What You Need To Know About Spark Plugs For You Car (Lesson 101)

[Dweller]

Lesson 101 for Driver.

 

The spark plug's location exposes it to extreme temperature variations, chemicals, fuels and oils. It is also attacked by cylinder pressures produced by the piston and cam timing, then it is also assaulted by high-output ignition units. As a result of all of this, one can effectively learn what the engine is doing by reading the firing end of the spark plugs.

 

By careful examination of the plug's color, gap, and any deposits that reside on it, you will be shown the efficiencies as well as deficiencies of what is going on in the engine. Spark plugs should be checked at least yearly, and replaced as often as necessary. In most cases you can follow the manufacturers recommendations for replacement intervals.

 

How a Spark Plug Works:

 

The basics of a spark plug is that it must perform two primary functions.

 

To Ignite the Air/Fuel mixture

To REMOVE the heat out of the combustion chamber

 

Spark plugs transmit electrical energy that turns fuel into working energy. A sufficient amount of voltage must be supplied by the ignition system to cause the spark to jump the across the spark plug gap, thus creating what is called Electrical Performance.

 

Additionally, the temperature of the spark plug's firing end must be kept low enough to prevent pre-ignition, but high enough to prevent fouling. This is called Thermal Performance and is determined by the heat range of the spark plug.

 

It is important to understand that spark plugs CANNOT create heat, only remove it! The spark plug works as a heat exchanger, pulling unwanted thermal energy away from the combustion chamber and transferring the heat to the engine's cooling system. The heat range is defined as a plug's ability to dissipate heat.

 

The rate of heat is determined by:

 

The insulator nose length

Gas volume around the insulator nose

Materials and/or construction of the center electrode and porcelain insulator

 

Now to the actual function:

 

As the Ignition is triggered it sends the spark through the rotor, to the cap, down the wire and then it jumps the gap of the spark plug, a spark kernel is created that ignites the air/fuel mixture in the combustion chamber. Proper timing of this spark is not the only concern as described above. You must have the proper heat range as well as the correct gap.

 

Opening The Plug Gap:

 

On weaker or stock ignitions, opening up the gap CAN increase the spark kernel size, thereby creating a more efficient burn. The problem lies in that any added gap creates more strain on the other ignition parts.

 

Coils may not have enough stored energy to fire, or in the least case, not enough energy to cross the gap, creating a miss-fire.

Plug wires will break down due to the added resistance as the spark tries to reach ground.

Rotor and Cap, as well as points (if you still have an interest in prehistoric ignitions), and the carbon bushing in the center of the distributor cap will show early failures.

 

All of this is because the greater the gap and the higher the voltage requirement to jump the gap. Do not forget the gap between the rotor arm to the distributor cap too. A high performance rotor is a bit longer at the tip, allowing less spark loss or chance of spark scatter in the cap as the spark attempts to jump the plug gap.

 

It is also possible to slow down a car if the gap is too big.

 

Spark Plug Heat Range:

 

A spark plug's heat range has no relationship on the actual voltage transferred through the spark plug. Rather, the heat range is a measure of the spark plug's ability to remove heat from the combustion chamber.

 

The heat range measurement is determined by several factors:

 

The length of the ceramic center insulator nose

The insulator nose's ability to absorb and transfer combustion heat

The material composition of the insulator

The material composition of the center electrode

 

The longer the insulator nose gives you a larger surface area exposed to combustion gasses and heat is dissipated slowly. This also means the firing end heats up more quickly. We are talking about exposed ceramic length, not extended tip length.

 

The insulator nose length is the distance from the firing tip of the insulator to the point where the insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling.The spark plug tip temperature must remain between 450

Edited June 22, 2006 by Dweller

[Genie47]

May I add more. Type of fuel also determines the plug's heat rating. CNG and LPG will need colder plugs. No cooling effect like petrol plus higher AFR compared to petrol.

[Punkpun]

great knowledge.

 

 

thanks Genie ,

[Songbk]

I was asked to change my car spark plug -denso iridium by Richburg Service Center for my Estima when my mileage reached 60,000 km. When I revisited for regular servicing at 80,000- again I was asked to change and during this time I highlighted this to the new service manager that I had changes recently. She checked the system and confirmed not to change.

