L-Jet cold start delete 2.0
07-19-2004, 06:14 PM
#1
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L-Jet cold start delete 2.0
A year ago, I deleted my cold start air bypass valve, and moved the cold start injector to the front of the plenum.
Stock parts:
click pic for thread: Honey, I Shrunk the Parasitic Vacuum Connections
Now I've completely removed the cold start system:
Temp II bypass wire harness:
Banjo plugged with stainless bolt and cap nut, reusing crush washers.
The wire harness plugs into the cold start injector plug, and between Temp Sensor II and the ECU. Inside the heat shrink tubing is a normally closed 12V reed relay, which, when triggered, forces the coolant temp sensor output through an additional 20K ohm resistor which fools the ECU into thinking the coolant temp is extremely cold.
The cold start thermo-switch is retained, so the bypass circuit is only used below 80 degrees or so, for a maximum of ~7 secs, while the starter is engaged.
All the connectors are from mid-80's Audis in the U-Pull yard. (The male connectors are from outside temp sensors in the bumper.)
~thread~start~
Stock parts:
click pic for thread: Honey, I Shrunk the Parasitic Vacuum Connections
Now I've completely removed the cold start system:
Temp II bypass wire harness:
Banjo plugged with stainless bolt and cap nut, reusing crush washers.
The wire harness plugs into the cold start injector plug, and between Temp Sensor II and the ECU. Inside the heat shrink tubing is a normally closed 12V reed relay, which, when triggered, forces the coolant temp sensor output through an additional 20K ohm resistor which fools the ECU into thinking the coolant temp is extremely cold.
The cold start thermo-switch is retained, so the bypass circuit is only used below 80 degrees or so, for a maximum of ~7 secs, while the starter is engaged.
All the connectors are from mid-80's Audis in the U-Pull yard. (The male connectors are from outside temp sensors in the bumper.)
~thread~start~
Last edited by PorKen; 07-21-2004 at 12:12 PM.
07-20-2004, 06:11 AM
#2
Burning Brakes
Join Date: Aug 2001
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PorKen,
The question is...
Will it start when it's cold? (I mean like -20F cold). I know that a digital system can easily up the pulsewidth so the 'fifth injector' is not really needed, but have you found enough play in L-Jet by hacking the Temp II input to gain that pulsewidth? Just curious.
BTW- Look for the Volvos in the U-Pull. They're a treasure trove of electronic usefulness.
Greg
The question is...
Will it start when it's cold? (I mean like -20F cold). I know that a digital system can easily up the pulsewidth so the 'fifth injector' is not really needed, but have you found enough play in L-Jet by hacking the Temp II input to gain that pulsewidth? Just curious.
BTW- Look for the Volvos in the U-Pull. They're a treasure trove of electronic usefulness.
Greg
07-20-2004, 02:20 PM
#3
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2V4V,
It should, although it might take more revolutions to build up enough gas.
I could also use a larger resistor to mimic an open circuit; when the Temp II is unplugged, the injectors dump gas like crazy.
Temp II values from WSM:
-10C/14F 7...12 k-ohms
+20C/68F 2...3 k-ohms
+80C/176 250...400 ohms
I haven't checked out Volvos, I will. I like the Audi connectors because they have a push-to-release, versus the wire band, which tends to break old connectors.
It should, although it might take more revolutions to build up enough gas.
I could also use a larger resistor to mimic an open circuit; when the Temp II is unplugged, the injectors dump gas like crazy.
Temp II values from WSM:
-10C/14F 7...12 k-ohms
+20C/68F 2...3 k-ohms
+80C/176 250...400 ohms
I haven't checked out Volvos, I will. I like the Audi connectors because they have a push-to-release, versus the wire band, which tends to break old connectors.
07-21-2004, 01:28 PM
#4
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One side benefit, the occasional hard start (with smoke puff) on hot start seems to be gone.
...
I'm going to add a variable resistor, so I can tune the temp sensor running value...
*Update*
...
I'm going to add a variable resistor, so I can tune the temp sensor running value...
*Update*
Last edited by PorKen; 07-22-2004 at 02:45 PM.
