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Selling my 1980 Mooney M20K 231, 3175 TT, TSIO 360 LB with 1425 TSOH, Recently Installed 4 repaired cylinders with new pistons and rings as well as one OH cylinder. CHT's within 50 deg or less now- 325-360 average) Aircraft flies POH numbers and speeds per Merlyn Waste gate and intercooler additions. Registration N888BC. Flies great including both RNAV and ILS approaches. No Fuel Tank Leaks! Prices Flight speed brakes Built in 76 cf Oxygen system New main tires Useful load 945 #'s Just finished annual and IFR certification I bought the airplane from a BT member through Neal Schwartz two years ago through BT and the plane hasn't disappointed. Avionics: -Garmin GTN 750 -GMC 35 Remote audio panel -GTX 345 -Garmin Aera 760 hardwired to GTN -AP- KFC 200 (works great and flies approaches very well -SL 40 standby radio and BK KN 52 Loc only -Aspen 1000 Pro Max EFD New 2024 -Artex 345 406 ELT -EI UBG 16 Engine analyzer. (two new probes recently) -Standby vacuum system Engine: -TSIO 360 GB to LB -TSOH 1425 -Turboplus intercooler -Merlyn Black Magic waste gate controller, Critical altitude increases to 22K -Air Wolf M20 Air-Oil separator -recently installed 4 repaired cylinders with new rings and pistons as well as one overhauled cylinder Propeller: -Factory 2 blade electrically heated -600 TSOH Log Books available via PDF on request Asking $157,500.00 US Steve 519 589 7034 sdawson630@gmail.com Located CYKF , Kitchener Ontario

