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21 Nov 2025, 19:29 [ UTC - 5; DST ]


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 Post subject: Re: Piper Malibu Snafu
PostPosted: 29 Jan 2020, 18:32 
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I got the plane back in my hangar..... I’m going to download the data and do a savvy analysis..flying it home yesterday felt fine in climbs... shop might have done something...but won’t admit it....perhaps...
Turns out I have only 8 hours on new engine... still in breakin mode...anything interesting shows up I will post it..

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 Post subject: Re: Piper Malibu Snafu
PostPosted: 29 Jan 2020, 20:58 
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Joined: 08/12/08
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Hi Larry,

While I love my TAT TN 550 powered A36, I lust for pressurization. And that means a Malibu (most likely).

Please keep us posted.

Best,

Jim

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 Post subject: Re: Piper Malibu Snafu
PostPosted: 29 Jan 2020, 22:05 
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Joined: 02/27/08
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Location: Galveston, TX
Aircraft: Malibu PA46-310P
Username Protected wrote:
I got the plane back in my hangar..... I’m going to download the data and do a savvy analysis..flying it home yesterday felt fine in climbs... shop might have done something...but won’t admit it....perhaps...
Turns out I have only 8 hours on new engine... still in breakin mode...anything interesting shows up I will post it..



Drop the savvy link out for us if you have the time. A lot of good sleuths on this site.

Kevin


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 Post subject: Re: Piper Malibu Snafu
PostPosted: 30 Jan 2020, 19:30 
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Larry,

Can you ground run the engine and look at it with an IR camera? It would show you pretty quickly if you had an exhaust leak.

Also you can take temp reading using an IR temp gage.


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 Post subject: Re: Piper Malibu Snafu
PostPosted: 30 Jan 2020, 22:02 
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An exhaust leak will not cause a rise in CHT. The CHT probe is buried deep into the head and is unaffected by external heat sources. The airflow downward through the cylinder fins keeps the CHT stable. So if you have a rise, you either have insufficient airflow, or too much airflow if the inter-cylinder baffles are out of place, or the wrong fuel flow for that cylinder.

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 Post subject: Re: Piper Malibu Snafu
PostPosted: 30 Jan 2020, 22:35 
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Have another shop evaluate the problems.


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 Post subject: Re: Piper Malibu Snafu
PostPosted: 31 Jan 2020, 02:06 
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Username Protected wrote:
An exhaust leak will not cause a rise in CHT. The CHT probe is buried deep into the head and is unaffected by external heat sources. The airflow downward through the cylinder fins keeps the CHT stable. So if you have a rise, you either have insufficient airflow, or too much airflow if the inter-cylinder baffles are out of place, or the wrong fuel flow for that cylinder.


Thanks Glenn. I will say it one last time. Do a GAMI test and whatever else needed to understand what is happening with FF to that cylinder. Might be a partial block in the spider or maybe GAMI just needs to get you a different injector.

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 Post subject: Re: Piper Malibu Snafu
PostPosted: 31 Jan 2020, 11:00 
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Username Protected wrote:
An exhaust leak will not cause a rise in CHT. The CHT probe is buried deep into the head and is unaffected by external heat sources.

George Braly does not agree and there are few people who know and have tested their "theories" on these engines like George. (George practicality is GAMI.)

Mr. Braly writes, "You remarked that the CHT 1 would go up slowly in flight. THAT is associated with a subtle nearby exhaustust leak in many cases. Happens right after you lean and all the EGTs go UP - - then the leaking and now HOT exhaust begins to warm up the nearby cylinder."

viewtopic.php?f=37&t=117099&p=1568188&hilit=associated+with+a+subtle+nearby+exhaust+leak#p1568188

I personally have had an exhaust leak cause an elevated CHT indication.

Ron Hink likewise fixed a faulty elevated CHT indication by fixing an exhaust leak.

Ron Hink - "Fixed exhaust leak, fixed CHT problem."

viewtopic.php?f=37&t=167933&p=2546775&hilit=Exhaust+leak+CHT#p2546775

For more evidence use the BeechTalk search feature. It is not an uncommon phenomenon.

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 Post subject: Re: Piper Malibu Snafu
PostPosted: 31 Jan 2020, 12:20 
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Username Protected wrote:
An exhaust leak will not cause a rise in CHT. The CHT probe is buried deep into the head and is unaffected by external heat sources.

George Braly does not agree and there are few people who know and have tested their "theories" on these engines like George. (George practicality is GAMI.)

Mr. Braly writes, "You remarked that the CHT 1 would go up slowly in flight. THAT is associated with a subtle nearby exhaustust leak in many cases. Happens right after you lean and all the EGTs go UP - - then the leaking and now HOT exhaust begins to warm up the nearby cylinder."

viewtopic.php?f=37&t=117099&p=1568188&hilit=associated+with+a+subtle+nearby+exhaust+leak#p1568188

I personally have had an exhaust leak cause an elevated CHT indication.

