Axiom Home Page Forums General Discussion The Water Cooler Say no to straws

Ethanol blended fuels will make your engine run worse, unless it is designed to run with ethanol / alcohol. Depending on the blend, you can expect decreased power and fuel economy. It’s simple IC engine theory. If an engine is designed to run off alcohol, it is exactly that; designed to run on it. Take the 410 sprints for example. Small block, all aluminum engines of 410 cubic inches. They make an average of 750 hp, and they make power from off idle to 9000 rpm’s. Very respectable little engines to say the least. They run off alcohol. But they also run at around 16/1 static compression ratios and use downcomers that inject fuel directly into the combustion chamber in addition to the intake track.

Ethanol burns cooler than gasoline which lowers combustion chamber temperatures which ultimately lowers engine dynamic compression.

Power is made by applying a rapidly expanding force against the piston which drives the connecting rod down, twisting the crank shaft. The magnitude of this ‘force’ is derived by air, fuel, compression and ignition. When one of those is affected, power is affected. It just doesn’t get much simpler than that.

To expand a little further, but just a tad as IC theory is very complex……

Other issue that some of you are seeing with blended fuels is that the electronic engine management system is compensating for the different fuel characteristics. Ethanol has a higher oxygen content which in turns changes the air / fuel ratio that the sensors read at the exhaust manifold. The sensors send a signal to the PCM (power train control module) which will adjust the air intake throttle body blades admitting/restricting air flow to maintain a pre-set air/fuel ratio. When the engine starts to burn ethanol, a lean condition is met and the throttle blades close to raise F/A ratio back to set point. Power is loss and throttle position has to change to compensate (more fuel). Timing is also affected as blended fuels react differently than non blended fuels. They have different burn rates and the flame front travels slower, which means that timing needs to be advanced to compensate for this. Unfortunately, engine management systems adjust timing in reverse of this. They run a maximum, pre-set timing advance and retard timing when the knock sensors sense detonation. They do not advance over their pre-set maximum timing. In other words, you can not get this loss of power from inadequate advanced timing without going into the PCM tuning and re-setting the curve.

And one can’t forget how damaging alcohol is to gaskets and seals. – they get dry and brittle and fail prematurely.

I'm seeing more dual-fuel vehicles (presumably gasoline and E85 ?) becoming available from Detroit. Do you think those vehicles take all of these things into account, or do the gaskets and seals not get brittle and fall apart until after the warranty expires anyways ?

Geez I sound cynical today

Excellent post, Mike, thanks for all the info! You knowledge about IC greatly surpasses that of my own - what with my grade 8 - 1/2 credit distance-ed Power Mechanics course....I was aware of the properties of ethanol, but did not realize the effect they have on combustion. So would it be very out of the ordinary that i seem to get a comparable mileage b/w ethanol and conventional fuel? My car is by no means a "flex" fuel vehicle (3.4L 6 cyl).

I will now apologize to Ken for nitpicking, i suspect that's what you meant by your post - fuel economy was poor, not fuel efficiency of ethanol production. I will endeavour to track down that archived email with details on the studies.

Essentially, yes. There's also a pretty good article in the latest Road & Track about various alternative fuels.

any talk about biodiesel (canola derived) in the same magazine, Ken?

You mean rapeseed?

Bren R.

I believe there is.

Actually Bren, the majority of biodiesel production in the world is from rapeseed! In fact, rapeseed is better suited to biodiesel production because of the improved lubrication from rape varities (i believe due to erucic acid content).

Still the strangest town slogan i have ever witnessed - Tisdale, Saskatchewan (home of Corner Gas' Brent Butt) is called, "The Land of Rape & Honey."