Many of the applications of flowbenches and the data that they provide are often set apart from normal data because of the mystique associated with flowbenches and flow testing. Engine component airflow data is easy to compare if you know how.
An air flowbench is essentially a device that measures the resistance of a test piece (cylinder head, manifold, carburetor, throttle body, exhaust systems, etc.) to flow air. Many different designs and models are on the market today that allow the user to compare flow results before and after changes in the flow path.
The skillful use of tools makes the job of testing airflow much more fun than makeshift approaches and is very useful:
Magic Wand: Provides an indication of activity and direction of flow inside a port or device under test. The magic wand is made from a 1/16″ diameter welding rod that is 12″ long. The welding rod has a small round ball on the end (from placing the rod in a molten pool of metal), and a piece of Dacron or nylon type kite string is glued to itself to form a little flag about 3/8″ long. This is a good flow visualization indicator.
Pitot Tube: Provides a way to probe the port to supply local velocity numbers. Can be used with SuperFlow’s FlowCom, pressure manometer, or special port software to plot areas of activity in the airstream in a port. Difficult to use in very small ports. Requires one type for exhaust use and a different one for intake use.
Flow Ball: Provides a method to probe a port and verify if flow is attached or separated at some point in the port. Flow balls are made by tack welding various diameters of ball bearings to a 1/16″ diameter welding rod that is 12″ long. Flow balls typically start with 1/8″ diameter and go to 1/2″ diameter in 1/16″ increments. These tools are an easy way to find problem areas in the port without great difficulty. Very effective in evaluating the short-turn radius in a port or where a wall has a directional change.
Port Molding Rubber: Provides an easy way to look at a port. The mold is made of silicone based material (a two-part process) that is poured into the port (with valve in place); after it sets, it can be removed in one piece. The mold can be sliced and the cross-sectional profile drawn on graph paper to help measure the area at different locations in the port.
Graph Paper: An easy way to measure the cross-sectional area in a port. The paper cut-outs are trimmed to fit different places in the port, and the squares can be counted, providing an accurate way of measuring the areas.
Poster Board: An easy way to make patterns to help the developer reproduce the same port shape and size. The poster board can then be used to trace patterns in aluminum or plastic that provides benchmarks for the developer to use in duplicating an established shape in other ports and cylinder heads of the same type.
Radius Inlet Guide: Provides a smooth approach to the port or device being tested and is intended to decrease the “edge effect” at the port flange. The radius used should be as large as possible and at least 1/2″ radius. The thickness of the inlet guide should be at least 50% of the height of the port. The size outside the port cross section should also be at least 50% of the height of the port so all directions have a smooth approach. It is not uncommon for the inlet guide to improve the flow from 6% to 10% over no guide in use.
Exhaust Pipe: All testing of the exhaust side of the cylinder head should use a short section of exhaust pipe that is at least the diameter of the port. The appropriate length is about 10″ to 12″ long.
Bore Simulation Adapter: All flow testing of cylinder heads should use an adapter that simulates the bore size within 1/16″ of the diameter used on the engine. The length of the simulated bore should be at least equal to the diameter or more.
Wet Flow Adapters: Provides another reference of flow visualization that is valuable in evaluating what is happening in the combustion chamber and helps to sort out problems in that area. Best when at an air/liquid ratio that represents the normal air/fuel ratio an engine uses. This process has helped solve some problems that otherwise would go unnoticed.Calculator: Ever present when the flow tester is on the phone comparing numbers with another tester. Provides an instant indication of hype vs. truth because known numbers are compared to claims.