To intercool or not to intercool?

[T. Peterson]

2 hours ago, kortopates said:

If you don't want to fly at least in the upper teens and higher you won't get a benefit from an aftercooler since your CDT won't be high enough to ever restrict you. The aftercooler really shines in the flight levels.

I have decided against the “aftercooler”! (I wonder if @MikeOH will give me an “attaboy” for a technically correct term even though I don’t have a clue as to why it is technically correct!)

[kortopates]

1) I am generally cooler than 380 as most often the TIT is limiting, however sometimes the cylinders do reach 380 before the TIT hits 1580. This seems to occur more often in winter flying. I am sure that makes sense to some of you,but I am not engineer enough to explain it.
2) You have really flummoxed me with the 2400 rpm limitation! I don’t see that in the POH. As a matter of fact one of their cruise power examples uses an rpm of 2500, and the charts have columns out to 2700. I would sure appreciate

1) the colder winter air is more dense compared to warmer air, so can produce more power at a higher egt.
2) concur, lower rpm is smoother (especially LOP) and kinder on the engine, but they approve cruising at redline in the operating manual which was the input to the factory for the POH.

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[Crawfish]

2 hours ago, T. Peterson said:

I have decided against the “aftercooler”! (I wonder if @MikeOH will give me an “attaboy” for a technically correct term even though I don’t have a clue as to why it is technically correct!)

Both are types of "charge coolers" it just depends where in the system they fall. 

Aftercoolers are after the Compressor section whether it be turbosupercharger or mechanical Supercharger. Meaning they cool the air right before it enters the engine. 

Intercoolers are between one compressor unit to another. Think twin charged; where a an turbosupercharger feeds into a mechanically driven Supercharger and between the two you have the "intercooler" to cool the air from one compressor stage before the next. 

 

 

My grandfather was a big gearhead, Thanks to him for teaching me to get my knuckles dirty.

[T. Peterson]

3 hours ago, kortopates said:

 

1) the colder winter air is more dense compared to warmer air, so can produce more power at a higher egt.
2) concur, lower rpm is smoother (especially LOP) and kinder on the engine, but they approve cruising at redline in the operating manual which was the input to the factory for the POH.

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 1) I hope I don’t embarrass myself. I understand your point that the cold air is more dense, thus enabling higher power and therefore higher temperatures. What I don’t understand is why that manifests itself as higher cylinder temperature than TIT.

2) In a phone conversation with a friend of mine who is also on this forum, he told me that the Mcauley (sp?) two bladed prop is according to the manufacturer most efficient at 2500 rpm. It seems strange to me that any manufacturer would mate a 2500 rpm prop to a 2400 rpm engine.

[hubcap]

19 hours ago, T. Peterson said:

2) You have really flummoxed me with the 2400 rpm limitation! I don’t see that in the POH. As a matter of fact one of their cruise power examples uses an rpm of 2500, and the charts have columns out to 2700. I would sure appreciate further education on this subject!

The 2400 RPM is the maximum recommended operating RPM from Continental. I believe it is in the Continental operating manual for this engine. I have a copy of it somewhere.

[T. Peterson]

24 minutes ago, hubcap said:

The 2400 RPM is the maximum recommended operating RPM from Continental. I believe it is in the Continental operating manual for this engine. I have a copy of it somewhere.

I doubt you not one iota. Seems that contradictions in our aviation world are not as rare as we would suppose.

 I am very interested in how you fly your airplane. MP, Prop, FF and altitudes. What do you see for temps and TAS? My sole motivation is to learn, not question or criticize! I am especially curious as to MP/rpm combinations. Do you change them up based on altitude or trip length?

