[Diy_efi] WI, methanol, and corrosion

[Axel Rietschin]

----- 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. Then, some heat from the intake walls etc will help evaporate more
water thus create more vapor and start displacing air causing a loss. The
point is water takes much more space is vapor form so evaporation outside
the cylinders must be avoided as much as possible. I believe water should
enter the cylinders in liquid form (as "airborne droplets") and evaporate
during the compression stroke and for this to work it must be injected very
late in the induction system, if possible at the port just like fuel often
is.

> You get the benefit of an intercooler, plus the
> benefit of water injection.  Seems to me that having
> both would be a bit better than having just WI, but
> there's a lot of plumbing you don't have, plus the
> weight...  And of course, no pressure drop through the
> IC.  So it may end up being better than both together.
>  And it would appear on the face of it that WI is
> better than just a plain IC in terms of mass of air
> charge in the cylinder per cycle.



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