na performance

Naturally aspirated engines are simply engines that are not assisted with a turbo or supercharger. Most people that want their car to go faster will chose this way. Large power increases in automotive engines are not hard to get. Four stroke performance can be greatly improved over the mild factory setup. Four stroke tuning can greatly improve the power over stock conditions. The factory tuning is very mild because they need to pass emissions tests from the factory. Many people buy aftermarket computer chips with modified performance maps. This can improve many cars by 5 to 20 horsepower dependant on the vehicle. Aftermarket chips are also an easy install and can be purchased reasonably. As with all engines, moving air into the engine is the way to make power. Another easy bolt on performance modification is to install a high flowing air filter. Large gains can also be made with improved flow through aftermarket carbs or larger diameter throttle bodies. The import tuners usually purchase high performance intake tubes which try to draw in cool air. These kits usually give moderate performance gains. Most of the domestic car tuners do the same and tend to spend money on the actual intake manifold instead. Depending on the vehicle it came off the performance gains can be much larger some up to 40 horsepower on V-8 models.

 

Cylinder heads can make a huge difference and are the main contributor to airflow in an engine. The performance heads usually focus on using larger valves, multi angled valve grinds, using smaller valve stems to not restrict the cross sectional area, splaying the valves at a wider angle, and smooth flow in the ports and chamber as in ported heads. Many performance heads are also made of aluminum which allows about one point of compression increase improving power and torque without detonation. Most high performance racing heads are actually four valves per head. Four valves allow more air to enter the cylinder as the overall area can be higher with four than two valves. The weight of the smaller valves also allow much higher rpm to be turned without valve float. Camshafts are the complimenting force to the heads as they control when and how much air is allowed into the cylinder. Two factors affect how the camshaft works with the engine. The overlap and the lift affect when and how high the valves open. Cams are cheap and can give huge power gains, but if too aggressive without the rest of the setup flowing well enough and it will hurt performance. Lightweight titanium valves allow high rpm but come at a high cost. Roller lifters and roller rockers reduce friction and produce more power to your wheels while increasing the longevity of the engine. Performance rockers are sometimes aluminum and use 1.6 or 1.7 ratios vs stock 1.5 ratios on most v-8 engines. This increases the lift and affects overlap and are reasonably priced and easy to install. Exhaust headers are also an easy bolt on part that optimizes the exhaust flow by tuning the length of the individual tube so that the exhaust flows out faster. A cross over tube is also used to increase the torque by scavenging out the exhaust from the opposing exhaust bank in v style engines. Large exhaust pipes, better flowing catalytic converters, and performance mufflers also improve power at a reasonable cost. Increasing the displacement of an engine is also a common upgrade to domestic cars and is starting to gain popularity in the import crowd. This dramatically increases the torque and power dependant on the increase in displacement. This can be accomplished by increasing the stroke length of the crankshaft or increasing the bore diameter. Piston design has a large effect on combustion burn, compression ratios, bore sealing and friction. A large amount of power can be found in the design of the piston. Also the oil pan can be designed to “scrape” the oil away from the crankshaft and collect to the pump feed. This type of a pan is generally used with a dry sump pump. The crankshaft is knife edged to cut through whatever oil is missed by the pan scavenging. This also creates a vacuum in the crankcase which reduces pumping losses and helps seal piston rings. A good dry sump setup running at high rpm’s can make 40 to 60 horsepower on a nascar style v-8 engine. With an efficient, well designed, good flowing engine, alot of power can be had without the aid of turbos blowers or superchargers.