REFLECTOR: Water injection (Just to be clear)

Sat Apr 5 10:56:19 CDT 2014

Lean of peak is a term that refers to EGT peak.  EGT peak is not peak power which occurs about 50 deg ROP.

Larry Coen
N136LC

From: Dave Philipsen 
Sent: Friday, April 04, 2014 1:36 PM
To: geoff.gerhardt at gmail.com ; Velocity Aircraft Owners and Builders list 
Subject: Re: REFLECTOR: Water injection

Does your air/fuel monitoring system give you the exact ratio for each cylinder?  If not, the only way to tell is by monitoring EGTs.  The whole principle of running LOP is getting ALL of the cylinders on the lean side at the same time.  If your system just shows the overall air/fuel mixture it won't indicate if one cylinder is running dangerously near peak while perhaps others are well into the safety zone. Because of inconsistencies in the way that air and fuel are distributed to each cylinder it can't be guaranteed that each cylinder is getting the same amount or even the same proportion of each. 

And, at some point if you are running LOP correctly, you WILL see reduced temperatures even in climb. Basically peak power = peak temperature.  If you run lean of peak (temperature) you are generating less power and thus less heat also.

Have you ever thought about the idea of injecting water into the cooling air around the engine for evaporative cooling?

Dave Philipsen 
Velocity STD FG
N83DP

On Apr 4, 2014, at 8:52 AM, Geoff Gerhardt <geoff.gerhardt at gmail.com> wrote:

  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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