Ron Hink likewise fixed a faulty elevated CHT indication by fixing an exhaust leak.

Ron Hink - "Fixed exhaust leak, fixed CHT problem."

viewtopic.php?f=37&t=167933&p=2546775&hilit=Exhaust+leak+CHT#p2546775

For more evidence use the BeechTalk search feature. It is not an uncommon phenomenon.


An exhaust leak would be several inches away, at best, from the cylinder head. The CHT probe is sunk into the head by about 2 inches. It reads only from its tip. In operation, the airflow is coming down through the fins at high velocity, In order to have the CHT increase, you would have to have a massive exhaust leak directed at the cylinder head inboard of the exhaust stack on the affected head. Not a subtle leak. A massive one, and directional too.
I have fully instrumented an engine to refine the baffling in conjunction with a cowl modification project. A mild exhaust leak will result in a minor increase in air pressure below the engine, by only a few inches of mercury. I would have to saw off an exhaust riser to see if I could make the CHT rise on an individual cylinder. The effects would be more pronounced on a turbo engine because a pre-turbo exhaust leak will have more heat and more velocity available for transfer. Still, the rise in CHT would probably come from less efficient extraction of exhaust heat on the affected cylinder. Not from exhaust blasting on the head.
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 Post subject: Re: Piper Malibu Snafu
PostPosted: 31 Jan 2020, 15:46 
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Glenn, I totally get where you're coming from. I can only tell you what I've experienced and what George Braly says. You might want to talk to Mr. Braly, founder of GAMI.

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 Post subject: Re: Piper Malibu Snafu
PostPosted: 31 Jan 2020, 17:40 
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Username Protected wrote:
Glenn, I totally get where you're coming from. I can only tell you what I've experienced and what George Braly says. You might want to talk to Mr. Braly, founder of GAMI.

Also, while the CHT probe tip is indeed buried in the head, the temperature of any thermocouple can be greatly affected by the temperature of the wires running from the tip. This is not an electrical issue, it's all about thermal conductivity and it's inverse thermal resistance. Whenever there is a significant difference between the probe tip and it's wires there will be a gradient of temperature along those wires and along the thermal path from the thermocouple joint to the heat source in the cylinder.

The temperature rise of the thermocouple joint will rise in proportion to the temperature of the wires vs the monitored heat source multiplied by the ratio of the thermal resistance between the joint and wires vs joint and cylinder. That resistance ratio is probably on the order of 10:1 or 20:1 so for a slight elevation of the wire temp the effect will be small but if you're talking about wires heated several hundred degrees by the hot exahaust the end result will be significant.

The same situation exists for the cylinder itself, a small local hot spot some distance from the measurement point will have an effect on that measurement due to the temperature gradient along the path from the hot spot to the measuring point and beyond.

The possibility of an exhaust leak is by no means the only potential cause for an elevated CHT reading but I wouldn't discount it out of hand.

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 Post subject: Re: Piper Malibu Snafu
PostPosted: 31 Jan 2020, 22:23 
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Lance, Bob Kennedy, retired was my mechanic years ago. He is the one who found the source of my elevated CHT temp to be my exhaust slip joint. I'd never heard of it before then. Since joining BT nearly 10 years ago I've come across it numerous times, but no one puts it more eloquently than you.

... And as you said, it is by no means the only source of a spurious reading. Just one of several considerations.

BTW, the Einstein pic from years past still applies.

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 Post subject: Re: Piper Malibu Snafu/JPI DATA
PostPosted: 01 Feb 2020, 13:39 
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OK.... for you gents who gents who use this data and have a system for scanning/configuring take a look. I'm attaching the dump all i just did. Got the box last night.
What are your fav config srttings in the sw? I noticed that last few flights before OH are there too, for some comparison.


Please login or Register for a free account via the link in the red bar above to download files.

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 Post subject: Re: Piper Malibu Snafu/JPI DATA
PostPosted: 02 Feb 2020, 12:28 
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Username Protected wrote:
OK.... for you gents who gents who use this data and have a system for scanning/configuring take a look. I'm attaching the dump all i just did. Got the box last night.
What are your fav config srttings in the sw? I noticed that last few flights before OH are there too, for some comparison.

JPI's EZ-Trend SW doesn't like your file.

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 Post subject: Re: Piper Malibu Snafu
PostPosted: 02 Feb 2020, 15:54 
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I was able to open it in Savvy. All the CHT's are too high on the few flights I looked at. The coolest one was 399 degrees at the peak and up to 450. I don't see the fuel flow, but it seems to be low by the EGT's and CHTs.

https://apps.savvyaviation.com/flights/3734388/b1bc3e63-1fb0-416d-ab13-790660bbd5b2

I have the same plane and my CHT's peak at about 350-370 for the hottest in a climb. What is your climb speed. Have you tried a climb using takeoff power? Thats the way I run mine until leveling off at cruise.

Kevin


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