[DML] Re: PRV Performance - Set me straight please

["endotex23" <endotex23@xxxxxxxxx>]

--- In dmcnews@xxxxxxxxxxxxxxx, "Rick" <rdevaux@xxxx> wrote 
> 
> How does one go about tuning the K-Jet ECU for a Lambda less than 
> 1.0?  Greg, you mentioned that the Lambda controller could be 
> adjusted for both best performance and emmissions (with the flip of
a switch).  

Good choice. Those who tout open loop or carburation claim their cars
run great but they're going by the seat of their pants. If they drove
around with some metrology (a gas analyzer, wide band O2S, or even a
cheap A/F meter running in open loop) they'd soon see how poorly the
basic K Jet (or worse, a carb) meters fuel. And every time the mixture
deviates outside a narrow range they're losing performance. Not to
mention the pollution and wasted fuel. Such setups are anachronisims
of the automotive world best reserved for those unwilling or unable to
learn the very real benefits from not using them.

There are several ways to do what you want. You can shift the loop
hydraulically via control pressure or electronically through the
lambda controller. You can either dither the O2 signal or change the
internal controller setpoint. Or you can use something like the
Innovate LM-1 to drive the controller. You'll need a wide band O2
sensor, about $80. Even a narrow band heated O2S is a good upgrade for
a D, though not for performance reasons.

I can alter the lambda controller to do pretty much anything you like,
even electronically adjust mixture on the fly, but if you go that far
you'll need to know how not to abuse it. Depending on what mods you do
you'll likely also have to alter ING timing, both the curve and total
advance. Street cars always have a curve that brings in max advance
too late for performance and the B28 is no exception. At least it
usually uses full manifold source for vacuum advance, ported advance
is bad news.

I suggest you contact me off list when you know exactly what mods
you'll be doing and we'll go from there. Frankly, if you're going to
do serious power mods I'd suggest abandoning the K Jet and going with
EFI. Something like the MegasSquirt would dod the job.


John Hervey wrote:

>Activate the full throttle switch to enrich the system evenly. This
activates the FV to full operation and lowers the pressure on the
lower chamber of the fuel distributor to flow more fuel to the
injectors.<

The problem with that approach is it's not closed loop. It simply
outputs a fixed duty cycle and involves no feedback.  Btw, doing what
you suggest does not set the FV to "full" operation, it sets it to a
midpoint fixed dwell of 55 degrees. There are other inputs on the
lambda controller that can set both a nearly 100% or nearly 0% duty
cycle. These inputs are not used on the Deloeran but are there and can
be manipulated in many ways. Pulling them low still results in a fixed
duty cycle but they can be PWM for feedback purposes. 

>The control pressure can also be lowered to achieve more fuel flow,
but this would be more tricky.<

True but it's not all that tricky. I've done it that way but it's not
the most elegant approach because it involves adding another control
loop, same as employing the unused lambda inputs mentioned above. Plus
there is unacceptable hysterisis doing it by control pressure. I've
found doing it through the lambda controller is much easier and
retains normal operation of the O2S loop, only shifted to a richer
setpoint.








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