A year ago my old engine was switched out for a factory new engine. Both were/are TSIO360-LBs. The intention was to get the engine up and running LOP particularly at cruise. That could not be done immediately because TCM required that the factory injectors had to be used for engine break-in. The plan was to install GAMI's at the first annual after break-in and the first stage of that process has now been completed, that is, we have good working GAMIs in the engine and I will be conducting some tests to see if we need some fine tuning or if they are going to work as they now are. The process was not without hiccups. I thought it would be helpful, since over the years there have been many questions about how to run the 231 LOP, if I document what has been done and the fine tuning work I will be doing. The purpose of this post is to just lay some groundwork, and then I will write posts about the progress. I bought the plane in 2009, shortly after getting my PPL. It was in Scottsdale, and I flew home with my then-instructor (not a Mooney instructor). The engine was not in great shape. The turbo was rebuilt that summer at about 700 engine hours. A couple of years later I experienced a loss of oil pressure due to the quick drain eating a piece of plastic (I have written about it here ). That resulted in an emergency descent from 19k to a landing in Canada and shortly after the engine was IRANd because of piston slap at around 1200 hours. I then went to the GAMI live course in Ada, OK to learn how to run the engine and figured out a good way to run it LOP. From that point on the engine made it to nearly 2400 hours before it was replaced, and probably could have gone on living for quite awhile longer, but it was at that point more than 20 years old so I elected to replace it. Engine break-in is 50 hours, during which TCM wants the engine run ROP with their injectors. At cruise they want the engine to alternate every hour between 65 and 75% HP. That is what I did over a good part of last year, until the engine was well broken in. When I run ROP, my fuel flow is normally 13.3 gph or higher, RPMs 2450, MP at about 30". If the CHT's and EGTs start to go higher I ran the engine at as high as 14.5 gph to keep them cool. The engine was looked over by my A&P and borescoped once last year. He found that the break-in was going great and the cylinders were in very good condition. I have a Merlin wastegate controller and a Turboplus intercooler.On one or two occasions I tried to run the engine LOP to see if the TCM injectors were up to the task. I read that TCM has been putting "positionally tuned injectors" in engines and had some hope that the factory injectors would work but they did not, the engine would immediately go rough once on the lean side of peak and it was difficult to keep the temps down, so I waited for the chance to put in GAMIs, which came over this past winter. A few things about LOP operations in a 231. I have excellent instrumentation in my plane, a JPI 930 which has updated at least once by JPI. A GTN 750 TXi is my major GPS, and it is connected to dual revisionary 275's which drive my KFC200 AP through an Icarus SAM GPSS. It all works really well, and of course I see separate EGTs and CHT's for each of the six cylinders as well as TIT. My 930 also provides both Compressor Discharge Temp (the temperature of the induction air coming out of the turbo) and Induction Air Temp (the induction air temp after it has passed through the intercooler). IAT is the temp of the induction air when it is introduced into the engine. When the new engine was installed I also had new baffling put in and that has helped tamp down some of the CHT differences I saw in the old engine. The difference between the hottest (#2) and coldest (#6) in the old engine was generally around 85 dF and higher. It is now about 40 dF. The #6 cylinder sits in the big cowl hole that is unobstructed and tends to run cooler than the others, the others are within roughly 20 dF of each other in the new engine. Running an engine LOP in the 231 requires a clear understanding of what LOP is and how engine monitors generally operate in "lean function" mode. LOP is an air/fuel ratio, it is not by itself a power setting although it can certainly be used to make a power setting that is easy on the engine. As has been written about before in this forum and is taught by the GAMI people, there is a formula that can be used to determine %HP when operating LOP. The formula is fuel flow in gph times a constant that is dependent on the engine compression ratio, divided by rated horsepower. In the 231 the formula is GPH * 13.7/210. However, it needs to be emphasized that this formula only applies if the engine is operating on the lean side of peak. It does not apply at all if the engine is operating on the rich side of peak. %HP on the rich side must be determined from the POH tables. On the lean side, %HP is driven entirely by the fuel flow - increasing and decreasing the MP will not change the power output it will simply change the air/fuel ratio. More on that later. On the rich side, changing the MP definitly changes the power output. An engine is operating properly lean of peak when the EGT of the cylinder that is closest to peak starts to go down when the fuel flow is further reduced. If a reduction in fuel flow causes the temp to go up, then you are still on the rich side of peak and the power formula does not apply. There is a footnote to this which we saw when conducted the GAMI lean test on my new engine, which is that if the engine is already well on the lean side of peak and the pilot continues to lean it well out, there will be a point where the EGT may rise. However, this second rise is not the lean of peak point. An engine is operating rich of peak when the EGT of the cylinder closest to peak falls when more fuel is introduced. "Peak" of course, is the point where the EGT of a cylinder is hottest. It is preferable to use the temperature of the cylinder closest to peak, whether on the lean or rich side, because that means that all the other cylinders are running comfortably further away from peak EGT. Engine monitors have a "lean function." As has been said many times in this forum, the lean function operates using an internal algorithm that makes certain assumptions. The primary assumption is that the pilot starts the lean function while the engine is operating on the rich side of peak. When a pilot engages the lean function and begins to lean the engine, the engine monitor makes the assumption that all other parameters, mainly manifold pressure, remain where they were at the start of the lean function and only the fuel flow is changed. If the MP is materially changed then the entire lean function test is invalid. As I will write later, we ran into this issue in spades when ordering the GAMI injectors for the new engine. Also, when the engine monitor is put in ROP mode, the monitor assumes that the pilot is starting the lean function on the rich side of peak and leaning back towards peak, and because it is desirable to find the cylinder that is operating closest to peak, it finds the first cylinder to peak and uses that to display a "degrees rich of peak" number. Similarly, the monitor assumes that when conducting leaning in the "LOP mode" the pilot starts on the rich side of peak, leans across peak, and the monitor then finds the last cylinder to peak, which is the cylinder operating closest to peak on the lean side. It is important to understand that the monitor has no way of knowing whether the engine is actually running ROP or LOP, it is making assumptions. So ---- putting the monitor in ROP mode simply tells the monitor to find the first cylinder to peak, and putting it in LOP mode simply finds the last cylinder to peak, and that is all. If you have allowed the MP to change during this process, the process is invalid and the monitor has no idea whether the engine is running LOP or ROP. This is important in the 231 because the Merlin wastegate controller is not a truly automatic controller. It is a differential controller; it maintains a set difference between the induction air going into the engine and the air coming out of the compressor. The purpose of that is to tamp down bootstrapping (increasing the MP increases the exhaust flow into the turbo which then increases the MP even further). The Merlin does not maintain a set MP, it is up to the pilot to monitor and set the MP. Changes in the fuel flow in the 231 will change the MP for two reasons. One, there is an interlink in the 231 fuel system that is specifically designed to link fuel flow to MP, so that if the pilot makes a power setting and then decides he wants to slow to let's say, approach speed, he/she can simply pull back the MP and the interlink does its best to maintain the original air/fuel ratio by also pulling back the fuel flow. This does not work quite as well in the opposite direction, that is, when pulling the fuel flow back the relationship to MP is not maintained quite as well, but it does operate. The other factor is the turbo itself. If you pull back the fuel flow you reduce the exhaust flow to the turbo which further reduces its output, meaning the MP is reduced. The point is, if the 231 pilot starts the leaning process with a rich of peak MP and fuel flow and then leans the fuel flow back and does nothing to adjust the MP, the MP will start coming back as well, invalidating the "lean function" process. These are challenges in running a "GAMI lean function" in the 231 and in making power settings, but although it sounds complicated, it can be very much simplified in operating the aircraft. However, the 231 pilot needs to understand what is going on in this detail to operate a healthy engine. Next post: engine break-in of the new engine and ordering new GAMI's, and the mistakes we made and fixed.

