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 Post subject: Re: piper aztec
PostPosted: 26 Jul 2021, 22:15 
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Aircraft: C180
Let’s talk cooling. Is the big oil cooler still available/retrofit able to the NA E models?

I have to have cowl flaps open or half open to keep under 400 degrees. CHT and my oil temps measured at the front of the case on my EDM are 210 routinely.

LOP is cooler but SLOW at the 6-9k altitudes I normally fly.


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 Post subject: Re: piper aztec
PostPosted: 26 Jul 2021, 23:17 
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Joined: 01/19/16
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Location: 13FA Earle Airpark FL/0A7 Hville NC
Aircraft: E33/152A
Username Protected wrote:
Let’s talk cooling. Is the big oil cooler still available/retrofit able to the NA E models?

I have to have cowl flaps open or half open to keep under 400 degrees. CHT and my oil temps measured at the front of the case on my EDM are 210 routinely.

LOP is cooler but SLOW at the 6-9k altitudes I normally fly.




The last time I checked (years ago) the high capacity improved oil cooler kit was no longer available. It was eligible for installation on the all of the 64 and newer (C,D,E and F) NA or Turbo models. The coolers are still available new and have multiple applications. The installation kit consists of a new left rear cylinder baffle with an outlet duct attached. This replaced the original baffle that the cooler mounted directly to. The baffle was not strong enough to support the heavy oil cooler that vibrated with the engine resulting in cracked cooler flanges and cracked baffles. The new larger oil cooler mounts solidly to the engine truss. The kit came with a stamped aluminum bracket and a pair of small stand offs made from round stock and Adel clamps. There is an inlet plenum that mounts to the front of the cooler. The hardest part to fab or mod would be the rear cylinder baffle and the cooler inlet plenums I believe I have most of the parts required except for the rear baffles and the coolers. The last time I checked the coolers were reasonably priced-about $500. ea. They are better quality than the early style.

The factory turbo nose bowls (or my carbon fiber horizontally split nose bowls) will help it run cooler too. The turbo models induction air entered through the nose bowl inlets instead of having an induction scoop on the bottom of the cowling. For that reason the cowl inlets are larger.

The early carbureted models had a better system mounting the cooler to the firewall with a dedicated outlet duct.


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 Post subject: Re: piper aztec
PostPosted: 26 Jul 2021, 23:28 
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Joined: 01/22/19
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Location: KFXE
Username Protected wrote:
Let’s talk cooling. Is the big oil cooler still available/retrofit able to the NA E models?

I have to have cowl flaps open or half open to keep under 400 degrees. CHT and my oil temps measured at the front of the case on my EDM are 210 routinely.

LOP is cooler but SLOW at the 6-9k altitudes I normally fly.


With some attention to the baffles, I am able to fly a Turbo Aztec at 80 percent power, in a climb, with cowl flaps closed and CHT's under 400 dF. The biggest baffle leaks are around the nose bowl area. A lot of air bypasses the baffles near the alternator as well. Piper didn't pay much attention to sealing off the upper engine from the lower.

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 Post subject: Re: piper aztec
PostPosted: 27 Jul 2021, 15:14 
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Joined: 12/16/09
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Location: Snohomish, WA
Aircraft: PA-27 Turbo
On my Turbo F I can run the 70% power setting 26/24 and keep the left cowl shut but the right side needs to be half open to keep #6 under 380* in cruise. At the long range setting of 24/22 i can keep both shut.

I've spent a fair bit of time tweaking the baffles. John at Diamond Aire installed and set the baffles for me years ago and his opinion is the ram airflow combined with the prop rotation turning into the fuselage makes getting air to the #6 cylinder tricky on the right side.

Unfortunately I've kind of given up and live with right side cowl cracked open at 70% power.

Fortunately, I'm cheap with fuel and operate at the lower 24/22 most often to save gas and extend range.

Glenn, I believe you are the gentleman who posts a lot on Piper forum. Your Aztec knowledge is Yoda-ish in my opinion. I wish you lived closer. I would like to have your expertise give my Truck a good 'once over.' ;)


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 Post subject: Re: piper aztec
PostPosted: 27 Jul 2021, 21:08 
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Username Protected wrote:
On my Turbo F I can run the 70% power setting 26/24 and keep the left cowl shut but the right side needs to be half open to keep #6 under 380* in cruise. At the long range setting of 24/22 i can keep both shut.

I've spent a fair bit of time tweaking the baffles. John at Diamond Aire installed and set the baffles for me years ago and his opinion is the ram airflow combined with the prop rotation turning into the fuselage makes getting air to the #6 cylinder tricky on the right side.

Unfortunately I've kind of given up and live with right side cowl cracked open at 70% power.

Fortunately, I'm cheap with fuel and operate at the lower 24/22 most often to save gas and extend range.

Glenn, I believe you are the gentleman who posts a lot on Piper forum. Your Aztec knowledge is Yoda-ish in my opinion. I wish you lived closer. I would like to have your expertise give my Truck a good 'once over.' ;)


Closing up the gaps at the nose bowl will increase the ram air pressure that is supposed to flow down through the cylinders. It's the most neglected part of the baffle system. I did this to my friend's E model Turbo to fix his CHT issues. Now he can climb with cowl flaps closed. We did a test from sea level to 11,000 feet, and closed the flaps at 3000 feet. It could never do that before at any power setting. You also have to ensure the aft baffle seals are not bending backwards, or dropping down, in flight, so that they seal well to the cowl top. The top cowl has channels that support it, but they leak huge amounts of air at the back if they are not sealed with 1/2" foam in the channels. And you can put 1/2" thick foam blocks on the cowl sides, at the #5 & 6 cylinders, to keep the baffle seals tight to the cowl.

