Ancient History (now fuel economy)

[Mark Pitts]

As to the pressure in the manifold....

On the suck stroke... if you have HIGH DEPRESSION, the vacuum in the =
manifold tries to suck the descending piston up, or just plain doesn't =
help (grab a syringe, and see how hard it is to fill with water by =
pulling).

But, if turbo, or supercharge, or just plain acoustics is used to  get =
positive pressure in the manifold.. i.e. NEGATIVE depression, or comonly =
called pressure, this will (theoretically) help push the piston down the =
bore (now jam the syringe in the end of hose pipe, and the other end to =
the tap (faucet?)  you filled the bowl you were sucking from, and turn =
on the pressure (turbo), now dry yourself off, and go and find the =
plunger, cos that is probably the only accurate syringe you have for =
measuring head capacities).

Mark ;-)


----------
From:  Arnaldo Echevarria[SMTP:aec at ao.net]
Sent:  Tuesday, September 10, 1996 12:44 AM
To:  diy_efi at coulomb.eng.ohio-state.edu
Subject:  re: Ancient History (now fuel economy)


snip:

>The slower you spin the engine, then the higher the manifold pressure=20
>is for the same airflow (power), hence your pumping work (losses) is=20
>less.  Dropping the axle ratio (numerically) will give you benefits in=20
>fuel consumption at the same (road) speed simply because you have your=20
>foot on the throttle harder (strange but true! :)

Wait.  You said that the higher the manifold depresion, the higher the=20
power loss.  Now you say that the higher manifold pressure you get less =
pumping
work (ie better fuel economy)?? Now I'm really confused. Which is it?