I have used the original air intake below the nearside headlamp and behind the bumper to feed mine as they have done with ITG Maxogen and X-Power induction kits (pretty certain they know what they are doing). A lot of people shun this as they say that there is no 'Ram Air' effect and they are right! It also means that I dont ram bugs, grit, water, small children etc down the pipe and cause premature blockage and contamination of the filter. The time you want the most cold air is on acceleration, especially from a standstill and then there is no ram air at all. If you route this cold air ram feed pipe too near the engine/exhaust/radiator or have the pipe very long (somrthing you will have to do on the ZR unless you do some creative modifications/pipe routing), then you will suffer from the dreaded heatsoak as the pipework begins to heat up from the radiated heat of the engine when you are stationary.
If you put the pipe intake too low down then you will end up sucking/ramming even more crap into the filter but the worst problem, especially if you dont have a water trap, is that you could end up getting copious amounts of water sucked up into your engine, especially if you are unlucky enough to hit a deep puddle or some such. Water, unlike air is not compressable and if enough gets into your cylinders then as the piston try to compress it, then you end up with a hydraulic lock. This WILL destroy your engine with bent conrods being the least of your worries.
Sorry to go on at length, but I have studied aerodynamics and there is another fact you should be aware of when siting your air intake. If you must have it stuck into the airflow, then make sure that it is perfectly perpendicular to the airflow. If it is at any sort of an angle or a tangent to the airflow, then you will start to get a venturi effect and in the worst scenario, you could actually end up with airflow across the pipe causing suction and actually cavitating the airflow into the intake.
Even with the biggest intake in the world, it will all be goverened by the final size of the pipe into the TH (Throttle Housing). No matter how much air you ram in, this will be the biggest restriction. Imagine a door into a room that is only wide enough to let 3 people through at a time. if there are 30 people in the room trying to get out then going through 1, or 2 at a time is great. If they all rush at once, you will still only get a maximum of 3 through no matter how many there are pushing behind it. so even if there were 3,000 people only 3 at a time will go through. Its the same with the ram air effect. No matter how much you shove in the engine will only use what it needs, the rest will just stagnate (unless you want to start talking about plenium chamber technology and cavitation resevoirs)
To test the benefits of closed induction kits on a Rolling road is almost impossible. There is no way on a static car spinning its rims on the rollers to imitate aerodynamic forces and airflows. There will be no ram air effect and if you used some sort of fan then at best, unless it can simulate a 60+MPH winf there there is completely no point.
Dont know if anyone else has any views. As for the which is best, on a small engine like the ZR has (and I mean this for all of them, 18 is still relatively small)) then the amount of power increase you are going to get from just a filter change is never going to be much. I did a test on a rolling road between an open filter and a standard induction set up but with a performance panel filterin place of the horrible paper OE paper one. The panel gave 2BHP at the wheels more at the top end (6200rpm) and the open filter gave 7 bhp more at the mid range (4200rpm).
hwell:
