[Diy_efi] WI, methanol, and corrosion

[Greg Hermann]

At 7:29 PM 1/23/03, Axel Rietschin wrote:
>----- Original Message -----
From: "Adam Wade" <espresso_doppio at yahoo.com>
>To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
>Sent: Thursday, January 23, 2003 6:08 PM
>Subject: Re: [Diy_efi] WI, methanol, and corrosion
>
>
>>
>> --- Axel Rietschin <axel_rietschin at compuserve.com>
>> wrote:
>>
>> > I fail to see how the engine can swallow more air if
>> the
>> > air in question is diluted by water vapor.
>>
>> If you cool the intake charge, you can end up with
>> MORE air due to increased density.
>
>This is the very point where I tend to say no, not at all. The colder air
>after the water injector takes less volume, for sure, but the newly created
>space is filled with water vapor since the cooling effect comes from
>evaporation, thus there is not a single molecule of additional air in the
>intake mass, just - at best - the same amount, colder and diluted with water
>vapor.

Nope--

You have to consider the partial pressures to make sense of it.

Because of the huge heat of vaporization, the water vapor doesn't take up
nearly as much space as it saves by cooling the air.

You've GOT to realize that the pressure drop through the IC translates into
some expansion (and additional cooling, but THAT'S another story !!)  of
the air, too.

Compressible flows are _FUN_ to deal with !! :-)

Greg



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