231: is it really a lower tier version?

[Tx_Aggie]

Hi all - I'm new to the site. I'm curious to learn more about the 231 K with the LB engine and automatic wastegate/inter cooler mods. It seems like (from previous posts - I know the overall comparison has been beaten to death here before me) the 252 is more desirable than a modified 231. But can the modified 231 be piloted as efficient as a 252? I do see more modified 231 listings than 252's currently. My perspective is a bit different however from those looking to 'move up.' I currently rent an Ovation 2 in western Texas. I'm usually in the 10-12k altitudes where the Ovation has spoiled me with regular 200-230 Kt ground speeds. I enjoy flying fast! However I'm considering purchasing my own plane at some point in the future and the earlier K models seem to perform similarly at about 180 KTAS while the initial purchase price is half that of the Ovation. I'm an engineer so the more numbers the merrier, any thoughts? 

I appreciate it!

[kortopates]

The 231 with the Merlyn is not a automatic controller - its still a manual controller - it just gets rid of the fixed bolt wastegate replacing it with a pneumatically controlled wategate. But it does raise the birds critical altitude substantially. You can still overboost and still need to continue to adjust the throttle to maintain a target MAP as ambient air pressure or anything else changes (such as while climbing or descending) but its still far from the hydraulically controlled automatic wastegate used on the -MB and -SB engines that is a "set and forget" controller that will not overboost and really reduces pilot workload. The MB engine provides a critical altitude of 23K and service ceiling of 28K.. The later TSIO-360-MB & -SB also include a tuned induction system and many of them have dual alternators. Also the 252 were equipped as standard with all of the optional upgrades on the 231 including electric standby vacuum, built-in O2 systems, prop de-ice and speed brakes and rear folding bucket seats. The dual alternators and electric standby vacuum really adds to their redundancy for IFR flying and the dual 28v 70 amp alternators allow them to FIKI equipped. Plus 252's are field upgradeable to the Encore version to increase max gross weight by an additional 230 lbs.   

Perhaps your best bargain out there is to get the 262 which is a 231 converted to the -MB engine rather than finding one with added merlyn and intercooler. Then you'll have most of the benefits minus the 28V system and dual alternators and perhaps some other optional items. 

However, if you don't think you'll ever get above your present altitudes of 10-12K there is no point in going turbo. You'd be better off in a NA engine model. 

Edited May 17, 2016 by kortopates

[carusoam]

Welcome aboard TX Aggie Engineer.

Have you found the threads regarding turbo Mooney operations?  There are a few that make great technical reads.

We have a few talented K pilots around here that don't mind sharing their experience.

One question for you: Where do you rent an Ovation?

Best regards,

-a-

[LANCECASPER]

Where are you finding an Ovation that flies 200-230 kts? People who fly them usually flight plan for 180 kts or less.

[jlunseth]

Yes to Lance's comment, and the 231 at 10-12k is more like a 160 kt. aircraft, maybe 165, but not 180.  You have to put the whole crew on the oars, whip them up, and go up to at least 22,000 before you will see 180 at cruise power, and not likely then.  More like mid-170's.  GS in that range with a good tailwind, that I can see, but not TAS.

[peevee]

15 minutes ago, jlunseth said:

Yes to Lance's comment, and the 231 at 10-12k is more like a 160 kt. aircraft, maybe 165, but not 180.  You have to put the whole crew on the oars, whip them up, and go up to at least 22,000 before you will see 180 at cruise power, and not likely then.  More like mid-170's.  GS in that range with a good tailwind, that I can see, but not TAS.

With an intercooler I see 185-190 true much lower, like FL180.

[Tx_Aggie]

1 hour ago, carusoam said:

Welcome aboard TX Aggie Engineer.

Have you found the threads regarding turbo Mooney operations?  There are a few that make great technical reads.

We have a few talented K pilots around here that don't mind sharing their experience.

One question for you: Where do you rent an Ovation?

Best regards,

-a-

http://www.florisflightservices.com/aircraft-rental.html

 

A friend of mine rents his out at KMDD. And no I haven't found the threads, can you send me the link? I appreciate it!

[Tx_Aggie]

56 minutes ago, LANCECASPER said:

Where are you finding an Ovation that flies 200-230 kts? People who fly them usually flight plan for 180 kts or less.

