252 vs 231 with wastegate/intercooler

[StParkin]

Hello all,

I am planning to make my first aircraft purchase in the next couple years and am mostly looking at the M20J vs M20K models. I live on the west coast of Canada so there are large mountains going anywhere east, hence considering a turbocharger.

I have read about all the benefits of the upgrades that the 252 has compared to the 231, but the low useful load with that model gives me some pause. An Encore would be ideal but they don't seem to come to market all that often and when they do they come with quite a cost premium.

So, my question is whether there is substantial differences in performance and engine management between a 231 that has a wastegate/intercooler compared to a 252? I understand there are other differences (28V electrical, second alternator, etc) but I am just referring to engine performance and management. Is there a reason the 252 continues to seem to be so coveted despite the fact that many 231's now have WG/IC installed?

Thanks!

[Will.iam]

2 hours ago, StParkin said:

Hello all,

I am planning to make my first aircraft purchase in the next couple years and am mostly looking at the M20J vs M20K models. I live on the west coast of Canada so there are large mountains going anywhere east, hence considering a turbocharger.

I have read about all the benefits of the upgrades that the 252 has compared to the 231, but the low useful load with that model gives me some pause. An Encore would be ideal but they don't seem to come to market all that often and when they do they come with quite a cost premium.

So, my question is whether there is substantial differences in performance and engine management between a 231 that has a wastegate/intercooler compared to a 252? I understand there are other differences (28V electrical, second alternator, etc) but I am just referring to engine performance and management. Is there a reason the 252 continues to seem to be so coveted despite the fact that many 231's now have WG/IC installed?

Thanks!

Yes because the 231 turbo is still controlled by throttle and the 252 turbo is controlled automatically by a controller. I. E. The 252 you fire wall the throttle like any normally aspirated engine and the controller keeps the MP at 36 inches all the way to critical altitude (23~24k ft) where as the 231 you do not firewall the throttle and have to manage the boost yourself. Having said that it’s not hard to do but it is not automatic. Think stick shift compared to automatic transmission. Both do the same job but one requires manual intervention. Also when descending the 252 will automatically hold the boost at the set MP through the descent the 231 you will have to make adjustments like an NA airplane engine. The merlin wastegate controller is not an automatic controller. This commands a premium for the convenience. Whether that is worth it for you depends on if you have a choice to buy one in the first place. Mooney made far more 231 than 252 and even fewer encores. Good news is you can take any 252 and upgrade it to an encore and get 230 more lbs of useful load but it’s not cheap. Again what’s that premium worth for u. You can not upgrade a 231 to an encore and the company that used to upgrade 231 to 262 (a 231 with a 252 type engine) no longer exists but there are 262 out in the field. 

[PeteMc]

I can't speak to the 252, but I have a 231 with the Merlyn wastegate (no intercooler) and engine management is pretty straight forward.  You will see a bit if an increase in MP just after takeoff (I've always assumed to to increased airflow and a little better engine performance).  Then as you continue your climb above 10K you'll see a slow decrease in MP, both of which just require a minor adjustment of the throttle to correct. 

A J is a good plane, but I  think you're right that the 231/252 Encore, etc. might be better for you if you if you're constantly crossing the mountains.  And even when get east of the Rockies on a X-US flight, I am always still in the mid teens.  Usually you're above the Wx, better speeds and typically very little traffic, so you're not constantly getting call-outs from ATC or maybe even frequent vectors. 

 

 

[Slick Nick]

Where are you on the west coast? Don’t count out the J model. I live in Calgary but frequently take my MSE to our pace on the island, as well as the lower mainland with 2 people and 6 hours fuel. Does great and will happily cruise at 16-19k on 7gph. I mostly only fly IFR. One thing that you may want to consider is FIKI capability. Especially this time of year, ice can hang around for a few days and make it hard to fly if you really need to get somewhere. I work for an airline so it’s easy for me to just hop a plane if the weather isn’t ideal, but your needs may differ  

There are a couple decent 231’s for sale on the island, and a couple in Alberta that would make good birds if that’s what you’re set on though. A turbo would be nice, but there hasn’t been a flight yet where I haven’t been able to go because I don’t have one. 

