Today's Message Index:
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1. 02:34 PM - Engine combustion troubleshooting concepts (Ralph E. Capen)
2. 04:22 PM - Re: Engine combustion troubleshooting concepts (Shannon Miller)
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| Subject: | Engine combustion troubleshooting concepts |
Re-breaking in my engine after prop-strike by hangar door induced by tornado.
Considering the engine already had 160+ hours on it - I know how it was running
for a while.
I have one cylinder running not like the others. Before I tell what is happening,
I want to make sure I understand/remember the basic concepts.
EGT-only elevated - CHT reduced...unburned fuel going out exhaust and burning on
the way out - plug not firing
EGT-only elevated - ...unburned fuel going out exhaust and burning on the way out
- plug not firing completely
CHT-only elevated...not enough cooling air
EGT and CHT elevated...lean mixture - air leak
Refresh my memory here.
Message 2
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| Subject: | Re: Engine combustion troubleshooting concepts |
I'm no expert, but I can share my own understanding. See below.
On Mon, Dec 3, 2012 at 2:33 PM, Ralph E. Capen <recapen@earthlink.net>wrote:
> Re-breaking in my engine after prop-strike by hangar door induced by
> tornado.
>
> Considering the engine already had 160+ hours on it - I know how it was
> running for a while.
>
> I have one cylinder running not like the others. Before I tell what is
> happening, I want to make sure I understand/remember the basic concepts.
>
> EGT-only elevated - CHT reduced...unburned fuel going out exhaust and
> burning on the way out - plug not firing
>
Right. Possibly some sort of spark plug problem. Could be a fouled plug or
disconnected/broken plug wire. Consider a mag check (even if you're only
seeing this in flight -- just do it at a safe altitude and within gliding
distance to a safe landing spot) to identify the plug/wire; if the engine
quits, pull the throttle to idle before switching off the bad mag to avoid
backfiring.
> EGT-only elevated - ...unburned fuel going out exhaust and burning on the
> way out - plug not firing completely
>
Agreed. Same possible causes as above.
> CHT-only elevated...not enough cooling air
>
Or insufficient fuel flow, power too high for the air flow, mixture too
lean, or RPM too low for the power setting. Possible in-flight solutions:
lower nose to increase airspeed, open cowl flaps if you have them, enrichen
the mixture (confirm that you're rich of peak by noting a decrease in EGT's
as you enrichen the mixture), reduce power (MP), increase prop RPM. Now if
it's just one cylinder, I would guess it's either some sort of baffling
issue or fuel flow issue to that cylinder.
> EGT and CHT elevated...lean mixture - air leak
>
Agree, or possible magneto/ignition problem if it's all cylinders -- a mag
check would identify which mag/ignition source. If it's just one cylinder,
it could be a partially clogged fuel injector: go full rich mixture and
momentarily turn on the boost pump -- it might dislodge the clog!
> Refresh my memory here.
I assume you're talking only "somewhat" elevated EGT and CHT values, and
not values which are "sky high" which could indicate detonation or
pre-ignition and ultimate catastrophic engine failure!
That's all I can offer. No warranty, but I hope it helps!
--Shannon
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