This is an interesting article about reading spark plugs and in particular helping to set ignition timing through the rev. range:
http://www.4secondsflat.com/Spark_plug_reading.html

awesome article! in this week I ll remove my denso iq20 spark plugs after 15.000 kms. The motor is rebuilded.I will upload photos and we can discuss the condition of these plugs.Now I will use the original spark plus q20r-u11 cause in a year I do not travel more than 5.000 kms with the corolla gti.

today i removed after 15.000 kilometers of my rebuilded 4age 16v engine the denso iridium iq20, lets see what we have:

denso iridium iq20 just removed

are these in good condition for 15.000 kilometers?

Here is a better article on spark plugs...

http://www.max-boost.co.uk/max-boost/internet_articles/Spark%20Plug%20Reading.htm

Your plugs look perfectly fine for a car that is used for everyday driving. What you
need to understand is that during everyday driving, the engine runs under a wide
range of different load conditions. Therefore, plug condition will not be a good guide
as to the state of tune.

If you want to tune by plug condition (as mentioned in the article) you can really only
check the WOT tune by doing a "plug chop". On the road (under safe conditions) this
would mean installing fresh plugs, finding a nice long straight uphill gradient, and doing
a WOT run in (say) 4th gear. De-clutch, turn the ignition off (being careful not to lock
the steering !!!) and knock the engine out of gear while you coast to a stop.

Doing this on a dyno would definitely be the better option. And it is really only worth
doing on a race engine. For Joe Average a light tan insulator is good, white will be on
the lean side, and black rich. Even this will depend on what kind of use your vehicle
gets, as freeway running will show a lighter colour than suburban shopping trips.

Cheers... jondee86

Or you buy a wideband and other monitoring tools.
These days reading spark plugs is a very antiquated method of doing things. There are much better tools that are more accurate and easier to use.
On top of that with modern EFI it's irrelevant unless you have a motor modified too far outside the stock parameters for the ECU to be able to compensate. In which case you will be so much better off using a wideband.
Your motor could run lean at 3500 RPM and be running way too rich by 5000 RPM. To test this not only would you have to do a plug chop as jondee86 suggests but you would have to do one for every 500 RPM or so just to get a rough idea of how the motor behaved across the spectrum. Even then I don't trust reading plugs nearly as infallibly as the person that posted that. It looks like they have some serious real world experience to back up their theories and I am sure it would be your best option 30 years ago but not anymore.

Also, our cars, for the most part, aren't carbureted, and if you don't have some aftermarket engine management, there is little, if any adjustment you could make.

good morning guys!
I am not trying to tune my engine from the spark plugs condition. I want a confirmation about the condiition of the spark plugs cause my engine was rebuilded about 15.000 kimometers before ! thank you

It's not necessarily about air fuel ratios.
Setting ignition timing from the spark plugs looks interesting and I'm going to give it a try sometime, det cans ready tho' !

do you mean increace the spark advance above 10 ?

Zissou wrote:Also, our cars, for the most part, aren't carbureted, and if you don't have some aftermarket engine management, there is little, if any adjustment you could make.

There is a ton of adjustment you can make but it's not necessary unless you are drastically changing the VE from stock. If so then you should have a wideband to monitor those changes.

apsogosGTi wrote:good morning guys!
I am not trying to tune my engine from the spark plugs condition. I want a confirmation about the condiition of the spark plugs cause my engine was rebuilded about 15.000 kimometers before ! thank you

The tips look good to me but you sure have a lot of oil on your threads for a freshly rebuilt motor. Are your valve cover gaskets leaking?

totta crolla wrote:It's not necessarily about air fuel ratios.
Setting ignition timing from the spark plugs looks interesting and I'm going to give it a try sometime, det cans ready tho' !

See but once again you have a monitoring system in place. Even then you would have to confirm on a dyno that you had actually optimized your timing. In which case you might as well just use the dyno and advance the timing till you stop making power.
On a fairly stock engine that's going to be pretty close to stock timing so not really worth it. On a well built performance engine it should be right around where you start to knock so the detcan would be more important.
You also have to remember that AFRs, timing and other cylinder conditions will effect combustion temps and other things that will change the appearance of a spark plug.

apsogosGTi wrote:do you mean increace the spark advance above 10 ?

If your car is pretty stock then you should just use the stock timing.
If your car is modified then you should have the right monitoring equipment before tampering with the timing.