[Chris K]

On 10/29/2024 at 9:57 PM, LANCECASPER said:

paging @Jeff Shapiro from TurboPlus (http://www.turboplus.com/)

http://www.turboplus.com/mooney231-intercooler.asp

Nice article starting on page 19: https://themooneyflyer.com/issues/2019-MayTMF.pdf

 

My first Mooney was a 231 without a Merlyn or an intercooler and was very much temperature limited. Once you fly with an automatic wastegate and an intercooler, you'll never go back. Thankfully you already have the Merlyn.

x2.  Read any article regarding the differences between a 252 and 231, the Merlyn was just one part of the equation.  The intercooler helps reduce the temps of the pressurized air coming from the turbocharger which is how the 252 is capable of managing the higher power setting at higher altitudes (this plus a better cowl flap).

[T. Peterson]

58 minutes ago, Chris K said:

x2.  Read any article regarding the differences between a 252 and 231, the Merlyn was just one part of the equation.  The intercooler helps reduce the temps of the pressurized air coming from the turbocharger which is how the 252 is capable of managing the higher power setting at higher altitudes (this plus a better cowl flap).

You are quite right, but at the altitudes I fly, I don’t think the 10,000 AMU investment which would push the whole project to 80,000 is worth it.

 I have instructed the builder to install GAMI injectors as I believe that for the money their benefits would be more advantageous at my favorite altitudes of 11 and 12000 feet than would be the aftercooler at 10x the cost.

@1980Mooney really put his thumb on the target when he stated that I probably bought the wrong airplane for my mission. Hopefully I will be able to rectify that someday, but now I will be content with what I have and continue to enjoy it. She has faithfully conducted my wife and I to several different states over the past 3 years to visit family and friends. It is a blessing to own any Mooney, and I would not want to displease the Lord Jesus by being ungrateful.

 I am also grateful to all you folks for your expertise and advice.

[hubcap]

4 hours ago, T. Peterson said:

I doubt you not one iota. Seems that contradictions in our aviation world are not as rare as we would suppose.

 I am very interested in how you fly your airplane. MP, Prop, FF and altitudes. What do you see for temps and TAS? My sole motivation is to learn, not question or criticize! I am especially curious as to MP/rpm combinations. Do you change them up based on altitude or trip length?

I typically fly fairly conservative numbers -

Take off - 36” MP 2700 RPM Cowl flaps open Full rich

Climb - 33” MP 2,600 RPM Cowl flaps open Full rich

Cruise - 30” MP 2400 RPM Cowl flaps closed or in trail. I typically fly LOP with this setting. I get 150 Kts TAS at 9,000’ with these numbers and the speed goes up from there as the altitude goes up. I will typically get 170 Kts TAS @ 17,000’. My TIT will typically be 1550 - 1570ish and a fuel flow of 10.0- 10.2 GPH. My hottest CHT will run at 350 ish degrees.

[T. Peterson]

1 hour ago, hubcap said:

I typically fly fairly conservative numbers -

Take off - 36” MP 2700 RPM Cowl flaps open Full rich

Climb - 33” MP 2,600 RPM Cowl flaps open Full rich

Cruise - 30” MP 2400 RPM Cowl flaps closed or in trail. I typically fly LOP with this setting. I get 150 Kts TAS at 9,000’ with these numbers and the speed goes up from there as the altitude goes up. I will typically get 170 Kts TAS @ 17,000’. My TIT will typically be 1550 - 1570ish and a fuel flow of 10.0- 10.2 GPH. My hottest CHT will run at 350 ish degrees.

Thank you for that! I’m going to try the cruise setting you describe.

[hubcap]

18 hours ago, T. Peterson said:

Thank you for that! I’m going to try the cruise setting you describe.

It will be interesting to see your CHT’s and TIT with those settings.

[T. Peterson]

1 hour ago, hubcap said:

It will be interesting to see your CHT’s and TIT with those settings.

Airplane is in annual right now, but my first trip I will try your numbers and let you know. Keep in mind my engine is tired and I don’t have the aftercooler.

[M20F]

On 10/30/2024 at 5:01 PM, 1980Mooney said:

This might be a case of the wrong plane for the owner's primary mission. 

Thank you for the most useful post here. 

