Getting ready for rusefi on my '03 - questions and experiences
 

Some of you may have read about the new open source EFI- rusEfi
My '03 which is completely stock from an engine standpoint (so far) will be serving as a test-mule. In preparation I have installed a Wideband (MTX) and an external MAP sensor. I'm stil waiting for a connector and PC board to hook it up.

Two questions:
- I need to fake out the stock ECU, that I'm still running for now, into thinking that it still has a stock narrow-band O2 sensor. Setting the MTX to emulate the narrowband signal is easy and works, but I still need to add a resistor for the heater circuit. How many Ohms do I need?
- Stock ECU runs pig-rich in full throttle: around 12AFR at lower rpms, and it goes down to below 10 at higher rpms. Did anybody else experience something like that? Or is my MAF reading wrong?

Tuning VVT and controlling the alternator will probably be the most interesting tasks...

Why do you need a resistor for the heater circuit? My AEM UEGO fed the stock ecu a signal it was perfectly happy with just the narrow band simulation.

The richness is a know thing on NAs, duno if the NBs are tuned any better, but my 1.6 would run 14.7 until it hit 4k, then switch into open loop, jump to 11.8 and taper to 10.8 at red line.

The VVT and alt should be fun. You shhhhhould be able to bolt up an internally regulated alternator off an NA8 I beleive?

O2 sensor:
The ECU checks if the heater on the O2 sensor works. It does so by measuring the current through the heater circuit. With that circuit open we get a CEL. So in order for the stock ECU to be happy we need to waste a few watts....

AFRs:
I was just surprised to see WOT AFRs below 10. That's just horrible. I'll actually be doing the environment a favor by putting in a rusefi!

Future fun:
I can also build an analog alternator control circuit in the proto area- these circuits are well proven. But where would be the fun in that :)

Right, OBDII and multi wire O2 forgot about that.... Measure the resistance of the heater in the stock O2 sensor? Or just ignore the light :P

Actually, I bet the service manual would tell you the expected resistance of the O2 heater circuit.

Yeah, just measure what you have in your old stock sensor. Should be in the neighbourhood of 5-10 ohms. The heater is usually PTC so resistance will increase a bit when it warms up. I guess it's possible for an ECU to tell if it's warmed up from the current dropping a bit and complain if it doesn't behave as expected, but I have no idea if the NB ECU does that (sounds like something just German cars would do). If you don't have a resistor available that will convince the ECU, you can always hook up the stock sensor just to the heater.