Parts testing
Note: You can try the tests again if you fail both attempts.
Brake test: This consists of three tests. Even if you pass the first two and fail the last you have to restart. Rev up fully before the timer reaches zero in all tests.
Dampers: This is easy in theory and harder in practice. Rev up before timer reaches zero. The hard jumps will fill the meter during the course. Brake only enough so you can pass the turn and avoid hitting too many cones. Clear the stage with full green meter and you will have passed the test. The hard part is avoiding cones and keeping a good speed. If you move at too slow a speed, the meter will not fill in time.
Engine test: You must reach 9 (or 7 depending on car) gears and hold them for a while. Here you have to shift gears manually. Rev up and just before reaching the green area, release the accelerator. If you have too high rpm, brake or just let it fall to the correct rpm. When done correctly it revs up and continues within the area during the needed time. Shift up a gear and repeat this until you reach fifth gear (or fourth gear for some cars, for example, the MG). Downshift and continue until you reach first gear again. Sometimes this goes well but other times several tries may be required.
Exhaust test: Rev up before the timer reaches zero. Head for the left side and brake hard before the first (right turn). After braking you can use the handbrake and steer shortly to provoke the car into harder turning. Cut the next right corner with the same technique. Then square left, square left and full throttle on the straight. Brake hard just before the crest and steer left. The next right turn can be passed by full throttle. Brake the slightest amount before the crest so you can see the bridge from the top of the crest. Full throttle after the bridge, then brake very hard in the right turn. Throttle up and brake slightly in the left corner. Flat out over next crest and you will have made it (if not knocking down too many cones at the sides).
First test: Hold slightly left in first corner. Brake the least possible so you still manage the corner (avoids the cones). Aim to stop before the red square. You can always drive the extra meters then brake hard again.
Gearbox: This is the same as engine test except the gears are random. You also must pass more gears.
Second test. It is slightly longer that the first test. In the section with the stripes, aim slightly to the left of the stripes. If done correctly, you will pass the left-right-left turns straight through. Then, brake extremely hard and you will make it.
Third test. This is longer than the first two tests. Hold slightly left at the start (avoids the cones). Brake the slightest amount possible so you can still pass the turns. Just aim to get on left side where cones are on the right and vice versa. Aim to stop before the square and drive the extra meters slowly.