The map is pretty easy to understand. It's correction, by RPM @ a specific boost level:
So for example, if you want to see the value used at a 4500 RPM @ 10 PSI, you'd look here:
If you watch a live pull, where it shows you which square it's using, you'll see a pattern like this, for example:
If those are the cells you are hitting at this specific boost level (10 psi in this case) you only worry about changing those cells to smooth out your A/F curve.
There are also areas of the map you will NEVER use. For example if your turbo can't make boost under 2000 rpm, the cells crossed out below would never be used:
Another way you can view the map is graphically. One thing that is important is that it is smooth looking. If there are large changes between cells, you've got the tune wrong an the TCCS will fight you on it. If you have "follow" turned on while you make a pull, you'll be able to see which cells it is using in this view as well:
Tuning with a MAP-ECU takes a lot more finesse than with other systems. You kind of have to have a knack for it. Some people have an easy time, others struggle. I will forewarn you though that tuning a karmann vortex car (ie. - MKIII Supra) on one if these is a real pain in the ass. Cars with AFM's (ie - MKIV Supra) are a lot easier.
One thing that will really mess you up is Vf. If you don't tune for Vf you are toast. The ECU will keep tuning out your changes. This goes for ANY piggyback, not just the map-ecu.
By using a system called LEARNED VALUE {Vf} or the FUEL TRIM correction system. The TCCS uses its best guess or BASIC FUEL CALCULATION plus a +/- 40% floating correction factor determined by the LEARNED VALUE Vf system to give the engine the correct required amount of fuel under all conditions.
This + or - correction amount is controlled by an active control system in the TCCS called the LEARNED VALUE SYSTEM, Vf fuel trim. Under this system the TCCS uses two types of fuel trims called the long and short fuel trims.
The LEARNED VALUE Vf system is used by the TCCS during both open and closed loop operation to fine tune the fuel control to the engine in relation to engine wear, sensor shift and other problems such as combustion leaks and intake air leaks.
This long and short fuel trim is an automatic on the fly correction system that uses the engines sensors to add or subtract fuel from the BASIC FUEL CALCULATION to keep the fuel mixture going out the tail pipe on target under the fast and slow changing engine conditions, examples: Hot, Cold, idling, redline, wear in cylinders and head, or any number of engine operation conditions.
The current amount of fuel correction the long and short fuel trims systems are adding or decreasing from the BASIC FUEL CALCULATION can be read by reading the voltage coming out of the TCCS's Vf data output terminal in the diagnostics connector under the hood of the Supra. The Vf line feeds five stepped voltage values of 0,1.25, 2.5, 3.75, 5.0 volts. Each step in voltage is an indication of the amount of fuel trim to the BASIC FUEL CALCULATION that is taking place. The TCCS will always output one of the five voltages to the Vf terminal in the diagnostics connector under the hood. The voltage is measured at anytime between the E1 and Vf pins in the diagnostics connector when E1 and T1 are not shorted. Remember that the voltages are stepped in 5 levels as mentioned above! Depending on your car you may see 3.5 volts rather than 3.75 volts, this is normal and you can ignore the difference in the voltages.
The whole goal is to tune the system so that the Vf data is normal while getting the car to do what you want it to.
No mater what you set any piggyback to in closed loop mode the ECU will compensate back to 14.7 until you max out the ECU's capabilities. The best bet is to tune everything under 4000 rpm to Vf and then use the piggyback after 4000 RPM in open loop to get the right tune.
Since you are tuning over 4K and only at boost, you pretty much will wind up doing most of your tuning in the area indicated below:
It really
is best left to someone with a lot of experience in it. That goes for the S-AFC as well. If the guy tuning your car isn't working with Vf, he doesn't know what he's doing and you should find someone else. Any idiot can get a car to run right with a S-AFC for a short time. Getting it running correctly in the long term is far more difficult.
Tread very lightly until you learn quite a bit about the way things work. Everything you need to know is on this site. And the people who wrote the FAQ's and tech-tips you find around the Internet for this car are (for the most part) on this site as well.
Start reading, and when you get stuck, start asking questions. If you really want to do this yourself, and to do it correctly and safely, you need to learn a LOT before touching a single setting.
