Are GAMI Useful for M20J IO-360 Engines?

[Philip France 13]

Hello

with G3X EIS now installed should i consider to change the injectors for GAMI on my M20J IO-360 200hp ?

I know they allow to run LOP ON 6x Cylinders’ what about on 4x IO-360 running 9 to 10 gallons ROP?

Thanks

Philip

[ArtVandelay]

Next time you fly at high enough altitude to be at 65% hp or less. Lean the engine slowly and note (or download data to check later) at what fuel flow the cylinders peak. If they all peak within 0.5 gph range you don’t need them.

[A64Pilot]

Why does altitude matter? I concur with the 65% though

I had Gami’s on my IO-540 and it just wouldn’t run LOP smoothly, had them on my IO-520 and they seemed to help a little, it would run LOP before and after.

I do not have them on my IO-360 and it will run smooth deep LOP, way deeper than it needs to.

 

[Philip France 13]

Thank you i will test reach of peak , measure how the reach the peak 

and keep yuo informed

Philip

[ArtVandelay]

Why does altitude matter? I concur with the 65% though

I guess it doesn’t matter, I thought that the balance at full throttle is what’s important.

[Ragsf15e]

34 minutes ago, Philip France 13 said:

Thank you i will test reach of peak , measure how the reach the peak 

and keep yuo informed

Philip

A lot of the io360s will be fine lop without them, but if you do the test as @ArtVandelay suggested, and see greater than.5 gph difference between first and last cylinder egt peak, gammis will allow you to fine tune that.  Even with them, there’s some delta and it takes playing around switching injectors and sending them back in order to get your best results.

[Philip France 13]

Thanks I will start with the current injectors. Going LOP should i go also minus 50F?

 

[Ragsf15e]

1 minute ago, Philip France 13 said:

Thanks I will start with the current injectors. Going LOP should i go also minus 50F?

 

No, that’s likely too far.  Depends on your objectives, but if you’re around 65% power, much closer to peak will be fine.  This discussion can be really long, but here’s the quick… first, set up normal cruise at full throttle, rpm set (2500?), and lean until the last cylinder peaks. If you’re around 65% power, just barely past peak will be fine.  Check your CHTs and make sure they will be acceptable.  They’ll be cooler than rop.  If that last one to peak is a little warm, lean slightly more.  It’ll be very sensitive to leaning at lop.

Before messing around with lop at higher power, do a lot of reading and learning.  You can’t really hurt anything at 65%, but it might be possible to hurt things playing around at 85% (for example).  CHTs will be your guide.  I look for less than 380.

[Philip France 13]

Thanks : I will need to read some more. Will do a quick check at FL085 and see 1st Philip

[Ragsf15e]

12 minutes ago, Philip France 13 said:

Thanks : I will need to read some more. Will do a quick check at FL085 and see 1st Philip

As you lean, the one that leans first may go to 50lop or more/less because you have to continue leaning until the last one peaks.  You want to keep leaning until the last one peaks.  Note the gph difference between the two peaks.

[Greg Ellis]

19 minutes ago, Philip France 13 said:

Thanks : I will need to read some more. Will do a quick check at FL085 and see 1st Philip

This may help you.  It is the GAMI lean test pdf file.

Microsoft Word - GAMI Lean Test.doc (advancedpilot.com)

[Aerodon]

One of my planes is a C172N with a 180hp. On long flights I usually use WOT and 2500rpm, then lean until just before it gets rough, around 10GPH.  Recently we did a top overhaul with 4 overhauled cylinders.  Now following the same leaning procedure, the engine runs smoothly at 9GPH with no noticeable difference in speed.

The old cylinders were mix of 2 original and 2 overhauled cylinders, the problematic ones were the overhauled ones with valve issues.  I think the previous owner 'cheated out' and put some crappy cylinders on.

I am a big fan on GAMi's on my 6 cylinder Continental turbocharged engines.  The principle isn't as repeatable with a 4 cylinder IO360 without a test flight or two.  If I had a 4 cylinder IO360, I would take it to my usual altitude and power setting and do the GAMI test, then have a discussion with GAMI on the expected results.

Nothing like balanced mixture to make an engine run smoothly and economically.

 

Aerodon

 

 

 

 

 

 

 

 

[Philip France 13]

Thanks in particular the GAMI CHECK LIST. Philip

[kortopates]

Here is our Savvy instructions for doing this. With a free Savvy account you can upload your data and use our much easier tools to measure your Gami spread size for free; which are far easier to work with than using a spreadsheet. Don't try to actually measure the sweep size in the cockpit, you won't be able to get accurate results that way, instead just do your best to collect good data and then review it on the ground. One big problem is pilots pausing while they are leaning the engine because their monitor is indicating a cyl is peaking. Any pausing while changing while you should be slowly changing the mixture will result in in accurate results due to hysteresis in the system. Its really important to be constantly yet slowly changing the mixture monotonically without stopping or pausing from the ROP side to the point of roughness LOP and then slowly reverse back in the opposite direction; then repeat at least 3 times.

