Engine Options

[saghost]

Also, E85 is better suited for Atkinson-style engines and is better able to cope with lean-burn environments without spewing out massive amounts of NOx.

This part puzzles me. I understand with its higher octane number it allows higher compression ratios. The part about NOx in lean burn I don't get. In diesel, HCCI, and stratified charge/lean burn engines, the NOx emission problem comes from atmospheric nitrogen reacting with the remaining oxygen in the cylinder at elevated temperatures to form nitrous oxide. If there's still surplus oxygen from the reduced fuel charge, how could any fuel make a difference in this pollution?

[Ladogaboy]

the NOx emission problem comes from atmospheric nitrogen reacting with the remaining oxygen in the cylinder at elevated temperatures to form nitrous oxide. If there's still surplus oxygen from the reduced fuel charge, how could any fuel make a difference in this pollution?

The NOx forms only at higher temperatures. I forget the exact numbers, but E85 burns at several hundred degrees lower in lean-burn than gasoline. That's part of the reason tuners like to run E85 in turbocharged engines: It helps to significantly lower the intake charge temperatures as well as lowering the exhaust gas temperatures.

Here's a random link I found referring to a drop in EGT (racing environment): http://e85forum.com/about597.html

[Ladogaboy]

Here's another link where the tuner is seeing EGTs ~ 200* Celsius lower using E85 versus gasoline at the equivalent Lambda (stoich air fuel ratio). http://forums.evolutionm.net/alterna...notes-afr.html

[saghost]

The NOx forms only at higher temperatures. I forget the exact numbers, but E85 burns at several hundred degrees lower in lean-burn than gasoline. That's part of the reason tuners like to run E85 in turbocharged engines: It helps to significantly lower the intake charge temperatures as well as lowering the exhaust gas temperatures.

Here's a random link I found referring to a drop in EGT (racing environment): http://e85forum.com/about597.html

Interesting. I knew it was the high temperatures, but I hadn't realized that some of the fuels could stay low enough to make a difference. Lower temps means some loss in efficiency, of course, but you might be able to offset that by increasing the compression ratio since the fuel resists knock so well. Of course, then you're looking at a car that can only run (or at least only run at design condition) on E85, and you still have to deal with the corrosive and hydrophilic aspects for long term storage as well as the availability of fuel, but its interesting information.

[Ladogaboy]

Well, the other thing to remember is that most of the ICE systems are computer run, and it can be set to run different ways on multiple fuel grades (think GM's Flex fuel vehicles). Systems that can detect the various fuels are already in place, and the computers can adjust on the fly based on the information that is fed into them.

Also, in terms of differences between the ICE and fuel-delivery components: The main difference in modern engines is that you need to be able to flow a 30% greater volume of E85 for the same power. Outside of that, most modern vehicles are already standard equipped with materials that are resistant to ethanol corrosion. And the Volt already seems very ready to accept E85 since it has a sealed-pressurized fuel tank.