ECO Mod: Howto reduce level of enrichment when cold

[mohammad]

Doesn't this mod prevent some of the engine diagnostics/functionality from working? in particular i believe we have a trouble code that is for a stuck open thermostat. I think a mod like this may prevent that diagnostic code from appearing.

[mohammad]

Wonder how much fuel this actually saves. My car goes into closed loop literally in less than a minute after cold start and well before the coolant gets anywhere near up to temp. The o2 sensors warm up very fast and when in closed loop you are running at stoich. So you are only saving a small portion of fuel for a small portion of time.

how are you able to tell that the engine is operating in a closed loop? idle rpm? scan gauge?

[foama]

UPDATE!

The mod as described in the very first post has been in this car for years and works well. After some thought, I found a simple way of greatly improving the effects of this mod. That method has meanwhile been thoroughly tested too. It greatly reduces the enrichment when cold, much more than the cautious Mitsubishi recall years ago did. The chances of getting chapped cylinders, worn piston skirts and piston slap from too much wear due to injected fuel washing off the oil is now very much reduced. It also saves fuel during warm-up. Another plus: If you start the cold engine and turn it off after some seconds and try to restart it, it will not become flooded any more.

How does it work? How is it done?

With regard to post 1 of this thread, the series resistor was eliminated and replaced by a thermoswitch that opens above 50°C. Simply said, the thermoswitch replaces the resistor. The switch is a KSD 301 B 50°C, and it is mounted with thermal contact to the cylinder head. Mounting it together with the second thermostat is probably the easy way to do it. Anybody familiar with electronics will know what a KSD 301 B 50°C is, and where to get it for a few cents.
What happens electrically? In the cold vehicle, the second thermostat is simply parallel to the first OEM one. The ECU gets told the engine is roughly 20°C warmer than it is. Therefore the enrichment is greatly reduced. (With the original mod according to post 1 there was a lot less temperature difference.) During warm-up when the engine reaches around 50°C, the closed contact of the Thermoswitch opens, and the second thermostat is no longer parallel to the first. The enrichment and everything else that is regulated according to temperature, is exactly as it was without any modification. When the engine cools off to about 35°C or so, the thermoswitch closes again.

I have not added pictures to this update, and trust that what was said is simple and logical, quite easy to understand for anyone familiar with mechanics and/or electronics.