Re: air - fuel ratio

Tegger wrote:
> Dyno <dyno@[EMAIL PROTECTED]
> wrote in news:481dcd15$0$20205
> $4c368faf@[EMAIL PROTECTED]
> 
>> BobJ wrote:
>>> What are the thoughts on the air-fuel ratio values using todays fuels.
 
>>> How much does the (varied) alcohol content of todays fuels modify the 
>>> 'de facto' standard of 14:1 as the target mixture?
>> Virtually all newer vehicles use three-way catalyst exhaust 
>> after-treatment systems. For maximum catalyst efficiency the A/F target

>> average is stoichiometric (or the chemically correct mixture ratio).
For 
>> 100% gasoline this is nominally 14.6:1. Most engine control systems 
>> purposefully dither on either side of stoich to maximize catalyst 
>> efficiency.
>>
>> As alcohol(ethanol)is added, the feedback ECU controls will adjust the 
>> fuel system to keep the mixture at the mixture's stoichiometric value.
>> Here's a simple table to illustrate how stoich varies with %EtOH
>>
>> %EtOH    Stoich A/F
>> 0         14.6
>> 5         14.16
>> 10        13.74
>> 15        13.35
>> 20        12.98
>> 85        9.55
>> 100       9.00
> 
> 
> 
> Interesting information. But no road-legal US/Canadian gasoline is 100% 
> gasoline.
> 
> How do the above numbers compare to fuels with other oxygenates, such as

> MTBE? And what if the fuel contains MMT or TEL, neither of which are 
> oxygenates?
> 
Really? The certification fuel used by the automakers does not contain 
alcohol. And I believe, AMOCO still sells alcohol free fuel.

FWIW, the 0% gasoline shown above IS for pump grade unleaded regular. 
So, I guess I'm not sure what you are driving at here.