...In every phase of flight it is a really great improvement in performance and in cylinder temperatures! Last Year I bought a Turbo Plus intercooler kit from Jeff Shapiro for my Mooney M20K 231. First, the delivery was very fast and second he gave me a special price for me as member of MAPA. When I unpacked the kit, I was very happy about the really great quality of all the parts. Welding, tolerances and so on. I installed the kit in two days and it was a great pleasure to do. The fiberglass work at the cowling is also very easy, but needs a little bit of trim. When I had finished all that work and the final adjustment of the TCM injection system, I went flying to see what it will improve. First was, that the intake air immediately cooled down about 30 deg. Celsius in the takeoff run. I operate my Mooney from a 750 meter asphalt strip. After takeoff, in the climb it was cooling by 45 deg. Celsius and raised to 55 deg. in higher altitudes. I think the NACA duct is at the optimum position. Much better and more efficient than by the 252 model, because it gets directly cool air from the outside and not via the cylinders inside the cowling on the right side in the engine compartment. In cruise I have now much cooler cylinder head temperatures , mostly about 320 deg. Fahrenheit with 75-85 percent of power. I was flying now for approx. 9 month with the intercooler and in every phase of flight it is a really great improvement in performance and in cylinder temperatures!! So finally I think that is one of the best mods for a 231 model. Regards, Alex Haselmann D-EMLL Mooney M20K

No, not full throttle movement. "Full power" depends on your TSIO360 engine configuration. I have an intercooler so it is a little different in my engine than in the factory, non-intercooled engine. Full power in the factory engine is 40MP at 2700 RPMs per the POH. You can, but never should, exceed that limit as it is an overboost. With the intercooler the information is a little more complicated but can be reduced to simple for actual flying. The intercooler theory is that cooling the induction air that comes out of the turbocharger increases its density and therefore its oxygen content. So there is a chart that comes with the intercooler that the pilot uses to adjust the POH settings down, depending on the Differential Temperature. The DT is the amount by which the air coming out of the turbocharger has been cooled before going into the induction system. The DT is pretty good, it ranges around 85-125 dF at cruise. Lots of people use 36" and 2700 RPMs as full power and there is nothing wrong with that. It comes out of an old article recommending using the 252 settings for the intercooled 231 engine. However, the STC for the Turboplus contains instructions for adjusting the MP downward from the POH setting in order for the A&P to make a full power fuel setting on the ground. Per the STC instructions the actual MP varies with OAT and approaches 37", although as I recall it does not quite get there. In practice, say for takeoff, I use 36" as max power even though it is a little low. But as the aircraft picks up speed that may increase a little. I don't take offense unless it reaches 37, then I will adjust it down a little. I don't like adjusting during takeoff if I can avoid it because you wind up chasing your tail (you adjust down, that slows the turbo so the adjustment winds up being more than you wanted, so you adjust back up, etc.). The odd thing is that a setting that is a little less than full power can make the engine quite a bit hotter. I don't know the mechanics of it, but it is my perception that the fuel flow bumps up more rapidly as the engine approaches full power. So although it may be counterintuitive, a cure for a fuel flow that is showing too low and CHTs that are getting a little too hot may be to add MP rather than to subtract, because that allows the fuel flow to get to its max setting. JimF - thanks for the comments. I too like Paul K's idea of setting the max fuel flow to 25 GPH rather than the 24 in the POH, you can always adjust it down, but once it is set on the ground you can't adjust it up, and the usual problem is that it just starts to drift down on takeoff to 20-21, and the CHTs then get warm. Also, I completely agree on the baffles, keep them as tight as possible. You are lucky you are an A&P, I keep trying to get my A&P to do what Paul recommends, sometimes it happens and sometimes not. They are getting better.

