[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]
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: 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 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~