Rick360
Electrical
- Feb 12, 2004
- 17
I have seen in many places the calculated (using Bernoulli theory) limit of airflow of 146cfm/in² with a D/P of 28"wc. This holds very true when flow testing intake ports on cylinder heads. The very best intake ports can flow close to 140cfm/in² at the throat area (mcsa) of the port.
Why is it that exhaust ports will flow (on a flowbench) much more than the 146cfm/in²? I've seen them around 175 - 180 cfm/in², 270cfm with throat area of 1.50in². I've heard some of the best will flow 300cfm with the same area (200cfm/in²). These tests were done on SF600 flowbenches and agree with many head porting shops as well so these are not off-the-wall numbers, but very typical of racing exhaust ports.
What is going on here for the exhaust to flow so much more cfm/in², and even more than Bernoulli says?
Rick
Why is it that exhaust ports will flow (on a flowbench) much more than the 146cfm/in²? I've seen them around 175 - 180 cfm/in², 270cfm with throat area of 1.50in². I've heard some of the best will flow 300cfm with the same area (200cfm/in²). These tests were done on SF600 flowbenches and agree with many head porting shops as well so these are not off-the-wall numbers, but very typical of racing exhaust ports.
What is going on here for the exhaust to flow so much more cfm/in², and even more than Bernoulli says?
Rick