On Fri, 19 Mar 2004 13:23:57 UTC "Stephen Bigelow"
<
[email protected]> wrote:
>
> "Nom" <[email protected]> wrote in message
> news:[email protected]...
> > Bruce Chang wrote:
> > > Performance mods can increase your fuel economy.. If the engine can
> > > use what it has more efficiently, then you'll get better gas mileage.
> > > In other words, if you can get more power out of the same amount of
> > > fuel, then you're likely to get better gas mileage.
> >
> > Agreed.
> >
> > However, the air-filters he's referring to, are designed to let more air
> > into the engine. The only possible byproduct of this, is that more fuel is
> > injected too !
> > They aren't an "efficiency" mod - they're simply a mod to let the engine
> > cram more mixture in ![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
>
> But if the mixture isn't needed (I'll have to assume his power requirements
> for steady state driving have stayed the same) then *efficiency* has
> increased.
>
> Simply put, the throttle plate won't have to open as far for a giving speed.
Somehow, this discussion seems to be missing the point. The computer
is going to try to achieve a specific air-fuel ratio - not matter HOW
the air gets there. Power output depends on just how much air/fuel
there is in the cynlider when the mix burns. Assume the computer uses
the temperature and manifold pressure (I still feel that mass air flow
works a bit better, but that's another argument) to fire the injector
to get a perfect mixture. You step on the throttle, MAP goes up, fuel
increases, total mass of fuel/air sucked into the cylinder increases,
Viola! more oomph when the mixture ignites so you accelerate. Doesn't
matter how the air got in, just that it got there.
The only limitation on this is full throttle (WOT). If something in
the system (like the filter or the throttle body size) prevents the
cylinder from pulling in as much air as it possibly can then you gain
- but only at/near WOT. Anything less and the system could care less
as long as there is no limit on how much of the demanded air is
available. The only other factors are whether the injectors can
supply sufficient fuel to the mix (again, a WOT issue, not cruise) and
how the computer uses the TPS info to modify the fuel/air ratio. Even
if the TPS causes the computer to richen the mix, the O2 feedback will
in turn lean it so you are back where you started.
Of course, this all assumes that the computer is WAD and playing by
the rules and we all know how infallable computers are... Carbs
depend on air flow characteristics to get the mixture right so all
this intake stuff becomes important but it is much less so with
computer controlled FI.
--
Will Honea <
[email protected]>