Hi T.Peterson, I am in a similar position and am planning an overhaul mid 2025. I have an 81 231 and apparently the only 231 left without a Merlyn or intercooler. I am planning to install a Merlyn wastegate and a Turboplus intercooler before I do the overhaul so that I can do a PIRP on both. My position on the Merlyn is that a higher critical altitude would be helpful and allow me to fly 75% power in the flight levels at 2500RPM. Currently I need to be >2600RPM to get enough MP out of the turbo for 75% power. On the intercooler, my thought process is why did Mooney not put an intercooler on the 231 and why did Mooney add an intercooler to the 252/Encore (I know the engine is TCM). The 231 was a low-cost entry into the turbo market and in general the industry considers the 231 a hot running engine. After market feedback Mooney decided that the addition of an automatic wastegate and intercooler was what customers wanted, and I do think that was a great decision. Everyone with a 252 or Encore raves about their Mooney being the best option for their mission. On our 231s the compressor discharge pressure can get very warm, and that warm air charge can really push the CHTs up in the 400s on hot days with a slow climb. I look at any aftermarket add-on to see if the manufacture released a similar solution in later years. With the wastegate the fixed wastegate is a pain to deal with and has a low critical altitude, so the automatic wastegate makes sense. On the intercooler, the hot running 231 when you add an intercooler it has a much better CHT margin from red line. For me these are reliability decisions, the Merlyn will not be spinning the turbo at as high of an RPM so in theory it should last longer. The intercooler will have a cooler air charge and should lower the CHTs ~20d and the cylinders should last longer when running cooler. Remember after the engine change and intercooler add, if your aircraft is faster, you are producing more horsepower. Also, make sure the fuel system is set correctly once the intercooler is installed. The intercooler cools the air charge and at that lower Max MP(~36in) you need about the same FF as MP 40in on your non intercooled engine. Refer to the Merlyn and intercooler documents. I fly 75%HP, 100d rich of peak at 17.5/16.5ft, 13.9FF, ~30.0in MP, 1550TIT and I see 181Kn. After I added fine wire plugs, I am now able to run lean of peak, but I don't very often. Also, I love the fact that I can pick up ~2kn TAS per thousand feet, so I cruise high almost always. At 17.5 65%HP, 12.4FF I get 170kn. Fly fast, Jim

paging @Jeff Shapiro from TurboPlus (http://www.turboplus.com/) http://www.turboplus.com/mooney231-intercooler.asp Nice article starting on page 19: https://themooneyflyer.com/issues/2019-MayTMF.pdf My first Mooney was a 231 without a Merlyn or an intercooler and was very much temperature limited. Once you fly with an automatic wastegate and an intercooler, you'll never go back. Thankfully you already have the Merlyn.

How much more critical altitude gain can be achieved if I add a Merlyn automatic wastegate to a m20k 231 that already has a turboplus intercooler installed. I see data showing intercooler alone can raise critical altitude to 21000, while automatic wastegate alone can raise it to 19000. How about a combination of the two?

