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M20M LOP Discussion


DVA

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15 minutes ago, TNIndy said:

I know this is a little off topic and may have been discussed before. I've been considering purchasing a Bravo and noticed the exhaust and uneven cylinder head temps were a reoccurring issue. I called Ryan at Power Flow Exhaust and asked if they had any plans to offer an exhaust for the Bravo anytime soon. He said it wasn't in their plans and would basically take 30 customers, potentially willing to make deposits, and 3 years to complete. Doesn't sound promising but I thought I would mention it. 

Only 3 years? ha

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Aren't PowerFlow exhausts normally aspirated only?.. not turbo?   I see only O-  not even IO- in their STC list. 

The issue with the exhausts is that 1750 is essentially Iconel's limit, and the welds crack. 

The cylinder life was basically fixed by the Bravo mod, as long as you don't push the Aluminum yield temperature, 380C is where the bend starts. 

The TIO-540AF1A&B basically pushed the envelope in power, and heat dissapation in a small cowl and compact form factor.   It will run there, but will burn through parts if you keep it in the hot/high power corner.   Run it back at the limits for other TIO-540s (1650 etc) and it will run without complaint to TBO. 

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5 hours ago, LANCECASPER said:

If you get the Bravo to run smoothly at LOP at one power setting, with GAMIs, you'll be one of about three Bravo owners that I've heard of in the world that was able to make that work. If you run at settings where CHT is over 400 consistently, you have two choices: Budget for new cylinders every 500 hours or do whatever it takes to keep the hottest cylinder below 400 (open cowl flaps, add fuel, etc.). I try not to exceed 380.

Based on all the discussions about how challenging it can be to get this engine to run LOP, I fully expected to go up, discover it ran rough LOP, and do a GAMI sweep to see how bad it was.

I was shocked at how well it behaved.  It runs well lean all the way from 60% power through 75% (at 75% the cylinders are getting a little warm - over 400).  It has to be severely leaned to start to get rough.  It supports LOP better than my TSIO-360-LB in a 231.  I told @PilotX he was lucky and GAMI injectors wouldn't make a difference for him.

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Just now, Warren said:

Based on all the discussions about how challenging it can be to get this engine to run LOP, I fully expected to go up, discover it ran rough LOP, and do a GAMI sweep to see how bad it was.

I was shocked at how well it behaved.  It runs well lean all the way from 60% power through 75% (at 75% the cylinders are getting a little warm - over 400).  It has to be severely leaned to start to get rough.  It supports LOP better than my TSIO-360-LB in a 231.  I told @PilotX he was lucky and GAMI injectors wouldn't make a difference for him.

My experience as well.  Runs fine LOP.   TIT is my limiting factor.  I like 1625 or under.  LOP my CHTs get nice and cool averaging 325.  My AC  spent most of it's life oconus.  I often wonder if someone tuned the injectors to combat higher fuel prices.   I'd check the logs but they are written in French. :)

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12 minutes ago, slowflyin said:

My experience as well.  Runs fine LOP.   TIT is my limiting factor.  I like 1625 or under.  LOP my CHTs get nice and cool averaging 325.  My AC  spent most of it's life oconus.  I often wonder if someone tuned the injectors to combat higher fuel prices.   I'd check the logs but they are written in French. :)

Sounds good, what's your hottest EGT out of curiosity when you are running over 1600?

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Let’s see if we can handle @TNIndy’s thoughts…

Adjusting and improving airflow through the engine is always a good idea…

It is a balance that starts at the front…runs through the engine… and ends with the tail pipe….

The Bravo has an incredibly well developed power plant…

The intake system was well designed… the turbo, MP controller, and intercooler are perfect…

The exhaust exiting turbo system is pretty much unencumbered…

 

Known improvements on this older system…. Some things that can be done today…  balancing FF to match the unbalanced AF…

The Log style intake system is really good at one set of engine conditions… most likely T/O conditions.

depending on where you run it… the balance may change…

The Gami injector people are really good at matching the flow of injectors to what you want to do….

 

Adding a different exhaust system after the turbo on this engine… probably will add to the ownership cost…. It won’t be able to add any significant HP…

It may affect the cabin heat system… if it added any HP…

It would be really cool if a balanced air intake system could be added at a realistic cost…

A pair of turbos with matching intercoolers would be dreamy….

Increasing the cubic inches is always helpful…

Wait a sec….

