Re: [DML] Upgrading the Air Filter?

[Martin Gutkowski <martin@xxxxxxxxxxxxxx>]

Some maths to ponder

Maximum throughput of air filter is when the engine is at top speed (for 
argument's sake, let's say 6000rpm)
Capacity of engine 2.849 litres
Assuming 100% volumetric efficiency (hah!)
That's 2.849 x 0.5 (in a 4-stroke, each piston only draws air in on ever 
second rotation) = 1.4245 litres per rev
Which multiplied by 100 equals 142.4 litres of air every second. 
(multiply by 6000 and divide by 60)

Someone who knows more about this stuff than me could work out how fast 
this air must be travelling given the size of the air intake tube. I bet 
it's shifting at quite a lick! Part of me also wonders if the air box is 
a specific shape. Certainly Renault fans go to great lengths to retain 
the original air intake venturis on the 25 turbo and alpine engines 
because they're a very specific shape. A properly designed venturi will 
actually increase the volumetric efficiency of an engine.

I'm not trying to make a point here, just musing some figures. I have in 
the past read several articles that point out that the cost of a "free 
flow" K&N air filter would otherwise buy an awful lot of regular 
filters, all of which perform just as well as long as they're replaced 
regularly

Martin

Dave Swingle wrote:

>
>I first-hand witnessed a dyno test where the owner swapped between 
>stock and the K&N filter. On a turbo car (which you would expect to 
>be even more sensitive to this sort of thing) the improvement was in 
>the neighborhood of one HP. 
>
>I have never understood how changing the intake/filter could have any 
>impact at less than Wide open throttle. At anything less than that, 
>the throttle itself is the restriction, and you can vary that. How 
>often to you-all drive around with your foot on the floor? 
>
>Dave S
>
>  
>






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