Using Spark Plug colors to tune...?

[teh_mugen18]

I know that when an engine is running ~perfect air-fuel ratio, the spark plugs tend to look like a brownish, coffee-color or a greyish-tan color, but what does it mean when the spark plugs are just GREY. Not white, just grey...:???:

I know that white spark plugs mean the engine is running too lean, and black/sooty ones mean the engine is running too rich, but im not sure about grey... I can post pics if anyone needs to see what im talking about

[Vteckidd]

No offense but i highly doubt you can look at a plug and know what it means. It really is a lost art. There is tons of misconceptions of what to look for.

http://www.ngksparkplugs.com/techinfo/spark_plugs/faq/faqread2.asp
http://www.corvetteactioncenter.com/forums/general-automotive-discussion/19739-what-its-worth-smokeys-outlook-spark-plugs.html

Smokey Yunick has written some good things on how to read plugs.

But for you, you cant use it to TUNE a car, a wideband is much more efficient

[SuperChicken]

It is much harder to read spark plugs when using unleaded gas. Leaded allowed for easy color judgments to be made, but a proper burn using unleaded is going to be gray or white. Also, unless you do a proper plug chop (WOT in third, then cut ignition), you are not getting a 'true' reading anyway, even on leaded or race fuel. Basic around town driving is too variable to allow proper readings of the plugs.

[teh_mugen18]

Leaded allowed for easy color judgments to be made, but a proper burn using unleaded is going to be gray or white. .


So, i guess that means that its not running "lean", thats what i understood from that. right?

EDIT: I based this entire thread on the back of the Haynes manual, lol, where it shows all the different "running conditions" of the engine

[Init2winit]

I know that when an engine is running ~perfect air-fuel ratio, the spark plugs tend to look like a brownish, coffee-color or a greyish-tan color, but what does it mean when the spark plugs are just GREY. Not white, just grey...:???:

I know that white spark plugs mean the engine is running too lean, and black/sooty ones mean the engine is running too rich, but im not sure about grey... I can post pics if anyone needs to see what im talking aboutFor driveability tuning, you can't read spark plugs due to the fact that the only accurate reading will be from a wot shut off, under a load. The only way you can take advantage of reading plugs, is if you have a power adder, and make wot pulls so you can see where the timing needs to be and what the fuel is doing.

[SuperChicken]

So, i guess that means that its not running "lean", thats what i understood from that. right?

EDIT: I based this entire thread on the back of the Haynes manual, lol, where it shows all the different "running conditions" of the engine

Yes, that's what it means.:goodjob: And read the other replies, 'cause they pretty much echo what I said.

[Big Baller]

I've seen guys check plugs on cars on the dyno but they usually make a full pull and shut the car off they don't even let it cool down. Its a huge pain in the ass so why bother.

[teh_mugen18]

Its a huge pain in the ass so why bother.

Lol not running so lean as to blow-up an engine is a good reason i think :rolleyes:

[Big Baller]

Lol not running so lean as to blow-up an engine is a good reason i think :rolleyes:

Quit being a fucking cheap ass and buy a wideband, the only thing you can tell from plugs is how rich it was when you stop the pull, you have no idea how lean it is in different load zones....you sound like someone should be tuning your car....besides you.

[green91]

Quit being a fucking cheap ass and buy a wideband, the only thing you can tell from plugs is how rich it was when you stop the pull, you have no idea how lean it is in different load zones....you sound like someone should be tuning your car....besides you.

x2

my thoughts exactly LOL.

[Init2winit]

Quit being a fucking cheap ass and buy a wideband, the only thing you can tell from plugs is how rich it was when you stop the pull, you have no idea how lean it is in different load zones....you sound like someone should be tuning your car....besides you.A wide band doesn't tell you if you have too much timing. Optimal a/f ratio for different engines will not be the same either. A wide band is only good for driveability tuning, and is not an accurate way of tuning an engine with a power adder. Being "lean" is the last thing you need to worry about. Too much timing is what kills engines.

[green91]

To much time and to little fuel both share the same consequences though. You can't read detonation very easily from a spark plug either unless its destroying the electrode or insulation, so its fair to say that the OP was asking about tuning fuel by reading plug color.