BeechTalk - BT

Username Protected · **Posted:** 27 Jan 2020, 22:44

Username Protected wrote:

You said you switched the CHT probes. Did you try switching the probes while leaving the wires connected to the same leds from the JPI? It would be an incorrect cylinder indication on the JPI, but it would isolate whether the problem is truly an engine related issue, or a JPI related issue.

And heat the pipe or cylinder with a hair dryer or shrink wrap gun to simulate a warm cylinder.

Username Protected · **Posted:** 27 Jan 2020, 22:45

Username Protected wrote:

You said you switched the CHT probes. Did you try switching the probes while leaving the wires connected to the same leds from the JPI? It would be an incorrect cylinder indication on the JPI, but it would isolate whether the problem is truly an engine related issue, or a JPI related issue.

The wires???? No way that could happen on any engine I've ever seen.

Username Protected · **Posted:** 27 Jan 2020, 22:48

Username Protected wrote:

Ok... I’ve studied the maintenance and parts manuals... there are no good figures showing the exhaust system precisely in relation to the engine... any body have a good diagram? What’s near cylinder #4 in the exhaust system? Remember it’s a continental which numbers cylinders different from lycoming... it’d be the left middle cylinder...
I’m looking at the Piper manuals—-

Larry, open your cowling. Look at the exhaust headers. It should be obvious that the pipes exiting your two middle cylinders, 3 on the right and 4 on the left have slip joints...if they do.

I'll try to get you a picture. Maybe someone can beat me to it.

Username Protected · **Posted:** 27 Jan 2020, 23:05

Plane is at shop... this is my last week... then I give up...move on and fly...with a handicap...for awhile...I guess...
Yes.. I asked shop to double check exhaust system in that area...

Username Protected · **Posted:** 27 Jan 2020, 23:29

Using a camera and some other monkey tools I was able to show a friend that their newly overhauled exhaust had been tack welded but the shop had not completed the bead in 3 spots, making keeping the cowl warm inside and contributing to the CO in the flight deck.

Two shops missed it. How did I catch it? I was skinny enough to fit in the hell hole on the Huey and the lowest ranked guy and never wised up. The metal head remover slinging 16 inches to my left didn't bother me on a prop plane. ...but never say "Hey y'all watch this!

...and I still climb up in there to show my kids but it is a LOT tighter.

It might not hurt to mount a go pro or borescope camera safely and see if it picks up any exhaust leaks.

Username Protected · **Posted:** 28 Jan 2020, 01:10

Username Protected wrote:

You said you switched the CHT probes. Did you try switching the probes while leaving the wires connected to the same leds from the JPI? It would be an incorrect cylinder indication on the JPI, but it would isolate whether the problem is truly an engine related issue, or a JPI related issue.

The wires???? No way that could happen on any engine I've ever seen.

Username Protected · **Posted:** 28 Jan 2020, 07:57

This pic roughly shows what I'm talking about. See the joints on the middle headers. My exhaust simply has a slip connection without the clamps on the middle headers. It doesn't take much of an exhaust leak provided it's pointed at the CHT probe.

Attachment:

download.jpeg

As for probe wires following the probe when switching probes for a test... I guess anything is possible. On my installation the probe harnesses are fastened tightly to prevent chaffing and there isn't enough slack to switch wires between cylinders without significant intentional effort which would be completely counter productive.

But...I guess anything is possible...

Username Protected · **Posted:** 28 Jan 2020, 10:33

Username Protected wrote:

As for probe wires following the probe when switching probes for a test... I guess anything is possible. On my installation the probe harnesses are fastened tightly to prevent chaffing and there isn't enough slack to switch wires between cylinders without significant intentional effort which would be completely counter productive.

But...I guess anything is possible...

They had the entire engine out. It would not be too difficult to reinstall the harness incorrectly.

Username Protected · **Posted:** 28 Jan 2020, 12:01

It really would be nice to confirm that the cylinder is actually hot. What about a gasket (spark plug) probe for a test. Obviously the exhaust needs to be checked, but that cylinder will not last long if its truly 450 degrees.
Kevin

Username Protected · **Posted:** 28 Jan 2020, 13:09

Username Protected wrote:

It really would be nice to confirm that the cylinder is actually hot. What about a gasket (spark plug) probe for a test. Obviously the exhaust needs to be checked, but that cylinder will not last long if its truly 450 degrees.
Kevin

For that matter, steal the lead from another cylinder and use a spark plug CHT probe and test fly it. Then you will have two indications from the same cylinder at the exact same time... There may be a few degree difference, but not significant enough to skew the results...

Just make sure it goes back together properly...

Username Protected · **Posted:** 28 Jan 2020, 13:27

Username Protected wrote:

It really would be nice to confirm that the cylinder is actually hot. What about a gasket (spark plug) probe for a test. Obviously the exhaust needs to be checked, but that cylinder will not last long if its truly 450 degrees.
Kevin

For that matter, steal the lead from another cylinder and use a spark plug CHT probe and test fly it. Then you will have two indications from the same cylinder at the exact same time... There may be a few degree difference, but not significant enough to skew the results...

Just make sure it goes back together properly...

Username Protected · **Posted:** 28 Jan 2020, 13:51

Username Protected wrote:

I also agree with Jason that reinstalling the engine does raise the possibility that the cylinder that is actually hot may not be the indicated cylinder.

The issue was there with that cylinder before the engine overhaul. That leads me to believe it's an issue with the JPI and not necessarily the engine, or the exhaust that would have been completely removed and inspected (said it wasn't overhauled on page one).

Username Protected · **Posted:** 28 Jan 2020, 14:01

Username Protected wrote:

I also agree with Jason that reinstalling the engine does raise the possibility that the cylinder that is actually hot may not be the indicated cylinder.

The issue was there with that cylinder before the engine overhaul. That leads me to believe it's an issue with the JPI and not necessarily the engine, or the exhaust that would have been completely removed and inspected (said it wasn't overhauled on page one).

Username Protected · **Posted:** 28 Jan 2020, 14:09

Yeah, I think the instrument bears more troubleshooting. It is possible the instrument is broke, or there's bad wiring, or some such.

Also have them check all the inter-cylinder baffling for presence, security and correctness.

I don't trust exhaust systems either. A careful examination of the engine will show traces of exhaust gases if they're leaking.

I'd say it is all but unbelievable that you'd have the exact same problem with the exact same cylinder.

Curious - how are the EGT's and TIT's?

Username Protected · **Posted:** 28 Jan 2020, 19:29

Hi Larry

I have a 1988 PA-46 310. I had a factory reman installed last April. I saw some super high CHTs during and after break-in. No 2 cylinder hit a high of 415. Fuel flows and baffles were all within the norms.

Someone mentioned that it may be a timing issue. And it was! After adjustment, the CHTs all started behaving. Flew yesterday (admittedly, it's winter and I'm based outside Philly) and the CHTs were all below 300.

Maybe something to look at if you haven't already.

Piper Malibu Snafu