Frank
08-04-2006, 11:07 AM
Found some information about flow, etc. According to Corkey Bell's book, throttle body velocity on a turbo motor should not exceed 300-ft/s. What good is this too you? Well I have equated the following together for more practical usage. This is done with a combination of data from common throttlebody sizes, hp levels, and maintaining close to a 300ft/s velocity. 300ft/s velocities were used to show the minimum size needed for that horsepower level efficently while taking into account drivability. Dont forget that the manifold's neck has to be ported to the size of the throttle body also!
850cfm -> 75mm tb -> 298ft/s -> about 650chp
720cfm -> 70mm tb -> 289ft/s -> about 550chp
640cfm -> 65mm tb -> 298ft/s -> about 500chp
540cfm -> 60mm tb -> 296ft/s -> about 400chp
470cfm -> 58mm tb -> 276ft/s -> about 350chp
400cfm -> 52mm tb -> 290ft/s -> about 300chp
340cfm -> 48mm tb -> 291ft/s -> about 250chp
Now in order to run more HP (aka CFM) for any given throttle body, you need to increase the amount of boost. When you increase the boost you increase the velocity.... when the velocity starts increasing over 300 ft/s, the drivability (efficency of the system for things like fuel economy and power on tip in) decreases. Yes you could pull more power by upping the boost even more, but it becomes less efficent. By increase the throttle body size to match your mean power goals, you are ensuring good drivability and power combination.
Frank
PS> This thread is based on my original thread I created last year on turbo dodge. This has been revised, etc.
850cfm -> 75mm tb -> 298ft/s -> about 650chp
720cfm -> 70mm tb -> 289ft/s -> about 550chp
640cfm -> 65mm tb -> 298ft/s -> about 500chp
540cfm -> 60mm tb -> 296ft/s -> about 400chp
470cfm -> 58mm tb -> 276ft/s -> about 350chp
400cfm -> 52mm tb -> 290ft/s -> about 300chp
340cfm -> 48mm tb -> 291ft/s -> about 250chp
Now in order to run more HP (aka CFM) for any given throttle body, you need to increase the amount of boost. When you increase the boost you increase the velocity.... when the velocity starts increasing over 300 ft/s, the drivability (efficency of the system for things like fuel economy and power on tip in) decreases. Yes you could pull more power by upping the boost even more, but it becomes less efficent. By increase the throttle body size to match your mean power goals, you are ensuring good drivability and power combination.
Frank
PS> This thread is based on my original thread I created last year on turbo dodge. This has been revised, etc.