[Pinecone]

On 11/1/2024 at 3:17 PM, kortopates said:

You must have the TCM position tuned injectors then, which more typically yield 0.6-0.7 GPH - rarely 0.5 but occasionally 0.5.

I've seen hundreds of these and no one with stock injectors that can get a verified repeatable 0.3 GPH spread

Just going by what JP at GAMI said when he got my data.

You have looked at the same data.

 

[kortopates]

Just going by what JP at GAMI said when he got my data.
You have looked at the same data.
 

Indeed, but the average was twice that and in the range of TCM position tuned injectors. Can’t go by your single lowest one. It’s the repeatable average that counts.


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[Pinecone]

Tell GAMI, they won't sell me a set.
 

[T. Peterson]

17 hours ago, M20F said:

Thank you for the most useful post here. 

@1980Mooney certainly assessed correctly, but there are several other posts that were very valuable and reflected serious thinking by the poster. I am not suggesting that you are being dismissive of the others, but I want them all to know that I am very appreciative.

[M20F]

6 hours ago, T. Peterson said:

@1980Mooney certainly assessed correctly

They did, hence my call out to them.  Thanks for recognizing the post. 

[Schllc]

On 11/1/2024 at 5:52 PM, T. Peterson said:

I talked to Western Skyways a few minutes ago and they will order and install GAMI injectors as part of the build!

Thank you!

I have installed gami’s in three planes. None of them were correct from the first iteration. 
two were good after the second set, one took four rounds. 
You will likely need to do your tests in flight under real conditions to get it right. 
I would not have confidence with it being run on a test stand. (Maybe it was me doing the lean tests improperly)
Maybe someone with more experience can edify me, but I think real conditions are what is critical.
It isn’t a big deal and gami doesn’t charge you for the additional injectors, it’s just a tedious process. 
But the fuel savings will pay for them rather quickly. 

[kortopates]

I have installed gami’s in three planes. None of them were correct from the first iteration. 
two were good after the second set, one took four rounds. 
You will likely need to do your tests in flight under real conditions to get it right. 
I would not have confidence with it being run on a test stand. (Maybe it was be doing the lean tests improperly)
Maybe someone with more experience can edify me, but I think real conditions are what is critical.
It isn’t a big deal and gami doesn’t charge you for the additional injectors, it’s just a tedious process. 
But the fuel savings will pay for them rather quickly. 

The test stand is incompatible with testing mixture distribution but there is no rush to do. Mixture distribution shouldn’t be tested till after break-in is complete because we want to do slow sweeps below 65% power not at 75% power for breaking in.
Concur it usually takes a few iterations to get the mixture distribution dialed in but isn’t a concern.


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[802flyer]

What tends to happen when an engine with existing GAMI injectors gets overhauled? Is it typically necessary to rebalance afterwards ( and presumably GAMI charges something for this service)?


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[kortopates]

What tends to happen when an engine with existing GAMI injectors gets overhauled? Is it typically necessary to rebalance afterwards ( and presumably GAMI charges something for this service)?


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Not only is re-testing with likely re-balancing required but depending on how your engine is overhauled its unlikely to come back with your old gami’s injectors unless you take action at the start to ensure so.
Gami does charge a fee for updating with an overhaul.


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[231LV]

On 10/30/2024 at 9:47 AM, Jim F said:

