Fuel Economy of the Ethanol-Optimized turbo FFV

[b4black]

You usually have to buy these papers, but this is posted on the internet.

I here people claiming if a engine is tuned for E85, then the fuel economy penalty can be negated or at least dropped signifcantly. Saab tried it. SAE tested it.

http://www1.eere.energy.gov/biomass/pdfs/analysis_saab2007.pdf

 

[1outlaw]

Nice find. Generally these DOE sponsored papers do get made available for free after a while. I have the USA version of this car/engine (210 hp and with a six speed manual) but in a gas only version and not FFV. It is easy to get 31.8 mpg on E0 premium, E20, or E27 at 70 mph interstate driving (I have replicated this entire 3 fuel tests on 2 different 1100 mile runs). I was hopeful that the Saab car in this test was going to close the mpg gap more than it did (instead GM/Saab went for hp vs economy). GM redesigned this engine when it made the new 2L turbo FFV engine they are putting in the new Regal (now direct injection and not a variable vane turbo as was on the Saab). GM claims it has cut the mileage penalty to the single digit % -- we'll get to see soon because the first ones are finally landing in the dealerships (these were made in Germany).

A point made in the test is that every FFV gets better fuel efficiency on E85 in terms of miles per BTU than gasoline- just not volumetric (gallon) mpg. A retired Chrysler engineer who worked with all alcohols from the early 80's thru 2000 explained this to me- alcohols generate less waste heat that has to be dumped thru the radiator.

I wonder if the test cycles used penalized the economy on this turbo engine somewhat?? A better way to achieve best volumetric fuel economy on E85 is via a very high compression engine such as was done in the EPA labs a couple of different times. EPA studied both methanol and ethanol this way- one of the test engines was 19:1 (too high for street use AND was on straight ethanol- not E85). I lost most of these tests when I lost a PC harddrive but could look around for them if someone is interested.

 

[Hot Air]

FWIW, you are missing the point for running E-85 in a turbo Buick. The advantage is the higher latent heat of vaporization (chemical intercooler) and the high octane rating (higher boost w/o knock). Few of us are trying to get great fuel economy with E85...just more power! Having said that, it would be real nice to get better fuel economy with E-85 but with less BTU/gallon, it WILL be hard! I would be happy to just be able to purchase E-85 wherer I live. It is currently a 1-2 hour drive each way to find an E-85 pump!
Conrad

 

[BEATAV8]

Run it considerably leaner than stoich and increase the timing. Fuel econ wouldn't be too bad at all..... Easy enough to do with something like an old turbo Buick, or even a carburetor.

But for optimal emissions (lowest possible NOx / HC tradeoff), a factory tune has to bet set up around stoich A/F ratios for normal driving. Otherwise the EPA would be unhappy.

 

[BEATAV8]

thanks for the link Rich. I saved it for future ref.

Will you be at any of the CCGSCA meetings this winter? I'd like to get the skinny on what's going on in the world of fuels!

With the way things are going in the diesel industry, I often wonder if the world could use a new modern heavy duty gasoline / ethanol engine.

 

[1outlaw]

Run it considerably leaner than stoich and increase the timing. Fuel econ wouldn't be too bad at all..... Easy enough to do with something like an old turbo Buick, or even a carburetor.

But for optimal emissions (lowest possible NOx / HC tradeoff), a factory tune has to bet set up around stoich A/F ratios for normal driving. Otherwise the EPA would be unhappy.

Agree on the leaner bit for a low compression/ low boost engine that is not in the danger zone. A lot of folks who ran E85 straight in their non-modified engines (some worked very well/ some not) without suffering hardly any MPG loss were extremely dissapointed when they bought an FFV and they had to feed them more. One guy I know had 2 pickups he ran all over the Midwest ran them unmodified on E85 and when he replaced one of them (it had 300,000 miles on it) with an FFV he was really angry to find out how thirsty it was.

There is a lot of technology out there now to lower NOX- EGR being one of them. I am concerned about the fuel consumption of FFV's more than power modified engines because it is the success of the FFV that will determine the speed at which we get more adoption of E85 (and more stations).