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

[Martin Stark (MStark]

Good info, thxn Jeff.  To answer your question concerning duty cycle 
calculation, using an oscilloscope one could measure the pulse width and 
establish a ratio between pulse and no pulse (on/off time * 100) = duty 
cycle. I still am leaning towards installing a pair of NGK AFX A/F 
monitors.  Btw, Jim Conforti says he likes them a lot and he's about the 
most savvy guy I know.

Jeff Greenfield wrote:

> Here are couple of links I found that describe KE in more detail.
>
>
>
> http://www.aicautosite.com/garage/encyclop/ency07c.asp
>
>
>
> http://rb-k.bosch.de/resources/literatur/leseproben/u213e.pdf
>
>
>
> I am not sure if KE has the frequency valve or not. KE will have a
> rectangular shaped sensor which is either white or black on the side of the
> fuel distributor, this is not the same as the frequency valve.
>
>
>
> The frequency valve is a small cylindrical device, usually mounted in the
> vicinity of the fuel distributor, it will be round, with a fuel line going
> in one end and out the other. There will be an electrical connector with two
> pins in it as well.
>
>
>
> On the KE system, the mixture is set by measuring the current at the sensor.
> One of the links above describes how to do this.
>
>
>
> Yes, on the K-lambda system you can set the mixture by measuring the duty
> cycle at the frequency valve. You do this by back-probing the frequency
> valve with the oxygen sensor disconnected with the engine at idling at
> operating temperature. I don't see any reason you couldn't do it with a
> scope instead of a meter that measures duty cycle. If your scope doesn't
> read the duty cycle directly (some newer ones do), then you may have to do
> the calculation to figure out what the duty cycle is. (I don't remember how
> to calculate it without digging out some old text books).
>
>
>
> You may want to consider investing in this book before you get in too deep .
>
>
>
> http://www.bentleypublishers.com/product.htm?code=GFIB
> <http://www.bentleypublishers.com/product.htm?code=GFIB&subject=25>
> &subject=25
>
>
>
>
>
> Jeff
>
>
>
>
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>
>
>
>
> -----Original Message-----
> From: Martin Stark [mailto:MStark [at] Copper.net] 
> Sent: Friday, April 06, 2007 2:21 PM
> To: Jeff Greenfield
> Cc: 'The FerrariList'
> Subject: Re: [Ferrari] NGK Powerdex AFX Wideband O2 Air Fuel Ratio Monitor
>
>
>
> Yes, it is a KE system, and the screw adjustment affects the mixture at idle
> and throughout the power range. Aren't the frequency valves the black
> objects mounted on the sides of the fuel distributors, where are the
> additional sensors located on the fuel distributors to which you refer?
>
> Just so that I fully understand what you are saying: The procedure would be
> to set the screw adjustments on both fuel distributors so that the duty
> cycle of both frequency valves is approx 55% as a starting point?  I don't
> have a Fluke 88, can this be done with a Tektronix scope - connect to the
> frequency valve cable and measure the width of the square wave pulse or some
> such?
>
> Jeff Greenfield wrote:
>
>
>
> 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
> <http://www.ngksparkplugs.com/products/air-fuel/index.asp?nav=19000&country=
>  
>
> > &country=
> >    
>    
>
> U
>  
>
> S
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