 

Today, 13 th Aug 2011, I came again for 90,000 servicing, again a newly service manager asked me to change as the technician recommendation to change as the tip is carbonized. I told the service manager that I had googled the web that most of the iridium spark plug can last till 100,000 km. She told the technician to show me the spark plug. I told her put it back.

 

I am suspecting that the service center has too much stock or to have clearance or have some sprk plug target to hit. They are charging S$30x4 plus labour $30 on top of my servicing package.

 

Can someone here advice me how to determine is time to change the spark plug. I goggled and found out that many indication such as misfire, high fuel or under power and bla bla.

[Good-Carbuyer]

I was asked to change my car spark plug -denso iridium by Richburg Service Center for my Estima when my mileage reached 60,000 km. When I revisited for regular servicing at 80,000- again I was asked to change and during this time I highlighted this to the new service manager that I had changes recently. She checked the system and confirmed not to change.

 

Today, 13 th Aug 2011, I came again for 90,000 servicing, again a newly service manager asked me to change as the technician recommendation to change as the tip is carbonized. I told the service manager that I had googled the web that most of the iridium spark plug can last till 100,000 km. She told the technician to show me the spark plug. I told her put it back.

 

I am suspecting that the service center has too much stock or to have clearance or have some sprk plug target to hit. They are charging S$30x4 plus labour $30 on top of my servicing package.

 

Can someone here advice me how to determine is time to change the spark plug. I goggled and found out that many indication such as misfire, high fuel or under power and bla bla.

2 spark plugs rusted and stuck druing 40k km servicing. They broke into two (centre electrode and ceramic insulator apart) during extraction.

I believe most copper electrode spark plugs can last beyond 50k km.

[Vinceng]

Usually I change my normal copper spark plus at every 10,000km servicing every 12 months.

 

Can I stretch the replacement to once every 20,000km or 24 months?

 

I travel only 10,000km a year.

[Kangadrool]

Usually I change my normal copper spark plus at every 10,000km servicing every 12 months.

 

Can I stretch the replacement to once every 20,000km or 24 months?

 

I travel only 10,000km a year.

No problem for a car. In fact, 10K is a waste. Change every 20-30K for copper. For motorbikes, you change at 10K interval.

[Pisces69]

I was asked to change my car spark plug -denso iridium by Richburg Service Center for my Estima when my mileage reached 60,000 km. When I revisited for regular servicing at 80,000- again I was asked to change and during this time I highlighted this to the new service manager that I had changes recently. She checked the system and confirmed not to change.

 

Today, 13 th Aug 2011, I came again for 90,000 servicing, again a newly service manager asked me to change as the technician recommendation to change as the tip is carbonized. I told the service manager that I had googled the web that most of the iridium spark plug can last till 100,000 km. She told the technician to show me the spark plug. I told her put it back.

 

I am suspecting that the service center has too much stock or to have clearance or have some sprk plug target to hit. They are charging S$30x4 plus labour $30 on top of my servicing package.

 

Can someone here advice me how to determine is time to change the spark plug. I goggled and found out that many indication such as misfire, high fuel or under power and bla bla.

 

The ws earns much more with those iridium etc plugs. Cost of plugs plus labour to change.

 

Those long life plugs r usually used in engines where its very difficult to reach the plugs to change so long life makes sense as u dun have to change so often.

 

Otherwise just use the normal copper plugs n change every 20K km or as recommended in yr handbook. Copper plugs r very cheap (abt$3 ea) n its always better to change a fresh set more often than have a long life plug sitting in the engine for 100K km.

 

I suggest u go back to the correct type of copper plugs n change every 20K km for a smoother engine.

Usually I change my normal copper spark plus at every 10,000km servicing every 12 months.

 

Can I stretch the replacement to once every 20,000km or 24 months?

 

I travel only 10,000km a year.

 

Most cars recommend change copper plugs every 20K km.

 

It sud b ok but if u find the plugs badly rusted after 2 years, then maybe u sud change every year.

 

I change my copper plugs every 20K km n thats abt 1.5 years, without any problems.

