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Reading spark plugs as a tuning aid

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Nice find and thanks for posting it Ray!! I remember quite a few of those pointers, but learned a few "whys" from reading it. I did bookmark it, so thanks again!
 
We do this with the race car at the end of every practice session (races have cool down laps, so the information it would give you could be false). We use an old set of race plugs to warm the car up, and change them before going to the grid. Do a WOT plug chop before entering the pits, and change the plugs back to the warm ups (after getting tire temps/pressures) on pit wall.

This only works with new or relatively new plugs and you must do a WOT throttle chop (run up to near redline, under load, and kill the ignition). Motorcycle and car tuners have been doing this for decades. We also run a wideband A/F guage, but it's only supplementary to reading plugs as it doesn't tell you the full story.

Since I don't come here a lot, I'll add that there is no replacement for dyno tuning. Get your ignition and fueling right on it, and everything else is to maintain that state of tune. Since a properly tuned race motor is on the verge of detonation, plug chops are critical in maintaining peak performance and longevity. You can see detonation on the plugs before you'll ever hear it (you need a magnified plug reader to do it right) Obviously you wouldn't run a street motor with that aggressive of a tune.

Also, unleaded fuels color plugs differently than leaded fuel.
 
Thanks for that. I knew some, but not all of it; proves that you learn something new every day.
 
What I learned today is that I can't understand the expression he uses several times - "too much timimg". Does he really mean "too far advanced" ? I understand "too far advanced" and for this I know what to adjust. For "too much timing" I don't know what to adjust. How do you get "less timing" ?

Any ideas or explanations ?
 
"Too much" would be my guess for advanced as well.

Still a stickler for defining terms here - perfect example of potential problem/disaster... :wink:
 
"Too much timing" is another phrase for "too far advanced". It fires the plug too early creating a lean condition and detonation. Can cause bearing failure too.
 
TFR said:
"Too much timing" is another phrase for "too far advanced".
Click to expand...
:iagree:
 
"Too much timing" as in too many degrees of it.
 
Good timing on my part...


Commonly called a "spark plug viewer", which makes more sense than what I called it :crazyeyes:

Basically it's a smaller magnifying glass with a light built into it. A really good one probably costs in the $40ish range.
 
Monkeywrench said:
Basically it's a smaller magnifying glass with a light built into it. A really good one probably costs in the $40ish range.
Click to expand...
Something like this?

0654684-11.jpg


https://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=948821&PMAKA=505-1936
 
I used to have one of the Champion spark plug viewer it was a CT-456A if I can read the old faded receipt right. I lent it to a friend a decade or so again and haven't seen it since,

You should be able to find something similar from one of the other plug manufacturers if Champion has quit selling it..

Also here is a another site on plug viewing, some of the info may be the same or similar.

https://www.dodgeram.info/Engine-Gas/SparkPlugs/spkplghnbook.html
 
On the 4secondsflat page ther is a section on reading the timing of your engine from the heat mark on the ground strap.
I am aware that timing does affect where this mark appears, however, the article indicates that you have correct timing if the mark is on the elbow of the ground strap, on my '73 TR6 the mark is halfway between the elbow and the threaded body indicating too advanced timing, but that is where the car runs properly. Of course my car is not stock; 100 thou off the head and a TH5 cam.
Isn't the mark just an indication of the cylinder temperatures and wouldn't that be affected by a lot of other things?
 
Refering to some of those sites keep[ in mind the running conditions of the "dragsters" just prior to pulling the plugs. I'm not sure that information is applicable to 35 to 40 year old British sportscars driven on the street.
 
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