from
http://forum.ectune.com/viewtopic.php?t=248&postdays=0&postorder=asc&start=0umm... no . .. depending on where you look online, you will get about 10 different ideas when it comes to reading plugs, and they tend to contradict each other. 8s are NOT too cold.. I run 9s in some all motor cars with 12.5:1 + compression. Reading plugs is an art form and it really takes alot of practise.. If you have a plug that is too hot, you can be running 10:1 A/F and the insulator will look clean (which is one of your fuel indicators).. If you have too cold a plug you could be running 14.7:1A/F on top end WOT and your plug could have tons of carbon build up and look like its running to rich.. You have to combine different indicators on the plug to determine
A: Proper Heat range (has to be correctly chosen or reading the plugs are useless) B: Idle Fueling C: WOT Fueling D: Ignition Timing
This is from what I have learned from experimenting
Selecting the proper heat range in most important.. To know if you have the right heat range there are 3 indicators that you must collectivly observe. First is the threads on the plug. You will notice the threading on the plug will have a color change from heat. You must clean the plug with some kinda of solvent to see this properly. Often combustion gasses will sneak past the crush washer and get on the threads and will look like its hotter than it really is, you HAVE to clean it first and look at the color change from heat.. You should have 2-3 threads OR LESS of heat tempered threads.
You also have to look at the insulator.. You can't see it with your naked eye, you need a magnifying glass. Look at the porcelin and see if its smooth and glassy looking. If it is then this indicates that its too hot, OR that your experiencing det, also look down the insulator at the base of the plug you should see a greyish ring that indicates fueling.. If you know your running 12.0:1 A/F and theres just a tiny little fuel ring then your probably too hot, and the plugs self cleaning is burning off your fuel indicator.
Also if the plugs are too hot the ground straps CAN show complete color change.
So you have to kinda combine the info..
If your running a 6 in a N/A car and you have little or no fuel ring, your wideband says 12.8:1 you have 4 threads that are color changed and your ground straps are completely color changed or have color change almost to the threads then your plugs are too hot..
If you have a 8 and you have a thick fuel ring with 1 thread thats got color your running 13.5:1 A/F, then your plug may be too cold.
If your threads are showing a 2-3 color changed range and your fuel ring is tiny but compeltely circles the insulator, your wideband shows 13.5:1, your insulator is not glazed and a good white or light tan color.. THEN you have the correct heat range..
At this point you can use the color indication on your ground straps to determine cylinder temps from ignition.. if you have perfect ignition timing your ground straps should be color about 3/4 the way.. YOU HAVE TO CLEAN THE PLUG FIRST.. Don't mistake deposits as color change. Once you have the proper ehat range you can use the color change indicator on the plugs to determin individual cylinder ignition trims.. Also you can compare fuel ring depths/thickness to determine if you need to trim fuel on a per cylinder basis. These things can be very helpfull in know what your engine is ACTUALLY doing... Just cause your wideband says the fuel is good doesn't mean that its good on all cylinder exactly the same. But if you have the proper heat range plug you can compare indicators between cylinders and trim out fueling and timing.. You may have 1 cylinder thats running too hot and too lean, and because your wideband is the sum of all cylinders, when you tuned it you ended up with 3 over rich cylinders and 1 sightly lean, or vis versus. So by using the plugs you can see which cylinders are lean/rich and trim the fueling.. Then once you get them all the same you can lean out/richen up the over fuel and you'll probably pickup a few extra HP..
Same thing goes for timing. Just cause your sitting at MBT on the dyno doesn't mean that you can't make more power.. If you can read your plugs, you may find a cylinder thats running hotter than the rest. You can back out timing on that cylinder so it matches the others and then at that point you may be able to add more timing over all and pickup another couple HP..
Also I've seen that if your running to hot a plug you can also loose power from mild detonation.. It may not be detectable but it can still rob power. I've had all motor cars making like 195HP with 7s put in an 8 made 200.. Applied individual trims made 205.. Same thing with boost but the returns on power are usually bigger. try it for yourself..
Plugs are also a good tool for tuning at the track.. if you have chosen plugs with the proper heat range, you can make adjustments based on the timing/fuel idicators without having a dyno, datalogging or a wideband..
Key here is YOU MUST HAVE THE PROPER HEAT RANGE, or reading the plugs is useless..
I'm not claiming to be an expert, so use this infomation as a guideline for your own testing. And if you find anything new to add to this let me know cause I'm always looking for new info..
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Topic: Decent how to for Reading plugs (Read 25329 times)