Strange engine event

[Paul Mennen]

For the last 200 hours I've recorded all the data from my engine
analyzer which makes it easy to look at such things. Anyway a week
ago I was flying along steady at 12 thousand feet when I noticed
an unusual shift in the engine bar graph display. Looking at the
recorded data I see that all flight data is rock steady and all
engine data (and fuel flow) is also rock steady except for EGT1
and CHT1. From the beginning of the event this is what it looked
like:

Time after event EGT1 CHT1
---------------- --------- ---------
t = 0 1355F 300F
t + 20 seconds 77F rise 7F drop
t + 80 seconds 100F rise 19F drop
t + 3 minutes 114F rise 25F drop

After that it was pretty much steady, but I reduced power after
a few more minutes. (By the way, this is a Turbonormalized IO550.)
So EGT1 which was the coolest (as usual), rose to the level of the
warmest few cylinders. And CHT1 was the coolest (as usual) and
dropped away even more below the average. Still the final temps do
not seem that alarming, but when you look at the graph it looks
really strange since I've never seen such step changes unless it
was in response to some control input.

In the few flights I have taken since that event, I haven't seen
anything unusual like this happen again.

So to those of you who understand internal combustion engines -
what can cause a sudden drop in power in one cylinder like this?
Could something have fallen into this cylinder or could a
valve stick for a while or something? Or is this a sign that
something is breaking? What would you do about it? -
- Keep a close eye on it?
- Do an oil analysis?
- Ground it?
- Have a mechanic look at it?

Can a bad mag or spark plug cause such a thing? (BTW the engine
is a factory remain with 300 hours on it).

Thanks in advance for any insights you may have.
~Paul

[Your Name]

Loose or wearing-out probe wire?

"Paul Mennen" > wrote in message
om...
> For the last 200 hours I've recorded all the data from my engine
> analyzer which makes it easy to look at such things. Anyway a week
> ago I was flying along steady at 12 thousand feet when I noticed
> an unusual shift in the engine bar graph display. Looking at the
> recorded data I see that all flight data is rock steady and all
> engine data (and fuel flow) is also rock steady except for EGT1
> and CHT1. From the beginning of the event this is what it looked
> like:
>
> Time after event EGT1 CHT1
> ---------------- --------- ---------
> t = 0 1355F 300F
> t + 20 seconds 77F rise 7F drop
> t + 80 seconds 100F rise 19F drop
> t + 3 minutes 114F rise 25F drop
>
> After that it was pretty much steady, but I reduced power after
> a few more minutes. (By the way, this is a Turbonormalized IO550.)
> So EGT1 which was the coolest (as usual), rose to the level of the
> warmest few cylinders. And CHT1 was the coolest (as usual) and
> dropped away even more below the average. Still the final temps do
> not seem that alarming, but when you look at the graph it looks
> really strange since I've never seen such step changes unless it
> was in response to some control input.
>
> In the few flights I have taken since that event, I haven't seen
> anything unusual like this happen again.
>
> So to those of you who understand internal combustion engines -
> what can cause a sudden drop in power in one cylinder like this?
> Could something have fallen into this cylinder or could a
> valve stick for a while or something? Or is this a sign that
> something is breaking? What would you do about it? -
> - Keep a close eye on it?
> - Do an oil analysis?
> - Ground it?
> - Have a mechanic look at it?
>
> Can a bad mag or spark plug cause such a thing? (BTW the engine
> is a factory remain with 300 hours on it).
>
> Thanks in advance for any insights you may have.
> ~Paul
>

[[email protected]]

I'm no expert, but the symptoms seem compatible with a partially obstructed
fuel injector. This would cause the mixture in the affected cylinder to be
leaned (ergo higher EGT if you are running ROP) and power to decrease (ergo
reduction in CHT).

From your post I can't tell if the temps stayed at their altered values on
subsequent flights or reverted to the "before t = 0" norm. If my guess is
right, the latter would indicate that whatever was clogging the injector
passed through. If the temps are still shifted, I'd have my mechanic check
the #1 injector.

BTW, this doesn't sound like an instrumentation problem since it's unlikely
that both the EGT and CHT probes and/or receiving units would go bad at the
same time.

