[Diy_efi] OL operation - How lean at cruise?

[hugh at sol.co.uk]

I read on here a while back that an AFR of 16 : 1 was the most economical
cruise mixture.

I have experimented with 16 : 1 and 17 : 1 without much to choose between
on economy.

My Exhaust gas temperature creeps up to 800?C when doing about 90 MPH on
the UK motorways at 16 : 1, so tend to run near 15 : 1 at higher cruise
speeds.

I have 280? degree duration cams with 10.8mm lift, so probably suffer a bit
from overlap making the Exhaust gas temperature high.

Hugh


Original Message:
-----------------
From: Daniel R. Nicoson A6intruder at myo-p.com
Date: Wed, 30 Mar 2005 10:20:25 -0500
To: diy_efi at diy-efi.org
Subject: [Diy_efi] OL operation - How lean at cruise?


I'm back to tuning my 1994 Mustang GT, snow is gone, the daily driver, an
"ultimate driving machine" isn't as reliable as this old Mustang (BMW
currently apart in my garage awaiting parts).  So I'm driving the Mustang.

I don't have a very good tune going right now, sucking lots of expensive gas
( I drive about 45 miles each day). So I decided to run Open Loop full time
and try to run pretty lean at low LOAD levels (no cats to worry about right
now).

I'm just curious what others have found to be good AFR for highway cruise
and around town.  I plugged in a program last night that commands about
AFR=15.5 at these conditions.  Seems to run fairly smooth down the highway.

My combination is a stock bottom end, AFR-165 heads, cam is really just a
high lift version of the stocker, nothing really wild.

Thanks,

Dan Nicoson


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