Re: [Amc-list] E-85 Engine Design

[Frank Swygert <farna@xxxxxxx>]

I may have been off on the 30-33% difference between E85 and gasoline on a flex fuel vehicle, may be more like 15-20% as was pointed out, but I do know that in some cases (larger vehicles, like GM Suburban, or whatever they call it now, and maybe pulling a load) the difference can be as high as 25-30% (more ethanol than gasoline). So a small to mid sized rather efficient vehicle would do better, at least on average. I would think that if you put it under a heavy load efficiency with E85 would suffer more than with gasoline just because it's a known fact that there is less total energy available in E85. 

Altering cylinder pressure can be done by adjusting cam duration. That's technically possible now with variable timing cams, and may be the reason some flex engines are in the 15-20% range of gasoline. We more or less do the same now when building a budget stroker six from the 4.0L -- use a longer duration cam to effectively lower compression (cylinder pressure) so regular gasoline can be run with stock type pistons and no special machine work. 

Most flex fuel engines run around 10:1 compression, and I have seen the specs on one (Ford Focus?) that was 10.5:1. Timing is altered to run on regular fuel. The higher compression helps when running E85. The computer should be smart enough to tune the engine for premium fuel and a lot better performance since it has to be able to adjust to the higher octane E85 and any mixture of gasoline and E-85. 

Small turbo engines are great on economy even under boost. I believe the reason more auto makers don't go this route is due to the added complexity and possible warranty issues that go with turbos. Still, a turbo 2.0L could easily replace a non-turbo 3.0L (maybe larger) and get much better mileage. I think that too many Americans equate turbos with performance though. Even with a turbo engine it has to be driven in an economical manner to get the best economy. The performance relation will turn a lot of people off (average Joe types, not the more knowledgeable ones, such as the majority of this list) from turbo motors, so marketing could be problematic. 

AMC never used hardened seats in any engines. Well, I don't know about the 2.5L four, but I would think not since the 4.0L never got them. My understanding is the slightly tougher castings allowed induction hardening of the entire lower surface of the head, valve seats, combustion chamber and all. That would have occurred on roughly 78 and later engines though. I don't know if hardened seats are a requirement for E85/alky, but most likely is due to no lubricating qualities. Doubt it's any worse than unleaded gasoline though.  

=================================================
Date: Fri, 30 May 2008 16:22:22 -0400
From: Brien Tourville <hh7x@xxxxxxxxxxxxx>

>From Wrambler: 
His engine is DUAL fuel, that kills the equation.
To get the engine back to close to equal footing with a gas engine it needs to be built specifically for E85.
His will run on both, but till they get the science to alter compression ratio by fuel used the E85 will not do what gas will.
  With electronic valve timing they can likely get this done.
But, when?
--------------

from hh7x:
Makes the case for a Turbo - low boost on Regular Gas.

For the cheap seats, using the GM Turbo Sunbird '7749 ECM
can be used on an AMC V8 in the EFi conversion.

Sensors would be for E-85, probably not optimum for
Regular Gas low boost running.

A Flex Fuel ECM as I understand are newer Flash tech
so specialized knowledge to map to a 360.

What about valve seats / valves - a 1978 AMC would
have the hardened seats - but are these correct for
running E-85 'Alky' ?



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