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Fuel enrichment - was: (RE: Semi O/T: Got a pickup with 2.016V,do I need Motronic?)



Toby, I would like to see a schematic if available.
In the mean time, here is a site to the simple version.

http://www.geocities.com/MotorCity/Lot/8341/Tech/CIS-E.html

Rick Kellner.

Original Message:
-----------------
From: David Utley mr.utility@highstream.net
Date: Fri, 12 Mar 2004 10:19:47 -0500
To: treed2@wsu.edu, vwdaun@yahoo.com, scirocco-l@scirocco.org
Subject: Re: Fuel enrichment - was: (RE: Semi O/T: Got a pickup with
2.016V, do I need Motronic?)


Although electronics is not my strong suit, I am interested, especially if
we 
can figure out a way to build it where it would indeed be weather tight,
and 
perhaps a better, long-lasting design?  Toby, what type of design would be
mo' 
better than the Autotech one?  I am interested if and when you have the 
chance/inclination to design something...

TIA,
  David Utley

Quoting "T. Reed" <treed2@wsu.edu>:

> > > > No, stay away from the fuel enrichment modules.  Almost
> > > > everyone I've ever heard of having one eventually
> > > removes
> > > > it because it ends up causing running issues, either
> > > with
> > > > the 1.8 or 2.0.
> >
> >  Daun, any recommendations
> > > for an expose' on
> > > those?  I shall have to look at that more carefully...
> >
> > No expose, just an observed thread that pops up on the list
> > every now and then, and at least three friends off the top
> > of my head have had issues.
> 
> I too have had issues with my homebrew TT-style (relay+resistor) module,
> as well as my brother with his..
> 
> In both cases, replacing the relay fixed the problem. A dissection
> revealed that water had gotten inside and corroded the relay terminals,
> adding a significant amount of resistance.
> 
> A better solution would be to use a watertight relay, or design a
> solid-state FET circuit to do the switching (without a relay).
> 
> 
> On another note..
> 
> I have an Autotech module (due for installation Real Soon Now) and I took
> it apart to see what's inside. I found an LM311 (voltage comparator)
> driving a small relay, a rotary switch and a bank of resistors.
> 
> It appears to be bringing in the tach signal, running it through a
> half-wave rectifier to produce a dc signal, then comparing that to a
> reference voltage (corresponding to ~3000 rpm) and when the comparator
> output turns on, activating a relay to switch one of the resistors
> (the one selected by the rotary switch) in series with the DPR to change
> the current. A lower DPR current corresponds to a richer mixture, so this
> makes sense. Oh yeah, and there is also a BJT that prevents that device
> from activating unless the full throttle switch is closed.
> 
> I might be able to post pictures and schematics at a later time, but
> unless you want to build it on a wire-wrap board or etch a PCB, it's
> probably too "busy" of a circuit to build your own (lots of components).
> 
> 
> To be honest, I was expecting better (from autotech?! i know, i know..)
> Granted, you're getting a lot more than the TT module (it's adjustable,
> it doesn't activate below 3000rpm and cause bogging, it modifies dpr
> current directly which doesn't suffer from the same problem as tricking
> the ecu with the coolant temp sensor.. that the enrichment lasts only as
> long as it takes the o2 to detect and undo it), but the circuit they
> used is primitive. I thought maybe they would use a current amplifier to
> do a linear enrichment based on rpm, or something along those lines.
> 
> 
> Since the module housing has no grommets or seal sealing whatsoever, I
> suspect that the reports of failure with the autotech module are due to
> the same thing as the others.. water getting inside the relay.
> 
> -Toby
> 



David Utley
-----------
Cable Volkswagen
405-470-3129
1-800-522-6793

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