if I get a bigger throttle body for my car, do I need to increase the size of my plenum intake?

Answer 1

Generally speaking the "size" of the throttle body is not a mechanical measurement. Like the old carburetors "size" is determined by CFM or cubic feet per minute of air that can pass through it.

There are physically bigger carb's but if you moved up from say and 550-650cfm or 650-750cfm you would not see an obvious dimension change. The interior dimensions would be either larger or smaller and the jets would be larger or smaller.

Similarly, if you bump up your throttle body a few hundred CFM's you will not see an obvious external change in dimensions unless you are already at the maximum sized throttle body for that intake manifold.

Even if you went drastically higher like from a 300 to a 850cfm you would not likely need to change intake manifolds. There are several adapters on the market to make things match up if you slap something bigger on something smaller.

The thing about intake manifolds is that they are rated to a maximum RPM. Many stock manifolds have a maximum RPM rating (Red Line) of 4,000 to maybe 6,000 RPM's. If you are in the 6,000 RPM range then this is a good medium range and can be pushed to 8,000 RPM's at idle without any noticeable power loss.

I suspect that you will not need any adapters or new intake manifold to make your new throttle body fit or work OK.

Good Luck!

Answer 2

Short answer: No. Long answer: Get a cold air kit first, then redo the exhaust completely. Headers, high flow cat, free flow muffler, mandrel bent piping. My personal opinion is that bigger throttle body is money better spent elsewhere. Good Luck!