What do you really really expect to get when you strap that little halfords filter on to your german engineered machine? Seriously? 5BHP? You would notice nothing thats for sure.
I havent had time to read all the posts but I noticed 1 or 2 people who have sense and have mentioned that all of the hot air in the bay will get sucked straight up in to your intake. I would suggest a heat shield, and it would need to be a decent designed one too to.
Alternativly, you could save yourself the hassle of worrying about wether you have made 5BHP or lost 5BHP and buy a Gruppe M from a reputable tuning company and be done with it.
And fyi the Dave F was a very popular induction kit for the E36's, I have one on my 328i Sport and it is nothing like this halfords special. It is quite and oversized K&N filter with a well made heat shield, it gives you a good 10BHP (again its not day and night difference so you wont even notice it) I have this with an M50 inlet and BBTB's which helps.
Its all to do with Airflow thats measured in CFM, the stock box restricts a certain amount of airflow so using a cone like this will fre it up.
But it doesnt matter how big the cone is, or wether you had no cone on there at all the CFM flowing through the inlet can only be so much due to the diameter of the intake hose, Throttle bodys and inlet manifold etc.
So if you wanting more horses I would look in those places also.
Also, you talk about making your own heatshield using plastic. Have you ever thought of googling what materials reflect heat the best? Carbon fiber ring a bell for one?
And lastly, I dont want to sound patronising but comparing certain modifications over a range of different cars and engines really isnt the way to look at it, remember BMW really do know what they are doing (most of the time) I have dabbled with BMW lumps for years to come across that spending money on some parts really isnt worth it.
My 2 pence.
Last edited by e90-dave; 07-01-2012 at 04:19 PM.