Bravo engine surging while leaning at cruise power

[Rick Junkin]

Greetings all, I'm looking for information about engine surging at cruise power while leaning to cruise fuel flow, and resolutions to this issue that others may have discovered.

I promised my wife I'd start with this - "Riddle me THIS, Batman..."

I've encountered this on my last two flight attempts, after having convinced myself that I induced the anomaly on the first sortie with too rapid throttle/mixture adjustments. Flight conditions for the first sortie were 15,500 MSL at the top of the climb out, 34/2400 and 24.5gph (leaned slightly) set on the climb. After leveling off and reaching cruise speed, I set 30/2200 and began leaning fairly quickly to get to about 16gph, but the engine began surging well before then. It caught me by surprise, so I didn't catch all of the parameters during the fluctuations as I enriched the mixture to stop the surging. I tried leaning again with the same results, this time MP looked to be cycling between 30"and about 20", and I'm guessing that RPM was between 2200 and about 1000, based on sound as I didn't see the numbers. Unfortunately I don't have the instrumentation on board to capture the exact numbers. The surging stopped when I went full rich on the mixture and I left it there for an uneventful RTB. I did a run up post flight, and everything was normal. I convinced myself that I had induced this anomaly due to leaning in the climb (first time I had tried that technique) and percolated the fuel with higher than normal temps (1550TIT, CHTs 370-390), leading to a surge condition.

 

On the second sortie (today), I was very deliberate in my adjustments and encountered the same anomaly. Today's flight conditions were 6,500 MSL at 30"/2200RPM, leaning from a cruise climb fuel flow of 25-26gph (full rich) at 34"/2400RPM. Leveled at 6,500MSL with 30/2200 set, I was leaning at a rate of about one full twist of the mixture control every 5 seconds. Leaning through 18.3gph the engine began to surge. I started enriching the mixture at the bottom of the second surge cycle and the surging stopped, so I then went full rich and I left it there for an uneventful RTB. Again, I did a normal run up check on the ground and everything was normal. I then did a high power run up to replicate the inflight engine parameters of 30"/2200, and leaned all the way through RPM decay with no surging. The peak TIT/CHT during the ground run was 1610/376. I also ran my prop through a complete min/max cycle at 2000RPM to hopefully rule out a prop governor issue, with no anomalies noted.

 

Up to this point I have set cruise power and leaned to find peak TIT usually between 15gph and 14gph, and enriched 100DF. I've never had any surging. With the CND ground run results, I'm at a loss for what to look at. Could it be that one of the controllers is having issues? Or perhaps the mixture controller? It only happens inflight...

 

Thanks for any insight you may have, I'm meeting a Mooney expert mechanic at the airplane tomorrow morning to take a look and will report back with our findings.

 

Cheers,

Rick

 

 

 

 

[Mcstealth]

What year is your plane? GAMI's? Tempest? Massive? Hours? Maybe post this on Main board as not all read the Bravo link.

david

[LANCECASPER]

Are you sure it's not the prop governor ?

[Rick Junkin]

The airplane is an 89 TLS/Bravo, roughly 700 SMOH, 120 STOH with flow balanced cylinders from Lycon. No GAMIs with a spread of 1.2gph with 1, 2, 3, and 4 less than .5gph apart and bracketed by 5 and 6, high and low respectively. Massive plugs, with Tempest fine wires ready to go in. The intent of the last two flights was to baseline the parameters with the massives for direct quantified comparison with the fine wires.

 

As to the prop governor, I'm headed out to the airplane this morning to have a look with my mechanic. It performed fine during the ground runs I did yesterday, but I did correct a 15RPM overspeed at full power on initial climb out immediately after takeoff, so we'll be looking to see if anything has come loose there.

 

Thanks for the point outs!

 

Cheers,

Rick

[Cruiser]

does the TIO540 have an altitude compensating fuel pump?

[kmyfm20s]

I don't fly a turbo but I would guess waste gate or prop governor. There was a couple recent Bravo threads that mentioned mid time issues withe the exhaust. It would be worth a search if you haven't already read them.

[carusoam]

Is there a JPI on board collecting data shareable data?

Or a G1000 that can't quite hold the data?

this would help what the surge is and what might be causing it.

MP controller, rpm controller, fuel pressure,  that kind of thing....

