Odd readings from NB02.

[Minami Kotaro]

At idle, the NB02 reads about .62 volts. As the engine gains RPM, the voltage reading drops, indicating a leanout, even though the engine is so rich huge clouds of raw gass are being emitted from the pipes.

On the MSFAQ, it says that extremely rich conditions can confuse a narrow-band 02 sensor into reading lean. Accel enrich is disabled and I've leaned out the VE table quite a bit (now I've only got small clouds of gas vapor) but it still reads lean.

I've got a three-wire heated unit, so that shouldn't be a problem, nor is there any way air is leaking into the header upstream of the 02 sensor. The only thing I can come up with is the aforementioned mega-rich condition or a faulty 02 sensor.

Any ideas?

[donjr5]

What motor? TBI or MPI? What kind of injectors? What settings/constants?

[Minami Kotaro]

It's a 1915cc air-cooled VW engine, port injected, four high-impedence 32 lb/hr injectors. Ignition is via Bosch 009 with Pertronix Ignitor II and 45,000 volt coil.

My req fuel is 9.5 (what Megatune calculated) and I'm using two squirts, alternating. Barometric correction is off, EGO correction is off.

I'm running 35 psi of static fuel pressure, if that means anything.

Anything else I'll have to pull off the laptop tomorrow.

The engine starts and idles fine.

[Bernard Fife]

Minami Kotaro,

I could be that you are seeing a rich miss-fire. Certainly if you are seeing huge clouds of raw gas, something isn't right.

What is your VE like at idle. What is the VE when it gets extemely rich? A datalog would be very nice to be able to have a look at, if you have one available.

Lance.

[HotStreetVw]

What are you using for your warmup enrichments and cranking pulsewidths? I have a motor that is very similar to yours, and a base setting for these values would help me alot.

At idle, the NB02 reads about .62 volts. As the engine gains RPM, the voltage reading drops, indicating a leanout, even though the engine is so rich huge clouds of raw gass are being emitted from the pipes.

On the MSFAQ, it says that extremely rich conditions can confuse a narrow-band 02 sensor into reading lean. Accel enrich is disabled and I've leaned out the VE table quite a bit (now I've only got small clouds of gas vapor) but it still reads lean.

I've got a three-wire heated unit, so that shouldn't be a problem, nor is there any way air is leaking into the header upstream of the 02 sensor. The only thing I can come up with is the aforementioned mega-rich condition or a faulty 02 sensor.

Any ideas?

[Minami Kotaro]

Darndest thing, but everything worked fine yesterday.

Dad and I were able to tune it and we got it running rather nicely in the lower speeds. It's still rich but that's always how this engine was. Going to try tuning with Megatweak next.