reading sparkplugs - tell me what u think

[Disturbed1]

went out road tuning last night with innovate lm1 o2 datalogger.

motor is a 7mgte with plenty of supporting mods running an aftermarket ems 8860 ecu

was tuning mainly wot keeping to around 11.6:1 ratios when on boost (8 psi) but after approx 6000 rpm the afrs drops to around 11.3 afr (sensor located on dump about 150mm away from turbo)

i seem to experience a slight missfire every now and then up top however without havign a tacho installed - im not exactly sure when it is - guessign around 6500 rpm. i have the soft limiter set at 6800 and the hard limiter at 7000.

anyway, after a few half hart pulls approaching house, i let the car cool before i removed the plugs for inspection... and this is what i got





so feel free to give your take on what u see.

BTW - is on 17 degrees timing whilst on full boost

[willwal98]

Leaking injectors or bad spark on 4 and 6?
2 and 5 almost look too lean, they all should have a bit of a bronzy colour on the intake side.

This site looks pretty good for a description, never heard of the timing indication part.
http://www.usaimports.co.uk/Mopar_Te...ug_Reading.htm

Here is a pic from what looks like an old haynes manual

[Admiral coFF33]

looks exactly like my 1J plugs after a track adventure

[abently]

Did you cut ignition at 6000rpm ? Or did you cut it at idle to then read plugs ? Always good to get your injectors tested... but you have to remember that very little OEM Intake manifolds flow the same from runner to runner, which is why cylinder specific tuning is important.

[Disturbed1]

my custom ffim prob doesnt either

cut the revs at idle also - wouldnt go turning ooff motor after several 7000 rpm pulls with thrust bearing turbo

[abently]

Setup an egt/or AFR bung on the lean cylinders and then take it from there.

[Turdinator]

my custom ffim prob doesnt either

cut the revs at idle also - wouldnt go turning ooff motor after several 7000 rpm pulls with thrust bearing turbo

Then the pics of your plugs are really only showing us how things are running at idle...

[The Real Roadrunner]

they aren't telling you anything actually, the only way to read the plug properly is to cut off the thread and see what the insulator looks like where it meets the steel sleeve.

different heat range plugs will give different insulator colour as will the amount of load placed on the engine.

different chemicals in fuels will also give different colours etc.

cheers
linden

[amichie]

Can you just have all your injectors cleaned and tested then you can rely on your wideband for tuning?

[slow laser]

+1 to roadrunner


You have to get a light and a magnifying glass, or cut the thread off and read the smoke (or soot) ring, and the colouration of the ceramic.

You also need a close up pick of the electrode to determine the timing also.... should be able to see the line on it and adjust the timing accordingly.... (which looking at the few that you can see the timing line on, you could add ~2 degrees or so imo.)

[jeffro ra28]

There are really only 2 things a plug can tell you despite what many people will say. The discoloration of the ground strap tells you how ignition timing is and the heat ring on the porcelain how the fuel mixtures are.

Because of the massive variety of chemicals in different fuels the old "tan" look doesnt mean much.