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[SPAM] DIY Fuel Enrichment Device



The text below describes a do it yourself fuel enrichment device for
CIS-E.  I am not the author and have not attempted to build one yet.  
 
PLEASE NOTE THAT THIS IS ONLY AN INTRODUCTION AND DESCRIPTION!  The
complete text, parts list, sources and schematic are too large to post
to the list since it exceeds 50k (~100k).
 
This one seems a little more sophisticated than the simple version with
one resistor and no ability to change the point, via RPM, when the
enrichment kicks in.
 
As stated above, I have not included the schematic etc; since it exceeds
the list limit and contains an attachment.  I will send it along to
anyone that would like a copy however; it would be best if someone can
host it.  That way we can all review the complete package and
comment/discuss on the list.
 
Rick K.
 
 
 
 
 

16v Fuel Enrichment Device 

 

INTRODUCTION 


This is a fuel enrichment device designed to work with 16-valve
Volkswagen engines using the CIS-E (Bosch KE-Jetronic) fuel system, for
example, the Scirocco 16V. I've heard of using a similar device on
8-valve engines which use the CIS-E system, but I don't have one to
test, so yer on your own. This device will NOT work with standard CIS
(non -E) systems, Digifant systems, or Motronic systems. If you don't
know which system your engine uses, stop reading now, because you
probably aren't qualified to be mucking with your engine management
system. 

ACKNOWLEDGEMENTS 


Thanks to the following for their assistance on this project: 

Chris Ng, who sent me plans for his enrichment device, which I based
mine on. 
Craig Castle, who also sent me plans for a similar device. 
European Car, who published a good article on the Techtonics Fuel
Enrichment module in the November 1997 issue. 

HOW IT WORKS 


The CIS-E system monitors combustion stoichiometry, intake air rate,
engine temperature, and several other factors to determine what fuel:air
ratio to run the engine at. It controls the fuel:air ratio with a
differential pressure regulator on the fuel line. The more current
supplied to the DPR, the higher fuel pressure that is supplied to the
fuel injection system. 

It has been observed that the fuel:air ratio in the 16V engine using the
CIS-E system is too lean at high RPMs. In order to correct this
situation, earlier fuel enrichment systems used a relay to add
resistance to the engine temperature sensor when the engine is running
at full throttle. This fools the CIS-E control system into thinking the
engine is in a cold operating situation, and increases the fuel flow.
The problem with this type of enrichment device is that it increases
fuel flow at all RPMs. The engine does not need enrichment at low RPMs,
in fact it makes the mixture too rich, causing hesitation. One solution
to this is to add a manual switch to engage the system only as desired. 

I decided to improve on this design by adding adjustable RPM sensing
ability. This is done by using a National Semiconductors LM2907-8
frequency to voltage converter. This is a versatile chip which is
commonly used in digital dwell meters, tachometers, capacitance
measurement devices, and ABS systems. I also made the boost level
adjustable. I could have used a rotary variable resistor for this, but I
wanted an accurate and precise method to select a specific resistance
value. I did this by creating a resistor network connected to a DIP
switch. By varying the settings on the DIP switch, I can select a
specific resistance. Using a 4-position DIP switch gives me 16 choices.
I chose a 6-position dip switch to allow some room to expand if
necessary. Adding each additional resistor doubles the number of choices
available. 
 
END OF PARTIAL TEXT.