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 Post subject: Re: piper aztec
PostPosted: 27 Jul 2021, 21:55 
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Aircraft: C180
Good stuff. I’m on it. Thank you both. Nose bowls first.


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 Post subject: Re: piper aztec
PostPosted: 08 Dec 2021, 12:47 
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Aircraft: Be35
Username Protected wrote:
Let’s talk cooling. Is the big oil cooler still available/retrofit able to the NA E models?

I have to have cowl flaps open or half open to keep under 400 degrees. CHT and my oil temps measured at the front of the case on my EDM are 210 routinely.

LOP is cooler but SLOW at the 6-9k altitudes I normally fly.




The last time I checked (years ago) the high capacity improved oil cooler kit was no longer available. It was eligible for installation on the all of the 64 and newer (C,D,E and F) NA or Turbo models. The coolers are still available new and have multiple applications. The installation kit consists of a new left rear cylinder baffle with an outlet duct attached. This replaced the original baffle that the cooler mounted directly to. The baffle was not strong enough to support the heavy oil cooler that vibrated with the engine resulting in cracked cooler flanges and cracked baffles. The new larger oil cooler mounts solidly to the engine truss. The kit came with a stamped aluminum bracket and a pair of small stand offs made from round stock and Adel clamps. There is an inlet plenum that mounts to the front of the cooler. The hardest part to fab or mod would be the rear cylinder baffle and the cooler inlet plenums I believe I have most of the parts required except for the rear baffles and the coolers. The last time I checked the coolers were reasonably priced-about $500. ea. They are better quality than the early style.

The factory turbo nose bowls (or my carbon fiber horizontally split nose bowls) will help it run cooler too. The turbo models induction air entered through the nose bowl inlets instead of having an induction scoop on the bottom of the cowling. For that reason the cowl inlets are larger.

The early carbureted models had a better system mounting the cooler to the firewall with a dedicated outlet duct.


Diamond aire out in Montana sells the truss mounted oil cooler setup. They work well the cooler is about 50% larger. Your split cowls that you mentioned; where can i get a set?

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 Post subject: Re: piper aztec
PostPosted: 08 Dec 2021, 14:31 
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Aircraft: C180
Username Protected wrote:
On my Turbo F I can run the 70% power setting 26/24 and keep the left cowl shut but the right side needs to be half open to keep #6 under 380* in cruise. At the long range setting of 24/22 i can keep both shut.

I've spent a fair bit of time tweaking the baffles. John at Diamond Aire installed and set the baffles for me years ago and his opinion is the ram airflow combined with the prop rotation turning into the fuselage makes getting air to the #6 cylinder tricky on the right side.

Unfortunately I've kind of given up and live with right side cowl cracked open at 70% power.

Fortunately, I'm cheap with fuel and operate at the lower 24/22 most often to save gas and extend range.

Glenn, I believe you are the gentleman who posts a lot on Piper forum. Your Aztec knowledge is Yoda-ish in my opinion. I wish you lived closer. I would like to have your expertise give my Truck a good 'once over.' ;)


Closing up the gaps at the nose bowl will increase the ram air pressure that is supposed to flow down through the cylinders. It's the most neglected part of the baffle system. I did this to my friend's E model Turbo to fix his CHT issues. Now he can climb with cowl flaps closed. We did a test from sea level to 11,000 feet, and closed the flaps at 3000 feet. It could never do that before at any power setting. You also have to ensure the aft baffle seals are not bending backwards, or dropping down, in flight, so that they seal well to the cowl top. The top cowl has channels that support it, but they leak huge amounts of air at the back if they are not sealed with 1/2" foam in the channels. And you can put 1/2" thick foam blocks on the cowl sides, at the #5 & 6 cylinders, to keep the baffle seals tight to the cowl.



Glenn, where did you mount baffling at for the front of the nose bowls?
I inspected that this week with eye towards what you had discussed above. My channels on the top cowl are blocked already.

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 Post subject: Re: piper aztec
PostPosted: 08 Dec 2021, 21:09 
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there should be baffle seal riveted to the cowl inlets, on the bottom of the inlet, and up the sides by the engine case. You also can fill in the large gaps between the engine case, and the front cylinder baffles, with 736 RTV.

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 Post subject: Re: piper aztec
PostPosted: 08 Dec 2021, 22:00 
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Aircraft: C180
:scratch:
Mine are naked. This explains a lot.
Thank you kindly


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 Post subject: Re: piper aztec
PostPosted: 08 Dec 2021, 22:30 
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Location: KFXE
Username Protected wrote:
:scratch:
Mine are naked. This explains a lot.
Thank you kindly


You can also add propeller vortelators to the prop blade root area. If you don't have hot props. This helps smooth the airflow into the inlets. In my B model cowls, adding them reduced the temperatures by 20 degrees. And in combination with closing up all the holes Piper left around the alternator area, I gained 4 knots. Cooling drag is one of the biggest, and most mis-understood parts of the speed equation. Any air going into the cowl, that doesn't cool the engine, is just extra drag. https://www.wicksaircraft.com/shop/prop-kits/

The company had an STC for them, but later the FAA determined it wasn't needed. I ordered the STC'd ones anyway. In combination with lots of little tweaks, I probably have the fastest, coolest running Aztec there is. Leveling off at 11,500, 172 KTAS on 23 GPH. After ten minutes, the CHT's drop to about 330-350 overall. And, this is the carbureted O-540-A1D5 engine, which is normally hard to get even EGT/CHT numbers, and fuel efficiency, compared to the fuel injected counterparts. You really don't need bigger oil coolers, you need better cylinder cooling.


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

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