Your air inlet should be about filtration! how good it is at getting the stones and dust etc out of the air flow, if you don't want any restriction then, can the filter and put a mesh screen over the throttle body aka racing engines!!. I personally want my piston rings and bores to last longer than 10,000 miles so I use a filter. The filter I have is a K&N cone this will give me about 5 mbar loss across it at 7200 rpm ! I know this because I have measured it . There may be a slightly higher diff pressure at a lower air flow but that's because the filter is doing it's job properly. K&N have been developing filters for years ! I don't believe that piece of non closed cell sponge can offer the same engine protection as an impregnated cloth filter!
So it's up you, have no filtration or one that requires cleaning every 5000 miles or get something that will do what it was designed to do, protect the engine! There's a really good Auzzie web site called Autospeed that bangs on about this and where best place is for an intake etc,etc. ps don't put holes in your bonnet it won't increase the air flow!
The best piece of advice is to have a sealed inlet tube front the front of the car to the TB with no holes! This way you will get a sort of ram air affect as the car is travelling the air is forced through the air intake, this is only a few 10's of mbar but everything counts !! The disadvantage is that anything dust dirt diesel soot will be rammed down the intake as well!! So your filter will need cleaning more often. The standard air boxes have special catch pot area where heavy particles fall out of the airflow and are trapped! just check how much grit/leaves/twigs/flys are in your airbox!! Remember your intake in like a vacuum cleaner !! it will get blocked and then the air flow will be affected! So clean it as often as you can especially after a long run.
The next big problem with a ram air system is how to tune the thing! You can't do it on the RR as you will need a lot of air flow through the front to replicate the airflows at different speeds, most tuners will map the car to run richer the higher up the rpm we go. It's not an exact science so don't be surprised if the RR results don't show massive gains. In fact I would be a bit concerned if my car ran such a high bhp with little air flow into the engine. This means the engine in potentially could be running lean on the road! as the ram effect has not been allowed for and the engine may be prone to detonation at high rpm ie the 'knocking' increases due to the VVT advance timing system kicking in.
Hope this helps,
Cheers,
Dave