--
-Elliott Drucker

[PaulH]

Doesn't sound like a probe problem, as unlikely the 2 probes on the
same cylinder would both defect at the same time, so has to be
something in the engine. Were you running lean, rich, peak? Fuel
injected?

I had this happen once with my IO360 but never again.

[Paul Mennen]

> Loose or wearing-out probe wire?

No that can't be the explanation. If it were just a CHT or
an EGT reading, sure the probe could be at fault. However since
both CHT and EGT change at exactly the same time I believe one
can only rationally conclude that something happened with the
engine itself. In fact I think the EGT rise is a direct consequence
of the CHT reduction although I can't quite remember how that
connection is made.

~Paul

[Aaron Coolidge]

: engine itself. In fact I think the EGT rise is a direct consequence
: of the CHT reduction although I can't quite remember how that
: connection is made.

One plug not firing will slow the combustion event, resulting in the burning
mixture exiting via the open exhaust valve. Results in higher EGT with a
lower CHT because the heat escapes instead of being converted to work
in the cylinder.
--
Aaron Coolidge

[Paul Mennen]

"PaulH" > wrote
> Were you running lean, rich, peak? Fuel injected?

Yes it is Fuel injected (I did mention that it was an IO550).
I was running 14.8gph at WOT (which is LOP).
OAT was 52F, OilT was 188F, TAS was 160Kts, Alt was 12000ft.

> I'm no expert, but the symptoms seem compatible with a partially
> obstructed fuel injector. This would cause the mixture in the affected
> cylinder to be leaned (ergo higher EGT if you are running ROP) and power >
to decrease (ergo reduction in CHT).
> -Elliott Drucker

Yes I agree that would be consistent. Although aren't there many
other explanations for the same phenomina?

> From your post I can't tell if the temps stayed at their altered values
> on subsequent flights or reverted to the "before t = 0" norm.

Yes I forgot to mention - on subsequent flights everything reverted
to normal.

Thanks for your inputs

~Paul

[WARREN1157]

The piston rings rotate whilethe engine is running. The grooves on all of the
rings could have aligned up with each other for a little while and then rotated
back into un - aligned positions. If thei happens reguarly the cylinder could
be out of round.

This condition would make CHT go up and EGT go down

[WARREN1157]

>Doesn't sound like a probe problem, as unlikely the 2 probes on the

If an exhaust valve stuck partially open it would raise your EGT and lower your
CHT

[Jim Carter]

"WARREN1157" > wrote in message
...
> The piston rings rotate whilethe engine is running. The grooves on all of
the
> rings could have aligned up with each other for a little while and then
rotated
> back into un - aligned positions. If thei happens reguarly the cylinder
could
> be out of round.
>
> This condition would make CHT go up and EGT go down

What causes the piston rings to rotate? Since the piston movement is
perpendicular to the cylinder wall, there must be some other mechanism other
than just piston movement causing them to rotate.

Also, why would the grooves on the rings have to be lined up to allow
leakage through the groove?

--
Jim Carter

[Paul Mennen]

> If an exhaust valve stuck partially open it would raise
> your EGT and lower your CHT

That seems like a more likely explanation than the blocked
fuel injector. The reason I think so is that on the previous
annual the other to cylinders on that side (#3 and #5) were
removed to have their exhaust valves replaced and guides
repaired. (At only 300 hours! I guess Continental still hasn't
figured out how to make cylinders like the did in the 70's
and 80's). So if the same wear is happening on #1 it might
cause it to stick on occasion.

~Paul

[Jim Carter]

"Paul Mennen" > wrote in message
...
> > If an exhaust valve stuck partially open it would raise
> > your EGT and lower your CHT
>
> That seems like a more likely explanation than the blocked
> fuel injector. The reason I think so is that on the previous
> annual the other to cylinders on that side (#3 and #5) were
> removed to have their exhaust valves replaced and guides
> repaired. (At only 300 hours! I guess Continental still hasn't
> figured out how to make cylinders like the did in the 70's
> and 80's). So if the same wear is happening on #1 it might
> cause it to stick on occasion.
>
> ~Paul
>
>
But for that to happen here, the exhaust value must be stuck for quite a few
cycles. Assuming 2500 RPM for the duration of your 3 minute event and
dividing by 2 for the four-cycle engine means that your exhaust value chose
to stick 3750 consecutive times out of the 22,500,000 cycles it has executed
up to that point (300 hrs converted to valve cycles). I still like the
partially clogged injector that continued to bleed fuel into the cylinder
after the exhaust cycle started.


