Tuning Cruise.
One of the great things about EFI is being able to lean out cruise sites so that you can get good gas mileage. My old 3.2SS was pushing 300Hp and would routinely get 26-27mpg on trips.
I like to do final cruise tuning manually. With the tuning software running and most importantly on an empty road, open the 3D VE fuel table map. Check the box “follow mode” at the top. This will put the adjuster cursor at the same place as the engine operating cursor.
As you are driving and without looking at the laptop (eyes up front) you can use the short cut keys (shift up/down arrow, or on a mac “<” for down and “>” for up) to manipulate fuel. Lean the car out under light load, On many cars this is in the 50-75kPa range. Do this from about 2500 - 4K. You will also want to bump the timing up a few deg in this area (if your controlling timing too via the ECU) As you approach AFR15 you will find the limit as the car will surge. Surge is not good and too lean.
Now, watch the MAP reading on the gauge Note the map range while normal cruise driving. On my car this is 55-78 kPa. Next, note the rpm range from 45-80mph. This range becomes your cruise island that you can match the lean cruise bins to the lean cruise target AFR. Blend outward from there. ( auto fill)
Tuning Idle
Use timing to set idle speed. Then set mixture to MAP minimum. When you idle rich the MAP reading will be minimal. Start to lean out the mixture until the MAP reading just starts to rise. this will usually be the most stable idle. I find this is around 13.5-13.8 AFR. Each engine is different.
Finally, the car runs great. It's time to lock down the idle. I usually make an idle “island”. All ECUs will use a linear interpolation between datapoints on the load/rpm space. I space the RPM bands to be about 200 rpm below and above the actual idle rpm. This means the idle rpm is in between 2 columns. Do the same for the idle load value. If you are scaled properly these should be rows 2 and 3 on the load axis. Now, your idle load and rpm true value is in the center of 4 points. Make all of these the same fuel value. This means the small fluctuations in engine parameters will not affect idle and cause it to drift. The result is a rock steady idle speed (that means within 50 RPM of your target). I call this the “idle Island”. You can see my example island highlighted below on the fuel table.
Ref Pic 10