Edited November 30 by Slick Nick

[hubcap]

Performance wise, I believe the 231 gives you more performance than any other model, for the money.
 

If you have the intercooler and the Merlyn along with a good EIS, management and temperature control are easy. The 252 is easier to manage but with a lower useful load and a price premium. Either will serve you well.

[Tx_Aggie]

I went through this same consideration 5 years ago. I ended up choosing a J as I wanted to make sure I could afford flying altogether. While I don’t live in the mountains I am at 3000’ msl and regularly cruise at 9-11k. The J has been perfect, routinely see 155-160 ktas. 
 

sometimes I do wish to have a turbo to get higher but the speed and range of these birds makes it east to circumvent building or established storm systems. 
 

also as onboard equipment wears out I’ve replaced with superior garmin equipment, at this point I would only sell/trade for something with equal modern equipment and a much larger power plant. I don’t think I’d make a move to the 231/252 as the incremental increase in spend only equates to getting there maybe 5-10 minutes faster and that’s not worth it to me. 

[Danb]

Our planes are marvelous when looking at the fleet as a whole, we have planes capable of 140-230 knots and 8-18 GPH alone with useful loads up to approximately 1150 lbs range up to 1400 miles. Entering prices between 90-650,000 dollars. Comparison to other fleets we’re hard to beat for 2-4 person planes. I’ve had J models a Bravo and Acclaim. If you don’t have a need for carrying much load want a sporty affordable plane stay here.

D

[Ethan]

I have a 231 with a Merlyn wastegate but no intercooler. I love it. Engine management is no problem. My useful load is 1000 pounds exactly, which is pretty good for any Mooney built after 1979, except for the Encore.
 

Some 252s have far less (hundreds of pounds less) useful load. My full fuel useful load is 568 pounds, that leaves me with room for only 3 (smallish) people and scant luggage. That’s pretty pathetic. Most of the time, my limiting factor is almost always useful load so I am happy to have my 231 rather than a 252.

[Pinecone]

You can convert a 252 to Encore specs and gain 230 pounds of useful load.

You need to convert the -MB engine to -SB, which is different RPM and boost limits (2700 RPM, 39 inches).  No internal changes.

You have to install the dual puck brakes.  And replace the control surface balance weights.

No STC, as it is two factory drawings, for the M20K, which they both are.

And the interior in the 252 is lighter than the Encore.

 

[kortopates]

On 11/29/2024 at 1:24 PM, StParkin said:

So, my question is whether there is substantial differences in performance and engine management between a 231 that has a wastegate/intercooler compared to a 252? I understand there are other differences (28V electrical, second alternator, etc) but I am just referring to engine performance and management. Is there a reason the 252 continues to seem to be so coveted despite the fact that many 231's now have WG/IC installed?

Long time owner/instructor, for near 25 years, that started with a 231 and then quickly upgraded to a 252 that is now a 252/Encore. 

The manual pneumatic wastegate is not directly comparable to an automatic hydraulic wastegate. The Merlyn is still 100% manual, What it really offers is a much higher critical altitude (~22K msl) over the fixed bolt wastegate (~15K) (which is very important to flying above the mid teens) but it doesn't improve or help with engine management in any way. That takes a hydraulic wastegate which makes flying the turbo essentially as easy as a flying a normally aspirated J model; except for temperature management since things happen very quickly in a turbo.

If you compare the cruise performance tables between 231 and 252 you'll see that the 252 has essentially 10kt faster cruise speed at max cruise power. Due to airframe drag reductions including the electric cowl flaps which are infinitely adjustable which means a much less speed penalty for flying with partially opened cowl flaps. 

