1.) Let's say I want to make the car faster, pick any 'simple' car to tune. I've read 400pp FR cars are good places to start learning. So say I upgrade the engine first. Should I go ahead and buy the upgrades for the fully customizable parts (transmission, springs etc) as well as whatever exhaust, brakes I want at the same time and then start to tune it? I guess more concisely, how do I know what I should buy without overpowering the car to the point it becomes too hard to drive? Sorry that's a long question, hopefully it makes sense.
2.) Once I buy the parts I need/want, what's the proper way to test the car? Find a speed you want, adjust the transmission first then customize each setting until it drives well? I'd assume all of this would all depend on what car/track you were driving with/on. Which leads to my last question.
3.) Is there an efficient way to find a 'balanced' tune that would work well on most tracks to use as a starting point or is that really impossible because of the wide variations of tracks?
Sorry for the long post, I'm just trying to wrap my head around all of this as a complete tuning noob and simple commuter driver in real life, thanks for any help and any extra advice you have that goes beyond what I've asked!
Right, a good place to start would be Mx5/Miata/Eunos Roadster (same car). This car responds really well to tuning and helps to illustrate what effect the changes you are making are having.
When it comes to what parts you should buy it's a case of what do you want to do with the car? Do you have a PP/Bhp limit? How often are you going to use the car? How much are you going to win in the event you want to enter.
Generally speaking, you want to be as close to the PP limit of the event, this will mean your car is likely to be on par with the performance of the other cars in the event.
If you are only going to drive the car once or twice (seasonals etc.) don't spend tons of money on it, you'll never make it back. (spend 500k on buying and upgrading a car to only win 40k back is not a wise choice!)
Tuning/Testing
Step 1. Buy a car
Step 2. Test drive car
I'd recommend Deep Forest Raceway or Grand Valley Speedway, they have a large variety of bends and straights which allows you to see how the car handles/reacts. Do enough laps to get the feel of the car, don't just spin it at the first corner and say its broken! Drive until you have learned the car and the circuit, concentrate on what the car does well where it needs improvement.
Step 3. Tuning the car
My first step in tuning is to give it the basic upgrades- brakes/clutch/driveshaft/gearbox, this should knock a few seconds off your lap time straight away because it smooths out the basic functions and makes the car more responsive to acceleration/deceleration.
Test again - Any improvement to lap time/performance?
Step 3 - Adding performance
If you decide the car need to be faster, my first point of call would be reducing the weight. This relates to the power to weight ratio which is extremely important in terms of performance. The less weight the motor has to drag around, the more efficient/fast the car will be. It also helps greatly with handling because it means there will be less mass to resist the effect of turning during corners. (this can also be used to effect the weight balance but i'll explain that later)
Test again - Any improvement to lap time/performance?
If you still want more power, start by adding the cheap bits (sports computer/catalytic converter/intake tuning). Be mindful when adding power, too much too soon can completely change how a car feels. Adding power may make the car faster in a straight line, but it can also encourage understeer/oversteer in the corners due to the increased forces on the suspension components.
Test again - Any improvement to lap time/performance?
Once you have got the power to where you want it, it is time to move on the suspension. I'm not going to write out exactly how I'd go about setting up a car, but I'll explain the basic ideas.
Weight distribution - this is how much % of weight is over either end of the car
Weight forward = understeer (car wants to go in a straight line instead of turning)
Weight backwards = oversteer (heavy back end swings around like a pendulum when car is turning)
Ideally you want the weight as close to the centre of the car as possible (achieved by adding and moving ballast) and as close to the ground as possible (ride height)
This will give you a neutral (50/50) handling car which is generally the easiest to drive and the fastest.
Now you can start playing with all the other bits mentione4d in the guide.
The best way to know what a car can/can't handle is to try it. Make changes then test, its the only way of knowing.
Pick a track that you are comfortable with and can lap consistently, there are only a few circuits that require specialist set ups, a setup that you are comfortable with will work reasonably well everywhere. You will only really need to adjust the gearing and that is simple enough.
Simple Gearing Setup
To keep it simple, test drive the track in question. Get a good run onto the straight carrying as much speed as you can, the ideal situation is having your top speed set at the speed you reach by the end of the straight, you want to be just hitting the rev limiter as you get to the braking point. That way your car is setup to be as fast as it needs to be. The basic rule is that the higher your top speed, the slower your acceleration or vice-versa. Theres no point setting your top speed at 200mph if the track only has a 500m straight because theres no real way you'll ever reach that speed, setting it too high will just hamper you around the rest of the track because of slow acceleration
(note: if you are racing rather than doing a time trial, set the top speed a few mph higher to account for the effects of slipstreaming)
So, to answer your original questions
1. Testing is the only way to find out what a car is capable of
2. Pick a track that you like driving and has a variety of curves/straights/incline. Keep driving it until you learn to lap it consistently, that is the only way to know if you're improving
3. Yes, most tunes will work on most tracks. A simpler top speed adjustment is all that is required to suit long/short straights
Make sure you are driving with all the active aids such as traction control, skid recovery force and active steering OFF during testing! Leave ABS at 1 though because it is pretty much essential to stop the brakes locking.
hope this helped, feel free to ask any further questions