--
Jim Carter

[Paul Mennen]

> But for that to happen here, the exhaust value must be
> stuck for quite a few cycles. Assuming 2500 RPM for the
> duration of your 3 minute event and dividing by 2 for the
> four-cycle engine means that your exhaust value chose
> to stick 3750 consecutive times out of the 22,500,000
> cycles it has executed up to that point (300 hrs converted
> to valve cycles).

I was at only 2300 RPM, although your 3750 is still a strong
underestimate. This is because the 3 minutes I reported was
how long it took for the cylinder to stabalize at its new
lower temperature after the event began. Despite reducing
power to 10.8 gph at about t = 3.1 minutes, the unusual
EGT order (i.e. cyl 1 being the hottest) remained until I
pulled back to near idle for the landing (at t = 16.5 minutes)

Not knowing much about engines I didn't realize that it
is inprobable that a valve could stick for that long.

> I still like the partially clogged injector that
> continued to bleed fuel into the cylinder after
> the exhaust cycle started.
> Jim Carter

Ok, not knowing any better I'll go with your suggestion.
Do you think I should have the injector checked out, or
should I just monitor it to see if it ever happens again?

~Paul

[Greg Copeland]

On Sat, 26 Jun 2004 16:02:16 +0000, Paul Mennen wrote:

> Not knowing much about engines I didn't realize that it
> is inprobable that a valve could stick for that long.
>

Well, I'm actually not sure you have the evidence to support that it stuck
consecutively. Would it still cause the problem if it stuck and released,
worked, and got stuck again over that same period of time? Whereby, it
stopped being stuck following some amount of wear-n-tear of the various
parts? Meaning, just for sake of explanation, if we alternated events of
open, closed, open, stuck, open, mostly closed, open, stuck, etc, or some
other random combination, wouldn't you still see the same type of
measurements? My point being, do you really have the evidence to say that
it simply stuck open over all those cycles?

Cheers,

Greg

[Greg Copeland]

On Fri, 25 Jun 2004 14:03:16 +0000, Jim Carter wrote:

> "WARREN1157" > wrote in message
> ...
>> The piston rings rotate whilethe engine is running. The grooves on all of
> the
>> rings could have aligned up with each other for a little while and then
> rotated
>> back into un - aligned positions. If thei happens reguarly the cylinder
> could
>> be out of round.
>>
>> This condition would make CHT go up and EGT go down
>
> What causes the piston rings to rotate? Since the piston movement is
> perpendicular to the cylinder wall, there must be some other mechanism other
> than just piston movement causing them to rotate.
>
> Also, why would the grooves on the rings have to be lined up to allow
> leakage through the groove?

On car motors, isn't this the reason the that you hone and crosshatch the
cylinder wall? That way, during breakin, the rings are encouraged to
rotate and mate in such a manner? Once the rings mate, they'll naturally
want to follow the same rotational, mated path. I ***assume*** the same
thing is done with plane engines. I believe the closest analogy would be
to picture a bullet in a barrel, where the spin in placed on the bullet by
the rifling. Now, just imagine the bullet traveling back and forth in the
barrel, whereby, it natually wants to rotate along the length of the
barrel, in spite of the direction of travel.

Any AP guys, feel free to correct as needed.

Cheers,

Greg

[PInc972390]

>Well, I'm actually not sure you have the evidence to support that it stuck

Piston rings rotate to keep from scoring the cylinders and valves rotate or
they would score and burn. If a piece of carbon was under the valve and holding
it partially open it would lower CHT and raise EGT.

If an injector was plugged it would probably go over peak and lower CHT and
lower EGT.

If the injecter was stuck open it would flood and lower CHT and raise EGT,

The reason for raised EGT on this one is the fuel burning in the exhaust
system. This should make the EGT noticably more on this cylinder than the
others.

Life was easy before computers and analyzers. This is an interesting problem
and I swear that I am no expert on this.

[kage]

****If the injecter was stuck open it would flood and lower CHT and raise
EGT, *****

Aircraft fuel injectors don't open and close, they are always open and
providing fuel. That is why they are called "constant flow."


