RE: EGT problem

RE: EGT problem

360 engine, traditional mags, Dynon D100/120 instrumentation, RV7A
700 plus hours, fuel injected.

Last flight during some aerobatic stuff the pilot noted the #2 cylinder EGT redlined at 2000 Immediately retarded throttle and headed home. Throttled back the EGT fell back into the Green.

Thinking it might be an anomaly, and after the plane sat for a cool down, saddled up for an other flight. Everything normal until full throttle and lift off the same thing happened along with noting the EGT immediately up to 2000 and CHT higher than normal (didn't note the temp???). So immediate throttle retard and back to the hanger.

Maybe an injector problem....Cleaned the injector and

So a static run up .... brakes on throttle in to about ??? 2000 plus rpm and at about 15 or so seconds the EGT again made the immediate climb to 2000 plus and the CHT climbing. Again retard the throttle and start the trouble shooting process. Local engine gurus will be consulted today, will try to round up a scope to eyeball the internals of the #2 cylinder in question.

My thought is maybe a mag problem, probe problem, instrument problem??????

Any ideas from you engine gurus would be greatly appreciated.

I've had so many probes (EGT, CHT) go bad that when the readings go wild that is the first thing I suspect. Even several brand new probes have turned out to be wildly inaccurate.

Swap the probes on an adjacent cyl and see if the problem follows the probe or stays on the cyl. You'll have your answer.

JDanno said:

I've had so many probes (EGT, CHT) go bad that when the readings go wild that is the first thing I suspect. Even several brand new probes have turned out to be wildly inaccurate.

Click to expand...

+1

Actually, engines are much more reliable than the instrumentation, so, checking sensors etc when something goes wild (not just creeps off) should be first on the diagnostics list. But don't just fly off to see what happens.

???and i can show you the data file and photos of a trashed engine when an A&P in OKC did that to a cirrus owner.

Believe your instruments until proven otherwise.

An EGT of 2000 is suspect (might be probe) but combined with a CHT running high is a sign of an intake leak or a partially blocked injector.

Simple test lean the mixture to attempt running it LOP, if that cylinder peaks long before the others and the EGT/CHT start dropping well before the others, then you have either a injector issue or a intake leak?or both! In this case it will run rough before the rest get anywhere near peak as the cylinder quits firing.

If you can get on the class in a few weeks in Ada, you will learn a massive amount about fault finding. But you might need to email John Deakin soon as he was telling me they are pretty much booked up.

It would seem that a high EGT indication could be caused by three things.

1) cylinder going lean but not LOP - unless you'd seen it go to 2000 during leaning operations this would not cause it. Once LOP the temps would drop again. If it was a lean cylinder from a fouled injector it would peak early but at about the same temp as always.

2) exhaust valve problem

3) instrumentation problem

Like any other indication like flight instruments, EGT can be cross referenced. Any loss of power or noise or other indications? High CHT?

One other indication of probe function is the indication on the ground with a cold engine. All temps (EGT, OT, CHT, OAT) should read close to ambient.

I recently had an EGT probe go bad low without loss of power or roughness. It turned out to be a connection that had gotten loose and dirty. It worked fine once cleaned up. I also re-crimped the connectors to make sure those were tight.

OZ's post has pretty good info too.

EGT probe

My bet is th EGT probe. Check the connection. When a EGT probe goes to an open condition (broken connection or failed probe) it goes to 2000 degrees on a Dynon. EGT temps can't go to that level (if I recall correctly).

It happened to me. It was a bad Dynon crimp on the EGT connection. It was intermittent.

RE: Results

The EGT probe was toast....replaced with a new one so all is well again!!!!