Junkyard TBI tuning ????

[MikeGyver]

The problem is:
O2 sensors, even the best of the best in the best situations and best etc are still more than 4% off
The colder they are, the more off they are going to be
O2 sensors can't function in high flow environments, like ~3k rpm + - ie, they can't react fast enough
O2 sensors can't distinguish between a little and a lot lean/rich - they only know one or the other

So the colder they are, the more error they have, and the slower they react to changes. Meaning, by the time a cold o2 sensor realizes your lean, you've already burned up your motor.

So if it's in the proper place, or using a heated one, you lessen the risks and increase their efficiency.

Cycling oxygen sensors are a requirement for closed loop operation. There is generally another parameter in the tuning establishing closed loop countdown vs engine temp. (longer warmup countdown when engine is cold)
Oxygen sensors do not cycle until they are warmed up.
Oxygen sensors can cycle several times per second.
Oxygen sensors will work at any RPM, once long term fuel trims are established, accurate fueling correction is realtime and essentially seamless. Although at high rpm's (more accurately high manifold pressure), fueling switches to open loop power enrichment mode and no longer takes active feedback from the oxygen sensors.
Oxygen sensors are not used in situations where your motor can 'burn up', only in low power closed loop operation. Motors can safely run a very lean AFR while cruising, although due to increased combustion temperatures this creates very high levels of nitrogen oxides (NOx) and is not permitted.

 

[ProStreetZ28]

First question is which ECM are you running? Single wire O2 sensors will not work in the collectors (if long tube headers). What fuel pressure ar e you running? If you have it in the collector I would swap to a 3 or 4 wire O2, it's an easy swap. I don't like the heater running while the engine is not, so I use a relay for the heater that gets it's signal from the fuel pump wire (if the fuel pump is controled by the ECM). When I was burning the chips for my 454 after the cam swap I used TunerCat software and I have my own chip burner. If you are going to rasie the fuel pressure, there is a constant that needs to be changed to reflect the change in the size fo the fuel injectors becasue of the added fuel pressure, also it should reflect the size fo your engine (actually cylinder volume). If it's just running a little rich it shodln't be much work at all to clean it up. How are you running the spark timing? I've done a few of these swaps and seen a few where the guys ran them with a standard dist sending a signal to the ECm but no spark control. I do them a little different, I use a magnetic pickup dist and wire the pickup through a GM TBI module. It takes a little work getting them to sync depending on what dist you use, but I like having spark control. If you're going to swap to a 3-4 wire O2 I can tell you where to buy all fo the connectors and terminals to make a plug in adapter harness, I used to build harnesses for an EFI retailer, but I don't have any of my materials left anymore.