I bought my aircraft in 2009 with a Turboplus in it. About a year later I installed a JPI 930. Compliance with the Turboplus STC requires knowing the Differential Temperature, which is the difference between the Compressor Discharge Temperature (the air coming out of the turbo and before the intercooler) and the Inducation Air Temperature (the air going into the induction system after the intercooler). The 930 has that feature, and it allows me to see with some precision what the intercooler contributes. As those who have the factory (nonintercooled) engine know, there is a CDT redline of 280 dF. The purpose is to protect against detonation caused by overly hot induction air. On my JPI, I can see what would happen if the intercooler were not there, and what does happen with the intercooler present. I don’t see how it would have been possible to fly a factory 231 much above 17k at least in the summer because the CDT hits redline. One could make the climb more shallow which helps a little, but there are no cooling fins on the turbo, it does not help much. Meanwhile, the IAT is somewhere around 100 dF cooler. This renders CDT essentially a meaningless number and better yet, helps the engine run much cooler. At high altitude cruise the Diff Temp is usually around 100 to 125 dF. My aircraft has no problem climbing to the Critical Altitude that the Merlyn allows, which is around 22,500 depending on day temps. I don’t doubt the OPs numbers. I have a new engine in my aircraft which is now broken it. I installed new baffling with it. In the late winter, which is chilly around here, the cruise cylinder temps were in the 320 range. Except I have one cylinder, #5, that is doggedly colder than the rest (it sits in the big hole in the cowling) and generally ran in the 285 range. Overall, the Turboplus is an excellent addition. It helps the engine run much cooler. I would say that the power setting charts are a little conservative, but whose counting? A few years after I bought the aircraft I had the Turboplus sent in to be cleaned by the manufacturer. At that point it was about ten years old and the fins were pretty dirty. Really helped, and the temps went down a noticeable jump. Need to do that periodically, and carefully following their instructions so as not to damage fins.

Is the connector attaching the wires to the gague a simple pull out or is there an additional fitting securing the plastic fitting in? Anyone with actual experience please.

Just finished up the installation of the Turboplus intercooler on my M20K. We took this project on during our "Annual". Flew this morning. Would like to hear from other's who have this installation on their M20K model to compare notes. I want to make sure that my temps and fuel flows are similar to what others are seeing with this install. I flew up to 16,000' this morning. Have not gone higher than that.

Does anyone know where I could get a used or new turbo plus intercooler for a 1981 m20k before Oshkosh next week?

Once again MooneySpace members were a good percentage of M20K 231 intercooler sales in 2020 and continue to keep our team busy building a great, reliable product. If you need an updated cowling sticker please request a free one through our website contact page. Thanks in advance. Jeff Shapiro Www.Turboplus.com

Just purchased a turbo plus intercooler kit and was wondering if anyone has installed one before, any hints or tips tricks a little nervous about cutting the Cowl but seems straightforward on that. Also filling out the pre-install flight data sheet.

My airplane does in fact have the TurboPlus system. AS far as the merlyn, the company is out of business so I didn't pursue anything. I ended up purchasing 3 new cylinders for 2/4/6. I can't diagnose or control metal fatigue and have no clue how this engine was taken care of prior to my purchasing it. I am well aware of slower throttle advance while the Turbo spools up but I often fly out of shorter runways and I rarely over boost this engine. I spoke with the machine shop that rebuilds engines, cylinders etc. They also told me a small over boost for a very short time (couple of seconds) should not do the damage they saw on this cylinder. I will be more focused on takeoff roll and am excited to be adding three new cylinders.

This is the only one STC'd for your airplane. https://www.merlynproducts.com/blackmagicm.html Thirty years ago I flew a 231 for three years and this upgrade plus a TurboPlus intercooler would have been much welcomed http://www.turboplus.com/mooney231-intercooler.asp @Jeff Shapiro from TurboPlus stops by once in awhile

We have a full team working on this issue, but given the knowledge and experience residing within this forum - I thought I would ask if anyone else has had the problem (and what the fix was!). To clarify, I am not an engineer and I am not doing any of the work. We have a 1984 M20K. The TSIO-360LB failed last year and we completed an engine overhaul. In addition to the 'new' engine, we overhauled the turbo and took the opportunity to add a Turboplus intercooler (the plane had a Merlyn wastegate and that part was sent to Merlyn in order to accommodate the new intercooler). Here is the issue: when pulling power back from max power, the engine quits. Thus it runs at idle and it runs at max power - again - when pulling the throttle back from max power the engine quits. The fuel pump, flow divider, and throttle bod were sent to Consolidated. The only part working properly was the flow divider. The parts were repaired and reinstalled.......but the issue persists. The wastegate was then disconnected, but this did not prove to be the issue. Again, I think we have a competent team working on this (including Savvy, the overhaul shop and now Continental). I could not find the issue elsewhere on Mooneyspace, but I have to assume someone else has had this problem. Any thoughts would be greatly appreciated. Many thanks

PS I find it necessary to provide my A&P with the instructions in the Turboplus STC pretty much every time the fuel flow is going to be reset. A&P’s tend to default to just using the SID and don’t think about the Turboplus STC, because they are used to setting fuel flows in the more modern engines where the intercooler is not aftermarket. If they do that, chances are pretty good that they are not making the max power FF setting at actual max power.

