Gas friendly base compression with a variable turbo boost is an ideal way of running a flex fuel vehicle with E85.

 

Yes Eric, that is true. I do agree with you there, that in a flex fuel setup forced induction can provide some benefit for peak power production when using E85.

Any and all flex fuel vehicles will always get lower MPG (exactly how much is up for debate) on E85 since they CANNOT fully utilize the E85, turbo or not. To optimize a motor for E85, the capability to run gasoline must be left behind. The reason is that the compression ratio required to get equivalent mileage with E85 would be way too high for gasoline. Running gasoline would thus result in a quick death for the E85-only motor.

There is nothing I would like to see more than a manufacturer come out with an E85 only motor option (with high compression for the E85). Kind of like the early "premium fuel only" motors. I think they could sell more than a few of them out here in the midwest, where we have E85 pumps. Especially when it would get equivalent mileage to a gasoline powered motor AND make more power.

Oh, and EPNCSU2006, definately keep us informed!

 

Turbo boost can largely make up for the lack of compression at many power levels, not just WOT. There have been studies performed with this setup that you can Google for. I have seen them but did not save the links.

 

Um, no? That's why we have a throttle valve. If the engine is running under boost all the time, the engine is waaay too small for the vehicle. At part throttle cruise, the turbo will make absolutely no difference!

If you're more packing air into the cylinder, you're putting more fuel in there with it. More air and fuel = bigger bang. No way to get around that.

Say you had two engines. Both 4 cylinder, 9:1 static compression, same displacement, etc. Equip one with a turbo. At part throttle cruise, both are going to have the exact same amount of air and fuel going into the cylinder. Same effective compression ratio.

Now, a larger displacement engine with the same number of cylinders and the same static compression ratio will have a lower effective compression ratio than the smaller one at part throttle cruise! This is simply because the smaller engine has to work harder to keep the same amount of power output. Edit: This may be the reason smaller engines get more miles per gallon than larger ones...

So you can have a smaller engine equipped with a turbo, or a larger NA engine with a high static compression ratio.

With your variable vane turbo, now you can bring in boost a lower rpms. So now you have a small engine, with a variable vane turbo, running high pressures. Great! Only one problem. What just happened to your octane rating? It went through the roof. Now not only do you have the high effective compression ratio to deal with, you have turbo heat!

Flex fuel is always a comprimize. No way around it.

 

Small engines are the way it is done. See if you can find some of those articles with some data in them.

 

heat from the turbo is not too hard to deal with if you have a proper intercooler and a place to vent the underhood heat. I have a 87 Turbo Coupe Tbird with the 2.3 that Ford rates at 190HP at 15psi of boost. I have done some unscientific study with that car, blending E85 to about 35%. Driving the car like I stole it MPG is about equal to running 92 prem. under same driving conditions. 35% ethanol and easy driving burns more than straight gas. So the high compression ratio seems valid.

 

The high compression ratio benefit has been verified in many scientific studies and experiments.

 

So, is this a computer controlled variable vane turbo? If so, that, in conjunction with a very small engine, might just work. Computer senses percentage of ethanol in the fuel, signals turbo to compensate. That might just work.

When I initially heard "turbo" my initial reaction was "That'll never work." But I now see that if you have a small engine, running under boost at cruise, with a computer controlling it, it might just work.

Find those articles! I'm interested in reading them.

Edit: Although, I just cant get past my initial reaction. If the turbo cuts boost with gasoline, wouldn't the driver just push the gas pedal down farther, taking the effective compression right back up where it was?