Spark plug life.

[DonMuncy]

I know that spark plugs should be changed if the center electrode is eaten away to too much of an oval, and if the resistor resistance is over 5000 ohms, but how many hours does one ordinarily get from massive plugs in a turbo Continental.

[manu damaschin]

Better to test them on the special device the shops usually have (they can test them under the pressure, same as  in the cylinder, and check is they work properly)...I have mine for 200h and they are fine...

[mike_elliott]

Why not test them by doing  LOP mag check in flight? That tests the entire system and does it under the operating pressures and temperatures, something the pressure box cant do on the ground. Much easier and cheaper also.

[N201MKTurbo]

I have gotten well over 500 hours on a set of massive plugs. Always Champion. Not that I have anything against the other plugs I just never tried them. I have never checked the resistance, I don't think it matters. I talked to the Champion technical rep about it at this years FAA Aviation Maintenance Symposium at CGCC and he says that the resistance thing is just a gimmick. He says that the plugs have been made the same way for a long time and have been the industry standard for decades. I have never had a Champion plug fail except for a few cracked insulators. 

 

As long as you can gap them and they pass the bomb test and run OK in your engine you are just throwing money away replacing your spark plugs. And I agree the LOP full power test is better then the bomb test.

 

The Champion service manual AVR-6 gives a bit of vague guidance for how much erosion is permissible. At one point they show a picture of a plug and say it is warn too much, but that is very subjective. In another part of the manual talking about re-conditioning plugs it states that they must be taken out of service when half the electrode is gone. Again very subjective they don't give actual minimum electrode thicknesses or the original thickness. They now have the CT-482 erosion gauge which is piece of sheet metal with a couple of holes in it. I was given one for free at the maintenance seminar and it will allow what most mechanics would consider to be a very worn plug to pass. But then mechanics and Champion both make a lot of money selling spark plugs and it is easy to blame any problem on bad plugs.

[jetdriven]

There is documented proof over on BT of Champion plugs with open resistance and arc trails inside the plugs bypassing the resistors. This can also cause mag failure, as the current required to jump the gap damages the mags. One guy with a 421 had engine problems and spend a lot of money to discover the plugs were the culprit. Many were missing the ceramic from te electrodes or it was cracked, and he tested them with a power supply capable of supplying several thousand volts, same outcome.   They claim they havent changed anything, but the recent spate of problems with Champion plugs is overwhelmingly against them.

 

check this:

From: George Braly ,redacted>

Subject: FW: cracking spark plugs

Date: October 25, 2012 11:38:22 AM CDT

To: <redacted>

- Hide quoted text -

Kevin, Peter, Jurgen, & Mark:

 

Below (and in the attachments)  is a copy of  documents that  Champion is currently providing as an “explanation” for their fine wire spark plug cracking problems.

The email and the attachments  came to me this morning from one of their frustrated customers.

 

Champion’s Kevin Gallagher wrote the following in the email, below:     

 

“When a pilot visits Texas to take George's class on LOP operation, his test engine set up performs the transition from rich to lean flawlessly,

probably without ever exposing the engine to detonation and pre-ignition…” 

 

This is interesting for several reasons.   One,  Kevin Gallaher  has not, so far as I know, ever been to the APS class.   Second,  if he went to Texas to take the class,  it was not one that I have ever taught, and certainly the engine test stand is still located well North of the South bank of the Red River,  which Napoleon and Thomas Jefferson defined as the boundary between what is now Texas and what is now Oklahoma.

 

So far,  in 1100 hours of operation of the current TN IO-550 engine on the test stand,  with standard massive champion spark plugs in the bottom of the cylinders and custom Champion pressure sensor fine wire plugs in the top spark plug position in the cylinders  of the engine - - we have never yet seen a cracked spark plug ceramic insulator.   That includes  more outrageously abusive hours of detonation and extreme temperature operation of that engine than what, in my judgment,  any  group of 1000 pilots would ever accumulate in a lifetime of engine operation.

 

The SDRs show this problem going back to at 1996,  before  anybody ever paid any attention to GAMI or its products.   Recently one shop I know filed a number of further SDRs.  He checked the FAA data base a couple of weeks later,  and the SDRs he had filed had not shown up.

