Redd, the sound improvement is pretty good and as for power, well, that's difficult to judge. Its certainly not perceivably worse. The drive to work on the motorway was fast but that may be because I love the sound
It may not be to everyone's taste as it obscures some of the exhaust note.
As I have LPG fitted too that is a good test bed for changes such as these. The 'brain' is much dimmer than the Alfa ECU and reacts to change much slower. I have found that the revs are a little too high at tick over and the car seems a little more keen to get on at higher (5K+) revs, both of which would suggest better airflow. An LPG problem I have always had of the engine getting flooded with too rich a mixture causing the odd stall in traffic queues has gone as the engine seems much quicker at recovering from very the low revs that happen before it stalls (that sells the whole idea for me there and then!). I have a big drive mid-week that involves more single carriageway roads so I`ll give it a good check out for overtaking then.
I`m not sure of the physics you are using there. A small aperture opening into a larger space will cause a drop in pressure and velocity, but it will smooth out fluctuations in pressure and especially returning pressure waves, like sound. Maybe the sound that I`m getting is one that would get absorbed by this 'chamber'. The inlet also has a shoulder 'kink' that looks like it goes around a pipe, but there is no pipe for it to go around! Very odd. Maybe that is also there for some similar sound baffle reason?
I think you are correct, Dupes, that a ram from the from grill would work, but I too rejected that idea because of water ingress. The original pipe would avoid that problem with its high-up intake - and that is all I can really see that it does do ( we DO need a designer to comment!). I don`t think that the air input from under the headlight is of much use as its a tiny little slit.
The mod I have made puts the intake hole (about 80mm BTW
) at right angles to the bumper grill but a decent distance back. As long as the gravel under tray remains on then only water spray through the bumper grill can get in. I didn`t notice much muck in that area when I took the under tray off. I have to accept that I will get more water spray and dust getting in but its a compromise that has given me great sound and a colder air supply to the intake so its worth it so far. The engine wont care if it gets some water vapour in it - direct water injection is a known good high tuned engine cooling method (
) and the exhaust gas I create from burning LPG is mainly water vapour so I don`t see it causing much of an issue. It might even clean the throttle body
I don`t think it will be possible for a huge bucket of water to get in the aperture so my only concern is what increased water spray will do to the K&N.
With a K&N filter and not paper I can physically rotate the side of the filter facing the hole easily without removal and can clean it much more often. I do a lot of miles so can give it a check after 5K miles in 2 months time. I may switch to a foam filter which is easier to clean and will be more resilient to water - anyone know what a K&N does if water hits it?
BTW I also removed the gravel tray soundproofing as it was shot to hell anyway.
Really, its such an easy mod and so simple to reverse that its worth any V6 owner giving it a go just to see what they think. It should take 30 mins max to do and most of that is removal of the under tray. You don`t even need to remove the pipe, just disconnect and tie-wrap out of the way.
Oh dear, I`ve written an essay again