You actually found most of the right ones. You should be able to find knock retard and fuel cell # with a little more hunting. The fuel trims are labelled as B1B2 (bank 1 bank 2) since there are two sets of both long term and short term trims. The Kewl one suggests just starting with the long term trim - I will pick Bank 1 just for fun. If you have any trouble, email me and when I'm back with the right computer, I'll check it out for you.

 

I would use both LTRIM bank 1 and 2, just for comparison. Also, the fuel trim cell is under fuel system with the LTRIMS, and the knock and spark timing are under the IGNITION section.

I use the DOS version, as I could never get the windows version to work well. I also hear the DOS version is faster (ie more data per sec...)

Dave

 

The new Windows version, 1.11 available for download on Autotap's website, seems to be working fairly well for me, admittedly on a newer Dell laptop (PIII 800mhz) running Windows 2000 Professional. It may be that this version cures the earlier problems. My problem is that I couldn't get the DOS version to work right - the scaling was off on some of the parameters. I'm going to try it again - the log-on might have been screwed up.

 

I go into the theory in depth on my site but in general:

The engine parameters are controled as two banks.

B1 drivers side B2 passenger side.

The engine has basically two fundemental modes of operation:

Non WOT (true closed loop control)
and
WOT (basically open loop mode with no feedback)

Since the engine must adapt to environmentally and fuel efficient standards during normal driving, the PCM must have a way to control the air fuel ratio. When the engine is sucking in air, the MAF meters it and tells the PCM so it can determine load and fire the injectors to meet the airflow needs. This happens in real time. However the PCM must tune to a scientically "perfect" air fuel ratio to meet epa and fuel consumption needs, and that ratio is 14.7:1 air to fuel ratio. Thus Fuel trims were developed for feedback control after the combustion cycle has taken place. There are two fuel trim registers. Short term and long term. Short term changes all the time to quickly adapt to changes. Long term is the primary register which adds its values to the base pulse width equation. The base PW equation is the equaiton in the PCM which fires the injectors. A digital signal is sent to the injectors to fire them. Changes in pulse width determine how quickly or slowly they will fire. When the MAF tell the PCM the air flow, the PCM also adds the fuel trim registers to the MAF input to claculate the overall injector pulse width signal. Thus we have complete closed loop control to achieve 14.7:1 air fuel ratio during non WOT. THink of it constantly increasing and decreasing the fuel to get as close as possible to 14.7:1 during long term operation. Since the short term trims adjust for variances in metering, if they are consistantly at a ceratin rate, long term fuel trims are updated and the short terms are reset to 0.

During WOT operation, the fuel trims are frozen. This is because the PCM isnt concerned about fuel economy etc, and goes into power enrichment mode. This mode lowers the air fuel ratio (richens it) to about 13:1 due to the nature of combustion engines a enrichened mixture is required for power.

The PCM takes a "snap shot" so to speak of where it has been operatiing during non WOT operation, and tries to meter fuel flow based on that in the timing and fuel tables. It relies virtually 100% however on the MAF to meter the load and deliver fuel in during WOT operation. Because theres no feedback during this mode, air fuel ratios are often off, especailly with mods.

We first want to dial in non WOT operation by analyzing the fuel trims in specic fuel cells. Once we dial those in, we then look at WOT operation to dial in any WOT air fuel needs.

Remember that BASE is the fundemental frequency on the MAFT, and it is used throughout the Frequency range. WOT is only used for fine tuning the signal above 8 Kilohertz.

When we tune for WOT, we only look at the O2 sensors. They are not used during WOT, but are what we have to look at to know how the air fuel ratio looks during that time.

 

"LTerm Fuel Trim B1" is listed under "Fuel System", and "Ignition Timing Adv" and "Knock Retard" are under "Ignition".

You have to actually be connected to your car to get all of these to show up.

Dave