See The M20M Charlie edition….  AKA Acclaim….  :)
 

With the quirks of the Log style air intake… there is an interesting opportunity for GAMI injectors… that isn’t available to a four cylinder engine…

PP thoughts only…

Go Bravo!

:)

Best regards,

-a-

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2 minutes ago, carusoam said:

Let’s see if we can handle @TNIndy’s thoughts…

Adjusting and improving airflow through the engine is always a good idea…

It is a balance that starts at the front…runs through the engine… and ends with the tail pipe….

The Bravo has an incredibly well developed power plant…

The intake system was well designed… the turbo, MP controller, and intercooler are perfect…

The exhaust exiting turbo system is pretty much unencumbered…

 

Known improvements on this older system…. Some things that can be done today…  balancing FF to match the unbalanced AF…

The Log style intake system is really good at one set of engine conditions… most likely T/O conditions.

depending on where you run it… the balance may change…

The Gami injector people are really good at matching the flow of injectors to what you want to do….

 

Adding a different exhaust system after the turbo on this engine… probably will add to the ownership cost…. It won’t be able to add any significant HP…

It may affect the cabin heat system… if it added any HP…

It would be really cool if a balanced air intake system could be added at a realistic cost…

A pair of turbos with matching intercoolers would be dreamy….

Increasing the cubic inches is always helpful…

Wait a sec….

See The M20M Charlie edition….  AKA Acclaim….  :)
 

With the quirks of the Log style air intake… there is an interesting opportunity for GAMI injectors… that isn’t available to a four cylinder engine…

PP thoughts only…

Go Bravo!

:)

Best regards,

-a-

The acclaim is nice but it also comes with 2 turbos that wear out and intercoolers on top of your plugs…

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Just now, Davidv said:

The acclaim is nice but it also comes with 2 turbos that wear out and intercoolers on top of your plugs…

Waiting for the Acclaim Bravo before I go all in… :)

Best regards,

-a-

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Just now, carusoam said:

Waiting for the Acclaim Bravo before I go all in… :)

Best regards,

-a-

I've been trying to convince to folks at the factory to go all lycoming for Ultra 2 but I have a feeling I'll face some resistance :). 

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Just now, Davidv said:

I've been trying to convince to folks at the factory to go all lycoming for Ultra 2 but I have a feeling I'll face some resistance :). 

That would be cool…. There has been a lot of development shown at KOSH for the turbo 540…

And that was more than a year ago…

Of course… they were advertising to the experimental crowd… where the decision makers were individual owners…

 

Keep the door open for…. STCs that go back and re-power older LBs… :)

Hanging a Turbo on an Ovation sounds like a really good idea…

Best regards,

-a-

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The Bravo engine is a stout fellow. Once the ex valves were directly oiled instead of the "lets let the lifter bleed off drip down and take care of everything" concept of Lycoming lubrication, the engine really last a long time if properly ran. The mags could use some help, and once you hang a sure fly on it, that "problem" is mitigated somewhat. Tuning up the intake and fixing the ignition would allow for a more economical cruise setting like the Continental's only with out the continental issues (starter adapter, etc)

Perhaps now the Chinese ownership of Mooney has ceased, the brain trust at Mooney can look at other than Chinese owned engine options. Undoubtedly this will take a large bucket of $$$ to go thru the fed thithe

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Regarding RPM- you will have great difficulty running LOP smoothly at a lower RPM than 2400. This engine doesn't benefit from a tuned induction system, which helps balance the power developed per cylinder. GAMI injectors help but can't be as effective as they are with a tuned induction system. Lower RPM simply magnifies the vibration from imbalanced power.

Cylinder cooling is also better at 2400 than 2200, ROP or LOP. There is very little reason to slow the engine down below 2400 unless you are running at very low power settings for maximum range.

Edited by philiplane
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18 hours ago, Warren said:

Based on all the discussions about how challenging it can be to get this engine to run LOP, I fully expected to go up, discover it ran rough LOP, and do a GAMI sweep to see how bad it was.

I was shocked at how well it behaved.  It runs well lean all the way from 60% power through 75% (at 75% the cylinders are getting a little warm - over 400).  It has to be severely leaned to start to get rough.  It supports LOP better than my TSIO-360-LB in a 231.  I told @PilotX he was lucky and GAMI injectors wouldn't make a difference for him.