 

 

There is something wrong with Champion’s process or design of their fine wire spark plugs.   Unless they address the problem,  somebody is going to get killed as a result of one of these preventable failures.  It is that simple.

 

Unless the problem is addressed,  then it is not a question of “IF”  - - it is only a question of  “WHEN”.

 

Regards,  George

 

 

From: byron rodgers [mailto:bdr737@gmail.com] 
Sent: Thursday, October 25, 2012 11:06 AM
To: George Braly
Subject: Fwd: cracking spark plugs

 

George:

 

I expected more than a copy of  "experts are everywhere" and "Spark plugs are the weakest link".   Sure. 

 

byron

 

Begin forwarded message:

 

From: <redacted>

Subject: Re: cracking spark plugs

Date: October 24, 2012 6:15:24 AM PDT

To: byron rodgers

Hello Byron, 

We are quite familiar with the threads on beechtalk as well as their origins.  The link you copied in your email came from George Braly of tornado alley and Gami injectors.  In order for George to sell his Gami injectors, he needs a value proposition.  His value proposition is that his injectors are so good that you can regulate fuel flow better than with other injectors, thus allowing you to fly lean of peak.  So...... Gami injectors = LOP = save money on fuel.  Without this value proposition, there is no differentiation between his injectors and the OEM equivalent.  George uses beechtalk and its subscribers as a free advertising method to sell his products, and too many members are not getting all of the information, and definitely not all of the facts from him on beechtalk. 

This is a paper that was written by the previous chief engineer at Continental Motors:       

LOP operation has been around since people started setting records with flight duration.  Done properly, there is little risk to engine damage.  When a pilot visits Texas to take George's class on LOP operation, his test engine set up performs the transition from rich to lean flawlessly, probably without ever exposing the engine to detonation and pre-ignition.  The fact is that most of the pilots attempting LOP operation are not so successful.  Here is a piece that suggests, in the last paragraph, that 98% of pilots may not do it correctly: 

Serious damage occurs with detonation.  Here is a fact for you that not too many people think about.  The spark plug is the weakest link in the combustion chamber in an internal combustion engine.  A "canary in a coal mine" of sorts.  When an engine goes into detonation, the ceramic insulator on the spark plug is the most fragile component and may crack due to the shockwave produced at the moment of detonation.  If your plugs are cracking, you have an operational problem and your pistons and cylinders will be next.  I talk to real live A&P mechanics who see the damage everyday, and even go so far as to say that they love LOP operation because it keeps them in business.   
Way back in the 70's, Champion published the premier document in spark plug maintenance and information called the AV-6R.  Here is a copy: 

Cracked core noses are discussed on page 9 of the document.  There are a few causes, but what we see most, as of late, has been caused by detonation.  Cracked core noses are not new at all, nor is the information regarding what causes them.   Most importantly, core nose cracks are not limited to Champion spark plugs.  Any fine wire plug can be cracked with improper operation.  The market just sees 19 cracked Champion plugs to every 1 competitive plug because of our 95% market share. 

Please feel free to call me if you would like any further information on the subject.  I would be delighted to speak with you.  Also, if you are ever flying around South Carolina, I would invite you to tour the only aviation spark plug facility where all of the production is done on site in the United States at one facility.  We can walk you through the manufacturing process from design to packaged products.  It's an honest to goodness invitation and we would love to have you visit. 

I hope this information helps .................kevin 

Kevin Gallagher
CHAMPION AEROSPACE, LLC
Piston & Airframe Manager

[harrispa]

My friend just changed his plugs in a Columbia 400.  4 of the 12 fine wire plugs ceramic was cracked.  See attached jpg of the one with the most damage.  Strange the engine ran fine.  He changed to the massive type.

[N201MKTurbo]

Ya'll can use what ever plugs you like, I don't care. My Champions work just fine and I'm not changing them.

[PTK]

A data point in this discussion.

My engine has been running Champions for just short of 700 hours. 697.1 to be exact. They get cleaned, gapped and rotated at every annual. It runs well deep LOP (typically 90 degrees LOP) with GAMI spread of 0.0 and LOP mag test is excellent. Stock injectors.