Crawfish

Great success I think I got the pictures to work!

This was on a Dallas to Asheville leg @ 16,000’. I was trueing about 165-170 so roughly 60 knots on the tail. 231 with no mods at the time. (Now it has Gamijectors, and GI 275 EIS.) I’ve been contemplating doing full write up about how awesome the 231 is even without intercooler and waste gate. Since these pictures I've discovered at least with the summer heat I can't run 65% LOP without cowl flaps in the trail position. (Thanks to the GIS 275 EIS I keep hottest CHT 380 now) So I lost 5ish IAS, is this a typical experience for everyone?

I use Savvy's second tier "SavvyQA," through work I know several A&P's but most of them have only been wrenching on Jets for the past 10+ years and while all of them are excellent MX they take a while with researching Piston issues. Having Savvy recommend and provide documentation for jobs or help with the trouble shooting has been very nice as well as recommending shops to send parts for overhaul. And Savvy analysis has also been insightful.

@1980Mooney I did include baggage but I can see why it wasn’t easily seen thank you. Edited my response for clarification. I was trying to point out the M20K would be a little more likely than the Bravo due to lower fuel burns without much lower speeds.

My wife and I fit in our M20K fine, I’m 6’1” and 275#, my wife about the size of yours. I’ve also done flights with two buddies and the one in the back had no complaints he was in the 6’ range. CG should be no issue, but W&B can be tricky good news moneys are so efficient it makes life easy. 270+135+215+85+55 leaves you with 240# for fuel. That’s 40 gallons in my M20K that’s enough for a 2.5 hour flight plus 1 hr reserve. Block to block I average 11.3 GPH, And 175KTS at altitude that’s 400NM I think a 252/encore would be probably a better bet vs Bravo I believe there’s some out there with 1100# useful loads that would give you an extra ~1.5 hours of range or 575NM and they burn less effectively giving you a higher useful load. And will still be quicker than a Saratoga. Realistically I don’t think adult sized 3 people and dogs would be comfortable, but maybe for a once a year type thing?

Also have a 231, no Merlyn though. Full power climb and pitch for 115-120IAS cowl flaps full open. Keeps temps cooler than pulling the power back.

@LANCECASPER CHT’s were somewhere in the mid to high 300’s (still rocking the stock CHT gauge, GI275 scheduled for install in January) TIT were sitting between 1530-1550. At 16,000 about 1500 at 13,000 Not sure how far LOP I was, as I do the “big pull” then verify I’m lean of peak by enriching to make sure TIT rises then pulling back to where I wanted to be at.

Little more data for anyone curious. M20K no intercooler no merlyn 4+29 hour take off to touchdown 16,000’ started at 165KTAS finished 175KTAS Total trip burn was 50.5 gallons. Was leaned to the mid 10GPH range in cruise. 4+36 T/O to Touchdown 13,000’ 155-160 KTAS. Total leg burn 51.7 gallons, same leaned to mid 10GPH range in cruise. Fuel burn was measured at the pumps by topping the plane back off. Reason I say mid 10GPH range is my fuel flow bounces a little bit in cruise .3 of a gallon or so.

Little late to the conversation but my 1979 M20K CG is 43.9 only real change is a GTN650 and added a fire extinguisher. No built in O2. She has been weighed twice in the past 10 years, came out to within .5# on both weights, done by independent shops. Although on the first weighing it gain 15 pounds from the calculated W&B from the factory. Cheers! Crawfish

@McMooney From what I understand it’s lead.

I thought embry riddle did some testing on G100UL back in the mid 2010’s?

Got my fuel system tweaked (so it doesn’t bounce around so much) while waiting on a couple parts for the EIS And took it on another trip! 11500 60% power 152 TAS 8500 63% 145 TAS both power values were LOP. Plane has a semi severe right turning tendency inflight so hopefully it will gain a few knots once that’s sorted out!

I only have about 7 hours in my Mooney now! Buutttt one of those flights was 4 hours literally 4:00, on that flight I set power at 2400 RPM 31” and leaned until rough and enriched just enough to smooth it out. At 6500’ it gave me 148TAS 8500 155TAS and 10500 160TAS and burned 12.3 GPH averaged over the whole trip which included a rejected Take off, and long taxi back. 135IAS at all three altitudes temp was 4°c at all three altitudes I don’t know what my percent power was as the fuel flow gauge was bouncing between 9.5 and 11GPH at constant power. But I was lean of peak so somewhere in the 60-70 percent power range I’d venture to guess I want to play around with more power settings but planes going into the shop to get an full engine monitor. So hopefully only a week or so.

I believe @kortopates meant was that if it was hotter than 1400°F at T/O power full rich it might be an indication your T/O fuel flow was set to low. Not that you were busting a limitation. Not that I want to put words in his mouth.

I’m not sure you realize you’re about to start a war in the comments. While this is not for the M20K specifically I think it’s better to understand why you’re doing things and this will definitely help you in that regard. turbocharged engines really make leaning simple. (I believe the MB is limited to 36” MP)

If you’re open too it I would suggest not overhauling your engine until it gives you signs it’s in need of overhaul, there’s a ton of really good information on what those indicators might be. To do that though you need to be looking for the signs. Which means having oil samples taken, looking at engine monitor data, inspecting the oil filter every oil change etc. I recommend several of Mike Busch's videos on the subject as well as books. (Side note a EIS is much cheaper than an overhaul) I see no point in overhauling a strong running engine. Poor use of money and time. Best of luck, Austin

@jlunseth thank you for the awesome explanation! I’ve read lots of your posts regarding 231 operations and it’s been a wealth of knowledge. I’m sure everyone appreciates the time and effort you put into your posts!

@hubcap that’s what my understanding of the wastegate did, but a couple mechs said it could help with the CDT as well. I couldn’t wrap my head around their reasoning of how it would lower CDT, because the compressor still had to compress the air thereby heating it up.

Reviving an old thread for a quick question! I was told that just the Merlyn UDC will help lower CDT due to more efficient Turbo operations, has anyone seen this in real world operations? (obviously an intercooler is the best way to lower CDT) Thank you! Austin

I really appreciate the write up on it @philiplane, PJ has it in his shop right now going through prebuy, and will also be doing a functional test flight on it as well. Beautiful paint job, but that could be a whole lot of makeup. Only one way to find out!

Holy cow! I’ve got plenty to read now! Good thing it’s a couple weeks until pick up the plane! (Once again assuming satisfactory pre-buy) thank you!

Thank you for the breakdown!

@1980Mooney Thank you!

Hello all! I have had my offer accepted on a 1979 231, with a LB engine no intercooler or Merlyn. Would someone share a PDF of their POH and MX manual if they have it? I want to start studying the POH before we pick up the plane. (assuming I still like it after the prebuy) I searched the downloads for both and could not find a 231 model one. Parts catalog yes, 252 mx manual yes but not the 231 POH. Thank you, Austin

I believe you are correct @ArtVandelay