UEGO and alcohol

[Greg Hermann]

At 4:24 PM 9/28/00, Chris Conlon wrote:
>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.

And--the extra oxygen tends to increas flame speed. this is one of the
major effects on timing requirements.

Greg


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