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

[Jeff Greenfield (coyote]

First of all, is this a KE or K-lambda system we are talking about?

KE systems will have an additional sensor mounted to the side of the fuel
distributor. K and K-lambda does not have this sensor. 

KE is a bit of a different animal ... I think that most of the principles
apply to both systems but am not 100% sure as I am as familiar with KE.

I could be wrong, but I believe that the mixture adjustment at the set screw
on the k and K-lambda jetronic controls the mixture at idle AND throughout
the range. 

At WOT, the throttle switch closes, which bypasses the O2 sensor, and opens
the frequency valve to a pre-determined point.

So, in a nutshell, there is no way you can set the mixture on a CIS system
at WOT (outside of the design parameters that is), and still have the
mixture correct elsewhere throughout the range.

Sure you could set it way rich, and leave the O2 sensors disconnected, and
you 'might' get a little more performance at WOT, but the idle will be
awful, you'll dilute the oil with fuel, wash down the cylinder walls with
fuel causing premature wear to the rings and cylinder walls.

One other thought, if you are dealing with a 12 cylinder with two
independent systems, the first thing I would do is a full series of fuel
pressure checks on both banks. CIS mixture is largely controlled by fuel
pressure. There are several things in the system that control pressure, so
you should be sure that the pressures are the same (or reasonably close) on
both banks before going any further.

A failing warm up regulator, a misadjusted or shimmed fuel distributor,
among other things could wreck havoc with the system. This along with a
vacuum leak somewhere could literally make it impossible to get both banks
to be equal not only at WOT, but anywhere throughout the range.

After years of working on cars with CIS I swore I would never own a car with
CIS and then what do I do ... I go out and buy a 308QV :-)

Jeff

-----Original Message-----
From: Martin Stark [mailto:MStark [at] Copper.net] 
Sent: Friday, April 06, 2007 1:15 PM
To: Jeff Greenfield
Cc: 'The FerrariList'
Subject: Re: [Ferrari] NGK Powerdex AFX Wideband O2 Air Fuel Ratio Monitor

I really want to adjust A/F at WOT.  Also, doesn't a KE Jetronic system 
become purely dependent on the mechanical screw adjustment at WOT?

Jeff Greenfield wrote:

>One more thing I forgot too mention ...
>
>If all you are doing is tweaking the fuel mixture on the stock CIS system,
>you can read the duty cycle at the pulse (or sometimes called frequency)
>valve with a meter that has this capability (fluke 88, for one). Simply set
>the mixture such that the duty cycle is the same on both banks at idle and
>you are done.
>
>Typically, the duty cycle should be around 55% or so. My QV won't run well
>there, and I need to set it around 65-70%.
>
>There are other shade tree methods to do this too, but I won't admit any
>knowledge of them :-)
>
>Jeff
> 
>
>-----Original Message-----
>From: Jeff Greenfield [mailto:coyote [at] acme-ltd.com] 
>Sent: Friday, April 06, 2007 12:53 PM
>To: 'Martin Stark'
>Cc: 'The FerrariList'
>Subject: RE: [Ferrari] NGK Powerdex AFX Wideband O2 Air Fuel Ratio Monitor
>
>No experience with the NGK unit.
>
>I have used some of the stuff from these guys (LM-1 and related stuff) with
>good results. In the last few years they've come out with many new
products.
>
>http://www.innovatemotorsports.com/products.php
>
>Whatever you use, you want to make sure that the controller has a
>'conventional' output. IOW, you install the wide band sensor in the
existing
>holes in your exhaust replacing the conventional o2 sensor. You then run
the
>output from the controller to the cars ecu.
>
>However, when you are tuning the engine, you want to do it in open loop
with
>the cars ecu disconnected from the oxygen sensor(s) otherwise you will not
>get accurate results.
>
>Once you get the AFR where you want it (which should be close to 14:1
during
>part throttle cruise, and about 12.5:1 during WOT) you then reconnect the
>oxygen sensor so that the ecu can help fine tune it within the range.
>
>If you are too far out of range, the system won't be able to compensate.
>There is no reason to leave the ecu disconnected from the sensors, this
will
>only hurt performance and fuel economy. 
>
>Regardless of what mods have been done, tuning for performance, etc., and
>internal combustion engine will still run best and make the most power at
>close to an ideal AFR which is 14:1, which is exactly what the oxygen
sensor
>is designed to do.
>
>Jeff
>
>
>
>-----Original Message-----
>From: Martin Stark [mailto:MStark [at] Copper.net] 
>Sent: Friday, April 06, 2007 12:35 PM
>To: Jeff Greenfield
>Cc: The FerrariList
>Subject: [Ferrari] NGK Powerdex AFX Wideband O2 Air Fuel Ratio Monitor
>
>I've been making small adjustments to my TR's fuel distributors' mixture 
>settings and then reading the spark plugs to see if the banks are 
>running at about the same A/F ratio.  In an effort the make the process 
>more quantitative, I'm considering buying a pair of the NGK A/F ratio 
>monitors and wonder if anyone on the list has had experience with them.
>http://www.ngksparkplugs.com/products/air-fuel/index.asp?nav=19000&country=
U
>S
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