Its also important to do this at WOT, but RPM can me reduced to ensure a power setting less than 65%. But you need the altitude to keep the MAP down; hence the need to climb up.

Flight Test Profile – Savvy Aviation Resources

 

Edited September 12, 2022 by kortopates

[MisfitSELF]

I've read (probably on Mooneyspace) that the Lycoming IO-360 injectors are already very well balanced and likely will not gain much with GAMI's.  For instance my M20J has a "GAMI spread" of about 0.2gph with the stock injectors.

Bruce

[Shadrach]

I think most angle valve IO360s will run far leaner than needed to control CHTs.  There are exceptions, but I think those are more injector quality control and intake assembly problems than any imbalance in the engine's design.  When I first started working on this plane we noted the injector flanges were cracked because the B-nuts were over tightened at some point.  I ordered four new injectors and installed them in no particular order.  There was no discernable difference between the two sets of injectors in terms of temps, peaks or available mixture spectrum. I don't know my exact GAMI spread and really don't care.  It will smoothly run leaner and cooler than I need it to at any throttle position from 29" on down.

[kortopates]

From my experience probably only about 10% of the Lyc IO-360's need gami, the vast majority do not. Almost all 6 cyl engines though will benefit, even with the TCM positioned tuned injectors which tend to come in at 0.6 or 0.7 GPH. 

[carusoam]

Great question…

and great responses…

 

1) Learn the Gami spread test…

2) use it to determine how well your fuel injectors are working already…

3) Four cylinder engines are least likely to need Gami injectors…

4) Six cylinder engines have more air flow challenges… See log style intakes vs. curvy pireps…

5) Tuned intake pipes are more common in Continental powered Mooneys…

6) Above 8k’… the red box is finished… lean as close to peak as you want… you will be below 65%bhp… the line of safety…

7) once at peak, 100% of the gas is being used for power…. Going further LOP you will see how much power drops off with FF…

8) A Gami spread of 0.0 or 0.1 is nice to have…. Down low you can lean to about 90°F LOP…

9) Up high you can get to about 50°F LOP…

10) Leaning more than that… the fan gets quieter and quieter…. Enrichen slowly, the noise comes back on…

PP summary only, not a mechanic or CFI…

Best regards,

-a-

[Frank B.]

I don’t know how you do it, give up all of that speed or should I say trade all of the MPH for MPG. I get the added range thing, but I just can’t bring myself to do it. I guess if I covered my airspeed indicator(s) which we seem to have on just about every digital box in the airplane now … I might be able to do it. I just love the speed. If the air is smooth I am always searching for that altitude with a tailwind and running 72 to 75% power. I hear the pros and cons of engine health but I am not sure what to believe. My second Mooney back in the late 80’s was a K model with a new factory engine, no engine monitor, I believe it was a 1981 or 82 vintage airplane, and with virtually no training on how to properly operate or treat that GB series engine I still flew it somewhere north of 1,500 hours without one single valve issue or cylinder change. Back then, very often, my method of decent was the “slam dunk” approach because I could only maintain flight following to my home airport if I was at 4500 MSL or higher. Maybe the factory TCM cylinders were better back then, but I don’t think that the GB engines were ever noted for long cylinder life.

[Shadrach]

7 hours ago, Frank B. said:

I don’t know how you do it, give up all of that speed or should I say trade all of the MPH for MPG. I get the added range thing, but I just can’t bring myself to do it. I guess if I covered my airspeed indicator(s) which we seem to have on just about every digital box in the airplane now … I might be able to do it. I just love the speed. If the air is smooth I am always searching for that altitude with a tailwind and running 72 to 75% power. I hear the pros and cons of engine health but I am not sure what to believe. My second Mooney back in the late 80’s was a K model with a new factory engine, no engine monitor, I believe it was a 1981 or 82 vintage airplane, and with virtually no training on how to properly operate or treat that GB series engine I still flew it somewhere north of 1,500 hours without one single valve issue or cylinder change. Back then, very often, my method of decent was the “slam dunk” approach because I could only maintain flight following to my home airport if I was at 4500 MSL or higher. Maybe the factory TCM cylinders were better back then, but I don’t think that the GB engines were ever noted for long cylinder life.

Tell me you don't have a lot of experience flying LOP without telling me you don't have a lot of experience flying LOP.  Next time you're zooming along at mid mach numbers, note your 100 ROP CHTs. Then go to the lean side and run as close to peak from the lean side and wide open throttle (given an NA A36) as needed to produce the previously noted ROP CHT from the lean side. If you get to peak EGT on the richest cylinder before hitting your ROP CHT then you've found the intersection of best BFSC and power and consequently MPG. If you get to your ROP CHT before peak EGT then you must be cruising at a lower altitude. Either way the speed hit just isn't that big of a deal unless you run ultra conservative from peak.  I almost never need to be more than 45 LOP and that's at low alt pushing 80%hp.  Typical setting is peak to 25 LOP depending on CHTs.  There is almost no operational reason to run leaner than Peak EGT at 70% power or below unless it's a hot day and cooling is a challenge. My POH is clear that peak is fine at 70% power or less and my experience confirms it. If peak is fine at 70% then leaner is certainly not harmful.  True LOP utility is at lower altitudes avoiding strong headwinds. In a case where you must throttle back or go full rich to keep things cool, LOP is the best option.  Under those circumstances, the difference in speed LOP vs ROP is almost imperceptible at said low DA/high power settings but the fuel burn delta is huge... In cool weather a NA engine can make 70% or more when LOP at usable but admittedly lower altitudes (5000 ft or less). One just needs to know what they are doing.

