How to modify your car - Stage 3
1. Performance brake systems:
By the time you reach stage three, chances are that your current braking power is ineffective toward handling the additional engine punch. Upgraded boosters, performance discs and street / performance brake pads are available to improve your cars stopping power.
Turbo's offer high power gains but don't exceed 6-8 psi on a stock motor. If you want to go higher than that, get ready for a seriously expensive investment in forged internals, sleeves etc.
Super-chargers or "blowers" (as they are called in the tuner circle) are another method of forced induction. More expensive to install, they are driven off the engines crankshaft, unlike a turbo which is driven by exhaust gas energy. Super-charger kits are readily available for some engines, though Indian tuners prefer turbo-charging.
4. Engine swaps:
When you have maxed out the power of your current engine, or simply want a bigger powerplant, engine swaps are a good option. Many tuner-friendly cars have a ready list of options available. D16 and B16 engines into Honda City, twin-cam Suzuki Swift GTi swaps into Maruti Zen and even Honda mills into Suzuki bodies are popular. Mitsubishi Lancers have various Mivec and EVO options. Swapping the engine is changing the "heart" of your car so consult only with tuners who have the necessary experience, knowledge and infrastructure; this is a very important consideration. Some swaps may not offer a bolt-on transition and will require heavy modifications to accommodate.
5. Upgrade clutch:
In stage three, a performance clutch may become a necessity to transfer the additional power effectively and quickly. Consider what the usage of your car will be before installing a performance clutch as varied options are available between street, drag and race applications. Some are a pain to use in bumper-to-bumper traffic.
6. Lighter flywheel:
A lighter flywheel will improve throttle response at all rpms, since the inertia is lower. It works well with balancing the crankshaft. However, don’t add one to a stock engine else you will lose torque at low-rpms. Lightened flywheels are a good option for racing and make for a superb modification with a short (close-ratio) gearbox.
The gearbox is one of the most important tools in extracting power from your engine, exactly where you want it (low, mid and high-rpms). You may choose to alter the final drive or go in for an entirely new custom gearbox. Your transmission may also require stronger drive-shafts to cope with the additional power.
8. ECU replacement:
The ECU (engine control unit) is the brain of your car and controls various engine parameters and functions. Custom ECU's can be tuned for specific engines where power gains vary from 5%(stock engine) to more than 30% (heavily modified engines). A stand-alone engine management system (Link, AEM, TEC-II etc.) allow great flexibility. With that flexibility comes complexity, custom fitting, and cost. As you progress within stage three, a replacement ECU will become necessary. A great feature of some stand-alones (with a toggle switch) is that they can be switched between performance and stock modes.