as said previously I dont know what this upgrade will do in real life although I have an idea or at least hope
The runners in the stock lower manifold are squares and not really "flow improved" and they have "dents" inside for the bolt threads. The upper manifold is widely open and jagged inside so that air can flow everywhere and is not directed but only collected.
The GT-R manifold provides air flow from the throttle bodies inside the outer collectors and then divide the air into 2x3 runners where it can accelerate and is not swirled. A continued round shape provides maximum flow vs. the angular design.
For a natural aspired engine the most important thing regarding air intake is to provide as few restrictions as possible - even better is to create a situation where the engine is offered more air than it would naturally aspire, called "ram air" and is e.g. used in motorcycles. You try to force a positive pressure into the cylinders which is nothing else than a turbocharger does by brute force.
It may be that Nissan rocket engineers have calculated and designed the manifold to create maximum torque and power and that my upgrade does nothing good but from a common sense I would say we actually will see an improvement of any kind whatsoever.
But Spoon is absolutely correct - this mod has proven nothing yet and until we put the car on the dyno and compare with our runs before nobody can say it was worth the money and the effort.
@Kingbaby
the runners cannot be any lower because otherwise the upper plenum will hit the valve covers - we chose the lowest position it can go. First I was hoping to work with strut bar spacers but it showed that the GTR manifold is a lot higher than stock plus doesnt have the notch for it like the stock one has plus the stock plenum is angled towards the front while the GTR sits at a constant level.
tomorrow we will continue the welding on the lower adapter and today the upper plenum goes to the powdercoater. Stay tuned for more pics soon !
Chris