When it comes to useful load the 231 has no upgradability unlike the gross weight increase available to every 252 with the Encore upgrade.  The 252 isn't really heavier it just comes with all the Mooney options as standard including heated prop, speed brakes, oxygen system, standby electric vacuum (less important in todays world) bucket seats that fold down in the rear (started in '84 or '85), and generally superior avionics and AP (if not already upgraded). But most important is the advantage of the higher output 28V electrical system (double the current output) and very popular option for dual alternators - which was a critical reason for why I upgraded to the 252 since no longer susceptible to an alternator failure. (I once flew back from Central America with a single alternator that I would otherwise have been stranded till repairing it).

Then of course doing the Encore upgrade increases your max gross weight by 230 lbs and almost all of that increases your useful load. My useful load is just shy of 1140 lbs! Probably the highest in the fleet but its been something I've been working on improving for over 2 decades. 

Don't make the same mistake I made initially which was not realizing the acquisition cost was a drop in the bucket compared to the recurring annual operating cost. i.e. the cost to operate any of the K's will be the same and in a short time will over shadow your acquisition cost. Therefore it makes the most sense to get the best and most complete example you can afford to begin with. 

If you can't get a 252 or Encore then my advice would be to look for a "262" which a 231 converted to the 252 -MB engine. (The STC is no longer available). Its still much less expensive than a 252 and is limited to a 12V electrical system but otherwise has the -MB engine with hydraulic wastegate with larger Garrett Turbocharger and tuned induction system and several other improvements. The MB engines makes them the cream of the crop of 231's. Some of them even have the electric cowl flaps too which is a big plus for their adjustability and lower drag.

But avoid an early 231 that still has the -GB engine versus the -LB - for one they don't have pressurized magnetos. But there are only a few around.

[Fly Boomer]

On 11/29/2024 at 3:24 PM, StParkin said:

So, my question is whether there is substantial differences in performance and engine management between a 231 that has a wastegate/intercooler compared to a 252?

I found this article by Bob Kromer to be helpful during my search.  Bob was the Mooney test pilot when the 252 was developed.  The article is titled "Flying The 252" but it is really a comparison of the 231 to the 252.

Bob Kromer - Flying The 252.pdf

 

[Slick Nick]

12 minutes ago, Fly Boomer said:

I found this article by Bob Kromer to be helpful during my search.  Bob was the Mooney test pilot when the 252 was developed.  The article is titled "Flying The 252" but it is really a comparison of the 231 to the 252.

Bob Kromer - Flying The 252.pdf 173 kB · 1 download

 

What an awesome article!

[kortopates]

29 minutes ago, Fly Boomer said:

I found this article by Bob Kromer to be helpful during my search.  Bob was the Mooney test pilot when the 252 was developed.  The article is titled "Flying The 252" but it is really a comparison of the 231 to the 252.

Bob Kromer - Flying The 252.pdf 173 kB · 1 download

 

Everything in Bob's write up is still very good information today except for his wisdom on engine management. We know today that operating at a mere 50F ROP at high power settings is about the worst possible way to manage your engine if you want to see longevity. His comments about leaning in climb are ill advised and I have no idea where he gets the notion that most engines fuel set up has the engine overly rich, since in actuality its just the opposite. Continentals recommended fuel settings are overly aggressive on the lean side for longevity. Just look at his CHTs for the proof - there is no need to run CHTs that high but then he also wasn't using his cowl flaps. But his numbers are all about getting optimum performance - not longevity.

But other statements like climbing at full power at 120 kts to the flight levels are right on. Reducing power a bit (e.g. using cruise climb POH numbers) will actually only serve to increase temps and climb time.

[StParkin]

Thanks everyone, that is super helpful information. It sounds like there are a number of small improvements to the 252 over the 231 (higher critical altitude and thus slightly better performance, easier engine management, 28V electrical, dual alternators, infinitely adjustable cowl flaps) that justify it's higher cost.

A few people talking about the possibility of upgrading a 252 to an Encore. From prior topics on the subject on this forum I got the sense that there was uncertainly about what exactly is required, whether parts for the conversion are readily available, and who is comfortable to sign off on the upgrade. Is that the case? Any updated info on cost for the upgrade?

