M20k 231 engine

[scottnelson903]

So I have been reading about the difference in the GB vs the LB engine. So does the GB run way hotter than the LB? I'm concerned about that could be a deal breaker when buying the 231.

[DonMuncy]

Under some circumstances the GB will run hotter. You just have to watch it closely, and reduce power or whatever to keep the CHTs under control. It should not necessarily be a deal breaker, but the LB is definitely superior.

[MB65E]

Not many GB's left. I didn't even look at GB engined aircraft while looking at several turbos. However, if there was a cream puff airframe, price it as run out and do the upgrade to LB. 

-Matt

[KLRDMD]

26 minutes ago, scottnelson903 said:

So I have been reading about the difference in the GB vs the LB engine. So does the GB run way hotter than the LB? I'm concerned about that could be a deal breaker when buying the 231.

I refused to look at any 231s with a -GB engine.

[Jim F]

Hi Scott,

I have a GB no intercooler no Merlin waste gate.  I bought it with 1250 hours and now it's at 1750.  I think the minor setbacks of a warm running engine can be easily managed. When I first bought my 231 I went through and sealed every leak in the baffle and baffle seals. I set the fuel flows on the rich side and I clean the fuel nozzles every 100 hours. I also put a JPI 830 so I could see the cooling degrees over time and all six at a glance.  On hot days I just climb through the first couple of thousand feet at 130mph  There has not been a top on my engine, one cylinder off before I bought her who knows why. I pulled one jug due to a crack in the exhaust port but I would say that crack was from a void in the casting.

 I can't speak to how much cooler an LB runs but I do plan on changing when I get it overhauled. 

If you like the 231 then get one, if your worried about the GB and you can't get past that get an LM or move up to the 252. From my experience if a GB is flown right and maintained right it's a great engine. 

My background, I have overhauled hundreds of engines and set twice as many TCM fuel flows  

Jim

[whiskytango]

I had a GB engine in my first 231.  It did not have a Merlyn or intercooler.  The biggest problem was the climb during summer months.  At times 200 FPM was the most I could do without pushing CHTs above 400 F.  The 231 I am flying now has an LB with a Merlyn, intercooler and GAMIs, and maintaining cool CHTs (below 380 F) in the climb is no problem, even in summer.

[N231BN]

The difference between the -gb and -lb is the latter has larger diameter throttle body and curved intake tubes. Both engines develop the same power but the -gb places more back pressure on the cylinders via the turbo as it has to generate more upper deck pressure to achieve the same manifold pressure.

This basically means the cylinders on a -gb need to generate more thermodynamic power(?) to achieve the same BHP at the crank. This requires more FF to control temps.

The other change between the two engines is the -lb fuel injection system operates at a lower fuel pressure so it has different injector nozzles.

[j3gq]

On August 3, 2017 at 3:32 AM, Jim F said:

Hi Scott,

I have a GB no intercooler no Merlin waste gate.  I bought it with 1250 hours and now it's at 1750.  I think the minor setbacks of a warm running engine can be easily managed. When I first bought my 231 I went through and sealed every leak in the baffle and baffle seals. I set the fuel flows on the rich side and I clean the fuel nozzles every 100 hours. I also put a JPI 830 so I could see the cooling degrees over time and all six at a glance.  On hot days I just climb through the first couple of thousand feet at 130mph  There has not been a top on my engine, one cylinder off before I bought her who knows why. I pulled one jug due to a crack in the exhaust port but I would say that crack was from a void in the casting.

 I can't speak to how much cooler an LB runs but I do plan on changing when I get it overhauled. 

If you like the 231 then get one, if your worried about the GB and you can't get past that get an LM or move up to the 252. From my experience if a GB is flown right and maintained right it's a great engine. 

My background, I have overhauled hundreds of engines and set twice as many TCM fuel flows  

Jim

Hi Jim, this is good insight and in line with a similar report on mooneyland.com    In order to explore the subject a little further 2 questions. Do you have any insight as to the cost of a -GB to -LB conversion at OH time ? And, could you please have a look and respond to another post on this engine which I just wrote 30 min ago on this board ? Thanks

[j3gq]

On August 3, 2017 at 7:30 AM, whiskytango said:

I had a GB engine in my first 231.  It did not have a Merlyn or intercooler.  The biggest problem was the climb during summer months.  At times 200 FPM was the most I could do without pushing CHTs above 400 F.  The 231 I am flying now has an LB with a Merlyn, intercooler and GAMIs, and maintaining cool CHTs (below 380 F) in the climb is no problem, even in summer.

Would you assume that all circumstances (flows, baffles, etc.) were correct when you had to limit your climb to 200fpm ? Thanks

[Jim F]

Hi j3gq,

I believe if your overhauler is using a TCM refeb fuel system then the cost is minor and it sounds like intake pipes. I was told that most overhaulers just convert GB to LB.  I hate to harp on it but baffles and a properly maintained engine and this combination is manageable. 

On the 200fpm climb on hot days:  something is not right, fuel flow, timing, baffles, or the CHT gauge. My hottest takeoff was 106F out of Deer Vally 200lb below gross and I climbed out at 135mph and did not go above 380F CHT with ~600fpm climb.   On a hotter day why fly its just unbareable  

Jim

[Marcopolo]

  I also have a 231 with the -GB(3) engine, no intercooler and no aftermarket waste gate.  1610 TSOH and do not have the climb out cooling issue mentioned above.  As long as the cowl flaps are either open or in trail I climb out at 33" 2600rpm 21.5-22gph and 110-120kias all day long 750fpm up to cruise altitude and CHTs usually maintained below 370.  On an extremely hot day I might see my #6 cylinder creep up to 382-385.