You might also try adding more air, in other words, use 33 or 34" MP rather than 32. If the fuel flow does not change, the power being produced does not change, at least according to the APS guys. What you are doing if you keep the fuel flow fixed and increase the air, is making the mixture leaner and therefore cooler running. That is what I have done in my 231 LB. My turbo has about 1400 hours since last OH and I had Willmar borescope it last year to make sure it does not need an OH, they said it is in good shape, so the higher cruise pressures are not bothering the turbo and they help the engine. I max out at about 71% HP, above that in summer temps I can't keep the TIT where I want it, which is at or below 1600.

It is a little counterintuitive to put more of something in, when you are trying to reduce CHTs, like making the mixture richer on the ROP side in order to control CHTs, which is a little counterintuitive also if you don't understand your engine.

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Will have owned my Bravo 29 years in August.  On engine number 3.  Have taken the APS Course and got a lot of value from it.  While I believe in LOP and run some Continentals smoothly that way, in short tests my previous engines were not happy campers running that way.  I have the GAMIs.  First engine made it to 300 hours past TBO as a result of the change to the Bravo engine. The 2nd would have made it to TBO were it not for an incident during an Annual that made it financially practical to get a new Reman at 1600 hours.  Turbos on the first 2 engines needed to be OH'd at mid time.  In spite of running ROP l had expensive exhaust issues with both the 1st and 2nd engines.  Run cross country 29/2400 (75% Power).

From my perspective of 10,000 hours flying Mooneys and 5,500 hours flying Bravos, I'd stick with ROP.  Keep a bucket of cash on hand if you rationalize for whatever reason and choose to run LOP.

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3 hours ago, philiplane said:

This engine doesn't benefit from a tuned induction system, which helps balance the power developed per cylinder.

Ill respectfully disagree, all engines benefit from being well balanced and tuned to have equal flow characteristics on all cylinders. Some benefit more, especially at high rpms as eluded to. Strong spark is important across all makes and models of engines, and especially true LOP

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4 hours ago, philiplane said:

Regarding RPM- you will have great difficulty running LOP smoothly at a lower RPM than 2400. This engine doesn't benefit from a tuned induction system, which helps balance the power developed per cylinder. GAMI injectors help but can't be as effective as they are with a tuned induction system. Lower RPM simply magnifies the vibration from imbalanced power.

Cylinder cooling is also better at 2400 than 2200, ROP or LOP. There is very little reason to slow the engine down below 2400 unless you are running at very low power settings for maximum range.

We ran all the power settings at 2200. Next up 2300 and 2400. I would like a little better cooling so if 2400 makes #1 cooler then that would certainly be better.

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2 hours ago, mike_elliott said:

Ill respectfully disagree, all engines benefit from being well balanced and tuned to have equal flow characteristics on all cylinders. Some benefit more, especially at high rpms as eluded to. Strong spark is important across all makes and models of engines, and especially true LOP

Let me rephrase- this particular engine doesn't HAVE a tuned induction system, and of course it would benefit from one. 

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1 hour ago, philiplane said:

Let me rephrase- this particular engine doesn't HAVE a tuned induction system, and of course it would benefit from one. 

agreed, and now understand your intent.

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I've applied several minor fixes to Bravo engines to even out the CHT's. You have to pay special attention to the baffle seals to the cowl, and to the forward seals around the alternator area. There are some large openings that need attention. I was able to run 80 to 85% power, with CHT's in the 340-375 degree range. I've done the same clean ups on Turbo Aztecs which share a similar engine, and similar heat issues.

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On 6/28/2016 at 1:02 PM, Danb said:

DVA beat me to the punch, treating your engines to nice temps will increase your odds on lower maintenance costs. You don't lose much by running your engine at 29-30 " max and 2400, I keep my tit close to 1600, chts generally under 380, still get good speeds on 17-18 gph. He has some good info on turbos a couple weeks ago a good read.

I'm running 29 inches,  2200 - 2300 RPM and TiT 1585 and achieve great fuel economy and speeds all day long!

My engine was converted to a B at 1000 hours. I purchased the plane with 1940 hours. Airmark is finishing up my MOH at 2050.

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On 6/16/2021 at 3:48 PM, Davidv said:

Sounds good, what's your hottest EGT out of curiosity when you are running over 1600?

I’ll have to check.   I only use EGT for troubleshooting.   If one jug is out of line I start paying attention.  Partial injector clog, induction leak……

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  • 2 weeks later...

179 on 14.3 gph, awesome, seems like ovation numbers. My M has been ok running LOP I just don’t do it often. With all the carbon buildup I see I’m likely to do LOP more often. Love your CHT ‘s

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