Here is a side-by-side comparison of the original factory 90° intake tube to the plastic Evo III straight trumpet.
Note that the diameter of the outlet of each tube (where they attach to the airbox) is identical.
Thus there should be no dramatic difference in throughput between the two intake tubes.
However, there are most likely improvements in other areas. The flow is probably more laminar with the E3 trumpet and
the benefits of a laminar intake flow should not be underestimated. The Motorsport guys were a bright bunch, and they
would not have pushed this mod past the bean-counters unless they felt it would offer a real benefit.
The path that intake air follows with the original 90° intake tube is shown here.
The point where the first green arrow enters the plastic "box" is where the American style
black plastic grill is located in the spoiler of U.S. cars. This grill is covered up when
converting to Evo III style "tow-hook covers". As you can see, if you add the tow-hook
covers, but do not convert to the Evo III intake trumpet, then you will be starving
your engine for air.
Note that the E3 trumpet sits roughly equal with the mounting point for the front bumper.
It is impossible to show here, but when the front composite bumper is fitted, the E3 trumpet
goes right into the "U-shaped" channel so that it can pull air from an undisturbed location.
Yet this location is essentially at the same pressure as the air which piles up in front of
the radiator. Read = a high pressure zone. And since the air has not yet traveled through
the radiator before it is sucked into the intake trumpet, then it is at roughly the same
temperature as ambient. Read = cool air intake.
Here is another Evo III intake trumpet mounted on Matt Weimer's car.
It is obvious from this photo how the Evo III trumpet is exposed to the very same air that is about
to enter the radiator. This air is still cool, as it has just arrived from out in front of the spoiler.
The air is also at high pressure since the radiator forms a flow restriction - the air piles up in
front of the radiator before it can squeeze through. The Evo III trumpet sticks protrudes into this
low temperature/high pressure region to draw in intake air.
This photo shows the European style Evo III tow hook covers installed on my car.