the AFI intake got me thinking that was my orginal ideal a long time ago. Please feel free to shoot holes in this so I don't waste time/money. HSR base for higher RPM's and a custom built very large bolt on plenum......thus not needing anything larger than a 52mm throttlebody for response......this would be for a high reving destroked 400 cid. I'm thinking of the plenum as a large a "airtank" sort of like painting.....the compressor doesn't kick on often if the tank is large. Right track or absurd? please only people in know answer. No noobies that haven't tried a few different combos. Thanks!

 

I hope 1989gtatransam chimes in with his research done on his intakes.

But this really depends. There are some formulas that can be used but those have to be real world tested.

From another forum...
""It depends on your RPM range, Engine size and intended use of the engine. For instance, an engine utilizing an automatic transmission will have a much smaller plenum than an engine using a five speed. An engine with a five speed behind it can use another 20% more plenum volume. You must be careful here! The dynamics of the race track vary slightly from the dyno and in this regard, they vary a LOT! On the dyno you can tune an engine to produce max power by adding a considerable amount of plenum volume. In some cases you can almost double the volume and see a considerable power gain. On the track the engine will lag against the converter or worse yet, just not accelerate at all. Smaller engines are much more susceptible to this than larger engines. We know from extensive track tuning that our Pro Stock engines will not take any more plenum volume but on the dyno, I could add more volume and see more power. In this case, equations take a back seat to experience and practicality.

Your total intake runner volume (head and intake) to your cylinder swept volume should be from 78% to 96%. Depending on the rpm range you’re looking for.""

So you can see applications are pretty specific. Can be sensitive to volume just as combination can be sensitive to runner length and cross section.

Regarding the tb size, just because you have a large plenum doesnt mean you reduce tb size. Still have to feed the motor. Yes there could be some throttle response tuning by changing plenum size and tb size but at wot, motor still needs air and if you are turning a 400" motor that high, it will need atleast a 58mm, maybe even larger. 1989gta uses a monoblade on his 6500 rpm 369" motor