Re: air - fuel ratio

jim wrote:
> 
> Dyno wrote:
> 
>> I was all set to fire off a followup, but you beat me to it, almost
>> point by point. A lot of the nonsense that gets posted could easily be
>> avoided is some posters would simple go buy an engine text book and
>> simply browse through it.
> 
> Here is what you said on how octane affects fuel economy.
> 
>> When I think of fuel economy, I think of light-load operation; cruising
>> down the highway or driving around town. On a time-weighted basis,
under
>> these conditions engine loads (BMEP levels) are relatively low. It is
>> also at these conditions that the octane requirement is also low.
> 
> 	 If you read your engine textbook you will find that the RON rating is
> made under light load conditions just as you describe. You are correct
to
No it is not. Apparently you do not know under what conditions the 
octane ratings are obtained. Contrary to what you said both the Motor 
method and Research method are obtained at WOT. Do I really need to list 
the specifics of methods used?

> The fuels properties to knock under light loads is exactly what the
> RON test determines. Engines do knock under light loads even if you
think
> they don't ( and even if you can't hear it) and that does impact on gas
> mileage.   
Interesting assertion here. Please provide a source for this. In my 30 
years of engine testing this is a new "fact" for me. And in much of my 
testing, I have acquired and viewed the in-cylinder pressure data and 
have not seen this.

> 
> 	The problem is you don't have any idea what the RON rating is for the
> fuel in your gas tank and it can vary quite a lot for any given posted
> pump octane rating. But in spite of the fact that you have no idea what
> the octane is in your gas tank under those conditions that could
> potentially be giving you better mileage, you are positive it has no
> affect on mileage cause you read something in a book.
> 
> -jim
This is absurd. You dismiss textbook information that has been verified 
over and over just because it doesn't fit your pet theory; a theory that 
you have yet to provide any refereed literature on. Have even read any 
of the books? Here's a good one: Heywood's "Internal Combustion Engine 
Fundamentals". This book not only explains the major phenomena but also 
provides literally thousands of technical journal articles as 
references. Can you do the same?