[Land-speed] Fuel Mixture Change?

[drmayf]

Forgot to delete the trailer... bummer here it is again..

mayf

Skip, here is why, I think.  YMMV, lol. The rootes is a positive
displacement device. It pulls the air from whatever ambient conditions
are. But the mass of the air is always the same per revolution. When
that air gets under the blower it is hot, but it is still the same mass
of air. That did not change. It goes through the intercooler and gets
chilled somewhat. But the mass of air does not change.  Just the temp
changed. The mass that goes into the engine is the same mass that the
blower pulled in. Since the mass is the same, the fuel requirements are
still the same. You just now have a much cooler combustion chamber and
are not killing pistons etc from detonation or heat. If you were still
running the turbo, which is a constant pressure device rather than a
constant volume, then yes, the fuel requirements would need changing
becuase the mass of air changes. Thats what makes a turbo the far better
choice for power adders (but efi required to make changes, lol). Cool
the turbo air and it puts more mass in to maintain teh constsnt presure.

mayf....



Skip Higginbotham wrote:

> List,
>
> I am adding an intercooler to my freshened, blown/injected BBC gas 
> engine (15 lbs and 8:1 compression).
>
> It seems to me that I should richen the mixture since the induction 
> temp is expected to go down about 300 degrees. BUT....the intercooler 
> and the blower companies say no that the mixture should be left alone 
> for the first pass.
>
> How can the engine make more horsepower with cooler induction air but 
> no added fuel?????
>
> First pass will be to the 1 and then shut off.........even with the 
> wide band O2 sensor. Because I'm "old school" and parts are expensive.
>
> Skip
> _______________________________________________