Dakota annual - engine observations

[gkainz]

What do you think of these tidbits?

PA28-236 Piper Dakota 3400 total hours
Lycoming IO-540 1000 hrs SOH

Mufflers replaced last annual - 360 hrs flown on these. Examination at this year's annual reveals significant distortion and damage to the flame cones on front and middle mufflers, rear muffler appears serviceable.

Operating too lean?

Spark plugs - 360 hrs on these. All 6 lower spark plugs show significant leading. All 12 show significant center electrode deterioration.

Operating too rich?

Compression checks show 1-4 high 70s, while 5, 6 show low 70s.

5 and 6 always indicate they're running cooler via JPI ... I don't recall by how much.

Thoughts?

 

[Tom-D]

Thoughts?

Buy new mufflers, and clean your plugs.

burned mufflers would not be cause by mixture. removing fuel makes things get cooler.

Timing maybe.

Age most likely

 

[Jay Honeck]

What do you think of these tidbits?

PA28-236 Piper Dakota 3400 total hours
Lycoming IO-540 1000 hrs SOH

Mufflers replaced last annual - 360 hrs flown on these. Examination at this year's annual reveals significant distortion and damage to the flame cones on front and middle mufflers, rear muffler appears serviceable.

Mufflers on the Piper installation of the O-540 are sketchy, at best. We've replaced ours 3 (?) times in the ten years we've owned our Pathfinder, which was renamed the Dakota in '76-ish.

For one, they are crap. The baffles need to be made of a heavier material, but, of course,weight is everything in an airplane -- so they keep them light, and guarantee future business for Dawley Aviation and other "muffler rebuilders".

Spark plugs - 360 hrs on these. All 6 lower spark plugs show significant leading. All 12 show significant center electrode deterioration.

What is meant by "significant leading"? Does the plane fail mag checks regularly? This is a continuous problem with our normally aspirated O-540, which was never designed to run on 100LL. The fuel we must buy nowadays has 400% more lead in it than the fuel the engine was optimized to use (80 octane avgas), and causes endless problems.

The solution is to run unleaded car gas -- which is becoming almost impossible to find. We ran 12,000 gallons of it through our Pathfinder, before moving to an island that doesn't have it.

Compression checks show 1-4 high 70s, while 5, 6 show low 70s.

5 and 6 always indicate they're running cooler via JPI ... I don't recall by how much.

Interesting. 5 and 6 usually run somewhat hotter, according to my JPI.

 

[Henning]

Too rich eats exhaust, not too lean.

 

[gkainz]

Buy new mufflers, and clean your plugs.

new mufflers purchased and installed.

Our club maintenance chief says he's not comfortable with the amount of electrode deterioration. New plugs installed.

Age most likely

These mufflers were new last year - 360 hours on them.

Mufflers on the Piper installation of the O-540 are sketchy, at best. We've replaced ours 3 (?) times in the ten years we've owned our Pathfinder, which was renamed the Dakota in '76-ish.

For one, they are crap. The baffles need to be made of a heavier material, but, of course,weight is everything in an airplane -- so they keep them light, and guarantee future business for Dawley Aviation and other "muffler rebuilders".

good to know ... thanks, Jay.

What is meant by "significant leading"? Does the plane fail mag checks regularly? This is a continuous problem with our normally aspirated O-540, which was never designed to run on 100LL. The fuel we must buy nowadays has 400% more lead in it than the fuel the engine was optimized to use (80 octane avgas), and causes endless problems.

The solution is to run unleaded car gas -- which is becoming almost impossible to find. We ran 12,000 gallons of it through our Pathfinder, before moving to an island that doesn't have it.

Interesting. 5 and 6 usually run somewhat hotter, according to my JPI.

I didn't see the plugs so not sure how much "significant" is ... it was my year to be upside down under the panel and into the floorboards ...

I've not had a mag check failure, nor have I heard any complaints from the other club members on that.

We maintain the Dakota, a Saratoga and a Bonanza, and do as much of our own work as possible. One of our guys also wrenches on a Reno race team, so I trust their assessments on "stuff"

 

[Skylane81E]

If the plugs were fouled badly enough to have fireing issues that too would raise the temps in the muffler, same way the EGT goes up during a mag check.

Aircraft mufflers suck anyway, piper units in particular.

 

[mikea]

To clear the lead deposits you have to lean at idle like the engine is on a fat free diet. Lean on landing and right after startup. Lean just past the RPM drop. Try iridium wire plugs.

The muffler can be blown out by a backfire by going too far on the mag chack - not that I know anything about that.

 

[Clark1961]

The solution is to run unleaded car gas -- which is becoming almost impossible to find. We ran 12,000 gallons of it through our Pathfinder, before moving to an island that doesn't have it.

Mogas isn't an option in the Dakota. In addition to the taper wing, Piper went with a higher compression engine. The result is not STC available to run unleaded.

On another topic, all that boat gas on the island and none of it alcohol free? Hmmm...