Date:         Sun, 23 Apr 2006 17:27:14 -0700
Reply-To:     John Bange <jbange@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Bange <jbange@GMAIL.COM>
Subject:      Re: air/fuel mixture
Comments: To: jbeaulie@nd.edu
In-Reply-To:  <1145832427.444c03eb569d1@webmail.nd.edu>
Content-Type: text/plain; charset=ISO-8859-1

>
> Bentley wants us to adjust the AFM based on the CO content of the exhaust
> gas
> (not measured with the above unit).  So, does anyone have good data on
> what the
> air:fuel ratio is supposed to be?
>

For gasoline, perfect AFR (called the "stoiciometric" ratio) is 14.7:1. No
engine achieves a perfect burn, though, so for "full throttle" the ECU goes
fairly rich. According tho the Bosch Fuel Injection & Engine Management book
(Probst), max power is at 12.6:1, best economy at 15.4:1. The EFI system
tried to stay on the rich side of 14.7:1, but as close to it as possible.
Generally when you tune with a wideband O2 sensor you aim for right around
stoiciometric and from there the ECU can handle the fine tuning. So long as
you get it into the ECU's effective self-adjustment range, the CO, NOx, and
HC should take care of themselves.


--
John Bange
'90 Vanagon - "Geldsauger"