Depending on the type of engine and valving and a few other points,
increasing air intake does improve response which some interpret to mean a
lot more power.  If you open flow the intake by increasing intake sizes and
less limiting filter and a few other points you will get no real increase
unless the exhaust is also opened up.  This means a more flowing cat (legal
of course) and a full flow muffler and larger diameter piping with more
gentle curves in it or straightened out.  Just increasing the flow on the
filter will only add minimal hp.  Opening up the full intake system can add
5 to 10hp. Opening up the exhaust as well can add 10 to 20 hp.  Anything any
further is going to need valve work.  With the correct valve work and intake
and exhaust work you can add as much as 50hp to an engine.  Then really flow
it by going turbo.

Now the major note and disclaimer...some systems have fuel systems
controlled to a point that there is no change whatsoever because they are
already close to the max.
With those you will need to also adjust injectors to next size and maybe
reprogram ecu.

jimt

On 11/27/04 3:53 PM, "Gary Lee, Vanagon Racks" <gary2a@TELUS.NET> wrote:

> The recent discussion about possible improvements to the intake air flow
> chain in the vanagon got me to thinking.
> Here are my theoretical assumptions:
> 
> 1. The volume of air required by a gasoline engine is directly proportional
> to RPM.
> The higher the RPM, the more air needed.  A gasoline engine needs to
> maintain a relatively constant air fuel ratio.
> 
> 2. The stock air filter - throttle body - intake manifold  system is capable
> of flowing enough air for the stock engine up to redline.
> 
> So, increasing the volume of air the intake tract can flow will have no
> affect on power or fuel economy (in a stock unmodified engine).
> 
> If you drive your van at less than redline, increasing the size of the
> throttle body and/or increasing the size of the intake tract will have no
> affect
> on performance.  Certainly everyday city driving is far below redline, well
> within the capacity of the stock AFM and air filter.  Even if the stock
> system is
> restrictive, there should be lots of headroom for normal driving with a
> stock engine.
> 
> If you do not accept the above, then some related questions are:
> - just how bad is the stock system?
> - do things like K/N air filters really honestly offer more hp and better
> mileage?
> 
> Corrections and rebuttals welcome.
> 
> Gary Lee
> Calgary
> 
> 

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jimt
Planned insanity is best.
Remember that sanity is optional.
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