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if you look at 99% of high HP cars in general, they share the same intake plenum (both V and I engine designs). Air is collected and drawn from the same cavity that feeds all the cylinders. In Z32s (and vipers(?)), the left bank of cylinders draws air from a seperate air cavity (plenum). the right bank draws from it's own seperate air cavity. Both plenums have their own throttle bodies too. So, you now have 2 plenums with the potential for unbalanced air pressures. If one turbo has a 'lazy eye' and doesn't produce the exact same pressure as the other, you will potentially cause a lean condition in an entire bank of cylinders.
So nissan included a balance tube to correct any imbalances. but for sick HP cars (300+rwhp imho), that balance tube is not enough. The compressed air being distributed doesn't have the ability to 'squeeze' itself through a little bitty balance tube. AND for that air to balance properly, it potentially has to go into reversion in the intake runners (very bad). Wait, there's more. Then, add in two throttle bodies. if the throttle bodies are not synced perfectly, you will not flow the same air into each plenum. You still have an inbalanced engine. If you have imbalanced flows, you will have a severely imbalanced engine. One bank of cylinders will generate substantially different power the the other bank. On higher HP engines, this difference will be very noticable both on the dyno, and in reliabilty.
I think this is the number one problem folks are having keeping their 500+rwhp engines to last, or from getting numbers that 'the book' says they should get. If you look at all the SICK hp cars in general, they all share a single intake plenum system (at the very least). Many have single throttle bodies. It just makes sense.
Petz #3
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