Thanks again. This forum is a great resource with a bunch of very knowledgable members!

 

Edited December 3 by StParkin

[StParkin]

On 11/29/2024 at 6:21 PM, Slick Nick said:

Where are you on the west coast? Don’t count out the J model. I live in Calgary but frequently take my MSE to our pace on the island, as well as the lower mainland with 2 people and 6 hours fuel. Does great and will happily cruise at 16-19k on 7gph. I mostly only fly IFR. One thing that you may want to consider is FIKI capability. Especially this time of year, ice can hang around for a few days and make it hard to fly if you really need to get somewhere. I work for an airline so it’s easy for me to just hop a plane if the weather isn’t ideal, but your needs may differ  

There are a couple decent 231’s for sale on the island, and a couple in Alberta that would make good birds if that’s what you’re set on though. A turbo would be nice, but there hasn’t been a flight yet where I haven’t been able to go because I don’t have one. 

Good points. I am in Vancouver and ice is a very frequent problem in the winter here. I think a FIKI Encore would be the dream but will depend on availability and how much I can save in the next 1-2 years. I have also been looking at the MSE. Good to hear the J is able to get to altitudes to be able to cross the Rockies, but I've heard the climb really slows down after about 10-12k feet?

There don't seem to be many Mooney's at the airport I fly out of (Boundary Bay), so if you ever find yourself in the lower mainland with an hour to spare I would love to take a look at your plane!

[Slick Nick]

6 hours ago, StParkin said:

Good points. I am in Vancouver and ice is a very frequent problem in the winter here. I think a FIKI Encore would be the dream but will depend on availability and how much I can save in the next 1-2 years. I have also been looking at the MSE. Good to hear the J is able to get to altitudes to be able to cross the Rockies, but I've heard the climb really slows down after about 10-12k feet?

There don't seem to be many Mooney's at the airport I fly out of (Boundary Bay), so if you ever find yourself in the lower mainland with an hour to spare I would love to take a look at your plane!

It depends. What's your weight? How much fuel are you carrying? The 64 gallon tanks mean I could carry enough to easily fly round trip from Calgary-Victoria and back with IFR reserves, so I often tanker out of Calgary since gas is so much cheaper. If I'm at max weight, I think I'm about 15-17 minutes to 16,000'. My departure airport is 4000'. Remember that in a Mooney, you're still moving pretty fast in the climb, it's not a 172. I usually climb out at 110-100 all the way up. The J can make it to 20,000+, there's no service ceiling and there's lots of posts on here that document that.

I would love a FIKI Encore myself, but when shopping, you'll find that the cost is basically double of what you'll pay for a nicely equipped, later J model here in Canada. Importing is a whole different story, factor in some massive import costs. The J remains the best "bang for the buck" airplane in my opinion. Not to mention operation cost, the J can be pulled back to 7.0gph if you want, the 252 is still burning 11.5-13.5gph.

Send me a PM with your contact info and I'll let you know next time I'm out in Vancouver. I tend to stick to Langley airport when I'm there, if you're willing to drive.

[Fly Boomer]

12 hours ago, kortopates said:

Everything in Bob's write up is still very good information today except for his wisdom on engine management.

Well, he was a factory guy and, if you are only flying new airplanes, and you have been charged with extracting max performance, his "wisdom" on engine management makes sense.  Lycoming and Continental also recommended practices that are not conducive to longevity, and you can run those engines the "factory way" but you sacrifice long life (and performance).

[wombat]

@StParkin I've been flying out of the Puget Sound area for about 15 years now.

If you want to fly in the winter, TKS (Preferably FIKI) is probably the most important factor.  The next is having a turbo.   Having both is the bee's knees.  But even if you don't have them you can still fly a lot in the winter through careful flight planning and some schedule flexibility.   

If you have a TKS but not a turbo you'll still have good enough performance in the winter due to cold temps and can make it over the mountains more easily. Then in the summer you can fly VFR and your lower performance will still get you where you want to go since you are not as limited on routes and altitudes.