Karl



"PInc972390" > wrote in message
...
>
>
> >Well, I'm actually not sure you have the evidence to support that it
stuck
>
> Piston rings rotate to keep from scoring the cylinders and valves rotate
or
> they would score and burn. If a piece of carbon was under the valve and
holding
> it partially open it would lower CHT and raise EGT.
>
> If an injector was plugged it would probably go over peak and lower CHT
and
> lower EGT.
>
> If the injecter was stuck open it would flood and lower CHT and raise EGT,
>
> The reason for raised EGT on this one is the fuel burning in the exhaust
> system. This should make the EGT noticably more on this cylinder than the
> others.
>
> Life was easy before computers and analyzers. This is an interesting
problem
> and I swear that I am no expert on this.

[Matt Whiting]

PInc972390 wrote:

>>Well, I'm actually not sure you have the evidence to support that it stuck
>
>
> Piston rings rotate to keep from scoring the cylinders and valves rotate or
> they would score and burn. If a piece of carbon was under the valve and holding
> it partially open it would lower CHT and raise EGT.

I've never heard of piston rings rotating. Kind of makes staggering the
gaps a waste of time. What makes them rotate?

Yes, many valves are designed to rotate.


Matt

[tony roberts]

It's a fouled plug, burned valve or broken ring.
And that is straight fom the book on my engine analyzer

Tony
C-GICE


In article >,
"Paul Mennen" > wrote:

> For the last 200 hours I've recorded all the data from my engine
> analyzer which makes it easy to look at such things. Anyway a week
> ago I was flying along steady at 12 thousand feet when I noticed
> an unusual shift in the engine bar graph display. Looking at the
> recorded data I see that all flight data is rock steady and all
> engine data (and fuel flow) is also rock steady except for EGT1
> and CHT1. From the beginning of the event this is what it looked
> like:
>
> Time after event EGT1 CHT1
> ---------------- --------- ---------
> t = 0 1355F 300F
> t + 20 seconds 77F rise 7F drop
> t + 80 seconds 100F rise 19F drop
> t + 3 minutes 114F rise 25F drop
>
> After that it was pretty much steady, but I reduced power after
> a few more minutes. (By the way, this is a Turbonormalized IO550.)
> So EGT1 which was the coolest (as usual), rose to the level of the
> warmest few cylinders. And CHT1 was the coolest (as usual) and
> dropped away even more below the average. Still the final temps do
> not seem that alarming, but when you look at the graph it looks
> really strange since I've never seen such step changes unless it
> was in response to some control input.
>
> In the few flights I have taken since that event, I haven't seen
> anything unusual like this happen again.
>
> So to those of you who understand internal combustion engines -
> what can cause a sudden drop in power in one cylinder like this?
> Could something have fallen into this cylinder or could a
> valve stick for a while or something? Or is this a sign that
> something is breaking? What would you do about it? -
> - Keep a close eye on it?
> - Do an oil analysis?
> - Ground it?
> - Have a mechanic look at it?
>
> Can a bad mag or spark plug cause such a thing? (BTW the engine
> is a factory remain with 300 hours on it).
>
> Thanks in advance for any insights you may have.
> ~Paul
>




--

Tony Roberts
PP-ASEL
VFR OTT
Night
Almost Instrument :)
Cessna 172H C-GICE

[PInc972390]

>*If the injecter was stuck open it would flood and lower CHT and

This is kind of a visualising termanalogy, Sorry for the spelling.

[PInc972390]

>I've never heard of piston rings rotating. Kind of makes staggering the

I had a Chevy pickup years ago that I changed the rings on one cylinder twice.
(This was before I had enough money to do things right) All five grooves on the
piston rings would be in a vertical row letting the oil get by and smoke. The
machinest said that the one cylinder was way out of round and the rest were OK.
He said that the rings rotated on the pistons so I believed him. Before that I
wondered why a good mechanic cleaned the grooves and rotated the rings before
He installed them.

Now for the other side. I overhauled a 225 HP Johnson outboard (Never again,
Too many pieces) The piston rings have keepers on them to keep them from
rotating. The oil injection must keep them from scoring.

The terminology Stuck Ring. I wonder if that means Rotation or Stuck in the
ring land or groove?

