Throttle body model: Stock throttle body vs bored stock throttle body

Hello all,

Quick question regarding simple throttle body changes.

I am planning on swapping out my stock throttle body to a large bored out stock throttle body. As the course has made me aware. It would be smart to change the throttle body model to reflect this change.

Under throttle body model I have two maps

Predicted Throttle Angle

Effective Area

My assumption is that because this is a stock throttle body housing, the predicted throttle angle should stay the same. The only difference is the effective area of the throttle body at each angle.

Since the bore is going from the stock 80mm to 85mm total effective area should change by 6.25%. So effectively, all I should have to do is multiply the whole Effective Area table by 1.0625 and leave the Predicted Throttle Angle alone.

Is this a correct assumption, or am I missing a factor in my calculation?

By increasing throttle body size we are enlarging area available for air to go through. Total area of a circle is calculated by formula Area of Circle = πr2

If we'll plug in your numbers into this formula we'll get 5026.4 mm2 and 5674.3 mm2 total areas respectively.

Then we divide second figure by the first one and get the final result - 1.1289 times difference or almost 13 percent increase (not 6)

Ok, so I have to consider the the total area percentage increase and not just the diameter increase.

So new area is calculated based on new radius and resulting mm squared is the actual percentage difference.

Other than that is my thought process on what map to change correct?

It said "Effective Area", did it not?

In theory, it would be the cross sectional area (CSA) of the opening, minus the CSA of the shaft, but in practice it doesn't make that much difference for this application.

Just want to be really sure.

Still new to all this stuff and mistakes can mean thousands in repairs. For all I know throttle area could be linked to some other compensation maps that directly need to be tuned as well to account for the increase in area.