Ferrari Mailing List: Re: NGK Powerdex AFX Wideband O2 Air Fuel Ratio Monitor

[Todd Walke (racertod]

        I've got two VWs, one with K-Lamba and one with KE.

        On K-Lamba there is a round frequency valve on the side of the 
fuel dist.  It has fuel and electrical connections and buzzes like a bee 
when operating.

        You can use a dwell meter to measure the duty cycle.  Set the 
dwell meter to the 4-cylinder scale.  On a dwell meter 90deg of dwell is 
equal to 100% duty cycle so you have to multiply the degrees of dwell 
indicated by .9 to convert to percent duty cycle.

        On KE the squarish "sensor" on the side of the fuel dist is called 
the DPR (differential pressure regulator).  It has an electrical connector 
only.  The CPU sends an electrical signal the DPR (in milliamps) to alter 
the fuel mixture as required.  High milliamps is richer, lower is 
leaner.  On my VWs there is a testing harness that goes inline with the 
electrical connector and allows you to measure the current draw while the 
engine is running.

        On my GTI the normal DPR signal fluctuates between 9-11 milliamps 
with the CPU making constant adjustments based on O2 sensor 
information.  When the full throttle switch is closed AND rpms are above 
4000, the DPR signal rises to a constant 14 milliamps (i.e. full rich) and 
ignores O2 readings.

        I have the "Bosch Fuel Injection and Engine Management" book and 
it is full of both theory and practical diagnosing information.  Alos 
includes information on modifying CIS systems for racing.  A must-have is 
you're diagnosing or modifying a CIS-style system.


Todd
Seattle,WA
'86 GTI, Red of course. (exciting racey car)  264,000 miles
'87 Golf, Polar Silver. (boring work car)     610,000 miles <- Yeah, baby!
http://www.pureluckdesign.com <-Ferrari & VW stuff