Hi T.Peterson,

I am in a similar position and am planning an overhaul mid 2025.  I have an 81 231 and apparently the only 231 left without a Merlyn or intercooler.  I am planning to install a Merlyn wastegate and a Turboplus intercooler before I do the overhaul so that I can do a PIRP on both.  My position on the Merlyn is that a higher critical altitude would be helpful and allow me to fly 75% power in the flight levels at 2500RPM.  Currently I need to be >2600RPM to get enough MP out of the turbo for 75% power.  On the intercooler, my thought process is why did Mooney not put an intercooler on the 231 and why did Mooney add an intercooler to the 252/Encore (I know the engine is TCM).   The 231 was a low-cost entry into the turbo market and in general the industry considers the 231 a hot running engine.  After market feedback Mooney decided that the addition of an automatic wastegate and intercooler was what customers wanted, and I do think that was a great decision.  Everyone with a 252 or Encore raves about their Mooney being the best option for their mission.  On our 231s the compressor discharge pressure can get very warm, and that warm air charge can really push the CHTs up in the 400s on hot days with a slow climb.  I look at any aftermarket add-on to see if the manufacture released a similar solution in later years.  With the wastegate the fixed wastegate is a pain to deal with and has a low critical altitude, so the automatic wastegate makes sense.  On the intercooler, the hot running 231 when you add an intercooler it has a much better CHT margin from red line.  For me these are reliability decisions, the Merlyn will not be spinning the turbo at as high of an RPM so in theory it should last longer.  The intercooler will have a cooler air charge and should lower the CHTs ~20d and the cylinders should last longer when running cooler.   Remember after the engine change and intercooler add, if your aircraft is faster, you are producing more horsepower.  Also, make sure the fuel system is set correctly once the intercooler is installed.  The intercooler cools the air charge and at that lower Max MP(~36in) you need about the same FF as MP 40in on your non intercooled engine.   Refer to the Merlyn and intercooler documents.

I fly 75%HP, 100d rich of peak at 17.5/16.5ft, 13.9FF, ~30.0in MP, 1550TIT and I see 181Kn.  After I added fine wire plugs, I am now able to run lean of peak, but I don't very often.  Also, I love the fact that I can pick up ~2kn TAS per thousand feet, so I cruise high almost always.  At 17.5 65%HP, 12.4FF I get 170kn.  Fly fast, Jim

Wow! Those are great numbers for a non intercooled, fixed wastegate TSIO360GB. I seem to be temp limited on my TIT (1650) and can't get above 57% hp running LOP and I have a intercooled, Merlyn, TSIO360LB. I don't spend much time up in the FL's and rarely run ROP (unless I am in a real hurry to get somewhere then I'm running 80% at 18-19 gph) so I can't compare what you are seeing to what I am seeing but TIT seems to be my significant limiting factor

[Will.iam]

On 11/9/2024 at 10:40 PM, 231LV said:

Wow! Those are great numbers for a non intercooled, fixed wastegate TSIO360GB. I seem to be temp limited on my TIT (1650) and can't get above 57% hp running LOP and I have a intercooled, Merlyn, TSIO360LB. I don't spend much time up in the FL's and rarely run ROP (unless I am in a real hurry to get somewhere then I'm running 80% at 18-19 gph) so I can't compare what you are seeing to what I am seeing but TIT seems to be my significant limiting factor

What MP are you running at 57%? what is your CHT’s? Because that is 8.8 gal/hr which is low power. To get tit that high you would have to be shoving alot of air slowing down the wave front or 1 or 2 cylinders are not matched close enough in your gami spread and are dumping the exhaust when the combustion is still going on into the exhaust manifold.  If your cht’s are low try going more toward peak egt (less lop) and you should see egt’s go down as cht’s rise.  
 

[T. Peterson]

On 11/3/2024 at 12:29 PM, hubcap said:

It will be interesting to see your CHT’s and TIT with those settings.

Hello @hubcap!

 I flew my plane home from annual today. Your 2400 rpm setting (which I never used before, always opting for 2450 and higher) seemed to be the magic sauce! I was at 9000 feet and I set 2400 rpm, 28 inches mp and rolled back the mixture to 11.6 gallons an hour. All cylinders were well below 380 degrees and TIT was 1578. I was delighted to see 161 kts true, with a stronger oil pressure and temperature. I normally have to burn 12.5 or higher to achieve 161 kts, and my oil pressure straddles the yellow/green dividing line. Today solidly in the green.

My wife and I are flying to Lake of the Ozarks from our home in Ennis, Texas tomorrow. I will have 400 miles to experiment further.

 Thank you so much for the heads up on the 2400 rpm tip! Maybe that is exactly why Continental recommends no more than 2400 max continuous??? Sure wish that made it into the POH.