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On Mon, 2005-11-21 at 15:25, Constantino Tobio wrote: > Jim Adney wrote: > > >>Why the voltage regulator would cause a rich running solution is a mystery to > >>me, though. > >> > >> > > > >The system voltage also supplies the FI brain. I don't know exactly why it > >makes it richer, but it does. > > > > > My guess is this: You don't need to guess. http://classicvw.org/gallery/main.php?g2_view=core.ShowItem&g2_itemId=3448 http://classicvw.org/gallery/main.php?g2_view=core.ShowItem&g2_itemId=2609 > > The head temp sensor sends to the brain a voltage value based on the > resistance of the sensor. At a specific given temp, the sensor's > resistance is constant (at 60 deg, the resistance is x, and 90, the > resistance is y) so if the sensor is operating on a 14v system, the > voltage signal being sent by the sensor to the brain is known and > predictable. Now, what happens if you lower the voltage significantly? > The voltage coming out of the sensor has shifted downward, also, sending > a signal to the brain that the sensor is operating at a voltage for a > different expected temp. We know the head sensor is the main input on > whether cold enrichment is necessary. I believe the resistance of the > head temp sensor is highest the colder it is. If it's getting less > voltage as input, it will proportionately supply less voltage signal to > the brain, tricking the brain into thinking it's colder. If the brain > THINKS its colder than it is, then that would explain how lower than > expected voltage would make a car run richer than necessary. By this > argument, too high a voltage would make a car run leaner, but in my > experience with most cars voltage regulators tend to fail on the "too > low voltage" side. > > I'd go out on a limb and say 95% of the cause of "low voltage running > rich" is this head sensor thing. > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- Russ Wolfe '71 FB AT '66 FB MT '64 T34 (not running) '65 T1 (not running) '05 KIA Sorento SUV russw@classicvw.org http://www.classicvw.org