Performance DIY by DIY Guru

Engine Port Matching Principles and Basics Engine port matching helps make performance gains by making the airflow more streamlined. It is usually performed because the inlet and outlet ports on the engine block are usually larger than those of the manifolds that connect to them. This allows for scope in the manufacturing process to allow for mismatched alignment. Generally the engine ports are larger in the upstream flow direction avoiding turbulence but power gains can be made by matching these up. Most internal surfaces are far from smooth due to the casting process so small gains are there to be had by smoothing out the rough edges although polishing the insides offers little if any extra gain. Engines need to breathe as freely as possible and obstructions, seams and pits cause turbulence and this is not very good for airflow. Generally speaking most standard non performance cars will benefit greatly from even a little DIY head porting. A high performance engine ...

Backpressure : The myth and why it's wrong. I. Introduction One of the most misunderstood concepts in exhaust theory is backpressure . People love to talk about backpressure on message boards with no real understanding of what it is and what it's consequences are. I'm sure many of you have heard or read the phrase "Engines need backpressure " when discussing exhaust upgrades. That phrase is in fact completely inaccurate and a wholly misguided notion. II. Some basic exhaust theory Your exhaust system is designed to evacuate gases from the combustion chamber quickly and efficently. Exhaust gases are not produced in a smooth stream; exhaust gases originate in pulses. A 4 cylinder motor will have 4 distinct pulses per complete engine cycle, a 6 cylinder has 6 pules and so on. The more pulses that are produced, the more continuous the exhaust flow. Backpressure can be loosely defined as the resistance to positive flow - in this case, the resistance ...