Best regards,

-a-

[mike_elliott]

1 hour ago, Junkman said:

The airplane is an 89 TLS/Bravo, roughly 700 SMOH, 120 STOH with flow balanced cylinders from Lycon. No GAMIs with a spread of 1.2gph with 1, 2, 3, and 4 less than .5gph apart and bracketed by 5 and 6, high and low respectively. Massive plugs, with Tempest fine wires ready to go in. The intent of the last two flights was to baseline the parameters with the massives for direct quantified comparison with the fine wires.

 

As to the prop governor, I'm headed out to the airplane this morning to have a look with my mechanic. It performed fine during the ground runs I did yesterday, but I did correct a 15RPM overspeed at full power on initial climb out immediately after takeoff, so we'll be looking to see if anything has come loose there.

 

Thanks for the point outs!

 

Cheers,

Rick

RIck, with the MP fluxuating form 30 to 20 or so, you are not making exhaust to run the turbo when it drops to 20. 4 reasons cause this. 1)  fuel, 2) air, 3) spark 4) compression.

Lack of compression would not be intermittent, so eliminate that.

Since you have a set of Tempest FIne wires ready to go, why not put them in today and give it another shot. It would not necessary eliminate the spark as a cause, but from my experiences, putting in Tempest (even massives) does wonders for running a TIO540 A1FB motor leaned out.

The Slick mags are junk but we are stuck with them until an electronic system is approved to replace it. Don Kaye eluded to one in the works. Unfortunately I think it is still on the same path the BK KI300 is.

More worrisome would be a density controller/Fuel injection servo/pump issue

 

[Rick Junkin]

Thanks to all for the analysis and recommendations. I wanted to have an idea of what to look for when I went out to the airplane this morning and your inputs got me going in the right direction We identified two smoking guns.

 

The first one was easy and obvious, and most surely will eliminate the surging. The fuel injector reference line fitting had come loose behind the rear baffle plate. Ambient pressure was going to the fuel servo, rather than pressures from the injection system, so it makes sense that I was seeing normal operation on the ground (~445'MSL here in St Louis) but having a problem at altitude once I started to lean at 30/2200. I had my annual about 20 hours ago, so that was probably enough time for the fitting to work its way off from an under-torqued condition. Something to add to my post-annual inspection checklist.

 

The second one was the max RPM limit set screw on the prop governor (You were right, Lance). We discovered that the bushing the set screw goes through is stripped out, allowing the screw to migrate enough that the lock nut was starting to loosen up. It was only a change of 15RPM at full throttle climb out, but it was a change. This one would have been easy to miss because the screw was still safety-wired, and the max RPM was consistently hitting 2575. Right up until it wasn't. Prop control had continuously been positive, including being able to pull the RPM down on takeoff and work the the min/max range on the ground. We squared that away and I'm ready to go.

 

I'm starting the New Year off with an early morning flight tomorrow to confirm today's fixes, collect the GAMI check data with the massives installed (EDM 700 download for temps, time stamped GoPro video of the panel for correlated FF/MP/RPM), and then I'll R&R the plugs with the Tempest fine wires, rinse, and repeat. I'll share the comparative data with anyone who might be interested.

 

Thanks again for the point-outs on what to look for.

 

Cheers, and Happy New Year!

Rick

[kortopates]

Looks like you may be expecting too much of the turbo at 30" and only 2200 rpm at a DA over 16K. When it happens again, try a couple hundred higher rpm and a couple inches less MAP for the same power but asking a lot less of the turbo. I should add that's probably getting too lean for such a big spread.
I'd also discourage leaning in the climb. Keep the TIT and EGTs very cool at high climb power.

But seriously, you need a full engine monitor with that engine asap.


Sent from my iPhone using Tapatalk

[Rick Junkin]

Success! 1088F is back to nominal operation. I was able to record the massive plugs baseline data with that I was looking for, and will have it to compare with the fine wire plug data once I get them installed. I have about 7 hours left on my oil, so I've opted to wait until the oil change to swap out the plugs.

 

No more surging, everything was well behaved. Thanks for the help.

 

Cheers, and Happy New Year,

Rick

[carusoam]

The awesome power of MS suggestions at work!

Best regards,

-a-

[Danb]

I'd throw in the tempest fine's asap, I took out champion fine wires that had about 500 hours on them and replaced with tempest fines my Bravo clearly performed better with the switch. It's a shame I had to throw away a grand just because champion makes such garbage. for the first time since my guy was new I can fly close to lop just with a plug change. I also get almost a half gal per hour in fuel savings at similar settings.

