# Fuel enrichment module



## johnnyGO (Feb 23, 2009)

So yesturday I was going to make me one of the Vintage Watercooleds mudules :








I went down to radio shack with the parts list and they didint have s#*t, well atleast not the stuff I needed. So I was wondering whats a good place to pick up electronic parts?


----------



## johnnyGO (Feb 23, 2009)

Isint there a couple guys here that have made them "Any" help would be great.


----------



## antichristonwheels (Jun 14, 2001)

*Re: Fuel enrichment module (johnnyGO)*

that circuit is way overkill do some searching...


----------



## johnnyGO (Feb 23, 2009)

I have the parts list:
Component
Value
Comments

Var. Resistor
0-100 K
adjusts RPM set point

R1
120 K +/- 5%
Sets max. RPM

R2
10 K +/- 1%
Sets reference for voltage comparator

R3
20 K +/- 5%
Filters input from coil

R4
10 K +/- 5%
Drops voltage of input from coil

R5
1.1 K +/- 1%
Sets enrichment value

R6
510 +/- 5%
Drops voltage for LED indicators

C1
22000 pF +/- 10%
Timing Capacitor

C2
15 uF +/- 20%
Controls ripple in output voltage

C3
33000 pF +/- 10%
Filters input from coil

D1
1N4001
Prevents reverse current flow though LED indicators

D2
5mm red LED
Indicate status of device

F-V converter
LM2907N-8
RPM switch

Relay
SPDT
Turns enrichment on

Case
1.12" x 2.5" x 3.5"


PCB
2.79" x 1.81"


Cable
7 conductors, 5 ft


---------
I can find the 120k, 10k, ect... but there all above +/- 5 , and Im not sure what the issues will be if the tolerances are not the same as noted.


----------



## wclark (Mar 28, 2001)

*Re: Fuel enrichment module (johnnyGO)*

digikey.com
mouser.com is also good but they dont carry the lm2917n, only a high priced substitute part.


----------



## ziddey (Apr 16, 2006)

*Re: Fuel enrichment module (johnnyGO)*

part on the left is so it won't overenrich at suboptimal rpm's?
since it's a physical switch that you can feel as it engages, why not just go as wide as possible without triggering the button until revs get high enough


----------



## wclark (Mar 28, 2001)

*Re: (johnnyGO)*

The LM2907N-8 is not a good choice for the VW. The problem is it is set to trigger on transitions across ground and the VW coil signal is very noisy for about a volt either side of ground making the RPM (freq) inaccurate and irregular. The 14 pin version of the chip permits setting the trigger point anywhere so you can avoid that problem. 
Here is how I used the 14 pin version:








The IC and associated circuit on the left is a shift light - an easy add since you already have the tach, power and ground coming into the module...and a nice reuse of that otherwise stupid upshift light smack in the middle of the A2 instrument cluster. The upshift relay is removed. Not mentioned in the schematic...I also swapped out the yellow upshift LED for a high intensity T1 white LED which is much more attention getting.
The spelled out color on each in/out is just the wire color I used so dont look for them in your car. The abbreviated wire color is what is found in the CIS-E Golf. 


_Modified by wclark at 7:29 AM 6-16-2009_


----------



## iZOTOPE (Jul 2, 2006)

*Re: (wclark)*

well if the coil signal is noisy and sure it is







you could plug the wire to the pin 7 from the ignition module, i've wired my tachometer to that pin and works like a charm, before that i've tried to connect it to negative pin from coil and was bouncy and erratic.


----------

