making own bbb's

[illSHOyou]

Why doesn't somebody build a single large plenum with short trumpets and a single 75-80MM throttle body? Probably good for max power in the 8,500 rpm range.

 

[jonheese]

The fact is, the extra price you pay to have these full sized plates installed have no dyno proof to back them up and justify the cost. There also is no valid proof to back up that using stock plates with BBB's will reduce power.

There is a theory at work here though, and it's what the entire V6 SHO intake design is based on: Helmholtz frequency tuning. I know most of you know this, but I think it bears repeating here:

The intake runners (both short and long) are each tuned to a specific RPM where the pressure waves bouncing around inside the intake are moving at the perfect speed to ram air into the intake ports at the exact right instant that they open. It's kinda like a poor-man's forced induction. The long runners are tuned for a lower RPM and the short runners are tuned for a higher RPM, hence why the short runners open up at 3950 RPM and stay open til redline.

Now, if you allow the short runners to "leak" into the intake port while at low (<3950) RPMs (either with ill-fitting butterflies, or no butterflies), then it stands to logic that that will disturb the column of air and its bouncing pressure waves, lessening the effect of the long runner tuning, and lessening the performance at lower RPMs.

Now, exactly how much this will affect it is not obvious or easy to calculate, but it certainly does make sense that it will have a deleterious effect, especially if there is anecdotal evidence to support it.