[Rick Junkin]

1 hour ago, Danb said:

I'd throw in the tempest fine's asap, I took out champion fine wires that had about 500 hours on them and replaced with tempest fines my Bravo clearly performed better with the switch. It's a shame I had to throw away a grand just because champion makes such garbage. for the first time since my guy was new I can fly close to lop just with a plug change. I also get almost a half gal per hour in fuel savings at similar settings.

You guys just about have me talked into it. Re-cowling my airplane isn't one of my favorite things, which is why I was going to wait until the oil change to swap the plugs, but I'm thinking better of it now. I'm headed out of town on business for a couple of weeks, but if I don't have any immediate personal travel requirements when I get back I'll put the new plugs in then. 7 hours of better performance and fuel savings is probably worth it. And I can probably find someone to give me a hand with the cowling.

 

Cheers,

Rick

[Rick Junkin]

Done! The Tempest fine wires are in, and although I only had time to do a ground run tonight, I believe I can see/hear/feel the difference.

But it wasn't quite that simple...

I went out to the airport  today to fly "one last time" with the massive plugs (Champion RHB37E) to gather a bit more data before the plug swap, but on run-up I observed that #5 was not firing on the right mag. I assumed a fouled plug and was going to try clearing it, but I'm a bit superstitious and decided that it was an omen that I should swap to fine wire plugs today. And since I do my engine warm up and run-up on the ramp/non-movement area outside my hangar before talking to ground, it was a simple matter to taxi the 50 yards to shut down and push her back in. I don't think I mentioned that the temperatures were in the teens in STL today...

I'm a new M20M owner (May of this year) and have only seen the lower cowling off the airplane for the annual in August. So as I mentioned before, I wasn't looking forward to trying to do it myself. But thanks to Tony Armour's excellent posts about how to do it, I was successful. And my halogen work lights provided just enough heat to keep my hands functional.

After pulling the massives and inspecting the plugs, I'm really eager to see what inflight numbers I get with the new plugs. #6 has been first to peak and #5 has been last to peak on the two times I've attempted a GAMI check, and the plug conditions reflect that. It worries me that #5 lower was wet when I pulled it, but I had a good run-up with the new plugs. And I haven't done a good check on the "old" #5 lower yet to determine the condition of the plug. All of the other plugs look good/as expected.

I didn't change the oil today for a number of reasons, but the outcome is that when I change it in 7 hours I will also pull the plugs to take a look at how they are doing. Obviously I'm most interested in #5 and #6, but hopefully will have observed their performance numbers and know what to expect.

Thanks to all for the expertise and encouragement.

Cheers,
Rick

[carusoam]

Rick,

I've been thinking about this...  each time there is a skip caused by the spark plugs, there is probably an effect down stream caused by the skip... EGT/TIT effect and exhaust pressure effect.

Getting good spark plugs would make sense, if this is the problem...

Fun technical challenges you get with TCs...

This is solely PP thinking by a PP with no TC experience...

Best regards,

-a-

[Rick Junkin]

11 minutes ago, carusoam said:

Rick,

I've been thinking about this...  each time there is a skip caused by the spark plugs, there is probably an effect down stream caused by the skip... EGT/TIT effect and exhaust pressure effect.

Getting good spark plugs would make sense, if this is the problem...

Fun technical challenges you get with TCs...

This is solely PP thinking by a PP with no TC experience...

Best regards,

-a-

Thanks for your thoughts, one PP to another.

The things we found and corrected last weekend cleared up the surging problem I was having. The fuel injector reference line had become disconnected from the system, so the fuel servo was getting ambient pressure at altitude, rather than pressure feedback from the injection system, and that was causing the surging. I was able to confirm the fix on a flight on New Year's Day.

The new Tempest fine-wires are intended to improve performance and get things stabilized for selecting the correct GAMI injectors. From past performance, #1-#4 will be the same, #5 will be a smaller orifice and #6 will be a larger orifice. But I wanted to wait to get the data with the fine wire plugs before talking to the folks at GAMI. I hope to have that within the week.

