You could have dirt in your fuel nozzle. There could be a magneto/spark plug issue.
For example, if peak is around 1450, how would you interpret a sudden and steady rise up to 1650 on one cylinder ?
Detonation or pre-ignition, I would guess.
Or a faulty channel on the instrument. I think they use a single A-D converter with a multiplexer in front of it, but it’s not impossible.
I have never seen a steady and elevated EGT if the engine is already at peak EGT. There is no way the engine can achieve such a condition in normal operation, via a fuel issue alone (detonation can be caused by insufficient octane rating but not on just one cylinder, obviously).
One of the two spark plugs in a given cylinder being dud would also raise the EGT a bit. Not because the EGT itself has gone up but because you are getting a slower burn and are getting some still-burning mixture reaching the EGT sensor.
a sudden decrease to a low value ?
Fuel starvation (a blocked injector). Never seen that either.
Any engine related cause of any of the above would also show up as a CHT change.
There may be valve related explanations but I will leave it to somebody else to suggest those.
I don’t see how any ignition issue could raise the EGT in just one cylinder.
Thank you for your propositions.
An intake sticky valve should give low EGT ?
A sticky valve in flight is an experience you will never forget…
@Achimha
Would you tell us a little more about that experience ?
What were the symptoms in flight ?
Did you have some alarm, apart from the eventual “morning sickness ?”
When did you diagnose the sticky valve ? During the flight or after an emergency landing ?
Could it happen again or did you do some modifications ?
Why do you still fly SEP ? :-)
Please, tell us more !
I think I have found the source… :-)
Former Post
PetitCessnaVoyageur wrote:
Would you confirm a failed probe ?
I agree it does look a lot like a failed probe or bad connection. CHT’s appear totally normal. Seen it ‘often’ on my EDM, only to give engineering a ring.
Hello,
The EGT seemed to work normally today.
No obvious connection problem.
Part number is 86317.
$400 at Cessna Parts
€500 at my local shop
Some offers on eBay I am willing to consider.
A google/images for
86317 egt probe
digs out this
which isn’t going to be really cheap because it doesn’t look like a standard JPI product, as seen with a google/images on
jpi egt probe
which doesn’t show anything like that.
Also check out Macfarlane who do similar stuff (which may be for homebuilts though!).
I suspect you are paying a hefty price for somebody sitting in a shed and fitting that yellow thermocouple connector to off the shelf probes. But that connector is a completely negligent choice for something which clearly need environmental protection.
Have you checked Aircraftspruce?
I have removed all the fancy connectors and buy the basic version for about € 100. Then I put simple eylet conectors with screws on and try to protect them as good as possible with a shrinking tube and heat islolation around that. Works fine.