Like I say I am an amateur and the only way that I have learned is by doing it
myself because I didn't have enough money to let someone else do it.

Could a lifter have stuck open or closed? Had one stick on a 172 and knocked a
hole in the rocker cover.

[PInc972390]

>It's a fouled plug, burned valve or broken ring.

Fouled plug, maybe as it could clean itself up, a burned valve or broken ring
wouldn't fix themselves.

[Paul Mennen]

> >It's a fouled plug, burned valve or broken ring.
>
> Fouled plug, maybe as it could clean itself up, a burned valve or broken ring
> wouldn't fix themselves.

I certainly doubt something like a broken ring as well since the
problem has not yet re-appeared.

As far as the fouled plug theory - could a plug really get fouled
that quickly? Remember the plot looked like a sharp step function.
Most of the EGT/CHT change occurred in the first 20 seconds of the event.

So for now I think the injector theory, or the stuck valve or lifter
theory is more likely.

By the way I flew again yesterday for 2.5 hours and the problem
still has not repeated. So it may be awhile (if ever) before we
figure out the real cause.

~Paul

[tony roberts]

Hi Paul

The original reply that I gave you was for one cylinder.
Rereading your post, it seems that the readout was for all cylinders,
which changes the cause to Timing out or bad magneto.
(And no, I'm no expert on this stuff - I'm giving you these answers
right out of the book for my own engine analyzer).

HTH

--

Tony Roberts
PP-ASEL
VFR OTT
Night
Almost Instrument :)
Cessna 172H C-GICE


In article <nospam-1C6AA9.22284826062004@shawnews>,
tony roberts > wrote:

> It's a fouled plug, burned valve or broken ring.
> And that is straight fom the book on my engine analyzer
>
> Tony
> C-GICE
>
>
> In article >,
> "Paul Mennen" > wrote:
>
> > For the last 200 hours I've recorded all the data from my engine
> > analyzer which makes it easy to look at such things. Anyway a week
> > ago I was flying along steady at 12 thousand feet when I noticed
> > an unusual shift in the engine bar graph display. Looking at the
> > recorded data I see that all flight data is rock steady and all
> > engine data (and fuel flow) is also rock steady except for EGT1
> > and CHT1. From the beginning of the event this is what it looked
> > like:
> >
> > Time after event EGT1 CHT1
> > ---------------- --------- ---------
> > t = 0 1355F 300F
> > t + 20 seconds 77F rise 7F drop
> > t + 80 seconds 100F rise 19F drop
> > t + 3 minutes 114F rise 25F drop
> >
> > After that it was pretty much steady, but I reduced power after
> > a few more minutes. (By the way, this is a Turbonormalized IO550.)
> > So EGT1 which was the coolest (as usual), rose to the level of the
> > warmest few cylinders. And CHT1 was the coolest (as usual) and
> > dropped away even more below the average. Still the final temps do
> > not seem that alarming, but when you look at the graph it looks
> > really strange since I've never seen such step changes unless it
> > was in response to some control input.
> >
> > In the few flights I have taken since that event, I haven't seen
> > anything unusual like this happen again.
> >
> > So to those of you who understand internal combustion engines -
> > what can cause a sudden drop in power in one cylinder like this?
> > Could something have fallen into this cylinder or could a
> > valve stick for a while or something? Or is this a sign that
> > something is breaking? What would you do about it? -
> > - Keep a close eye on it?
> > - Do an oil analysis?
> > - Ground it?
> > - Have a mechanic look at it?
> >
> > Can a bad mag or spark plug cause such a thing? (BTW the engine
> > is a factory remain with 300 hours on it).
> >
> > Thanks in advance for any insights you may have.
> > ~Paul
> >

[Jim Carter]

I thought the values were only for cylinder #1 - hence the EGT1 and CHT1
headings.

