M20J MSE Turbo-Normalized

[zehutiman]

Is there anybody out there who owns one of these and can comment on the setup?  What kind of performance do you get?  Issues?

[carusoam]

There are a few… most are pretty happy with them…

Doc John and Rich both have written about theirs….

Expect getting the basics of TN’d power to higher altitudes….

Its nice to have more power up where the air gets thinner…

Of course it burns more fuel per hour as you go faster….  
 

It takes a new level of engine management to take care of…

Not a lot, but more than the basic NA engine… 

 

The M20K took it to the next level and adjusted the compression ratio for mechanical efficiency…

Then they added better boost controllers…

Then they added an inter-cooler…

Then they added more room in the back, an extra pair of cylinders, and doubled the turbo normalizers and intercoolers…

Sense the sliding for a few dollars more….

Got any specific questions to go with that?

Best regards,

-a-

[Pinecone]

The first M20K (231) did not have intercooler or boost controller.

Those were added when the 252 came out.

[Shadrach]

6 hours ago, carusoam said:

 The M20K took it to the next level and adjusted the compression ratio for mechanical efficiency…

Best regards,

-a-

Can you expound on this? I’m curious about how the term mechanical efficiency applies to compression ratio. I’ve never seen the term used in this context.

[Pinecone]

You lower the compression ratio and run higher boost.   IIRC the 252 runs 36" of manifold pressure and the Encore runs 39" for 10 more HP than the 231/252

Turbo normalized are standard NA compression ratios and run at 30 inches maximum manifold pressure.  So it is like flying at sea level all the time.

[carusoam]

8 hours ago, Shadrach said:

Can you expound on this? I’m curious about how the term mechanical efficiency applies to compression ratio. I’ve never seen the term used in this context.

Looks like my memory probably mixed up the proper words to describe the efficiency type obtained by using the low compression cylinders with the turbocharger…

Volumetric and Thermal efficiency…

Essentially stuffing more fuel into the smaller cylinder size…

and…

Using the hot exhaust stream to stuff more raw fuel into the engine…

not to be confused with better mpg…..

Classic thermodynamics for mechanical engineers…

 

PP thoughts only, not a mechanical engineer….

Best regards,

-a-

[Shadrach]

3 hours ago, carusoam said:

Looks like my memory probably mixed up the proper words to describe the efficiency type obtained by using the low compression cylinders with the turbocharger…

Volumetric and Thermal efficiency…

Essentially stuffing more fuel into the smaller cylinder size…

and…

Using the hot exhaust stream to stuff more raw fuel into the engine…

not to be confused with better mpg…..

Classic thermodynamics for mechanical engineers…

 

PP thoughts only, not a mechanical engineer….

Best regards,

-a-

I don’t know a great deal about aviation turbo applications, but I’m pretty sure the reason for low compression pistons is to increase detonation margins. I think ost TSIO engines are less thermally efficient than their naturally aspirated brethren. I think a look at the power charts will reveal a Continental TSIO360 (7.5:1CR) makes less power per volume of fuel than a NA Lycoming IO360 (8.7:1CR).

[M20F]

Google compression versus boost.  Drag car applications are the cleanest explanation.  In short compression doesn’t scale rapidly, boost does.  This is why turbos were all the rage for planes.  Drop compression and boost to the moon on planes until the 1990’s. 
 
Then somebody figured out that planes are not cars. Horsepower doesn’t make planes really go faster because of parasitic drag.  Thus getting into thin air is how you really get speed.  That is why pretty much everything is normalized now.  You get 100% power in thin air without pushing the engine hard.  

[Fly Boomer]

On 6/8/2022 at 7:22 PM, M20F said:

That is why pretty much everything is normalized now.  You get 100% power in thin air without pushing the engine hard.

Or pull back the MP a little if not "normalized".

[N201MKTurbo]

By lowering the compression ratio the turbo can compress more air/fuel into the cylinders. This will raise the engine power above its design power level. The turbo bullet did this and they had CHT issues. The M20Turbos is essentially the same setup without the low compression pistons. It regulates the upper deck pressure to 32 in/hg and has a manifold pressure red line of 30 in.

[Shadrach]

29 minutes ago, N201MKTurbo said:

By lowering the compression ratio the turbo can compress more air/fuel into the cylinders. 

The lower CR Turbo has to pump more air/fuel into the cylinders just to match the power of it’s higher compression NA sibling. Boosted engine make more power for a given displacement but not at the same BSFC. Turbos always have >100% volumetric efficiency but that’s from boost not lowering CR.  I’m pretty sure >CR  always equals >thermal efficiency.

[N201MKTurbo]

9 hours ago, Shadrach said:

The lower CR Turbo has to pump more air/fuel into the cylinders just to match the power of it’s higher compression NA sibling. Boosted engine make more power for a given displacement but not at the same BSFC. Turbos always have >100% volumetric efficiency but that’s from boost not lowering CR.  I’m pretty sure >CR  always equals >thermal efficiency.

The limiting factor is always detonation. That happens at some combination of pressure and temperature. With a lower compression ratio, more fuel air mixture can be put into the same cylinder on each stroke. This has the same affect as increasing the displacement of a non boosted engine. The only time efficiency is affected is by how close you get to detonation pressure. The closer you get, the more efficient the combustion is.