I do flight plan for 180 kts, however my home base (KMDD) is at about 3000' msl. It's sunny and hot in western Texas for more than half the year. To get above the turbulence requires being atleast at 10,000' unless you enjoy being tossed around like a rag doll. Most of my flying involves heading east to the hill country or to the gulf coast. Either way, west to east generally picks up atleast a 20kt tail wind. I eat it coming back, but even that's a relative term, 165 kts GS into the wind isn't anything to complain about, hence why I've come to love the power/aerodynamics in a Mooney!

[jlunseth]

53 minutes ago, peevee said:

With an intercooler I see 185-190 true much lower, like FL180.

At 100% power sure, but not at cruise power.  The intercooler does nothing to change the speed of the aircraft.  Remember, you must adjust your MP setting downward significantly from the setting that is in the POH, based on the differential temp. caused by the intercooler.  The differential temp. is the difference between Compressor Discharge Temp. (the air coming out of the turbo) and Induction Air Temp. (the air, after the intercooler, going into the induction system).  At 18k and cruise you are probably getting a 100 dF differential temp.  Your power setting should be somewhere around 3-4" less than what is in your POH for the standard engine.  So, for example, if your MP for 75% is 32", and you have the intercooler, you should be setting power at 28-29" to make 75%.

[DonMuncy]

8 hours ago, kortopates said:

....but its still far from the hydraulically controlled automatic wastegate used on the -MB and -SB engines that is a "set and forget" controller that will not overboost and really reduces pilot workload. 

 Are those automatic wastegates  retrofittable to the LB engine. I had originally contemplated a Merlyn for my 231, until I learned they were not "set and forget". If I'm going to have to fiddle with the throttle anyway, I'm not much better off.

[kortopates]

7 minutes ago, DonMuncy said:

 Are those automatic wastegates  retrofittable to the LB engine. I had originally contemplated a Merlyn for my 231, until I learned they were not "set and forget". If I'm going to have to fiddle with the throttle anyway, I'm not much better off.

Its possible in that Continental allows it and provides guidance on how to alter that engine data tag in the field (unlike Lycoming whom does not allow it), but its not practical as it would require altering the engine so that it entirely conformed to the MB specification which would include at least the exhaust, induction, intercooler, controller, wastegate, and starter adapter and probably much more. It would likely take salvage parts to make it even possible from a dollars standpoint and then you have the 262 STC for the airframe which I don't think anyone is providing anymore. Much easier to upgrade by trading up.

[jlunseth]

Don, you would need an STC and that does not exist.  You might also need a different turbo, don't know how the gate is incorporated into the turbo. 

Although the Merlyn is not "set and forget," it does have two major advantages.  One, it increases critical altitude by quite a bit.  In my aircraft that is about 22,500 ("about" means it varies from depending on the day).  Two, there is no bootstrapping.

However, it is not "set and forget."  You can't set 32" and expect it to keep 32" if things change, such as altitude.

[DonMuncy]

Thanks Paul. That was what I expected. If it was easy, everyone would have done it.

Thanks John, I am not so worried about whether the Merlyn would hold really close to a MP. What I would like is to be able to push the throttle full in and take off, without having to watch the MP while accelerating down the runway. (However, I admit is not a real problem when you get used to it.) I am also not particularly interested in the critical altitude increase. I have never flown my plane above 18K. I don't expect I ever will unless it was a temporary bump over some weather.

[peevee]

3 hours ago, jlunseth said:

At 100% power sure, but not at cruise power.  The intercooler does nothing to change the speed of the aircraft.  Remember, you must adjust your MP setting downward significantly from the setting that is in the POH, based on the differential temp. caused by the intercooler.  The differential temp. is the difference between Compressor Discharge Temp. (the air coming out of the turbo) and Induction Air Temp. (the air, after the intercooler, going into the induction system).  At 18k and cruise you are probably getting a 100 dF differential temp.  Your power setting should be somewhere around 3-4" less than what is in your POH for the standard engine.  So, for example, if your MP for 75% is 32", and you have the intercooler, you should be setting power at 28-29" to make 75%.

I get close to 190 true @ FL180 @ 29" MP and TIT of 1500-1515ish. Hard to see with the glare, but that's about 188, and yes, it's adjusted correctly.

Thanks for the lecture, I understand fully how intercoolers work

Edited May 17, 2016 by peevee

[jlunseth]

It was not meant as a lecture.  Sorry.

[peevee]

13 minutes ago, DonMuncy said:

Thanks Paul. That was what I expected. If it was easy, everyone would have done it.

Thanks John, I am not so worried about whether the Merlyn would hold really close to a MP. What I would like is to be able to push the throttle full in and take off, without having to watch the MP while accelerating down the runway. (However, I admit is not a real problem when you get used to it.) I am also not particularly interested in the critical altitude increase. I have never flown my plane above 18K. I don't expect I ever will unless it was a temporary bump over some weather.

