REFLECTOR: Water injection

[Geoff Gerhardt]

Richard,

I run LOP for every phase of flight except take off and climb.  I have a
Dynon Skyview panel that gives me all the engine data, plus I've installed
an air-fuel monitoring system that tells me the exact air/fuel ratio I'm
running at.  Rather than using EGT to find LOP, I just pull back the
mixture and watch the AFR - very slick.

Running LOP in cruise significantly lowers CHT's, but in climb, it doesn't
lower temps.  I'll easily go over 400F if I use LOP on climb.  I think the
climb attitude/speed does not produce enough cooling air flow in my
configuration.  That cooling that comes from evaporating excess fuel seems
to be very effective.  I think I will be able to get that same cooling with
water injection, but with much less water flow.  Back of the envelope
calculations - on full-rich climb, I'm burning ~12-13gal/hr where as in LOP
I'd be burning ~8-9gal/hr.  So, I'm using ~4gal/hr for cooling.  Water
should provide better cooling than fuel, so I'm guessing that I'll be able
to get away with half that flow, say 2gal/hr water to provide equivalent
cylinder cooling.  So, a 15min climb would require less than a gallon of
water, so a 5gal tank would last for several flights (could probably get
away with a 2gal tank).

Geoff


On Thu, Apr 3, 2014 at 11:59 PM, Richard J. Gentil <
richard at naples-air-center.com> wrote:

> Hi Geoff,
>
> You can achieve better cooling by climbing using lean of peak mixture
> setting if you have an engine analyzer especially with a turbo charged
> engine. If you are still a little too warm you can pull back the prop a
> little. The less explosions per minute, the cooler the engine will run.
>
> Richard
>
> Sent from my iPhone 5 Classic
>
> > On Apr 3, 2014, at 10:41 PM, Geoff Gerhardt <geoff.gerhardt at gmail.com>
> wrote:
> >
> > Guys,
> >
> > I've been considering using water injection to keep cylinder temps down
> on climb.  Seems like a better idea than running full rich all the way up.
>  It looks pretty straightforward, but I'm wondering if there's a reason why
> others don't use it more.  For those who are not familiar with water
> injection, essentially, you spray water (or a water/methanol mix) into the
> intake (typically before the fuel servo).  The large heat of vaporization
> of water pulls a lot of heat out.  Plus, you get a bit of a performance
> boost both by lowering the inlet charge temperature as well as the steam
> expansion during the power stroke.  Another nice benefit is that your
> pistons get a nice steam cleaning with every stroke.
> >
> >
> > I figure a 5gal tank would do more than enough for a few trips if only
> used on climb.  I have had some high temps when cruising at high altitudes
> as well, which it might help with.
> >
> > I'd welcome any
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