 

Ron

[KLRDMD]

On 9/8/2017 at 6:33 AM, Marcopolo said:

 I also have a 231 with the -GB(3) engine, no intercooler and no aftermarket waste gate.  1610 TSOH and do not have the climb out cooling issue mentioned above.  As long as the cowl flaps are either open or in trail I climb out at 33" 2600rpm 21.5-22gph and 110-120kias all day long 750fpm up to cruise altitude and CHTs usually maintained below 370.

You're *significantly* reducing power to get those temperatures in line. A non-intercooled TSIO-360 in a Mooney has take-off power of 40" and 2700 RPM.

[Marcopolo]

 

On 9/9/2017 at 7:02 PM, KLRDMD said:

You're *significantly* reducing power to get those temperatures in line. A non-intercooled TSIO-360 in a Mooney has take-off power of 40" and 2700 RPM

Hi Ken,

  Correct, take off power is 40" and 2700 rpm, my POH calls for "normal" climb power at 33" 2600rpm which gives me 750-850fpm at gross and the temps mentioned above.  Not sure what climbing at full power does for me except add a whole bunch of heat and just a bit of climb.   There's a reason you won't consider a 231 with a -GB engine, I'm guessing this is part of it.  You do have to baby it a bit which goes against everything "Mooney".  I'm not in a hurry...yet,  I'm finishing up my IR ticket and then we'll see how I feel.

 

Ron

[whiskytango]

On 9/7/2017 at 3:15 PM, j3gq said:

Would you assume that all circumstances (flows, baffles, etc.) were correct when you had to limit your climb to 200fpm ? Thanks

It is possible that baffles and / or fuel flows were the problem, but in my pre-Mooneyspace days I was following the POH, and operating at 40 inches and 2700 RPM on climb out.  In retrospect, that is asking for an overheating problem with the stock -GB engine.

[KLRDMD]

6 hours ago, Marcopolo said:

Correct, take off power is 40" and 2700 rpm, my POH calls for "normal" climb power at 33" 2600rpm which gives me 750-850fpm at gross and the temps mentioned above.  Not sure what climbing at full power does for me except add a whole bunch of heat and just a bit of climb. There's a reason you won't consider a 231 with a -GB engine, I'm guessing this is part of it.  You do have to baby it a bit which goes against everything "Mooney".  I'm not in a hurry...yet,  I'm finishing up my IR ticket and then we'll see how I feel.

What the POH states and what is best practice may be very different things; it is for the intercooled -LB engine. I don't know the -GB well enough to comment. Paul K. probably does.

I wouldn't consider a -GB engine since they run hot (I'm in Tucson where is is still over 100ºF every day even this time of year - I don't need a hot running engine), -LB engines are plentiful and since -GB engines get converrted to -LB at overhaul that means if you still have a -GB is was overhauled *many* years ago.

[Marcopolo]

 

1 hour ago, KLRDMD said:

What the POH states and what is best practice may be very different things; it is for the intercooled -LB engine. I don't know the -GB well enough to comment. Paul K. probably does.

I wouldn't consider a -GB engine since they run hot (I'm in Tucson where is is still over 100ºF every day even this time of year - I don't need a hot running engine), -LB engines are plentiful and since -GB engines get converrted to -LB at overhaul that means if you still have a -GB is was overhauled *many* years ago.

 

Yes Ken,  I would agree that the non-intercooled -GB engine runs hotter than the intercooled  -LB.   My opinion is if you were to intercool a -GB and balance the fuel flows via GAMI jectors or mix-matching the current injectors to a .2 or .3 gph spread then the temps would be very comparible between the two...again, my opinion, but balance is what helps the -LB, granted they balance the air better on the -LB also.

   My POH states the Best Angle and Best Rate climb should be as you stated 40" 2700rpm, normal climb is 33" 2600rpm.  I usually climb to 1000' agl at 40" 2700 rpm and then go to "normal climb" setting.  My -GB is original to 1981,  ~1610hr TTSN airframe and engine.

 

Ron

[jlunseth]

I haven't flown a GB but have a fair number of hours in an LB.  There are two circumstances where the innate ability of the TSIO360 to cool itself is challenged.  One is low very hot takeoff, particularly where a good rate of climb is required.  Think taking off from Scottsdale, which is in a basin, on a day when it is 114, and then having to climb to make the mountain MEAs to the north.  Fuel flow and cowl flaps are your friend, and you must make sure that your engine fuel flow is properly set up to make 24 gph at 40/2700,  If your flow is even a little lean you will see some remarkable temps.  That kind of high hot circumstance is something most of us don't see often, you would need to live in Scottsdale, or maybe Texas although you wouldn't have the climb requirements in TX.  

The other is flight in the O2 levels.  Anytime you get up in the upper teens or lower 20's the air begins to get too thin to do a very good job of cooling.  There are parts of the 360 that just don't have the ability to cool, particularly the turbo.  It has no fins, and just runs hot, hotter, or hottest.  So does the collector, the pipe that brings the exhaust to the turbo.  

These are the two regimes of flight where design changes to the engine over time helped a great deal.  The LB is a little better, the LB with intercooler is quite a bit better.  The 252 set up with its superior turbo and intercooler set up is better yet.  

In normal flight, up to 14 or 15k, you probably would not notice a difference I don't think.  The air itself still has plenty of ability to cool.  Start flying longer flights at cruise speed in the flight levels and there would probably be a difference in longevity.

Edited September 16, 2017 by jlunseth