Spark plugs - hot & cold - now with pictures of my plugs for diagnosis (please)

[anthonym]

Do I understand this correctly?

 

Plugs must be designed to burn off deposits that build up on the plug.

 

Plugs have a ceramic insert to insulate the electrical charge from the metal body while on it's way to the tip.

 

The more ceramic touches the metal body the hotter the ceramic gets and

the less ceramic touches the metal body, the cooler it will be.

 

 

A HOT plug has a ceramic insert that has a SMALLER contact area with the metal part of the plug.

so the plug has to get hotter before the ceramic gets hot enough for a given degree of deposit burn off.

 

 

A COLD plug has a ceramic insert that has a LARGER contact area with the metal part of the plug.

so the plug can be cooler before the ceramic gets hot enough for a given degree of deposit burn off.

 

In both cases the temperature at which deposit burn off occurs is the same, the difference is how much heat has to be generated before the ceramic gets hot enough to do its job of burning off deposits.

 

Begs the question:

Why not put cold plugs into engines that run very hot? As such the ceramic itself gets very very hot,

 

Answer:

If the ceramic gets too hot, it could ignite the fuel before the spark fires.

 

So it's all about the ceramic's temperature, not the temperature at the tip of the plug which is what I have always assumed.

 

Anthony

 

I used this for reference: http://auto.howstuffworks.com/ignition-system2.htm

 

Edited by - anthonym on 4 Sep 2009 18:06:43 😬

 

Edited by - anthonym on 4 Sep 2009 19:55:46

[anthonym]

oh, and my R500 NGK BCPR7ES plugs are not burning off their deposits, suggesting I am not running the engine hot enough.. or at least periods of slow running allow build up that doesn't then get burnt off.

 

So if I installed slightly cooler plugs for my non track use, would I get the ignition problem? Is that (btw) "pre-ignition"?

 

It does seem to me I consistently not running the thing as hot as is intended.

 

Edited by - anthonym on 4 Sep 2009 18:02:36

[anthonym]

yes I know I'm talking to myself 😬

[Jorgen]

You can only judge if your spark plug is the right by looking at it if you are sure the the fule mixture is right. Otherwise deposits could be from to rich a mixture

 

[anthonym]

yes I'm sure the fuel mixture is right so here is what they look like, these are from the front of the engine first two = No 1 Third one is No 4 and last two are No2. I cannot get No 3 out, too tight. Working on it. pictures here

 

any thoughts?

[F355GTS]

Look OK, maybe the mixtures a tad weak

 

Mark

[CageyH]

Yep,

 

Plugs look like they are overheating, either due to the wrong heat plug or running lean (as Mark says).

 

Only dead fish go with the flow....!

[anthonym]

I dare not guess whether that means use a hotter or colder plug..

The heat range must be carefully selected for proper spark plug thermal performance. If the heat range is not optimal, then serious trouble can be the result. The optimal firing end temperature is approximately between 500°C (932°F) and 800°C (1472°F).

The two most common causes of spark plug problems are carbon fouling (< 450°C) and overheating (> 800°C).

---

 

so if I am using a 7 I could try a 6.

 

Having said that ambient temps are no longer in the thirties. The engine just gets hotter and hotter and hotter until I stop, and this is hour after hour of driving, often high revs and under 42mph (airflow not enough)

 

"high revs" = revs at which the engine oil temp rises cosntantly

 

http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp?mode=nml

 

Causes of Overheating:

 

* Spark plug heat range too hot

* Insufficient tightening torque and/or no gasket

* Over-advanced ignition timing

* Fuel octane rating too low (knock is present)

* Excessively lean air-fuel mixture

* Excessive combustion chamber deposits

 

* Continuous driving under excessively heavy load

* Insufficient engine cooling or lubrication

 

---

 

those last two..as above, Not enough revs, running too hot.

Plus due to the nature

of the engine spec. it does respond to higher rpm.therefore a more

progressive throttle application around town will be required. Do not labour

the engine.

---

 

strongly advise that you do not labour the engine and the

engine will best perform from higher rpm thresholds in lower gears, i.e. it

will be better to be in second gear at 5000 revs than in third gear at 3000

revs.

---

 

and there it is: guilty, third gear at 3000 instead of 2nd gear at 5,000

 

it's because of the noise; so maybe I should change my ear plugs and not my spark plugs - as I know when ear plugged, I drive more noisily, meaning higher revs, lower gear.