--
Jim Carter
"tony roberts" > wrote in message
news:nospam-978501.00081830062004@shawnews...
> Hi Paul
>
> The original reply that I gave you was for one cylinder.
> Rereading your post, it seems that the readout was for all cylinders,
> which changes the cause to Timing out or bad magneto.
> (And no, I'm no expert on this stuff - I'm giving you these answers
> right out of the book for my own engine analyzer).
>
> HTH
>
> --
>
> Tony Roberts
> PP-ASEL
> VFR OTT
> Night
> Almost Instrument :)
> Cessna 172H C-GICE
>
>
> In article <nospam-1C6AA9.22284826062004@shawnews>,
> tony roberts > wrote:
>
> > It's a fouled plug, burned valve or broken ring.
> > And that is straight fom the book on my engine analyzer
> >
> > Tony
> > C-GICE
> >
> >
> > In article >,
> > "Paul Mennen" > wrote:
> >
> > > For the last 200 hours I've recorded all the data from my engine
> > > analyzer which makes it easy to look at such things. Anyway a week
> > > ago I was flying along steady at 12 thousand feet when I noticed
> > > an unusual shift in the engine bar graph display. Looking at the
> > > recorded data I see that all flight data is rock steady and all
> > > engine data (and fuel flow) is also rock steady except for EGT1
> > > and CHT1. From the beginning of the event this is what it looked
> > > like:
> > >
> > > Time after event EGT1 CHT1
> > > ---------------- --------- ---------
> > > t = 0 1355F 300F
> > > t + 20 seconds 77F rise 7F drop
> > > t + 80 seconds 100F rise 19F drop
> > > t + 3 minutes 114F rise 25F drop
> > >
> > > After that it was pretty much steady, but I reduced power after
> > > a few more minutes. (By the way, this is a Turbonormalized IO550.)
> > > So EGT1 which was the coolest (as usual), rose to the level of the
> > > warmest few cylinders. And CHT1 was the coolest (as usual) and
> > > dropped away even more below the average. Still the final temps do
> > > not seem that alarming, but when you look at the graph it looks
> > > really strange since I've never seen such step changes unless it
> > > was in response to some control input.
> > >
> > > In the few flights I have taken since that event, I haven't seen
> > > anything unusual like this happen again.
> > >
> > > So to those of you who understand internal combustion engines -
> > > what can cause a sudden drop in power in one cylinder like this?
> > > Could something have fallen into this cylinder or could a
> > > valve stick for a while or something? Or is this a sign that
> > > something is breaking? What would you do about it? -
> > > - Keep a close eye on it?
> > > - Do an oil analysis?
> > > - Ground it?
> > > - Have a mechanic look at it?
> > >
> > > Can a bad mag or spark plug cause such a thing? (BTW the engine
> > > is a factory remain with 300 hours on it).
> > >
> > > Thanks in advance for any insights you may have.
> > > ~Paul
> > >

[Dan Thomas]

(PInc972390) wrote in message >...
> >I've never heard of piston rings rotating. Kind of makes staggering the
>
> I had a Chevy pickup years ago that I changed the rings on one cylinder twice.
> (This was before I had enough money to do things right) All five grooves on the
> piston rings would be in a vertical row letting the oil get by and smoke. The
> machinest said that the one cylinder was way out of round and the rest were OK.
> He said that the rings rotated on the pistons so I believed him. Before that I
> wondered why a good mechanic cleaned the grooves and rotated the rings before
> He installed them.

Rings aren't supposed to rotate. No cylinder is perfectly round, and
we crosshatch cyinder walls and use mineral oil for a few hours so
they'll wear the rings and the rings will wear the cylinders until the
ring's outer circumference matches the imperfect cylinder bore. If the
rings rotate they'll spoil that match. If you find them rotating, then
the bore is probably badly out-of-round and the ring ends are seeking
the apex of the wider diameter; the pointy end of the egg, if you
will. Properly overhauled engines have been cylinder bored to get them
round before honing, or they've been honed on a rigid hone such as the
Sunnen CK-10 or CV-616, an expensive piece of machinery that I never
want to operate again. I wish I had as many flying hours as honing
hours.
The cylinder can be honed to a really close roundness, but
bolting it to the case distorts it somewhat anyway. As I said, no
cyinder is perfectly round.


> The terminology Stuck Ring. I wonder if that means Rotation or Stuck in the
> ring land or groove?

Stuck in the groove, usually by a buildup of carbon and crud
behind and around the ring. The piston will hold onto the ring instead
of letting it follow the cylinder wall, and a bad seal results. When
the crud gets hot it will sometimes let go, but seize the ring again
when cold. Poor compression and some smoke while warming up.