The MP used to set the fuel flow is specified in the STC for the Turboplus intercooler. I have posted the STC instructions before, you could do a search to find them, but you should have received them from Turboplus with the intercooler. The max MP to be used when setting the fuel flow varies with OAT but generally is in the range of 37. The SID is used, but is to be modified in accordance with the Turboplus STC. Setting the fuel flow is indeed tricky. I like Savvy’s max + 1 GPH for summer flying. It helps keep the engine cool. The fuel flow setting was not your problem I see. Just providing information for you to use in setting the fuel flow now that you have the problem solved.

We want to know how to correlate the cockpit intercooler readings to manifold pressure guage in the cockpit

How are you determining that you are running at 70% HP ROP? If you have the Turboplus intercooler, it came with a chart. You would use the differential temperature, that is, the difference between Compressor Discharge Temperature (before the intercooler) and Induction Air Temperature (temperature after the intercooler). The POH would give you a power setting (factory configuration, without the intercooler) in order to operate at 70% power. The chart would then tell you what MP you would need to use, given the intercooler and the diff. temp, to operate at 70% HP. The other way of determining percent HP would be to have an engine monitor, mine is a JPI 930, that displays % HP. It has been years since I operated the engine using either the chart or the %HP display, but back when I did, I always felt the plane was slow. I don’t recall the indicated airspeed, but it was in the high 120’s or low 130’s and I never got the airspeeds that the POH showed for a 70 or 75% power setting. When I began to operate the engine LOP, one of the first things I learned (from the GAMI seminar) is that %HP while LOP is directly a function of fuel flow. The formula is 13.7 x fuel flow=HP produced, divided by 210 (the rated HP)=%HP. HP does not vary with MP so long as the engine is operating LOP. I developed a power setting that produced 70% HP while LOP and magically, my indicated airspeeds since then have been in the 138-142 range and the TASs at altitude have been correspondingly higher. Researching why the ROP results were so poor I learned a couple of things. First, there were several articles, which I verified with some engineer friends, that the turbocharger manufacturers, in creating those charts, were making the wrong assumptions that there is no cost (in terms of power) to reducing the temperature of the induction air by running it through the intercooler. Actually, pushing the induction air through the intercooler creates back pressure in the exhaust and causes the engine to work harder. It also affects the combustion cycle because of the backpressure. IT “robs” some HP. My plane has been in the shop for several months getting a new engine (the old one was several hundreds hours over TBO), so I haven’t flown for awhile, and on top of that, I don’t fly ROP much anymore, so my memory about ROP power settings is poor, but my recollection is that at 13.5 GPH and 2450 RPMs, the charts say that the MP should be about 29” for 70%, but the actual setting that produces the same ROP airspeed as my known good 70% LOP setting is more like 31”. The “cost” in terms of MP to push the air through the intercooler is nearly as much as the charts would suggest is gained by dropping the induction temperature. I should explain that. The gas laws say that for a given pressure, the number of molecules of a gas varies directly with the temperature, in other words, cooler air contains more O2 than warmer air, and the number of molecules of O2 in a given volume of induction air directly affects how much fuel can be burned. In other words, you can burn more fuel and produce more HP with cool air than with hot air. So when an intercooler drops the temperature of the induction air by, say, 125 dF, the same MP will burn more fuel and produce more power. The engine monitor reading makes the same error as the charts. The JPI monitors use a proprietary algorithm and since it is proprietary, I don’t know for sure what it is. But after a few years of operating it, it is pretty obvious that JPI used the POH + intercooler chart settings. That does not mean that there is no gain from using an intercooler. There is quite a bit of gain. The cylinders run quite a bit cooler and there is some gain in the amount of O2 going into the cylinders because the induction air temperature is lowered. The gain is just not as great as the charts from the manufacturer says it is. The factory non intercooled engine had a CDT temp limit of 280 dF. Based on the temps I see in my engine, it is pretty clear that on most hot summer days, a non intercooled engine simply could not climb beyond about 17 or 18k without running into CDT issues, and those issues cause detonation. The cooling effect of the intercooler is enough that the CDT limit is never approached in the intercooled engine. Now, I am just a pilot, I haven’t run an engine on a test stand to verify all this. I am just telling you what I learned from experts and engineers, and experienced in running my engine. However, its is well documented in the engine industry that the initial claims of gains from lowering the IAT were not as great as originally thought. And there is the fact that at 70% LOP using the accepted HP formula, my indicated airspeed is 8-10 kts faster than a 70% ROP setting based on the charts and POH.

