FR Twin 65mm Calibration Glitch?

[CCS86]

Hey guys, I'm getting ready to put on a Ford Racing twin 65mm throttle body (M-9926-CJ65) and was looking over the calibration tables. I noticed something odd about the data in the 14.1 inHg row. Between 1.3* and 1.5*, the effective area drops. This doesn't happen anywhere else in the table. If you look at it graphically, the 1.0* and 1.3* values seem high relative to the curve:

Twin 65 Eff Area.png


It's not a huge amount. Maybe around 14% high from a smooth curve.

I know that Accufab mfgs these, but does anyone know whether Accufab of Ford generated the calibration tables? I'm curious whether it's an aerodynamic fluke, or skewed data.

[Thatwhite5.0]

Not a glitch, it's all part of a flow formula.
throttlebodyglitch.JPG

[CCS86]

Not a glitch, it's all part of a flow formula.

I understand how the two tables are linked, being the inverse of one another. That doesn't explain what I showed though.

The physics say that for a fixed TB opening area, increase in the engine's vacuum causes more flow, or a larger "effective area".

Geometry says that for increasing angles of TB opening, the cross sectional opening area increases.

So how, given a fixed amount of vacuum (14.1 inHg), and an increasing TB opening angle (1.3* -> 1.5*), can we get a reduction in the effective area?

[MRRPMBRP]

At low openings like that, the throttle blade cut angle will effect flow, same as valve seats effect flow at low lift, on valves.
Could be that. I would imagine this the importance of having actual flow data to enter, as opposed to just entering a linear flow value.

[CCS86]

I get that the flow rate will definitely not be linear with respect to blade angle. But it is hard to imagine the blade opening (albeit a very small amount), and flow rate dropping.