Failed mag check on Turbo Charged engine

Bluebird

Bluebird

Filing Flight Plan
Joined
Aug 27, 2008
Messages
18
Location
Phoenix, AZ
Display Name
Display name:
Bluebird
I have a 2005 Cessna T182T with TIO-540-AK1A Turbocharged engine that I had reman done at Western Skyways with less than 50 hours on it. It has never passed a mag check (per the manual or previous conditions) since overhaul. I picked her up at the factory so know what it used to do and what the book says. Mag check should be done at full rich, but I get a 200-250 drop per mag when I run up full rich. If I lean out some it is fine. Just got it back from maintenance and they reworked the fuel system thinking that was the problem, it was not. Any ideas? I'm thinking maybe the turbo charger waste gate???? Any ideas would be appreciated, thanks in advance. Rodney
 
Why would you think it's a waste gate? Is the manifold pressure reading higher than you'd expect?

I also think this sounds like a fuel metering issue. Namely "rich" is too rich which could just be a simple adjustment of the cable attached to the mixture knob.
 
Mag checks on the ground are mostly a waste of time and money, so I wouldn't read much into it. There's also no reason to do them full rich. Maybe WC adjusted the fuel flow to something more sane than the default Lyc setup.

If they work slightly lean, great. You could do an in flight high power check to make really sure.
 
Lyc allows for leaning of the engine to bring mag checks into spec
 
sba55 said:
Mag checks on the ground are mostly a waste of time and money, so I wouldn't read much into it.
Click to expand...
That's a pretty bold statement. Sure there may not be much value if you're the pilot that's always flying it and you check it in flight.

But when you're flying a rental, flown by who knows who, and you have no clue if it was working properly for them or not (perhaps they wouldn't know what improperly was) it really is in your best interest to check what you can check while you're on the ground.
 
thomascannon said:
Why would you think it's a waste gate? Is the manifold pressure reading higher than you'd expect?

I also think this sounds like a fuel metering issue. Namely "rich" is too rich which could just be a simple adjustment of the cable attached to the mixture knob.
Click to expand...

FWIW the only adjustments to the fuel mixture that can be made are the idle mixture, once off idle the non adjustable meetering jets take over.
 
Perfect, thanks for your input. I feel much better, it does run smooth when leaned out. As per another post I will start adding a cruise check also. Thanks again
 
Thanks to everyone for your help. Several answers... the waste gate was an uneducated guess (if it aint fuel, gotta be air). MP was 33" on departure yesterday and it seemed to hold, book say's it will allow 2-3" over (32") before opening and lowering the MP. And will definately start doing another in cruise flight. Thanks again.
 
Bluebird said:
Thanks to everyone for your help. Several answers... the waste gate was an uneducated guess (if it aint fuel, gotta be air). MP was 33" on departure yesterday and it seemed to hold, book say's it will allow 2-3" over (32") before opening and lowering the MP. And will definately start doing another in cruise flight. Thanks again.
Click to expand...

Just remember that the Bendix fuel injection system used on your lycoming engine would mask a wastegate issue so far as the mixture goes. If more air is supplied it will just dump in more fuel and vice versa.

Knowing your resoning behind the wastegate guess I understand it, but the fuel servo deserves a little more credit:wink2:
 
sba55 said:
Mag checks on the ground are mostly a waste of time and money, so I wouldn't read much into it. There's also no reason to do them full rich. Maybe WC adjusted the fuel flow to something more sane than the default Lyc setup.

If they work slightly lean, great. You could do an in flight high power check to make really sure.
Click to expand...

If the engine does not meet the required numbers in the type certificate how can it be airworthy?
 
Bluebird said:
Thanks to everyone for your help. Several answers... the waste gate was an uneducated guess (if it aint fuel, gotta be air). MP was 33" on departure yesterday and it seemed to hold, book say's it will allow 2-3" over (32") before opening and lowering the MP. And will definately start doing another in cruise flight. Thanks again.
Click to expand...


The question is if the fuel controller is set up and functioning properly.
 
jesse said:
That's a pretty bold statement.
Click to expand...

And as with many bold statements, I would not trust the source.

Sure there may not be much value if you're the pilot that's always flying it and you check it in flight.

But when you're flying a rental, flown by who knows who, and you have no clue if it was working properly for them or not (perhaps they wouldn't know what improperly was) it really is in your best interest to check what you can check while you're on the ground.
Click to expand...

Even then, there's value to it. Mag failures (or various other failures that cause the mag to not function) can and do occur between engine starts, as you've observed on my Aztec. You wouldn't necessarily notice if a mag wasn't functioning (or even if you would, a lot of people wouldn't). Then you end up taking off in a single with one mag.
 
Ted DuPuis said:
Even then, there's value to it. Mag failures (or various other failures that cause the mag to not function) can and do occur between engine starts, as you've observed on my Aztec. You wouldn't necessarily notice if a mag wasn't functioning (or even if you would, a lot of people wouldn't). Then you end up taking off in a single with one mag.
Click to expand...
Agree
 
sba55 said:
Mag checks on the ground are mostly a waste of time and money, so I wouldn't read much into it.
Click to expand...

