Re: Re: Air Filters

["Thomas Petersen" <bmw318is92@xxxxxxxxxxx>]

Rob,

You're absolutely right - K&N and simular's only raises the HP's by 0-2 HP's 
on a normally aspirated engine - however, on turbocharged or supercharged 
engines, the increase is somewhat higher. On my M42 supercharged engine, the 
increase was approx. 8-10 HP's in the high rev. area, measured on a 
dynometer!
Your thougths about the effiency of the filtering is questionable, I find it 
very hard to beleave that the filter effiency on the K&N is poorer than that 
of the original! So, that should *not* be the reason for not installing the 
filter... Another more important issue, is the intake air temperature. If 
you equip your engine with the cone-type K&N, you should do something to 
isolate it from the rest of engine compartment.
I guess the general thing with the 'performance' air filters is that, alone 
they don't make a rocket out of your car, but combining them with other 
things, such as performance exhaust, chip, manifold, superchargers, 
turbocharges etc. will add up to some measureble gain in performance.

Regards,
Thomas Petersen,
'92 318iS Coupe - Supercharged to 205HP (with K&N :-))

>Date: Thu, 25 May 2000 23:56:39 EDT
>From: GRobWorkII@domain.elided
>Subject: Re: Air Filters
>
>Paliava,
>
>   Beware the savvy marketing of aftermarket air filter >manufacturers...  
>At
>the risk of opening a "digestive can of worms" here, let's just say >that
>there are many halfway respectable dyno comparisons showing >negligible 
>(0-2
>hp) increases that accompany the use of filters such as the K&N...  >The 
>stock
>airbox on your M30 is VERY nonrestrictive, and provides a valuable >service
>that some of the aftermarket filters seem to overlook - it actually >keeps
>foreign particulate from entering the intake.  To illustrate;  I let >my 
>last
>paper filter go for 24k miles.  The incoming air side of the filter >and
>airbox were quite nasty, caked with a layer of fine silts and dust... 
> >(There
>is an obvious need for filtration of incoming air.)  The intake side >of 
>the
>filter and airbox were perfectly spotless.  Would a K&N have filtered >the 
>air
>the same?  Questionable...  Is that chance worth 0-2 hp?  Not for me.  
> >Keep
>in mind that as an oiled foam filter gets caked with filth, >restriction
>drastically increases.  I'd put my money elsewhere!
>
>Rob Workman
>'85 535i (Holga)
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