[JLMounce]

Originally Posted by Cliff R

Good points made on manual trans set-ups.

When I tuned HD twin cam engines, for example, I would install wide ban 02's and start with a "canned" map very close for the application. The companies selling tuners, like the Power Vision provide scores of maps and in that list somewhere is one that will get you pretty close right out of the gate.

At that point I would ride the bike and data log, and save the results to one of 6 places. Then I'd get the laptop out and custom tune some of the timing/fuel based on prior experience. The cool thing about that deal is that you can save all your tunes including the original and jump back and forth between them in minutes. I found that by custom tuning overtop of the learned tune I could make improvements in fuel economy and power. On my own bikes I was able to get them up to or near 50 mpg's when they were down in the low 40's before any changes were made. This tells us that relying on electronics and data logging doesn't always produce the best results and that you need to do your homework and get some seat time with your tuner, laptop and the system you have chosen to get the absolute most out of it.......

Yes, this is still true of modern self learning EFI as well.

The way the systems work is to start with a basic table that the software builds based on a few key parameters. Typically engine size, rpms limits, cam size, etc. From the base map that is built off of those customer provided inputs the system then uses the wideband oxygen sensor to modify the VE and spark tables in real time.

The real time inputs are your short term trims. The system is running off it's base map and based on what the oxygen sensor is telling it, it adds or removes fuel in the cells that it's functioning in. Based on what is necessary for the short term trims to create the commanded values from the user, those figures are saved to long term trims which is a modification of the base table.

That's really all that is happening. not rocket science. The problem comes when that base table is so far off of what is being commanded that the short and long term trims are beyond their adjustment windows. For short term trims, that's typically about 30%.

In the case of DFCO and manual transmissions for example, the system may make an assumption that at MAP values of 30kPA and below there is no load and fuel is completely shut off. But what happens on clutch in for upshift and you immediately drop all load from the engine. You may drop to around 25kPa and now the system shuts off your fuel. The engine uses up the fuel film on the intake walls and by the time you're throttle on and letting out of the clutch you're WAY lean and stumble.

The system has no learning values for DFCO, it's a commanded value only. So without knowing that and changing it, you may blame the system as being a pile. That doesn't really make it so, but the idea that you could just put it on the car and everything magically work 100% isn't based in reality.

And you've pretty much got to log that, or have somebody watching the values on the handhelds real time to discover that's an issue,

People that run these systems with manual transmission, I typically tell them to turn DFCO off completed, unless they are willing to log and make changes and absolutely need it for fuel economy reasons.