Today's Message Index:
----------------------
1. 05:32 AM - Re: Magneto P-leads (Gary Casey)
2. 07:44 AM - Re: Re: Lycoming EGT, IO 540 (Hinde, Frank George (Corvallis))
Message 1
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| Subject: | Re: Magneto P-leads |
Dean,
I'm a little confused about which resistance you are concerned about,
but here is what you can expect to measure: If the switch is
disconnected from the mag, a reading of the resistance from the P-
lead terminal to ground will be either (with the points closed)
essentially zero, or (with the points open) almost zero. The circuit
inside the mag is from ground through the primary ignition coil
winding to the points and back to ground. The P-lead is connected to
the connection between the coil and points. If the mag is rotated so
the points are closed only the point resistance is in the circuit,
which should measure as zero. When the mag is turned so the points
are open the only connection to ground is through the coil primary
winding, which will measure at something very low, but not zero. It
will probably be less than 1 ohm. I use this difference to set the
timing, eliminating the need for the "buzz box" that mechanics
normally use. You can, if you like, check the connected ignition
switch by turning the mag until the points are open (ignition switch
has to be in the "on" position to know this) and watching the
resistance of the P-lead to ground while turning the switch on and
off - there should be a small but noticeable change in resistance.
Oh, and when the switch is in the "R" position the right mag is on
(switch is open) and the left mag is off (shorted to ground).
Hope I didn't confuse things more.
Gary
>
> Time: 12:01:57 AM PST US
> From: "DEAN PSIROPOULOS" <dean.psiropoulos@verizon.net>
> Subject: Engines-List: Magneto P-leads
>
>
> I did a test on my magneto P-leads (one mag on left side,
> electronic on
> right side)with an ohm meter. Thinking that when the key switch is
> in the
> off position, the resistance across the p-leads should measure
> close to dead
> short and, it does. By the same logic, I thought that when the mag
> was
> ungrounded the resistance across the p-leads (I used a shielded
> wire with
> the shield grounded at the magneto through the key switch, no local
> grounding). But when I measured across the p-leads at the magneto the
> resistance only went from 0.2 ohms to 0.4 ohms when I turned the
> key. Not
> an appreciable increase in resistance but it was consistent
> (happens every
> time) and measurable. I thought maybe I had a faulty key switch but
> not so,
> I removed one p-lead from the mag and made the same measurement and
> the
> resistance with the key in that mag's position read infinite. I
> suspect
> that there is some thing about magnetos I don't know and that this
> is not a
> problem but would like to be sure. Anybody ever done this test?
> Did you get
> the same results? Thanks.
>
> Dean
> RV-6A N197DM
> closer to 1st flight.
Message 2
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| Subject: | Re: Lycoming EGT, IO 540 |
Not at all, The EI's will have both less and more advance depending on
manifold pressure. Mags are set at 25deg which is a compromise between
poor starting, high power operation and economy cruise.
Pretty much all EI's run at about 25 DEG at full power but can advance
to 40deg plus at low manifold pressure.
I wonder if this engine is truly running balanced...what does "withing
1.5%" mean?....If it means the cylinders flow the same amount of air on
the bench then this is meaningless as far as blancing the injectors.
Each cylinder needs to get to peak EGT at the same fuel flow (mine is
about 0.5GPH between richest and leanest)....Nothing else matters...If
the cylinder don't all peak at the same fuel flow (or close to it) the
engine will not run LOP very well.
I think what we have here is some cylinders running ROP while the others
are runnin so LOP that the flame is going out...I.e well LOP.
Frank RV7a IO360
________________________________
From: owner-engines-list-server@matronics.com
[mailto:owner-engines-list-server@matronics.com] On Behalf Of steve
korney
Sent: Sunday, November 11, 2007 3:49 PM
Subject: RE: Engines-List: Re: Lycoming EGT, IO 540
Gary...
What brand of electronic ignition do you have....? I would think the EI
would have a lot more advance then the mag at almost any manifold
pressure other then maybe sea level...
Best... Steve
> From: glcasey@adelphia.net
> Subject: Engines-List: Re: Lycoming EGT, IO 540
> Date: Sun, 11 Nov 2007 06:02:45 -0800
> To: engines-list@matronics.com
>
>
> Bob's comment brings up a question I have. I've got a parallel-valve
> IO-540 with 10:1 compression and electronic ignition on the top
> plugs, mag on the bottom, timing set at 22. The cylinders are very
> closely matched for air/fuel, within about 1.5%. When I lean the
> engine LOP the temperatures drop just a little before it goes rough
> and sometimes go flat or back up, so I typically operate just barely
> LOP. I don't have a good explanation for this behavior unless my
> ram air induction is working so well that the injectors have no air
> flow in them to atomize the fuel. However, I don't see any fuel
> stains around the injectors, so there apparently isn't any fuel
> coming out the vents. There is no way the engine would run 150 LOP
> as Bob suggests below. Any ideas on why this engine seems to operate
> different than the norm?
>
> Gary Casey
>
> > ....Once they all achieve
> > their peak temp at the same throttle position you should be able to
> > get
> > as much as 150 degrees lean of peak before missfire.
> >
&========================
>
>
>
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