As far as the Rockies go, by the time you get to them you'll have had plenty of time to climb to altitude, even at an extremely low climb rate.   You will be able to get to 15,000+ and while there are probably some mountains you won't want to go directly over you can pretty much pick any route you want.

 

[Pinecone]

The requirements to convert 252 to Encore are clear.

There are two factory drawings that need to be complied with.  IRRC, they are in the Downloads section here on MS.

1)  Engine - Convert from -MB to -SB.  This a purely an external conversion.  I do not recall if the prop governor and wastegate have to be replaced or just adjusted.  The difference is the -MB is 2700 RPM and 36 inches at max power.  The -SB is 2600 RPM and 39 inches.

2) Airframe - you need to install the long body dual puck brakes, which requires a different gear door.  The gear door is the harder to source part. But they are available.  You also need to change the control balance weights.  Again, they are available.

When I bought my 252 in 2022, the quoted cost to convert one to Encore was around $15,000.

I have posted the log entry for the conversion on mine.  But for the engine, they replaced the -MB with Factory Reman -SB.

 

[RJBrown]

A J cannot effectively fly above 17,000. 
it struggles mightily to get there. 
I had a 231. When the engine went I had it converted to a Rocket305. Best Mooney ever. Sold the Rocket and later bought a MSE (J). I hated the J. Heading into Denver from the SW it could not hold the MEA over LARKS intersection. The mountain wave just sucked it down. Did not have the ability to get above or around weather. 
The J is a flat lander airplane. 
The manual cowl flaps on the 231 are more reliable.  The motor for the 252 cowl flaps are $$$ and aren’t always available. The temperatures on a 231 are really critical. If you try to get “book” performance numbers you will burn it up. The book numbers were for the sales department to brag about not numbers you could use. 
After the engine on the 231 went bad I started looking at all the engine number of planes on the market. Most first run GB engines were replaced or rebuilt at about 1200 hours. I bought mine in 92 with 1100 hours and got 100 hours more before it needed replaced. 
The Rocket had an automatic waste gate like the 252. Much less work. Just set it and leave it alone. The (stock) 231 engine management was constant. Every altitude change required adjustment. 
That said I wish I had bought another 231 and not the J. 

[Slick Nick]

7 minutes ago, RJBrown said:

A J cannot effectively fly above 17,000. 
it struggles mightily to get there. 
I had a 231. When the engine went I had it converted to a Rocket305. Best Mooney ever. Sold the Rocket and later bought a MSE (J). I hated the J. Heading into Denver from the SW it could not hold the MEA over LARKS intersection. The mountain wave just sucked it down. Did not have the ability to get above or around weather. 
The J is a flat lander airplane. 
The manual cowl flaps on the 231 are more reliable.  The motor for the 252 cowl flaps are $$$ and aren’t always available. The temperatures on a 231 are really critical. If you try to get “book” performance numbers you will burn it up. The book numbers were for the sales department to brag about not numbers you could use. 
After the engine on the 231 went bad I started looking at all the engine number of planes on the market. Most first run GB engines were replaced or rebuilt at about 1200 hours. I bought mine in 92 with 1100 hours and got 100 hours more before it needed replaced. 
The Rocket had an automatic waste gate like the 252. Much less work. Just set it and leave it alone. The (stock) 231 engine management was constant. Every altitude change required adjustment. 
That said I wish I had bought another 231 and not the J. 

Have to disagree with you here. Maybe down in Colorado and Arizona during the summer months will a J run out of steam, but up here in Canada we’ve got about a 15*-20* head start on lower temperatures year round, which makes a big difference. The mountains are just as tall, and the MEAs are just as high, believe me. Maybe yours was down on power? 

I am not arguing that the J is the “ideal” machine for the job, but it can be made to work no problem. Depends on your priorities I guess. For what I paid for my MSE, no way was I going to get even into the 252 ballpark. They are expensive up here in Canada. Top level J money hardly gets you into a clapped out 231 here. If you’ve got the money for it, 252 all day long, but my point is that you don’t absolutely need one to fly in the Canadian Rockies. 

