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Mooney with TSIO 360 GB


Arthur

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I am a past owner (850 hours then sold in97) of a 1979 M20K with a GB engine with intercooler. I am trying to get back into flying and have been looking at the M20K. I would like to hear the opinions of pilots that owned and fly the K with a GB engine. All the talk I hear is negative about the GB engine. The Mooney I am presently looking at has a GB engine and none of the add-ons.

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From what I see, there are not too many planes left with GBs. Mine had been converted to LB before I got it. As you have heard, the GBs have a bad reputation. My belief is that one could get by OK with a GB, as long as they operated it with an eagle eye on CHTs. I think that the problem is that if you watch the CHTs that close, you lose a lot of the utility of a K model. If you want to fly high and fast, get an LB at least. 

Someone told me GB was for god-awful bad, LB is for a little better and MB is for much better.

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I expect it will come down to "pay now or pay later". I expect you're looking at one because its priced comparably to that an airframe with a runout engine - given calendar time SMOH if not the hours. So be sure to get a realistic idea of what it will take to overhaul it to the LB spec. I don't have first hand knowledge on this, but given all the changes I would expect it should be priced well under a similar airframe with a LB engine since I'd expect will cost much more to bring the engine upto LB specs. I suspect you might find it more sense to go with a factory reman or overhaul given the cost; if they will take the GB core. But even budgeting for the extra cost of overhaul you'll still want to want to add on the Merlin and intercooler if your at all concerned about turbo performance. And if not, just stick with a J model.

Hands down though, the best "deal" among the 231's is to find a 262 conversion. Then you'll have a real turbo with the MB engine used in the 252 without the cumbersome manual wastegate and another 10 kts on the same fuel flow if you believe the POH data. 

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One thing to check when buying an older 231(1979-81) is whether it has a VAR crankshaft or not. If the engine hasn't been overhauled since 1997 it may still have an airmelt crank. There is no danger to running these crankshafts, they are just unserviceable when you next overhaul the engine. A new crank is about $6600.

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On 12/6/2018 at 7:45 PM, JOR said:

Does adding a Merlyn waste gate alone to a GB bring/manage the CHTs to LB no waste gate levels?  

From my understanding, an intercooler is the biggest ticket for helping to keep CHTs at bay. The Merlyn UD controller raises the critical altitude significantly, resulting in “full” power up high and it also helps to quell bootstrapping/ surging MP. 

 

Adding those plus GAMIs to balance things out, and you’re as close to a factory MB as you can get. 

Edited by 81X
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It is my understanding that having a Merlyn wastegate does not eliminate the problem with engine management. It improves it and manages the bootstrapping to an extent, but you can't just push the throttle to the stop and it will be okay. 

Keep in mind, I do not have a Merlyn, just repeating what I have read.

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It is my understanding that having a Merlyn wastegate does not eliminate the problem with engine management. It improves it and manages the bootstrapping to an extent, but you can't just push the throttle to the stop and it will be okay. 
Keep in mind, I do not have a Merlyn, just repeating what I have read.
It is a differential controller. It just tries to keep a constant pressure drop across the throttle body.
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It is a differential controller. It just tries to keep a constant pressure drop across the throttle body.

True. But Technically it replaces a fixed wastegste (a bolt) with a manual pneumatic wastegate. It's principal advantage is by replacing the terribly ineffecient bolt, it is able to very significantly raise the critical altitude from about 15k something to the lower flight levels. But it's still a manual wastegate controller that provides a very major improvement to the birds performance at altitude over the stock configuration. The 252 is yet another leap with an automatic wastegate, ceiling to 28K and many other refinements.
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