UEGO and alcohol

Chris Conlon synchris at ricochet.net
Thu Sep 28 20:19:36 GMT 2000


At 07:12 AM 9/28/00 -0700, Matt Beaubien wrote:

>>>That is gonna be the biggest handful to get right,
>that you can 
>imagine, IMO
>The ports need to be rather large to allow any air
>into the motor you 
>got so
>much fuel displacing the volume of air that engine can
>even see.
><<
>
>This seems to be a pretty common misconception.  If
>you do the calcs for gasoline, the volume of fuel vs
>volume of air is <<1%.  Even if doubled for alcohol, 2
>* <<1% = <<1%.  

If you do the calculations assuming that all the fuel has
been vaporized (due to squirting on a hot valve), the
numbers get worse. For low molecular weight, oxygen
containing molecules (methanol, ethanol, nitromethane)
they get vastly worse. A mix of methanol vapor in air
is almost 12% methanol by volume iirc, even at stoich.

I'm not suggesting that *all* the fuel will vaporize, not
by any stretch, especially since many smaller oxygenates
tend to contain -OH and have higher heat capacity. I'm just
saying that even some fuel vapoization, with certain fuels,
can noticably cut down on your airflow. (c.f. LPG or CNG
as vapor vs. LPG injected as liquid.)

   Chris C.

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