View Full Version : flow rates


Monte LS....1
12-20-2009, 04:23 PM
All you ever see is flow rates on intake and heads, but i've yet to see any discussion on throttle body flow rates. The heads and intake can't flow anymore then what the throttle body will a flow, so why is this? Do the throttle bodies out flow the other two pieces by such an amount there's not much of a need to discuss this?

Dan Stewart
12-20-2009, 10:05 PM
It isn't discussed because a throttle body is simply a straight pipe with a butterfly valve mounted in it.

Increases in air flow are directly proportional to the increase in the inner diameter of the throttle body.

Unlike heads and intakes which typically have various diameters and radii which make simple calculation of airflow impractical and therefore necessitate live measurement of flow.

Plus under WOT, the surface area of the throttle opening doesn't change, unlike heads, which have valves that continuously open and close.

Dan Stewart
12-20-2009, 10:12 PM
Something else I should point out.....

A lot of guys claim "my car is faster with the new uber huge brand x throttle body", when in actuality it isn't.

It just seems faster because the larger diameter allows more opening than a smaller diameter at part throttle. This gives the illusion that the car is "more powerful" because one doesn't have to push the throttle as much to get the same acceleration.

This is an old trick that oem's use to make people think a weak engine is more powerful than it actually is. Typically seen on small displacement engines.

In other words, you size the throttle body based on the required max flow. Any bigger than that, and you add zero power. The only result will be hard drivability.

Monte LS....1
12-20-2009, 10:28 PM
I understand a little more now. Trying to figure out what I need to pick up, but was worried I'd have too small or too big of a throttle body so I was going to try and match things up and couldn't find anything to do this by.