[EricJ]

29 minutes ago, RJBrown said:

A J cannot effectively fly above 17,000. 

My J at 17,500.   It was still climbing pretty well but I stopped because I was VFR.

[Aerodon]

1 hour ago, Pinecone said:

The requirements to convert 252 to Encore are clear.

There are two factory drawings that need to be complied with.  IRRC, they are in the Downloads section here on MS.

1)  Engine - Convert from -MB to -SB.  This a purely an external conversion.  I do not recall if the prop governor and wastegate have to be replaced or just adjusted.  The difference is the -MB is 2700 RPM and 36 inches at max power.  The -SB is 2600 RPM and 39 inches.

2) Airframe - you need to install the long body dual puck brakes, which requires a different gear door.  The gear door is the harder to source part. But they are available.  You also need to change the control balance weights.  Again, they are available.

When I bought my 252 in 2022, the quoted cost to convert one to Encore was around $15,000.

I have posted the log entry for the conversion on mine.  But for the engine, they replaced the -MB with Factory Reman -SB.

 

I agree, the instructions and applicability are clear.  Both with Mooney (two drawings), and Continental (there is a parts list somewhere).

1) prop governors can be adjusted, but then have reduced operating range.  Better to send the governor off for upgrade, it's just changing one spring and setting up properly.  same with waste gate controller, send it in.  same with fuel pump, send it in.  Then there is also an additional support on the turbo (SB vs MB).

2) gear inner doors. new gear spindles (axles), new dual puck brakes, new master cylinders, new master cylinder bell cranks on the pedals, aileron, elevator, rudder balance weights.

If you can't get the new gear doors I would not start. Used spindles and brake parts are available.

 

Aerodon

 

 

[StParkin]

5 hours ago, Slick Nick said:

Importing is a whole different story, factor in some massive import costs.

Can you elaborate? From my (admittedly limited) reading, it looks like the major costs to import would be:

1) Cost to ferry the airplane to me, though I think this would apply to a Canadian registered aircraft as well. Something in the Pacific Northwest (Seattle/Portland for instance) would seem an easier feat than getting a plane over from say Ontario.

2) Import cost. From my reading, the cost for a new registration and the import fees shouldn't be more than about $2000-3000 and then maybe $2000 to have the new registration letters applied to airplane.

3) Taxes. My understanding is I would have to pay 5% GST at border crossing then 7% PST to BC if the plane comes from the US. However, sale of used aircraft is taxed at 12% PST by BC so the taxes seem to be a wash.

4) It sounds like there needs to be the equivalent of an annual inspection by a Canadian mechanic prior to issuing an Canadian airworthiness certificate, even if the plane is "in annual" following inspection by US mechanic. Presumably, major squawks would be dealt with in the negotiations during the pre-buy so hopefully no surprises however. I assume this inspection would also cost about $2-3000?

There is obviously the extra hassle of having to get new registration, extra inspections, and the time all of this will take. But from the cost side of things, I understand it may be something like a $6-8000 difference between buying a Canadian registered aircraft? Does that seem in the ballpark? If so, it seems like it may be worth the expense to significantly open up the options for available aircraft. Might save that much in a year of ownership if I could find a great plane in the US rather than having to choose from the much more limited Canadian supply (that often seem to be the older models with less avionics upgrades - you seem to have one of the unicorn MSE's in Canada).

Thanks again everyone, this is all extremely helpful info!

 

Edited December 3 by StParkin

[Ed de C.]

Have you thought about an Ovation?  It's normally aspirated but significantly more power at sea level than a J and will carry that up to the altitudes.  I find 15k feet is achieved easily and 20k is doable, albeit slowly achieved.  You get a few other advantages due to the more recent model years and it's a long body.  Might be comparably priced to a 252/encore depending on year/condition.  Of course, why stop there when there's the Bravo and Aclaim...