J-Rod
July 17th, 2009, 06:41 AM
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.
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.