>
> Like I say I am an amateur and the only way that I have learned is by doing it
> myself because I didn't have enough money to let someone else do it.

Some of us are glad for the company. Maybe most of us.


Dan

[tony roberts]

On re-reading it, you are correct.
Oh well - I already answered that one :)

Tony



> I thought the values were only for cylinder #1 - hence the EGT1 and CHT1
> headings.
>
> --
> Jim Carter
> "tony roberts" > wrote in message
> news:nospam-978501.00081830062004@shawnews...
> > Hi Paul
> >
> > The original reply that I gave you was for one cylinder.
> > Rereading your post, it seems that the readout was for all cylinders,
> > which changes the cause to Timing out or bad magneto.
> > (And no, I'm no expert on this stuff - I'm giving you these answers
> > right out of the book for my own engine analyzer).
> >
> > HTH
> >
> > --
> >
> > Tony Roberts
> > PP-ASEL
> > VFR OTT
> > Night
> > Almost Instrument :)
> > Cessna 172H C-GICE
> >
> >
> > In article <nospam-1C6AA9.22284826062004@shawnews>,
> > tony roberts > wrote:
> >
> > > It's a fouled plug, burned valve or broken ring.
> > > And that is straight fom the book on my engine analyzer
> > >
> > > Tony
> > > C-GICE
> > >
> > >
> > > In article >,
> > > "Paul Mennen" > wrote:
> > >
> > > > For the last 200 hours I've recorded all the data from my engine
> > > > analyzer which makes it easy to look at such things. Anyway a week
> > > > ago I was flying along steady at 12 thousand feet when I noticed
> > > > an unusual shift in the engine bar graph display. Looking at the
> > > > recorded data I see that all flight data is rock steady and all
> > > > engine data (and fuel flow) is also rock steady except for EGT1
> > > > and CHT1. From the beginning of the event this is what it looked
> > > > like:
> > > >
> > > > Time after event EGT1 CHT1
> > > > ---------------- --------- ---------
> > > > t = 0 1355F 300F
> > > > t + 20 seconds 77F rise 7F drop
> > > > t + 80 seconds 100F rise 19F drop
> > > > t + 3 minutes 114F rise 25F drop
> > > >
> > > > After that it was pretty much steady, but I reduced power after
> > > > a few more minutes. (By the way, this is a Turbonormalized IO550.)
> > > > So EGT1 which was the coolest (as usual), rose to the level of the
> > > > warmest few cylinders. And CHT1 was the coolest (as usual) and
> > > > dropped away even more below the average. Still the final temps do
> > > > not seem that alarming, but when you look at the graph it looks
> > > > really strange since I've never seen such step changes unless it
> > > > was in response to some control input.
> > > >
> > > > In the few flights I have taken since that event, I haven't seen
> > > > anything unusual like this happen again.
> > > >
> > > > So to those of you who understand internal combustion engines -
> > > > what can cause a sudden drop in power in one cylinder like this?
> > > > Could something have fallen into this cylinder or could a
> > > > valve stick for a while or something? Or is this a sign that
> > > > something is breaking? What would you do about it? -
> > > > - Keep a close eye on it?
> > > > - Do an oil analysis?
> > > > - Ground it?
> > > > - Have a mechanic look at it?
> > > >
> > > > Can a bad mag or spark plug cause such a thing? (BTW the engine
> > > > is a factory remain with 300 hours on it).
> > > >
> > > > Thanks in advance for any insights you may have.
> > > > ~Paul
> > > >
>
>




--

Tony Roberts
PP-ASEL
VFR OTT
Night
Almost Instrument :)
Cessna 172H C-GICE

[David Lesher]

"Jim Carter" > writes:


>What causes the piston rings to rotate? Since the piston movement is
>perpendicular to the cylinder wall, there must be some other mechanism other
>than just piston movement causing them to rotate.

Very Clever Design. I can't recall the details, but ISTM there are
[automotive] patents on making 'em creep along.

>Also, why would the grooves on the rings have to be lined up to allow
>leakage through the groove?

It does leak lots more; the gap between the rings is not all that
far, I guess...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

[WARREN1157]

>>perpendicular to the cylinder wall, there must be some other mechanism other
>>than just piston movement causing them to rotate.
>

I just can't get it into my head how that a ring can be put in and when the
engine is torn down all of the grooves will be in the same place as when
installed.