 

 

Edited by - anthonym on 4 Sep 2009 21:58:07

[Rob Walker]

If you want to try a higher heat range/harder plug then the the next one would be NGK BCPR 8ES not 6ES. Your plugs look OK to me, the electrode and ceramic insulator have a light grey deposit and show no signs of blistering or the sharp edges of the electrode burning off. Rather than guess how your engine is running throught the rev range the only sure way is to put it on a rolling road under load and have the air/fuel ratio measured throught the rev range, then you will know for sure that all is hunky dory.

 

Rob

[anthonym]

from what I have read, NGK plugs get hotter the lower the number. http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp?mode=nml

 

as regards the rolling road, it has just come off one (say a thousand miles ago).

 

The problems I am having relate to low speed /revs running when then flooring it suddenly, nothing happens, it's as if someone took all the plugs out(!) but gentle application of accelerator does allow progress and increasing amounts of accelerator gradually "clear" the problem. I say "clear" in quotes because the problem going away may not be the same as cleaning surplus matter from the plugs by attaining the burn off temperature of 450 deg c.

 

Now I have to think about what I have just written.

 

 

 

Edited by - anthonym on 5 Sep 2009 10:43:30

[anthonym]

so I have two saying they are running too hot / lean and one saying they look ok?

 

hmmm (I do prefer the "look ok" and having found some examples of plugs that look ok I wonder why they might look too heated? )

 

does it depend which plug you look at?

 

pictures here

 

 

 

Edited by - anthonym on 5 Sep 2009 10:47:38

[CageyH]

Looking at a picture of a plug is different than looking at a plug.

It is hard to work out exactly what is happening.

 

If you are putting your foot down and nothing is happening, I would look somewhere else other than the plugs. What ECU are you running? Is your accelerator fuelling ok?

 

Only dead fish go with the flow....!

[anthonym]

IT happens only after a period of slow running, such as in traffic, then some activity will clear the problem, hence my thinking it's plugs not being hot enough to clear the gunge

[Mickrick]

As Cagey says, it's difficult to tell from a photo. But I would say they look on the lean side.

I like my plugs to have a light brown colour.

I also do a "plug chop" Run the car at higher revs, then kill the engine. Then take out the plugs to check colour.

Could be ignition timing.

Only sure way is to put it on the RR.

 

 

[anthonym]

I have to do without the RR (luxury) for the time being

[Rob Walker]

I can well understand your confusion about hotter or colder plugs. You are getting mixed up between a plug running hotter and a plug that will run correctly or be suited to running at a higher temperature, they are opposite. What you have read is correct if you go down to a 6 the plug will run much hotter on its electrode and may damage your engine due to pre ignition. A 6 is rated as a stock plug heat range for a K engine and not an R500 with a high compression ratio.

 

Sounds like you have a flat spot and I doubt it will be the spark plugs causing the problem if BCPR 7ES are fitted .

[anthonym]

as long as I have been thrashing it (in my terms not the engine's) there's no flat spot, just wonderful never ending acceleration thrust 😬 😬

[anthonym]

flat spot....... I'm thinking

[Rob Walker]

I also wanted to add that if you want to try a change of plug then go up to an 8 , you won`t do any harm going to a harder plug it will simply foul or be hard to start if its too hard ( cooler).

 

Rob

[anthonym]

having reflected a bit I'm leaning to the idea that it's as simple as an R500 engine is not designed to go slowly and when it does, it clogs up a bit because the plug design is chosen to achieve 450c at higher operating temperatures, all part of the compromise choices for the particular engine - so it won't preignite on the track it may clog up a bit "round town" (meaning when going more slowly for any extended period). Minister do make it crystal clear that 5000 is to be preferred to 3000.

 

Edited by - anthonym on 6 Sep 2009 13:10:28

 

perhaps better I re-focus on ear plugs.

 

Edited by - anthonym on 6 Sep 2009 13:11:11

[anthonym]

reading book, Dave Walker Engine Management, ch 2, he comments that

"Fact Four: Precious metal plugs like platinum or iridium offer increased efficiency because the electrodes can be thinner and the gaps larger. This can reduce misfires and improve starting with cold/fouled spark plugs and rich mixtures. ......"

 

So if "improve starting" can be extrapolated to mean "improve firing fouled plugs" perhaps I could have a look at this possibility? Meaning precious metal plugs to match spec of NGK BCPR7ES, so same preignition and burn off characteristics (i.e. same temp ranges) with added MAYBE improved ability to spark when fouled?