Pretty sure that's how I'd found the plug wire had fallen off one of my plugs in North Platte, NE earlier this year... :dunno:
 
It's also how I found that 2 cylinders weren't firing a couple weeks ago.
 
Checking the mags also checks that the mag switch is working, too. You want to be able to shut off a renegade magneto. If the distributor gearing in the mag shifted (worn teeth, worn bearings) it can start firing the wrong cylinders on their intake strokes, say, and make the engine quit. Shutting off that mag saves the day.

Dan
 
Yeppers, inflight checks can give a better indication of the overall health of the system, but I want to know about problems before flight
 
Interesting Duncan mentioned the fuel controller. When I took her in the first time for the mag problem the mechanic sent the fuel injection servo p/n 2576592-2 back to Western for maintenance, stating; leaned idle mixture to 10 RMP rise, still has 130 RPM rise @ 1800 RPM and after shutdown drips fuel out of intake drain. Could I still have fuel servo issues? I flew yesterday and took some notes during mag checks...here we go.

Rich mag check per manuel and what has worked for 2300 hrs previously.
RM - 1800-1590
LM - 1800-1580 .... 210 and 220 drops

Leaned mag check
RM - 1800-1680
LM - 1800-1650 .... 120 and 150. acceptable per suppliment and smooth engine

Low idle mag check
RM - 1000-860
LM - 1000-880 140 and 120 ... not sure if this is good or not????

Cruise check 23" @ 2200 RPM, 1595 TIT, -68 ROP and 12.1 GPH Fuel flow
LM - 2200-2170
RM - 2200-2170 ... 30 RPM loss ... not sure if this is good or bad????

Bottom line... I'm having trouble accepting the fact that, after 50K plus my engine (supposedly built better than factory) now is behaving differently. Are these fine and should I just accept it and move on? Thanks in advance. Rodney
 
Fuel pump could also be at fault, IIRC it is vented to turbo discharge pressure on the lycoming turbo engines.
 
Spoke to Al Head at Western about this and he agreed it was too high. There is a Lycoming Service Instruction SI 1517 that allows timing set to 23 degrees in lieu of the 20 on the data plate. I'll let you guys know how that comes out. Thanks again for all your help.
 
Bluebird said:
Spoke to Al Head at Western about this and he agreed it was too high. There is a Lycoming Service Instruction SI 1517 that allows timing set to 23 degrees in lieu of the 20 on the data plate. I'll let you guys know how that comes out. Thanks again for all your help.
Click to expand...

Resetting the timing helps for sure... drop on mags were in range +/- 150 at full rich and 1800 and within 20 rpm of each other. Mag drop in cruise was +/- 20rpm and drop at 1000RPm was +/-50RPM. If you do this you need to get and install a new data plate before flying the plane (to be legal). Thanks for all your help..... THE END
 
Bluebird said:
If you do this you need to get and install a new data plate before flying the plane (to be legal). Thanks for all your help..... THE END
Click to expand...

IAW SI 1517

The timing change may be incorporated in engines already in service as follows:
1. Retime both magnetos using the 23° timing mark instead of the 20° timing mark on the starter ring gear. See Lycoming Operator’s Manual, P/N 60297-23P or P/N 60297-23 for the magneto timing procedure.
2. Replace the engine’s existing 20° BTC data plate with a new 23° BTC data plate.
a. Lycoming will issue a new 23° BTC data plate after receiving both a written request and the 20° BTC data plate. In the written request be sure to include the aircraft and engine serial number and documentation that the engine was retimed to 23° BTC. This documentation may be a statement from the aircraft owner or mechanic, a copy of the permanent engine record, or a copy of the engine logbook. Address all requests to:
Lycoming Engines
652 Oliver Street
Williamsport, PA 17701
Attn: Customer Service, 23° Timing Change
 
Last edited:
Ted DuPuis said:
Even then, there's value to it. Mag failures (or various other failures that cause the mag to not function) can and do occur between engine starts, as you've observed on my Aztec. You wouldn't necessarily notice if a mag wasn't functioning (or even if you would, a lot of people wouldn't). Then you end up taking off in a single with one mag.
Click to expand...

I try to remember to test he mags AFTER I am done flying to ensure they are ready for the next flight. It also confirms the P leads are working. I had one P lead fail in flight and I caught it on the ground after flying. Had I pulled the prop through I may have started the engine. :eek:
 
Last edited:
Geico266 said:
I try to remember to test he mags AFTER I am done flying alos to ensure they are ready for the next flight. It also confirms the P leads are working. I had one P lead fail in flight and I caught it on the ground after flying. Had I pulled the prop through I may have started the engine. :eek:
Click to expand...

Do we now understand why we pull the mixture to shut down. ?
 
You must log in or register to reply here.
Back
Top