[Diy_efi] WB O2 system

[Stephen Andersen]

I am assuming that the effects will then be similar if one is
running "standard" petrol (assuming there is such a thing) but
adding in water/alcohol injection?  The alcohol in the mix 
will screw things up same as if it is mixed into the 
fuel, and both constituents will significantly impact
the "moistness" of the mix and hence the recorded values?

Geez, this stuff is kind of messy!!!

Steve


> -----Original Message-----
> From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org]On
> Behalf Of Garfield Willis
> Sent: Thursday, June 13, 2002 2:25 PM
> To: diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] WB O2 system
> The reason is pretty obvious once you consider the additional 
> effect of
> the oxygenates in the fuel, which not only affect the 
> combustion ratios,
> but ALSO alter the amount of exhausted water vapor, which 
> since it's in
> gaseous/vapor form, dilutes the other components the sensor 
> is sensitive
> to. The alcohols are prodigious water vapor producers. This 
> happens both
> rich and lean of stoich, to different degrees. So all the partial
> pressures of the components are also skewed by the wetness of the
> exhaust. This is ALSO true of petrol combustion to a lesser 
> degree, but
> the effect is already built into the sensor's curve for 
> petrol, because
> the amount of H2O byproduct is known for petrol combustion. But change
> the fueling, and especially when adding oxygenates, and 
> that's no longer
> the same at all.
>
> If you need to understant these issues, and don't have a 
> meter/mfg that
> supports your alternate fuels, you need to find yourself a 
> good chemist
> that knows MRM Combustion Stoichiometry, and explain your situation to
> him. Plan on spending quite a few beers (or bucks) in return for the
> imparted knowledge. Then get ready for alot of hand calcs if 
> your meter
> doesn't support them. That's assuming you have a real honest2gawd AFR
> meter.

I hope that I now have this one covered!! ;-)





 


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