The keepers on a two cycle boat engine (not motor) are the only anti - Rotation
device that I have seen.

[Jim Carter]

Dave,
I've torn engines down before and the distance between the rings is
relatively a lot more than the gap between the ends of the ring when
compressed into the cylinder. It is such a big difference that I don't see
how the intra-ring distance could be restrictive to the flow of gasses
passing through the ring gap.

I'd really like to see some information on the "Very Clever Design" you
mentioned. Even if the cylinders were honed with a diagonal pattern,
shouldn't the ring just reverse direction at the end of the stroke and
follow the honing marks?

--
Jim Carter
"David Lesher" > wrote in message
...
> "Jim Carter" > writes:
>
>
> >What causes the piston rings to rotate? Since the piston movement is
> >perpendicular to the cylinder wall, there must be some other mechanism
other
> >than just piston movement causing them to rotate.
>
> Very Clever Design. I can't recall the details, but ISTM there are
> [automotive] patents on making 'em creep along.
>
> >Also, why would the grooves on the rings have to be lined up to allow
> >leakage through the groove?
>
> It does leak lots more; the gap between the rings is not all that
> far, I guess...
>
> --
> A host is a host from coast to
> & no one will talk to a host that's close........[v].(301) 56-LINUX
> Unless the host (that isn't close).........................pob 1433
> is busy, hung or dead....................................20915-1433

[David Lesher]

"Jim Carter" > writes:

> I've torn engines down before and the distance between the rings is
>relatively a lot more than the gap between the ends of the ring when
>compressed into the cylinder. It is such a big difference that I don't see
>how the intra-ring distance could be restrictive to the flow of gasses
>passing through the ring gap.

> I'd really like to see some information on the "Very Clever Design" you
>mentioned. Even if the cylinders were honed with a diagonal pattern,
>shouldn't the ring just reverse direction at the end of the stroke and
>follow the honing marks?

>--
>Jim Carter
>"David Lesher" > wrote in message
...
>> "Jim Carter" > writes:
>>
>>
>> >What causes the piston rings to rotate? Since the piston movement is
>> >perpendicular to the cylinder wall, there must be some other mechanism
>other
>> >than just piston movement causing them to rotate.
>>
>> Very Clever Design. I can't recall the details, but ISTM there are
>> [automotive] patents on making 'em creep along.
>>
>> >Also, why would the grooves on the rings have to be lined up to allow
>> >leakage through the groove?
>>
>> It does leak lots more; the gap between the rings is not all that
>> far, I guess...




I don't recall much more. I'll ask a friend who knows lots more
than I do on engine innards. But it was Detroit, not overseas...






--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

[[email protected]]

The piston really only approximately goes straight up and down.
Engines are not perfect machines. If you looked at the general
dynamic alignment of everything on the microinch level etc, there is
probably a slight amount of rotation inherent in the structure of an
engine including the crankshaft and rod deformations. When combined
with the varying pressure fluctuations on each ring, the ring
gradually rotates
in one direction or another. Remember you are dealiung with something
that is cycling back and forth 40 times per second, so that it doesn't
take very much rotation each cycle to give a lot of eventual motion.

Put it another way - why shouldn't it rotate?

[Jim Carter]

I don't think it should rotate because the action of scrubbing against the
cylinder walls will wear "micro" grooves in the rings that match up against
corresponding ridges on the cylinder wall. If the rings rotated there would
never be this ridge/groove result. Since you can see and sometimes feel the
grooves and ridges, I can only assume the rotation of the ring is not
happening.

--
Jim Carter
> wrote in message
om...
>
> ....
>
> Put it another way - why shouldn't it rotate?

[Orval Fairbairn]

In article >,
"Jim Carter" > wrote:

> I don't think it should rotate because the action of scrubbing against the
> cylinder walls will wear "micro" grooves in the rings that match up against
> corresponding ridges on the cylinder wall. If the rings rotated there would
> never be this ridge/groove result. Since you can see and sometimes feel the
> grooves and ridges, I can only assume the rotation of the ring is not
> happening.

That is why cylinders get a crosshatch pattern during the honing
process. The microgrooves go around the cylinder, not parallel to its
major axis.