[Ragsf15e]

I usually cruise pretty high out west and I’m NA, so around 65%.  I see about 4 ktas of speed loss to run LOP (which at that power is pretty much right at peak).  Fuel flow drops from ~10.5 to ~8.8.  So 3% loss in speed and 16% reduced fuel flow.  It’s not a bad trade off.

[Frank B.]

13 hours ago, Shadrach said:

Tell me you don't have a lot of experience flying LOP without telling me you don't have a lot of experience flying LOP.  Next time you're zooming along at mid mach numbers, note your 100 ROP CHTs. Then go to the lean side and run as close to peak from the lean side and wide open throttle (given an NA A36) as needed to produce the previously noted ROP CHT from the lean side. If you get to peak EGT on the richest cylinder before hitting your ROP CHT then you've found the intersection of best BFSC and power and consequently MPG. If you get to your ROP CHT before peak EGT then you must be cruising at a lower altitude. Either way the speed hit just isn't that big of a deal unless you run ultra conservative from peak.  I almost never need to be more than 45 LOP and that's at low alt pushing 80%hp.  Typical setting is peak to 25 LOP depending on CHTs.  There is almost no operational reason to run leaner than Peak EGT at 70% power or below unless it's a hot day and cooling is a challenge. My POH is clear that peak is fine at 70% power or less and my experience confirms it. If peak is fine at 70% then leaner is certainly not harmful.  True LOP utility is at lower altitudes avoiding strong headwinds. In a case where you must throttle back or go full rich to keep things cool, LOP is the best option.  Under those circumstances, the difference in speed LOP vs ROP is almost imperceptible at said low DA/high power settings but the fuel burn delta is huge... In cool weather a NA engine can make 70% or more when LOP at usable but admittedly lower altitudes (5000 ft or less). One just needs to know what they are doing.

I don’t guess that I have but maybe an hour total time LOP in my flying time unless I was LOP back in the Cessna 150 days of training when we leaned until it started cutting out and turned it back in just a little.

[Shadrach]

6 hours ago, Frank B. said:

I don’t guess that I have but maybe an hour total time LOP in my flying time unless I was LOP back in the Cessna 150 days of training when we leaned until it started cutting out and turned it back in just a little.

Smooth ops for a 150 are likely clustered around peak with cylinders on each side..

[A64Pilot]

On 9/12/2022 at 2:22 PM, Shadrach said:

I don't know my exact GAMI spread and really don't care.  It will smoothly run leaner and cooler than I need it to at any throttle position from 29" on down.

That’s really all that matters, there really is no need to become obsessed with things.

Honestly all you need to do is set up a cruise say 23 squared or whatever your usual lower power cruise is, start leaning continuously, at some point you will feel a significant reduction in power, when this occurs is your engine still smooth? If so then your way good because when that power went down your pretty deep LOP.

If not you may still be OK, but that’s when you should determine how LOP your richest cylinder is.

I don’t even have an engine analyzer and run LOP, people have for decades. I just run a power that you can’t hurt the motor with mixture is all.

Sure they are nice to have, especially for trouble shooting, but you don’t have to spend thousands of $$ to run LOP safely in a NA motor.

 

[Shadrach]

30 minutes ago, A64Pilot said:

That’s really all that matters, there really is no need to become obsessed with things.

Honestly all you need to do is set up a cruise say 23 squared or whatever your usual lower power cruise is, start leaning continuously, at some point you will feel a significant reduction in power, when this occurs is your engine still smooth? If so then your way good because when that power went down your pretty deep LOP.

If not you may still be OK, but that’s when you should determine how LOP your richest cylinder is.

I don’t even have an engine analyzer and run LOP, people have for decades. I just run a power that you can’t hurt the motor with mixture is all.

Sure they are nice to have, especially for trouble shooting, but you don’t have to spend thousands of $$ to run LOP safely in a NA motor.

 

No, and I could likely safely set my engine sans monitor just as I do now, but that is only because of years of seeing the cause end effect of various mixture settings.

Lycoming recommendations suggest leaning at 70% or less. any MP and RPM combination where 100ROP is permissible should be fine at peak EGT or leaner.  I could lean by airspeed alone, but it would leave significant amounts of speed and MPG on the table for no real benefit other than avoiding cost of an engine monitor...Yellow Tagged EDM730s are under $1000 so the price of entry isn't much.