I realized that after changing car setup options and finding the right setup of tires, shocks, gearing and weight distribution, I was able to tweak the transmitter settings to settle the car for each track type. The EXP and EPA settings are the most important to me. Here is what I found with my setup using my JR XS3 transmitter and the new RS310 receiver (that comes with the new JR XS3Pro which I did not want to pay for, so I ordered the receiver separately to cut down on weight and chassis mounting size):
1. Set the EXP initially using the long straight portion of the track. Run your car down the straight and make a few course corrections left & right as you go. At first, do this testing while standing at one end of the straight and at 75% throttle to make sure you don't destroy the car on the wall. If the car feels too twitchy, oversteers a lot and you find yourself letting off the gas to avoid hitting the wall or the car is slowing down too much, then you need to reduce your EXP setting to a negative number. Repeat this using incremental steps of -5 points on your EXP until you find a comfortable setting. As you get the setting more comfortable start going full throttle and then move to the drivers stand and tweak it some more if necessary.
2. Second, set the EPA for left and right SEPERATELY. Run your car through all of the tightest curves on the whole track and note what the rear end does mid-corner. If the rear end slides and causes you to oversteer too much, then reduce the EPA setting for the direction of the turn. If it was a left turn, then reduce the left EPA setting by -5 and vice versa for a right turn. One thing to note here is that if you can find a car setup that is near perfect, you should be able to set your EPA to the max for tight agressive steering and still have your rear end planted mid-corner. I've found this type of setup now by using the following rear setup options:
* Switched from 26mm 35 shore rear tires to 30mm 30 shore rear tires
* Switched from light blue rear springs to blue rear springs
* Switched from 30wt rear shock oil to 35wt
* Switched from rear upper shock position #4 to #3
* Switched from rear inner camber link position #1 to position #2 using new camber link studs that attach to rear shock tower (I also use 3mm shims on the outer camber link)
* Switched from 2 degree rear toe-in to 2.5 degrees
3. Fine-tune the EXP last. Go through the larger radius corners (sweepers and mid size corners) and note if you are able to put the car on multiple lines for corner entry curves at will. If you have to turn the transmitter wheel too much during corner entry and the car feels a little lazy to turn in, then increase the EXP setting by +2 and try again until you find a comfortable setting. If the car turns too sharply and you end up clipping the corner dots most of the time, then decrease the EXP setting by -2 and try again until you find a comfortable setting. This new EXP setting may conflict with what you found to be a comfortable EXP setting on the long straight test in #1 above. If it is a slight discomfort, then you should adjust your driving input on the transmitter wheel to compensate. I always tune the EXP for best comfort on the straight if the straight is not in front of the drivers stand and it is hard to gauge the distance from your car to the wall. If the straight is right in front of the stand, then I tune the EXP for best corner entry feel, since I can see the car down the straight and make corrections more easily. If the settings are too far apart to give you enough comfort for the straight AND corner entry, then I would suggest tuning the EXP for corner entry and changing one or more of the following settings on your car to gain stability down the straight:
* Decrease front toe by .5 degrees
* Add rear toe by .5 degrees
* Change body to a more stable neutral steering body
* Do not trim your bodies rear spoiler. Use its full height on the sides and back lip.
Today I set EPA to the max and EXP anywhere from -45 to -90. I use high negative EXP numbers to allow me to change lines more easily during any part of the corner for passing situations.
I always try to remember to repeat these transmitter tuning steps after every car setup change I make. However, I have forgotten to do this a few times and ended up chasing too many other setup changes to compensate before I remembered these steps.
There is a lot more to fine tuning the transmitter for other things, but these were the ones that greatly helped me in consistency and qualifying for the A mains instead of the B mains.