Plug colour reading

[Draven]

I've heard rumours that when using unleaded fuel, trying to "read" plug colours is basically useless. Can anyone confirm/deny?

And more importantly, what does a whitish/grey tip on the plug mean (after several full power runs, and maybe 150kms of driving)

[oldcorollas]

the colour comes from the additives...
supposedly, with lower metal content fuel, you can tell if it is rich or not.. or if the plug is getting too hot/detonation etc...

clean like that just means not rich could be lean?

perhaps more importantly, plugs should all be the same colour....

also, reading plugs required you to shut engine off immediately, or else idling/engine slowing would change the colour anyway?

[Ben Wilson]

I've heard rumours that when using unleaded fuel, trying to "read" plug colours is basically useless. Can anyone confirm/deny?

I've heard this, but the plugs in my Halteched (is that a word?) 20v used to come out the classic tan colour.

[YLD-16L]

the plugs in my Halteched (is that a word?) 20v used to come out the classic tan colour.

The plugs in my 4AGTE always come out the same tan/light brown colour. As olcorollas said too I always compare the plugs across cylinders for consistency in colour.

Some useful links that analyse different parts of the plug to read what is going on in the cylinder:

http://www.dragstuff.com/techarticle...ark-plugs.html

Another good link with pics:

http://www.4secondsflat.com/Spark_plug_reading.html

A lot of good info on reading spark plugs comes from the drag scene.

[Draven]

they're all the same

[clubagreenie]

Leaded fuel definately gives different colors to unleaded, which I've always found to unremarkably the same. (different from car to car but always the same for the given car). Champion used to have a chart for it, might be an online version available.

Checking...

[clubagreenie]

Champion USA

http://www.federal-mogul.com/afterma...ml?Country=USA

Not champion USA but useful links and info

http://www.championsparkplugs.com/sparkplug411.asp

[thechuckster]

if the motor was running lean or hot, you'd have depositions on the porcelain insulator.

the grey colour on the earth tip is a a good sign - clean porcelain i have no idea. it should have a light-brown/light-grey tinge.

[Draven]

they've been in there for less than a week, so maybe no chance for the porcelin to colour yet

[cambelt]

There not for the 2j are they , single earth electrode .

[Draven]

yep, were all I had around for a quick fix. new ones tomorrow.

[cambelt]

Well thats ok then , spose it only takes 20 min 2 change them
Dave

[Draven]

20?
pft, I've got it down to a fine art!
just hunting the cause of my pinging atm - hence the deformed plug on the left

[oldcorollas]

sticky injector?

[Draven]

I'm not thinking so stu.. so far cyls 4 & 5 have leaned out, so I'm thinking it's more likely to me FPR, fuel filter, etc.
I'm testing the sequential system at the moment, then I'll start replacing various parts of the fuel system (to handle a gt35/40 of course)