To go fast in Need For Speed Underground, just knowing how to drive isn't everything you need to know; knowing how to setup your ride for each track can greatly improve your results, especially with the slower cars.
There are a total of 9 TJs in the game, a player being allowed to equip normally only 3 of them at the same time in a specific order.
It greatly improves the power of the car and it should be your 1st option when you build your car. You can't go wrong with it.
Improves high RPM acceleration. It is essential for top speed tracks and drags.
Improves low RPM acceleration. Good for most of the tracks, especially if you have to shift up into the last gear of your car.
Decreases further the weight of your car, causing it to corner better and be more stable. You use it in combo with Engine and Turbo TJ if you want to have the most power or Engine and ECU for more handling, at cost of acceleration. Wallbouncing becomes a little easier from the increased cornering.
Increased rear tire grip. Yes, it doesn't help with shifting and such. Good only for drags and dirt tracks with less grippy cars (f.e. Atlantica Reverse, National Rail Fwd/Rev)
Increases the stability of your car. It is more useful than Weight Reduction in that regard, but you should only use it only when you really need the increased stability. Useful on Toyota Supra currently.
Increased grip. You have less grip than what Weight Reduction can give you. Pretty useless unless you are driving a bad car.
Greatly improves the nitrous power and use of the car. Almost mandatory for NOS Laps and drags.
Improves braking power. Useless in any other matter, unlike normal brake upgrades.
Some cars in the game benefit from “downgrading” some performance parts. The only ones you should always have maxed out are Engine, ECU, Turbo, Suspension, Weight Reduction, Tires and Nitrous Oxide.
Somehow, the higher the level of the brake kit on the car, except increasing brake power, you get slightly more downforce. How the downforce works in-game? Basically it applies on the turning radius of the car, not its grip nor jump speed, meaning it helps you not spinning out while drifting, double-tapping or double-steering, at the cost of some cornering. But fear not, its only by a little amount.
Every car has different power bands, them accelerating the fastest at different RPMs. Decreasing the upgrade will make you shift slower and with the early career cars, return them to a 5-gear transmission box. List of cars that benefit from the change:
These are the main ones that I know off. Please feel free to edit if you find something new.
Double-Tapping
RX-7
ENG, ECU, TRB - High Speed Tracks; stability on or off (how you like more) for Olympic Square, Atlantica, Stadium, National Rail and Port Royal, ENG, TRB, WGT - Cornering Tracks, Online; best used with stability off for Terminal, Market Street and Inner City
Integra ENG, ECU, TRB - All tracks; Stability On for OS, ATL, STD, NR, PR; Stability Off + lv0-lv2 Brakes (how you like, but lv3 spins out way too much) for Market Street and Inner City ENG, TRB, WGT - Online Consistency For Terminal, add Gearbox lv2, Stability Off and Brakes lv2
Neon (stab on only) ENG, ECU, TRB + lv2 Gearbox - Olympic Square, Stadium, Atlantica Reverse ENG, ECU, WGT + lv2 Gearbox - Port Royal, Atlantica Forward \\ECU is more important on Keyboard because it is way easier to DT the corners properly than with Turbo (both in combination with Weight TJ)
Peugeot 206 ENG, ECU, TRB - Stability On for OS, ATL, STD, NR, PR; Stability Off + lv2 Brakes for Term, MS, IC
Miata ENG, ECU, TRB, Lv2 Gearbox, Stability On - OS, ATL, STD, NR, PR ENG, TRB, WGT, Lv3 Gearbox, Stability Off - MS, Term, IC
Skyline ENG, ECU, TRB - Stability On, Lv3 Brakes for OS, ATL, STD, NR, PR and Stability Off, Lv0 Brakes for IC, MS, Term
Usually, for DT, you need to experiment if you feel like Lv3 brakes make you spin out with what you like.
Double-Steer
RX-7 ENG, ECU, TRB Olympic Square, Market Street, Terminal - Stability On for consistency, Stability Off for the record Atlantica, Stadium, National Rail, Port Royal - Stability On Inner City - Stability Off
Integra ENG, ECU, TRB - Stability On for OS, ATL, STD, NR, PR Stability Off + lv2 Brakes for MS, Term and IC ENG, TRB, WGT for Slipstream Online and Terminal Reverse
Miata ENG, ECU, TRB, level 2 gearbox - For every high speed track; level 3 gearbox for Terminal. Stability on should be good for beginning but stability off is better if you have to wallbounce on the track
Neon ENG, ECU, TRB, Gearbox lv2 - should be your main setup for Olympic Square, Atlantica, Stadium, National Rail Reverse (any brake level you like between 0 and 2), Port Royal (brakes level 3) Gearbox lv3 - National Rail forward, Market Street for stability on; this setup is the best for online, especially if you have wallbounces ENG, TRB, WGT, gearbox lv3 - stability off for Terminal and Inner City ENG, ECU, NOS, lv3 Gearbox (a.k.a. “FentNeon”) - for noslaps but ENG, ECU, TRB sometimes should be a better option For fishtailing, the lower the brake upgrades are, the smoother it is. Personally I use level 1 but its a prefference.
Drag Setup The best one is TRN, ECU, NOS. On Commercial and Main Street lowering your suspension upgrade may improve your jumps but it is relative.
Drift Setups
Main TJs are ENG, ECU, TRB
RWD - TRN lv1, Tires lv2
FWD, AWD - TRN lv1 or lv2, stock Tires
All of them should be played with stability on for longer drifts