A question re IO520/550 aircraft engines

[StrutlessDrKiller]

As some in here are aware, I am currently running in a new IO550 installed in a C210N.

The aircraft is fitted with an EDM800 all cylinder - without which I would not have any reason to ask this question regarding EGT/CHT temperatures.

The EGT/CHT temps for the 6 cylinders, taken at 50oC ROP are as follows:

1 - 740/173C = 1364/343F
2 - 758/174C = 1396/345F
3 - 768/179C = 1414/354F
4 - 770/176C = 1418/349F
5 - 723/194C = 1333/381F
6 - 741/183C = 1366/361F

These temps are for about 70% power (25/24) at 5000', OAT 18oC with the cowl flaps open.

You will notice that pot #5 has significantly (?) lower EGT and higher CHT readings.

I would be interested in any suggestions as to why this is so? Pot #5 is at the front, behind the oil cooler.

If I close the cowl flaps half way #5 goes to 197C and if I close them fully it heads for 200oC

Dr :8

[empacher48]

Does it have Gamijectors fitted?

My thoughts would be with the EGT cooler than the other 5 pots, and the significantly higher CHT that this one is running too lean, with pot 4 running richest.

Without Gamijectors it can be a bit of a lottery how much fuel each cylinder gets, some will run lean and some will run rich (thats why with a single EGT gauge most manufacturers recommed running 4 divisions rich of peak - the leanest cylinder may be at peak, but not lean enough to cause damage). By running with Gamijectors, each cylinder gets exactly the same fuel, so the EGT for each cylinder will be the same, and the CHT will be similar (depending on airflow etc). So technically you can run a Gamijectored engine at peak EGT without risking burning out a pot.

Well thats the way I understand it, and I'm no engineer.

[Capt Wally]

G'day Dr. I'm no expert but I did O/Haul Lyc engines some years ago now when I transfered from a motor mech to an AME whilst learning to pole rather than getting dirty. We found that often certain cyl's had quite a bit of diff with ref to cyl head temps for no obvious reason other than perhaps poor fitting cooling baffles or perhaps a difference in the spray pattern of the injectors, the latter will cause a diff in cyl temps usually.
I did read many years ago now that not every cyl runs exactly the same temp wise anyway efficiency wise (obvioulsy) 'cause of clearances, specific metal types/makeups, diff manufacturers etc, all account for slight & sometimes significant operating temps. Like a lot of the tollerances within an engine as long as the temp differences are withion tollerances that's acceptable.
I trust yr enjoying the 'shade'? I will admit tho that the Cessna 210 does slip along nicely at speed but not with 6 bums, too damn cramped!:bored:

Have you ever landed with a flat batt in a C210? flapless, manual gear ext & 6 pob? I did once,(in YSTW) at the time felt like a Learjet over the fence!:bored:



CW

[Jabawocky]

Hey Doc

Chuck will be along shortly with all the answers.......

J:ok:

[StrutlessDrKiller]

Chuck reckons that pot is running rich enough of peak to send the EGT down and the CHT up! Can't do nothin about it!

But of course he wants to fly the aeroplane himself on Sunday to check it out!

Dr :8

[RadioSaigon]

Like others, my 1st thought was an imbalance in the injector fuel-rates... has the owner fitted GAMI's? If not, is there a reason why not (just curious, not a criticism)?

[rutan around]

Does your C210 still have the Cessna supplied CHT? If so check to see which cylinder it's sender probe is screwed into. Odds are it's the one behind the oil cooler. In that case the EDM sender for that cylinder will most likely be an under spark plug type while the rest will be screw in types. The Under plug sender gives a different reading to the others. Swap it to another cylinder and see. E-mail EDM for more information. C210---Best aircraft ever built.

[Chimbu chuckles]

Not quite what I said....most likely answer is purely an airflow difference between cylinders...and we're assuming all the probes are in the same place in each cylinder too, as someone above mentioned.

I cannot remember which cylinder you said was 50F ROP but if it was not 5 then 5 may be slightly richer causing cylinder 5 to be closer to, say, 70F ROP.

My IO550's peak CHTs happen around 70-80F ROP EGT..70-80F ROP EGT will obviously display a cooler EGT than 50F ROP.

Tuned injectors like Gamis, and the TCM Tuned Injectors in the subject aircraft, don't ensure the same fuel flow to each cylinder they balance up fuel air ratios across the cylinders so each cylinder is developing, near as possible, the same power.

In the final analysis absolute value of EGT in a normally aspirated engine is nearly irrelevant...the difference you're seeing could be merely a difference in probe position in the exhaust manifold.

The EGT reading is just a snapshot of the temperature of the exhaust gasses exiting the cylinder through the exhaust valve...that is why, in a normally aspirated engine, the absolute value is not that important only that they all rise, peak and fall LOP in lockstep...the reason it is of greater interest in a Turbocharged engine is that the exhaust gasses drive the compressor turbine and the metal in that component has temperature limits to avoid creep at the extremely high RPM they operate at.

You're better off running the EDM in normalised mode anyway...it evens up the EGT display while also increasing sensitivity of the display.

[Jabawocky]

Sunday is gonna be a big day then....Video is coming to the Master Class!

Maybe we should do a YouTube educational series.........:ooh:

J:ok:

[Brian Abraham]

The type certificate for the 210 lists which cylinder the probe is fitted ex factory and varies with model. Guess does not change with the 550 upgrade.
210, 210A (1960-61 Model) Cylinder No 3
210B, 210C, 210D (1962-63-64 Model) Cylinder No 1
210E,210F,210G,210H,210J (1965-66-67-68-69 Model) Cylinder No 2
210F,T210G,T210H,T210J (1966-67-68-69 Model) Cylinder No 5
210K (1970-71 Model) Cylinder No 3
T210K (1970-71 Model) Cylinder No 5
210L (1972-73-74-75-76 Model) Cylinder No 3
T210L (1972-73 Model) Cylinder No 5
T210L (1974-75-76 Model) Cylinder No 1
210M (1977 Model) Cylinder No 3
210M (1978 Model) Cylinder No 1
T210M (1977-78 Model) Cylinder No 1
P210N (1978-81 Model) Cylinder No 5
210N (1979-81 Model) Cylinder No 1
T210N (1979 Model) Cylinder No 1
T210N (1980-81 Model)(Non-Air Cond) Cylinder No 5 or 1
T210N (1980-81 Model)(With Air Cond) Cylinder No 1
P210N (1982-83 Model) Cylinder No 4
210N, 210R (1982 Model and up)(Non Air Cond) Cylinder No 4
210N, 210R (1982 Model and up)(With AirCond) Cylinder No 1
T210N (1982 Model and up) Cylinder No 3
P210R, T210R (1985 Model and up) Cylinder No 1

[Bevan666]

The first thing I would do is swap the probes around, so see if its a probe problem.....

Bevan..

[flywatcher]

Just look on it as six separate one cylinder engines connected to a common crankshaft.

[Chimbu chuckles]

I think this is a case of less than optimum airflow control over the cylinders. Bonanzas suffer the same with standard fit baffles hence D'Shannon and Gami have STC'd aftermarket baffles that address the issue. You'd really have to ask the Cessna equivalent of ABS if there are similar mods available for 210s.

It is really interesting that the two front cylinders run warmest...maybe the same physics that caused them to find cowling and baffling radials in the old days was worth the expense and hassle.