I am almost 400 hours into owning my M20k 231. The engine had a little over 400 hours when I purchased it and it has almost 900 hours on it now. Compressions are great and I have spent almost zero $$ on repairs, other than oil changes and a mag inspection. I did add the TurboPlus intercooler and the Merlyn Black Magic upper deck pressure controller, but other than that, just oil changes. I have to believe that when people get poor results out of this engine, it has to be the result of poor management. If you talk to @jlunseth he is several hundred hours over TBO on his engine. I spoke with Don Maxwell about the bad reputation of this engine and he told me that if you run it in cruise at 65% or less power, it will make TBO every time. I enjoy the fact that I can get over the weather and the engine runs smooth lean of peak and I get 160 kts TAS running LOP at a little over 10 GPH and I can get 170+ TAS if I want to go up to 17,000' or higher, which I do on longer trips. This engine was brought to the market well before there were reliable engine monitoring systems. If you pay just a little attention you have no problem keeping CHT's below 380 degrees even in the climb. When the 231 first came out they were operating with 40" of manifold pressure, but I never get above 36" of MP during take off and I reduce to 33" in the climb. Running high MP will certainly heat up the cylinders if you don't watch what you're doing, but I have no regrets about my K model after almost 400 hours and 4 years of ownership.

We've had a fantastic year selling Turboplus M20K 231 intercoolers. Many sold through this sight with our MooneySpace discount. At this time we are offering a $300.00 discount for kits to be delivered in 2020. Your kit must be paid in full after you sign and return our invoice and Information document. Let us know 2 weeks in advance when you would like your kit shipped. We highly recommend the Merlyn wastegate with the intercooler installation. You may ask for an invoice through our website contact page. Please mention the $300 Mooneyspace discount approved by Jeff. www.turboplus.com

Sorry for the double reply. With regard to the MP setting, we were told to expect a differential temperature of -35 which translates to a max MP of 37.5. Looking at the chart from Turboplus, a max MP of 36 would suggest a differential of -55.....is this what you regularly see? Thanks again, Al

No, not firewall. I generally use 36” and 2700 RPM as full power. The 36”, as best as I can determine, comes from an old article on the 231 which suggests using that. Actually, full power appears to be in the vicinity of 37”. That comes from the Turboplus intercooler STC, which modifies the instructions for setting the full power fuel flow. According to the STC, full power varies depending on OAT at the ground when the work is done, but generally the number is 37”. I use 36, but if the power rises toward 37 I just let it. (The fuel flow does tend to rise on takeoff because airspeed is changing.) Although it seems counterintuitive, if you are doing a high hot climb and have an intercooler in a 231, it may help cool the engine a little to set power at 37 rather than 36 or lower, because the fuel flow will come up with the increased MP, and you need more fuel flow. If you do not have the Turboplus in your aircraft, full power is 40” and 2700. The MP only ever gets firewalled if you attain and/or exceed Critical Altitude, which varies a little with the day, but is about 22,500 in my Merlyn equipped engine. It will be quite a bit lower in the non-Merlyn equipped engine. The Merlyn does not affect the full power setting, the intercooler does affect that setting.

The situation with me is that I have a JPI 730 which does display TIT (not CDT) but in any case is not primary. With the loss of my original primary gauge - a dual TIT/CDT - I'm in "legal land" where I'm either replacing CDT/TIT with individual gauges or replacing my JPI, a far more expensive proposition. What is interesting is that JPI doesn't have a trade-in program. EI will take a trade-in but you only save about $1000 - so its a lot cheaper to go with individual gauges. I saw that EI has a standalone TIT gauge but I didn't see a CDT gauge on their website. I do have a TurboPlus intercooler (with gauges) which greatly reduces concerns about CDT temperature. But that doesn't make it legal. So I think I'm agreeing with what you are saying above (which is why I was looking into it). Thanks