M20K 231 critical altitude gain with turboplus intercooler and/or Merlyn automatic wastegate

[JC2020]

How much more critical altitude gain can be achieved if I add a Merlyn automatic wastegate to a m20k 231 that already has a turboplus intercooler installed. I see data showing intercooler alone can raise critical altitude to 21000, while automatic wastegate alone can raise it to 19000. How about a combination of the two?

 

[Pinecone]

Since the automatic waste gate will be closed at 19,000, I can't see that it would add more.

How high of a critical altitude are you looking for?  And why?

[jrwilson]

I think the critical altitude is 24,000 with the Merlyn.  I'm not sure if that is with the combination of Merlyn and Intercooler, which is what I have.  But the Merlyn install claims it gives critical altitude all the way to 24,000.  I've confirmed it will do it.

[hubcap]

2 hours ago, jrwilson said:

I think the critical altitude is 24,000 with the Merlyn.  I'm not sure if that is with the combination of Merlyn and Intercooler, which is what I have.  But the Merlyn install claims it gives critical altitude all the way to 24,000.  I've confirmed it will do it.

This is correct. The critical altitude is 24,000 with the Merlyn.

[carusoam]

Welcome aboard JC!

With great power comes great responsibility… - Peter Parker

Check the TUC chart if you plan to spend much time at that altitude, and plan accordingly… 

The flight levels can be a pretty harsh environment… When Plan A decides to take a break…

Go TC’d Mooney!

+1 for Merlyn and TurboPlus…

PP thoughts only, not a CFI… or a neighsayer….

Best regards,

-a-

[kortopates]

6 hours ago, hubcap said:

This is correct. The critical altitude is 24,000 with the Merlyn.

Sorry but not possible,
Merlyn claims that the critical altitude was between 14K to 19K which is more realistic but a big range.

See their claims here: http://www.merlynproducts.com/blackmagicm.html

Since much of its optimistic marketing it needs to be taken with a grain of salt 

[Will.iam]

are we talking critical altitude that the turbo can make full boost or we talking critical altitude the airplane can climb up to? I seem to recall the 252 had a turbo critical altitude of 24,000ft at which point the boost would start coming down as you continued to climb up to 28,000ft where the engine was producing 78% power with WOT.  I think maybe the 231 has full boost up to 19k but with boost dropping off the 231 can continue to climb up to 24,000ft and still hold cruise power just not maximum power. I think the merlyn wastegate controller will allow the turbo to provide boost without the turbo working as hard as a fix wastegate so your turbo longevity will be increased so there is that...

Edited April 5, 2023 by Will.iam

[carusoam]

Will,

Probably both…

Because we don’t know the OP… and the level of his turbo knowledge. 

He is asking the right questions though… and he is in the right place!

Best regards,

-a-

[kortopates]

On 4/3/2023 at 9:18 PM, JC2020 said:

How much more critical altitude gain can be achieved if I add a Merlyn automatic wastegate to a m20k 231 that already has a turboplus intercooler installed. I see data showing intercooler alone can raise critical altitude to 21000, while automatic wastegate alone can raise it to 19000. How about a combination of the two?

 

Intercooler don't raise the critical altitude. They can allow you to climb without CDT becoming a limiting factor.

[kortopates]

4 minutes ago, Will.iam said:

are we talking critical altitude that the turbo can make full boost or we talking critical altitude the airplane can climb up to? I seem to recall the 252 had a turbo critical altitude of 24,000ft at which point the boost would start coming down as you continued to climb up to 28,000ft where the engine was producing 78% power with WOT.  I think maybe the 231 has full boost up to 19k but with boost dropping off the 231 can continue to climb up to 24,000ft and still hold cruise power just not maximum power.

Critical altitude is the max altitude the engine can produce 100% rated power. Its a density altitude.

The service ceiling is the max altitude at which the aircraft at max gross weight can still climb at 100 FPM.

The certified ceiling is the max FAA authorized altitude the aircraft can be operated (also that it was tested to operate during certification). 

[carusoam]

Similar discussion for the Mooney Acclaim….

Examples of Critical Altitude vs. a marketing stated ‘cruise altitude’…  

-a-

 

According to Aviation Consumer… 

The engine’s full certified capacity is 310-HP, but for the Acclaim, it’s derated to 280 HP by dint of limited RPM, power it can maintain to the airplane’s critical altitude of about 21,000 feet.

 

Second, we profoundly wish Mooneys Web site didnt make the claim that 237 knots is “normal cruise” at FL250. Continuous cruise at this altitude is unrealistic and, in our view, an undertaking of too high a risk to make it worth any benefits. Dragging the airplane to those altitudes just to surpass the Joneses strikes us as a fools game.

https://www.aviationconsumer.com/aircraftreviews/mooney-acclaim-fast-and-flexible/

-a-

[hubcap]

8 hours ago, kortopates said:

Sorry but not possible,
Merlyn claims that the critical altitude was between 14K to 19K which is more realistic but a big range.

See their claims here: http://www.merlynproducts.com/blackmagicm.html

Since much of its optimistic marketing it needs to be taken with a grain of salt 

You are absolutely correct. I was mistaken.