Re: air - fuel ratio

Dyno wrote:
> 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

Excellent info, thanks...