These are the upgrade paths for the engine of your Swift/Cultus GTi if you want it to remain naturally aspirated. These step take from basic modifications (mods) to fully blown NA Tuned Swift/Cultus GTi. I  have yet to do all of these to my car, but they were gathered with a lot of research, experience and opinion from a few people that I trust.

Stage 1,         Stage 2,         Stage 3,         Stage 4,         Stage 5,         Stage 6

Intake System Mods

Your car needs to induct fresh air for combustion. These intake modification is to provide your GTi with better and more efficient air induction.  The more efficient the air entering the engine  the better the car performs. These are several guides that you can do onto the intake system.

a) K&N Inbox Filter

· It replaces the standard paper filter with washable K&N and uses the standard filter box.

· Advantage (s)

1. Cheap you do not have to make brackets or plates and the installation is easy.

2. The filter is long life and washable so no need to replace.

3. It takes cold air from outside. This is very good in traffic jam as air is not drawn from the hot engine bay.

· Disadvantages

1. Not much gain

2. You can't really hear the roar of the induction noise

b) Cone Shape Filter

· The biggest gain you can have. It removes the standard air box and replace with washable open filter element.

· The downside is that it sucks the hot air from the engine bay too.

c) Aluminium Air Intake Ram

· This mode is to eliminate any restriction or obstacle in the standard rubber hose so that the air is coming smooth and fast.

d) Intake Manifold.

· Yes its serious, if you have the Jap Spec manifold and a MK1, then you are safe but if you use the standard Swift GTi (square shape) manifold you have to change to the Japan Cultus GT-i (round shape) intake manifold. The Cultus intake manifold is hand made, so this means that  it doesn’t have any casting edges that can impede airflow like in the Swift GTi.

 

e) Re-bore the Throttle Body and MAF sensor

· Re-bore the standard throttle body so more air can enter because of the larger hole diameter

· It increase a little bit power at the upper band without the penalty of the low end power.

f) Big Bore Throttle Body

· Throttle body from Nissan SR20 Engine can be use it's 55mm in diameter.

g) Big Bore MAF

· MAF sensor can be use from Nissan bluebird 

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When your car can inhale air better for sure it has to find a way for the induced air to escape. The less is the restriction of the exhaust is better but too much flow equals to no go and the noise also becomes unbearable. A good Exhaust System can give you power without too much noise.

a) Exhaust Extractor

· If you have the Jap spec engine (Cultus) the stock extractor is good enough. But if you have a swift engine you can change to the Jap Spec G13B extractor or change to Hot Bits Extractor.

· Hot Bit extractor is better than the standard Cultus GT-i Extractor and the Swift GTi Manifold

b) Pipe Diameter

· Use mandrel bent tubing and make it as straight as possible.

· For better low to mid range power use 1.75" diameter piping

· For all Across gain you can feel use 2": pipe diameter

· 2.25"diameter pipe will shift the power band to higher rpm

· 2.5" and above forget it you are not under the influence of boost ;)

c) Mufflers

· Get the best muffler you can afford. Use ellipse shaped muffler in the middle for quieter exhaust and make sure the all the mufflers are straight flow.

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a) Spark Plug

· Splitfire is recommended. You can use any performance plug that is available with the proper gap of 0.8mm and can fit to the swift.

b) Ignition Cable / Wires

· Upgrade to better ignition wire. Hotshot cable from Australia is good. The better the Insulation the better. 8mm or higher is recommended.

c) Ignition Coil

· Standard ignition coil is good enough but it can always be upgraded.

· This mode is not easily available here in Malaysia so I can’t recommend any particular devices.    

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a) Replacing The Chip

· This mods is rally worth the money and pretty much very easy to acquire it here

· Stage I – Only removed the 180Km/h speed limiter.

· Stage II – All around gain you can feel from low to high rpm.

· Stage III rally (recommended) – Gains only occurs after 4500rpm to max rpm your engine can handle. Retain the standard fuel consumption at lower engine speed. But have the best max power from the rest.

b) Full standalone Engine Management System

· It completely eliminates the need of the original ECU. Example of these type system is the MOTEC fuel management system.   

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Engine Head

a) Port And Polish

b) High Lift Camshaft

c) Adjustable Cam Pulley

d) Solid Valve Lifter

e) High Tension Valve Spring   

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The G13B engine block is actually very good enough to withstand many mods done because the piston, connecting rods and the crankshaft is forged so this makes the G13B stock internal parts can withstand up to 9000rpm. The only mods need to be done if you don’t have a Cultus engine is to replace the piston to Japan MK2/MK3 G13B engine to increase the Compression Ratio (CR) from 10.0 to 11.5. But like any other parts of a car it can be upgraded.

a) Full Engine Balancing

b) Re-bore to 1.5l

· These mods are not easily done because the pistons with CR of 11.5 or higher is almost impossible to get.

c) Engine Block Strengthening

· To strengthen the engine so that it can endure higher RPM.   

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Follow the above mods according to its order and you can feel the difference without burning a hole in your pocket. The mods that are italic and black are the advance mod and the rest is basic. Advance mod should done after finishing all the basic mods.

Basic Mods from 1-4 estimated gain is around 15-30hp depending on model

Basic mods no. 5 will give gains around 20-30hp

If all the advance mods + basic mods that are done correctly expect a naturally aspirated Swift/Cultus with 150hp to 200hp