You adjust anything and the MP fluctuates, mixture, change altitude, prop rpm, sneeze etc but I tend to push up to 25" on the roll and wait for the turbo to spool, then push to what I need, 30-36, beyond that there isn't much of anything to watch.

[FBCK]

Don the other thing I believe the Merlyn waste gate does is lower the use of the turbo charger when its not needed, like when you are flying down low or when the just puttering around, lower overall temperatures and improving engine life.

[jclemens]

The Merlyn should be required equipment on any aircraft with the TSIO-360.  It reduces wear and tear, increases critical altitude, and makes controlling power easier.

[Tx_Aggie]

Great, thanks for all the input. Sounds like the 252 refinements might be worth the extra $20k in list price atleast. As far as useful load, why wouldn't it be possible to get the increase in the 231 variant? Isn't it only a landing gear modification? I think I have right at  1000# in the Ovation. 850# is what I've seen in available 252's. Is the 231 similar to the stock 252?

[jrwilson]

10 hours ago, peevee said:

You adjust anything and the MP fluctuates, mixture, change altitude, prop rpm, sneeze etc b

Your manifold pressure fluctuates too?  Mine changes about .5" or so with cowl flap changes and pitch changes...I thought maybe my butterfly valve needed adjusting.  It's always done it since I've owned it and it's a new engine.

[jrwilson]

10 hours ago, peevee said:

I get close to 190 true @ FL180 @ 29" MP and TIT of 1500-1515ish. Hard to see with the glare, but that's about 188, and yes, it's adjusted correctly.

Thanks for the lecture, I understand fully how intercoolers work

Is that mph?  I havnt seen one of those airspeed indicators that computes tas...trying to read the model but the glare

Edited May 18, 2016 by jrwilson

[Steve Dietrich]

Many options

231

231+ merlyn   ( gives higher critical altitude )

231 + merlyn and intercooler  higher critical altitude better performance   happier motor

231 converted to 252 FWF  (MB motor)      best,   former service ceiling   FL 280  (but will go well above that)

 

I believe one of the shops still does the 252 conversion but the cost is prohibitively  prohibitive .

 

The ideal is the 231 converted to 252 per the applicable STC's  Sadly Mod Works SCT has been parked since the shop was destroyed during a hurricane'

 

 

Edited May 19, 2016 by Steve Dietrich

[Yooper Rocketman]

On 5/17/2016 at 11:50 PM, Tx_Aggie said:

Hi all - I'm new to the site. I'm curious to learn more about the 231 K with the LB engine and automatic wastegate/inter cooler mods. It seems like (from previous posts - I know the overall comparison has been beaten to death here before me) the 252 is more desirable than a modified 231. But can the modified 231 be piloted as efficient as a 252? I do see more modified 231 listings than 252's currently. My perspective is a bit different however from those looking to 'move up.' I currently rent an Ovation 2 in western Texas. I'm usually in the 10-12k altitudes where the Ovation has spoiled me with regular 200-230 Kt ground speeds. I enjoy flying fast! However I'm considering purchasing my own plane at some point in the future and the earlier K models seem to perform similarly at about 180 KTAS while the initial purchase price is half that of the Ovation. I'm an engineer so the more numbers the merrier, any thoughts? 

I appreciate it!

Gee....I thought you were describing a Rocket.  Increased gross weight, faster than either the 231 or 252, and seem to be priced pretty good today.  I have 16 years of ownership experience and have been completely happy with it.  It will take a Lancair Propjet to make my next step up worthwhile.

Tom

[Tx_Aggie]

2 hours ago, Yooper Rocketman said:

Gee....I thought you were describing a Rocket.  Increased gross weight, faster than either the 231 or 252, and seem to be priced pretty good today.  I have 16 years of ownership experience and have been completely happy with it.  It will take a Lancair Propjet to make my next step up worthwhile.

Tom

I don't know too much about the rocket conversion, what has 16 years convinced or taught you about it?! I'm interested to hear your thoughts. How does the bigger engine increase the useful load on the same sized airframe?? What fuel rates do you see at cruise/what altitudes do you prefer?

 

thanks!

[carusoam]

Price vs. performance...

There aren't any bad Ks.  Some are better suited for the personal mission of the pilot.

The fun part of Missiles and rockets are the engines that drive them IO550 and TIO520...

Select your favorite engine, then decide which airframe to put it in...(within the possibilities of STCs)

Best regards,

-a-