned for premium on regular it is slower because it pulls the timing for the lower octane. When you put premium back in it, you can usually feel the difference. I just wonder if running premium in the flex fuel car would cause the car to tune itself to premium by octane or not. I know it runs way richer with E85 because the fuel has less BTU than gasoline but I am wondering if it would adjust the timing enough to take advantage of the octane in the premium as opposed to richer mixture for the ethanol. My guess is probably not, but I wonder if anyone here has any more info on it?
E85 has higher octane than premium.
That is how they recoup some of the lost power of the weaker ethanol.
That is how they recoup some of the lost power of the weaker ethanol.
Well first impressions on E85. The HHR got filled up with E85 today and at first it seemed sluggish off the line as expected. I guess it was running way lean till it realized what was going on. Seemed to adjust pretty good in about 3 miles or so. I have to say there is no doubt more power. My trip back home was all highway and the MPG went from 29.5 on gas to 29.2 on E85 so far. It was almost 100 miles home so it's not like it was a 20 mile trip or anything like that. I assume that will drop once it is not all highway driving. It is a 5 speed and it does drive better on this stuff. Sadly there is none available locally. It pulls better in the higher gears without having to downshift to continue where it would normally chug along. I would say it is more of a difference than I saw in my old HHR that required premium. In that one you would feel a difference in power going to premium from regular. In this one I would say the difference with the E85 is more than my old car with premium. I will ask my friend to run a few tanks of Premium in it to see if there is any MPG improvement over regular unleaded in daily driving. Maybe have him run a tank or two of regular in it to get the ethanol out so that does not affect the test with Premium. I will post back so anyone that is interested can know the results.
^Interesting, if you don't have to downshift with E85 as much you may have somewhat of a balancing out with performance while not losing MPG as anticipated.
My friend has a flex-fuel Titan, 2006, and he 'definitely' gets better performance running E85 in his setup.
My friend has a flex-fuel Titan, 2006, and he 'definitely' gets better performance running E85 in his setup.
Yeah I took it out again this evening and it is much better. Wish I had E85 locally it would probably get used more often.
That tank of E85 is done and it averaged about 26 MPG as opposed to regularly getting 29.5 on Regular. Going to run a tank or two of Regular now to make sure the E85 is all out and then going to try a few tanks of Premium to see if it compensates at all for it.
The almost pure ethanol has way higher octane than E10 premium.
this allows much more ignition advance to be used, with resulting power increase. but the inherent less BTUs per gallon the the E85 offsets the actual power/gas mileage benefits of the higher octane.
This is not a knock sensor issue. It is a computer programming issue. Various fuels will have different programming called upon
The KS is a safety that should never come into play [but it can and does].
this allows much more ignition advance to be used, with resulting power increase. but the inherent less BTUs per gallon the the E85 offsets the actual power/gas mileage benefits of the higher octane.
This is not a knock sensor issue. It is a computer programming issue. Various fuels will have different programming called upon
The KS is a safety that should never come into play [but it can and does].
Saab for several years has offered an engine they call the Biopower which increases the turbo boost when E85 is in the tank, for something like a 20% increase in power. A turbocharged vehicle has a much greater potential for taking advantage of higher octane fuel than a regular car.
Car and Driver recently had a 1 pager on a couple systems being proposed by suppliers (Ricardo and somebody else I can't remember). It suggested that these were unique and novel ideas, didn't acknowledge at all that Saab's been doing it for several years.
jeff
Car and Driver recently had a 1 pager on a couple systems being proposed by suppliers (Ricardo and somebody else I can't remember). It suggested that these were unique and novel ideas, didn't acknowledge at all that Saab's been doing it for several years.
jeff
My Grand Marquis gains alot more power and a "growl" under the hood on E85, but it goes from 23mpg highway to about 18mpg....
Originally Posted By: MuzzleFlash40
My Grand Marquis gains alot more power and a "growl" under the hood on E85, but it goes from 23mpg highway to about 18mpg....
With good factory tuning, identification of fuel used, and other parameters, this is expected.
The high octane of the E85 is the reason for possible power gains.
AS you note, fuel economy is down. it has to be with 1/2 the BTUs per gallon. Tuning can only recoup come of the loss.
My Grand Marquis gains alot more power and a "growl" under the hood on E85, but it goes from 23mpg highway to about 18mpg....
With good factory tuning, identification of fuel used, and other parameters, this is expected.
The high octane of the E85 is the reason for possible power gains.
AS you note, fuel economy is down. it has to be with 1/2 the BTUs per gallon. Tuning can only recoup come of the loss.
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