When you flow heads on a flow bench, you are primarily looking for things which increase flow. Sometimes you are looking for things which change the flow quality; how the flow enters the chamber, does it swirl or tumble, etc. For either of these goals, knowing where the high and low velocity areas are can be critical to making improvements.
Some head porters will call low velocity areas "lazy" because they are not contributing their fair share to overall flow. This is especially true around the circumference of the valve. You can make a port bigger or smaller or change it's shape, but you can not change the size (significantly) or shape of the valve. So you want the entire area of the valve to be flowing as much air as possible. This means knowing the air velocity around the entire circumference or "shower curtain area" of the valve. If you see a velocity that is only half of what it is at some other point, changing the port design to use that area more effectively will likely increase overall CFM flow.
To measure velocity in the ports, head porters have used pitot tubes. For measuring intake port velocity, these tubes need a 180 deg bend, which makes them quite large. They can not get into small, tight places in the port, and they will not fit at all into small or short intake ports.
The solution is Performance Trends' electronic probe, which is very small compared to standard pitot tubes, even our exclusive Mini Intake. In addition to mapping out port velocity, you can attach the small tip (sold separately) to the valve and check the velocity all around the “curtain area” of the port. This lets you check how efficiently you are using the entire flow area, giving you ideas on how to improve flow.
Port Flow Analyzer screen showing Port Velocity Map, which the probes
pictured above can measure.
To do this you need the Velocity Tip and Indexed Valve Retainer. Fig 6. You also need the signal conditioning and connector provided with the upgraded Plus Electronic Probe. Fig 7. A great feature of the Velocity Tip is it can be installed by any customer to most any location on the valve, either the top or bottom side. You can also easily remove the sensor and continue using the valve in the head, and move the sensor to a different valve yourself.
Valve with probe installed in head on flow bench
The probe tip can be easily glued to most any valve in any fashion you need,
using the new UV cured adhesives. When you are done testing, you can
easily break the tip off the valve so you can use the valve in the engine and
move the tip to a new valve.
Gluing tip to valve
Graphing valve velocity in Port Flow Analyzer and comparing data to
previous "baseline", the inner graph
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