Cylinder Head Porting Tools

What's Cylinder Head Porting?

Cylinder head porting refers to the means of modifying the intake and exhaust ports of your car engine to improve level of mid-air flow. Cylinder heads, as manufactured, are often suboptimal for racing applications on account of design and so are designed for maximum durability which means the thickness with the walls. A head may be engineered for maximum power, and minimum fuel usage and all things between. Porting the top supplies the opportunity to re engineer the flow of air from the head to new requirements. Engine airflow is probably the factors to blame for the character of the engine. This procedure can be applied to your engine to optimize its power output and delivery. It might turn a production engine into a racing engine, enhance its power output for daily use as well as to alter its output characteristics to accommodate a particular application.

Coping with air.

Daily human knowledge of air gives the look that air is light and nearly non-existent as we crawl through it. However, an engine running at high-speed experiences a fully different substance. In that context, air might be thought of as thick, sticky, elastic, gooey and (see viscosity) head porting allows you alleviate this.

Porting and polishing
It can be popularly held that enlarging the ports on the maximum possible size and applying a mirror finish is the thing that porting entails. However, which is not so. Some ports could be enlarged with their maximum possible size (in keeping with the highest degree of aerodynamic efficiency), but those engines are complex, very-high-speed units the location where the actual size the ports has developed into a restriction. Larger ports flow more fuel/air at higher RPMs but sacrifice torque at lower RPMs because of lower fuel/air velocity. A mirror finish with the port doesn't provide you with the increase that intuition suggests. In fact, within intake systems, the outer lining is usually deliberately textured into a level of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected aspects of the port could also alter flow by energizing the boundary layer, which may customize the flow path noticeably, possibly increasing flow. This really is much like just what the dimples on the golf ball do. Flow bench testing signifies that the real difference from a mirror-finished intake port and a rough-textured port is typically under 1%. The gap from your smooth-to-the-touch port with an optically mirrored surface is just not measurable by ordinary means. Exhaust ports could possibly be smooth-finished as a result of dry gas flow plus a persons vision of minimizing exhaust by-product build-up. A 300- to 400-grit finish followed by the light buff is generally accepted to be connected an almost optimal finish for exhaust gas ports.

The reason polished ports aren't advantageous from a flow standpoint is in the interface involving the metal wall and the air, the environment speed is zero (see boundary layer and laminar flow). It's because the wetting action from the air and even all fluids. The very first layer of molecules adheres on the wall and does not move significantly. Other flow field must shear past, which develops a velocity profile (or gradient) across the duct. For surface roughness to impact flow appreciably, the high spots must be sufficient to protrude into the faster-moving air toward the very center. Merely a very rough surface performs this.

Two-stroke porting
In addition to all the considerations presented to a four-stroke engine port, two-stroke engine ports have additional ones:

Scavenging quality/purity: The ports are responsible for sweeping all the exhaust out of your cylinder as is possible and refilling it with just as much fresh mixture as is possible without a great deal of the new mixture also going the exhaust. This takes careful and subtle timing and aiming of all the so-called transfer ports.
Power band width: Since two-strokes are extremely dependent on wave dynamics, their power bands tend to be narrow. While helpless to get maximum power, care must always be taken to make certain that power profile does not get too sharp and hard to manipulate.
Time area: Two-stroke port duration is frequently expressed like a objective of time/area. This integrates the continually changing open port area with all the duration. Wider ports increase time/area without increasing duration while higher ports increase both.
Timing: Along with time area, the relationship between all the port timings strongly determine the power characteristics of the engine.
Wave Dynamic considerations: Although four-strokes have this problem, two-strokes rely far more heavily on wave action inside the intake and exhaust systems. The two-stroke port design has strong effects for the wave timing and strength.
Heat flow: The flow of warmth within the engine is heavily dependent on the porting layout. Cooling passages must be routed around ports. Every effort must be created to keep your incoming charge from heating but simultaneously many parts are cooled primarily by that incoming fuel/air mixture. When ports undertake too much space around the cylinder wall, draught beer the piston to transfer its heat through the walls for the coolant is hampered. As ports read more radical, some regions of the cylinder get thinner, which may then overheat.
Piston ring durability: A piston ring must ride around the cylinder wall smoothly with good contact to prevent mechanical stress and assist in piston cooling. In radical port designs, the ring has minimal contact within the lower stroke area, which could suffer extra wear. The mechanical shocks induced during the transition from partial to full cylinder contact can shorten the life from the ring considerably. Very wide ports permit the ring to bulge out to the port, exacerbating the problem.
Piston skirt durability: The piston should also contact the wall for cooling purposes but in addition must transfer the inside thrust in the power stroke. Ports have to be designed in order that the piston can transfer these forces and heat to the cylinder wall while minimizing flex and shock to the piston.
Engine configuration: Engine configuration could be influenced by port design. This can be primarily one factor in multi-cylinder engines. Engine width could be excessive for two cylinder engines of certain designs. Rotary disk valve engines with wide sweeping transfers may be so wide as to be impractical being a parallel twin. The V-twin and fore-and-aft engine designs are utilized to control overall width.
Cylinder distortion: Engine sealing ability, cylinder, piston and piston ring life all rely on reliable contact between cylinder and piston/piston ring so any cylinder distortion reduces power and engine life. This distortion might be brought on by uneven heating, local cylinder weakness, or mechanical stresses. Exhaust ports which have long passages inside the cylinder casting conduct large amounts of heat to at least one side of the cylinder while on lack of the cool intake may be cooling lack of. The thermal distortion resulting from the uneven expansion reduces both power and durability although careful design can minimize the challenge.
Combustion turbulence: The turbulence residing in the cylinder after transfer persists to the combustion phase to help you burning speed. Unfortunately, good scavenging flow is slower and much less turbulent.
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