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General comments (archive)

[ Follow Ups ] [ 7-series (E32) Message Board ] [ Msg. Board FAQ ]

Posted by Wayne McKay on August 07, 2001 at 23:29:04:

In Reply to: Power Flow Intake kit from Bavarian posted by Adrian on August 07, 2001 at 11:51:11:

Three things to consider:
1) The hot air issue is real. A cylinder draws in a fixed volume of air on each stroke. A fixed volume of cold air contains more oxygen molecules than does the same volume of hot air. Oxygen is what mixes with the fuel and goes BANG, therefore more oxygen = more BANG = more horsepower. Cold air is better!
2) Increasing the fixed volume of air into the cylinder also increases the number of oxygen molecules in the mixture (e.g. turbo charging). Other means are larger valves/ports, honed manifolds, high performance cams, etc., etc., as well as the freer flowing air filter concept you refer to. However, all of the improvements to the intake side does no good if the limiting factor to increased 'breathing' lies elsewhere (e.g. exhaust valves, manifolds, piping, mufflers, etc.). The biggest bang for the buck in improving breathing will come from eliminating the "weak link in the chain" if you know what I mean!
3) Free flowing intake has to come at the expense of filtration. Dirt is the consumate engine killer and by far the most dirt enters the engine through the air side of things. You will have to judge where you draw the line on that one. You will find lots of controvercy on that issue in the archives - usually centered around K&N as that is the most popular brand out there.

Many times you will see comments about one free-flow filter system or another not doing anything except costing money. You can usually attribute the cause to one of the above first two reasons.

On the other hand, it will make your engine sound a little throatier if that is worth it to you. We used to flip the air cleaner lids over back 30 years ago. It made the inexperienced sidewalk gawker think our small block 289 cu.in. was a 390. Although it didn't help any when it came time to line up beside someone with a real 390 and we had to put our money where our mouth was!

Hope this helps,
'88 750iL



What do you guys think of Cone shaped air filter kit from Bavarian? I heard it is not worth it because all the hot air under the hood gets into the intake... Is it true? DO you think it is worth $220 for 750IL?





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