Cheers
Rick

[kortopates]

Glad you found the disconnected line. Sounds like a huge UDP leak. The fine-wires should improve how far each cyl can go LOP before missing, but they shouldn't alter the gami spreads. Have your injectors been recently cleaned to get your baseline mixture distribution? if not, I might be suspicious of a lean outlier just being dirty.

[Rick Junkin]

4 minutes ago, kortopates said:

Glad you found the disconnected line. Sounds like a huge UDP leak. The fine-wires should improve how far each cyl can go LOP before missing, but they shouldn't alter the gami spreads. Have your injectors been recently cleaned to get your baseline mixture distribution? if not, I might be suspicious of a lean outlier just being dirty.

Thanks for the insight. The injectors were cleaned about 20 hours ago, and #6 has been running the leanest since I've had the airplane. It isn't terribly gross, but the spread is about 0.8gph between #6 and #5, with #1-4 tucked between them with a 0.3 spread. I will have new data the next time I can get airborne, possibly tomorrow.

Cheers,
Rick

[Mcstealth]

On 12/30/2016 at 11:43 PM, LANCECASPER said:

Are you sure it's not the prop governor ?

Good call Lance

[Mcstealth]

On 1/8/2017 at 11:11 PM, Junkman said:

Thanks for your thoughts, one PP to another.

The things we found and corrected last weekend cleared up the surging problem I was having. The fuel injector reference line had become disconnected from the system, so the fuel servo was getting ambient pressure at altitude, rather than pressure feedback from the injection system, and that was causing the surging. I was able to confirm the fix on a flight on New Year's Day.

The new Tempest fine-wires are intended to improve performance and get things stabilized for selecting the correct GAMI injectors. From past performance, #1-#4 will be the same, #5 will be a smaller orifice and #6 will be a larger orifice. But I wanted to wait to get the data with the fine wire plugs before talking to the folks at GAMI. I hope to have that within the week.

Cheers
Rick

Were you able to set a new baseline?

[Rick Junkin]

26 minutes ago, Mcstealth said:

Were you able to set a new baseline?

Not yet, weather here in STL has been less than cooperative. I won't be able to get airborne again until February due to business travel. I really don't like letting the airplane sit that long, but my job keeps getting in the way.

Cheers,
Rick

[Rick Junkin]

Still no new GAMI baseline, but I flew the airplane round trip from St Louis (KSUS) to Jackson TN (KMKL) a week ago with the Tempest fine wires installed, and the airplane ran great. I had some vibration at 2200RPM that I hadn't seen before with the Champion massives, but it smoothed out at 2300 RPM and I'll be recalibrating myself to run at a higher RPM/lower MAP going forward. I know, there may be some further investigation into where the vibe came from, but I'm happy with everything else (easier start, smoother ground running, etc.). I'm planning to take my wife to Lambert's, Home of Throwed Rolls, in Sikeston MO (KSIK) for lunch tomorrow, so should have opportunity to gather more data. I'll let y'all know what I see.

Cheers,
Rick

[carusoam]

The throwed rolls are becoming more famous amongst the Mooney community.  Try to get another video posted! 

Best regards,

-a-

Edited February 19, 2017 by carusoam

[Tony Armour]

On January 2, 2017 at 5:07 PM, Danb said:

I'd throw in the tempest fine's asap, I took out champion fine wires that had about 500 hours on them and replaced with tempest fines my Bravo clearly performed better with the switch. It's a shame I had to throw away a grand just because champion makes such garbage. for the first time since my guy was new I can fly close to lop just with a plug change. I also get almost a half gal per hour in fuel savings at similar settings.

 

On February 18, 2017 at 4:34 PM, Junkman said:

Still no new GAMI baseline, but I flew the airplane round trip from St Louis (KSUS) to Jackson TN (KMKL) a week ago with the Tempest fine wires installed, and the airplane ran great. I had some vibration at 2200RPM that I hadn't seen before with the Champion massives, but it smoothed out at 2300 RPM and I'll be recalibrating myself to run at a higher RPM/lower MAP going forward. I know, there may be some further investigation into where the vibe came from, but I'm happy with everything else (easier start, smoother ground running, etc.). I'm planning to take my wife to Lambert's, Home of Throwed Rolls, in Sikeston MO (KSIK) for lunch tomorrow, so should have opportunity to gather more data. I'll let y'all know what I see.

Cheers,
Rick

 

Bravo guys using the fine wire Tempest 32's or 36's ? And how did you arrive at that number ?