[Fuelsaver]

hi bros / sis, can comment on below sparkies pix, as i'm unsure how to interpret engine condition / combustion -

 

 

 

TIA.

[Pisces69]

hi bros / sis, can comment on below sparkies pix, as i'm unsure how to interpret engine condition / combustion -

 

P1000771.JPG

 

P1000772.JPG

 

TIA.

 

 

I cant see the pix u posted but general rule when inspecting yr plugs.

 

Electrode tips sud not b worn down. Might b wrong heat range n plugs getting too hot.

 

Tips sud have a nice tan coating. AF mix is good.

 

Tips black n sooty cud b AF mix too rich or burning oil cos piston rings worn.

 

Plugs can tell quite a lot abt yr engine. I always inspect my old plugs when put new ones in.

 

Oh OK now I see the pics.

 

Top pic looks slightly sooty. U need to take yr car for a Italian tune-up.

 

Bottom pics looks OK. But some grey deposits on the plug? What fuel u use? Caltex?

 

Both pics plugs look OK lah. No real issues.

[Fuelsaver]

 

 

I cant see the pix u posted but general rule when inspecting yr plugs.

 

Electrode tips sud not b worn down. Might b wrong heat range n plugs getting too hot.

 

Tips sud have a nice tan coating. AF mix is good.

 

Tips black n sooty cud b AF mix too rich or burning oil cos piston rings worn.

 

Plugs can tell quite a lot abt yr engine. I always inspect my old plugs when put new ones in.

 

Oh OK now I see the pics.

 

Top pic looks slightly sooty. U need to take yr car for a Italian tune-up.

 

Bottom pics looks OK. But some grey deposits on the plug? What fuel u use? Caltex?

 

Both pics plugs look OK lah. No real issues.

bro, appreciate ur feedback; i guess was probably due to start-stop driving, hence 2 plugs kinda soot deposits. but strangely other 2 looked ok. i use esso 5000, RON 95 equivalent. at times may smell ammonia - dunno was cat or fuel issue. but since no issue, just continue pumping. maybe should pump v-power once in a while.

 

btw, read up sparkie topic oso. one article mentioned if only 1 or 2 with carbon deposit, check ignition cable for wear / crack. but since i changed to bosch plugs during last weekend car clinic, car felt smoother at speeds in excess of 110kph, compared to prev ngk one.

 

what u mean by italian tune up? very cheem to me.

Edited May 27, 2014 by Fuelsaver

[Pisces69]

bro, appreciate ur feedback; i guess was probably due to start-stop driving, hence 2 plugs kinda soot deposits. but strangely other 2 looked ok. i use esso 5000, RON 95 equivalent. at times may smell ammonia - dunno was cat or fuel issue. but since no issue, just continue pumping. maybe should pump v-power once in a while.

 

btw, read up sparkie topic oso. one article mentioned if only 1 or 2 with carbon deposit, check ignition cable for wear / crack. but since i changed to bosch plugs during last weekend car clinic, car felt smoother at speeds in excess of 110kph, compared to prev ngk one.

 

what u mean by italian tune up? very cheem to me.

 

 

Yes good tip.

 

Italian tune-up= Drive at high rev near to red line for a short distance when engine is fully warmed up . This wil help to blow out carbon in the engine(pistons n valves) n makes for a smoother ride after. Engine sud feel more perky after this. In SG one main reason of carbon build-up is like u said. Stop-start driving n short trips only.

[Fuelsaver]

 

 

Yes good tip.

 

Italian tune-up= Drive at high rev near to red line for a short distance when engine is fully warmed up . This wil help to blow out carbon in the engine(pistons n valves) n makes for a smoother ride after. Engine sud feel more perky after this. In SG one main reason of carbon build-up is like u said. Stop-start driving n short trips only.

i c i c, tks bro. nvr near redline - only 4-5k rpm at most occasionally.

[Fuelsaver]

Upz for awareness. Now I know how carbon fouled plug looked like -

 

http://www.mycarforum.com/topic/2689846-copper-spark-plug-40k-km-usage/?p=4927692

 

Bro octopus, don't mind me sharing ur post.

Edited May 28, 2014 by Fuelsaver

[Fuelsaver]

Edited May 28, 2014 by Fuelsaver