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Reading Spark Plug

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Can anyone read this spark plug.

Is it LEAN or Normal ?

I attached the pic of the plug

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Hi I would really like to have a guide how spark plugs must be read in terms of spoting detonation. Including some example pics.

My views on reading spark plugs with modern EFI are probably a little controversial. While I am well aware that it is a valid technique that's been used to good effect in carburettor applications, these days I believe the usefulness is more limited. We now have access to quality wideband air fuel ratio meters and knock detection equipment and this is what I rely on for my tuning. The other aspect that's often overlooked is that in order to read spark plugs and get useful information, you really need to start with a fresh set of plugs and cut the engine at the point you want to read. Most people show a picture of a set of plugs that's done 50,000 km and you really can't get much useful from that.

I personally look at plugs to get an idea of whether my heat range is suitable by looking at how far the earth strap has discoloured, and to check that all cylinders are running evenly - What I'm looking for here is an even colour across the plugs indicating the air fuel ratio but the actual AFR is derived from the wideband sensor.

In terms of detonation, under light detonation you will start to notice small aluminium specks on the ceramic insulator on the plug. More severe detonation will quickly destroy the plug, melting the electrodes and potentially fracturing the ceramic.

Thank you Andre, that's such an information .

actually what made me check the plug is my afr change from lean to rich after i installed 3'' intake pipe with 3'' maf housing

which made the car run really lean . and i was trying to tune it but unfortunately the injectors didn't flow that much. coz it seems i need bigger injectors to match that much of air ..

so after i reinstall the old intake which i used to have it before .. i release my afr change to richer area ( with this intake i my car was lean ) and i dont know why .. so i thought maybe the spark plug. and im still wondering why im afr change ..

Does it usually happened like that ? and what makes the afr change ?

Also does the fuel type change the air fuel ratio ?

Hi Ahmed,

The answers to your questions: [url=https://www.hpacademy.com/courses/efi-tuning/#core-courses]

We usually reply within 12hrs (often sooner)

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