NA Tuning
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IMO, NA tuning is a little harder than forced induction cos the gains are not as impressive! The typical NA street racer would be FW drive, and variable timing/lift engines like VTEC, MIVEC and VVTL-i. Other NA tuning types would be the high end RW drive cars like BMW M3 with variable timing/lift (double VANOS) with individual throttle control butterflies. Another would be the kit cars from Westfield and Caterham using motorcycle engines with sequential gearchange!
The inspiration of NA tuning will be based on the following great NA cars (IMO); Honda Integra Type R (DC model/B18C) and Renault Clio Cup Sports (172 bhp). Both these car manufacturers have had F1 experience and their influence are seen on both cars. ITR incorporates leading edge technology while the Clio Cup feature tremendous packaging at a terrific price.

1. ENGINE BREATHING
The usual mods apply like cone-type air filter with cold air feed/pressurized air flow and exhaust headers (4-1 or 4-2-1) with straight through system. Headers should have long primary pipes before joining together for the secondary pipe system. Longer primary pipes create a vacuum effect which extract the waste gases and create a vacuum effect drawing in the induction charge! That is why some guys called headers as 'extractors'. Personally, I prefer 4-2-1 systems for street use but then ITR uses a 4-1 system. BTW, I understand there is no gain from a aftermarket pod filter for ITR cos the OEM system is already very good.

2. ECU/CAMSHAFT
These 2 items need to be matched to optimized performance. The cam profile must be matched with ECU fuel map/ignition map. For 40 tiang, best cam profile should be high lift, short duration type (under 300 degrees) with emphasis on quick valve acceleration ie rapid valve opening and closing. Long duration cams (over 300 degrees) are for track racing only cos bottom end/mid range is non-existent. Vacuum effect is very poor when using long duration cams eg. track racers sound very lumpy during idling. Chipping standard ECUs is not a perfect solution. Hardcore racers and SMSC competitors used only ECUs and cams from famous tuners like Mugen, Spoon, Suzuki Sports, etc. Venier/adjustable cam sprockets are also necessary.

3. FUEL MODS
Aftermarket bigger capacity fuel rail, injectors and adjustable fuel regulator would be useful fuel mods. Increasing the diameter of your throttle body can also increase power but don't go too big. Also, Civic and GTi owners should change to ITR and Cultus intake manifold. The ultimate would be individual throttle bodies/butterfly system but will have problems with LTA/Insurance Cos. Before EFI cars,installing Webers and Dellortos carburettors with high lift cams were the way to make good power with NA cars in the old days. Weber carbs induction sound was even more garang than VTEC sound! Problem with Webers is that they do go out of tune due to fuel sediments clogging the jets and tubes-that's why old Alfa Romeos need regular tuning or cleaning. EFI cars don't need tuning - only regular cleaning of the injector system. The EFI fuel map don't deviate from the norm! Mechanics tell you that your EFI system need tuning cos they can charge you higher instead of telling you that it just needs cleaning! Ha ha ha!

4. ENGINE WORK
Head polishing and porting and changing to bigger valves are not critical for making power in today's NA engines. Those were necessary in the past with the old Mini Cooper S when production tolerances were poor and engines had poor airflow. Today's engines are designed using CAD/CAM tools and infinite analysis and manufactured to very close tolerances. In fact, the VTEC induction ports are a bit big for road use! That is why Spoon Racing offers a intake plate which constricts the port size to increase airflow velocity to improve acceleration! Airflow dynamics depends on sizing - smaller size allows for greater velocity but airflow maxed out faster whereas bigger size allows greater flow capacity but poor velocity which means lousy throttle response at low rpm. For 40 tiang and street racing, the trick is not to go big on induction ports/exhaust ports but match the intake manifold, cylinder ports and exhaust headers for smooth air flow and maximum vacuum effect. Oil catch tank would be useful to reduce crankcase pressure and keep the combustion chamber and spark plugs clean. Higher compression ratios using thinner metal gaskets can also increase power but must be weighted against fuel quality and octane level. You may need octane boosters.

5. CAPACITY INCREASE
Torque and HP can be up through capacity increases. VTEC B16A head can be matched to B20 CRV block for 2.0 litre VTEC hybrid engine. Suzuki GTi (G13 engine) can be increased to 1.7 litre using Vitara block and overbore pistons. There are also aftermarket stroker kits but can be very expensive!

6. ENGINE LIGHTENING
The most radical mod would be to fully lighten and balance the bottom end. Using lightweight pistons, titanium rods, knife-edged and lighten crank with a competition crank bearing brace - it's the ultimate for 11,000 rpm! Balancing smooths out the small out of tolerance vibrations which affect the performance at high rpm! For top end, changing over to titanium valves/retainers and flat coil double valve springs a-la-ITR would be ultimate.

7. GEARBOX/TRANSMISSION
Getting a close ratio gearbox or 1/2/3 close ratio gearsets. The gear ratios and final drive must be matched to extract the greatest power onto the road. Limited slip differential ensures power is laid on the road without time-wasting tyre spins. Lighten flywheel and competition clutch would complete the equation for great acceleration out of the holeshot. Short shift is optional but does marginally improve shift speed for a good driver. Sequential gearshift would be even better for 40 tiang.

8. CHASSIS SHELL
IMO, 2 or 3 dr cars are best for 40 tiang racing cos they are lighter and stiffer than 4 dr sedan body. Carbon fibre bonnet and body parts would help lighten body weight while retaining structural integrity. Stripping out the carpets and insulation would help lighten the car further. ITR and Clio Cup uses thinner glass to save weight. You can use persplex panels for rear quarter windows. Lightweight racing seats can also reduce weight. Body kits are a waste of money cos they are a aerodynamic drag and adds weight. BTW, the Spore Lancer MR is a classic example of poor packaging despite boasting a 175 bhp MIVEC engine. Why? The engine power and gear ratios are poorly matched. The FD ratio is far too high for the engine to pull and is further hampered by the added weight of the 4 dr car loaded with sunroof and accessories. The 175 bhp MIVEC engine is suited for 3 dr Colt Mirage body and the JDM-spec engine (Type RZ) comes with a close ratio gearbox with lower FD and LSD. The Mirage MIVEC racing series in Australia had the Mirage lapping a few tenths of a second faster than ITR.

9. FOOTWORK
Don't go to big diameter wheels for 40 tiang. They're only good for showing off and not performance. Go for standard diameter instead and light weight wheels ie magnesium/forged/split rims. Playing with rim offset can improve handling with wider track stance. Aftermarket dampers and lowered springs complete the equation here. Gymkhana coil/shock units are the best option but are very expensive.

10. BRAKES
AP Racing/Brembo systems are for track racing. They also required you to change up to a bigger wheel diameter. Instead change the brake disc to a slotted performance type and uprate the brake pads, change to DOT5 brake oil and swopped to braided brake hoses. Be careful of drilled brake disc cos they may crack due to higher temperature loading. Another mod to consider is aftermarket templates for the brake hydraulic reservoir.