I had an interesting discussion with someone about Throttlebody Scaler numbers when upgrading from a stock 78MM TB on a C5 Corvette to a GM 90MM TB.

Early on, I remeber that we changed the effective area of the TB from .255 to .320

The I see that there was another school of thought

http://forum.efilive.com/showthread.php?t=2684

B4349 ETC Throttle Area Conversion to .0320 from .0255.

V7.3
Engine Cal-> Idle ->General Parameters -> B4349 ETC Throttle Area Conversion

Area = pi * R ^2

R=1/2D, pi= 3.1416

A= 3.1416 * (1/2D) ^2

For 78 mm A = 3.1416* (1/2 * 78 ) ^2 = 4778.38 mm2 = 47.78 cm2

90 mm A= 3.1416* (1/2 * 90) ^2 = 6361.74 mm2 = 63.61 cm2

63.61 cm2 ( 90 mm) / 47.78 cm2 ( 78mm) = 133.13 % increase in surface area.


Then I see another thread on the subject
http://forum.efilive.com/showthread.php?t=837

Cross sectional area of 78mm= 4776 sq mm
Cross sectional area of 90mm= 6359 sq mm

Units for B4349 are %/sq mm

100%/4776sq mm= .0209 %/sq mm for the 78mm TB
(my factory tune had a value of .02077)

100%/6359sq mm= .0157 %/sq mm for the 90mm TB

So, I'm wondering. Has anyone definitely decided if the scaler needs to be increased or decreased? I've always increased it based on an increase in area. But, the person I discussed this with was decreasing the number in his tunes. I just want to see if anyone had decided which one was correct.