Help Me Read These Spark Plugs
Safety Car
Joined: Aug 2011
Posts: 4,454
Likes: 412
From: Portland OR
Isn't it kind of pointless to "read plugs" on anythign but a dedicated drag car? If you make one hit, coast back to the pits, and pull them out, then yes it could tell you a lot of great information. After you DD it at 14.7 and light load, wouldn't the plug be seeing so many varying conditions that it would be unreadable, besides extreme cases?
(These are not rhetorical questions. I am genuinely asking.)
Jack
(These are not rhetorical questions. I am genuinely asking.)
Jack
You are correct for reading plugs when the goal is to find the full load heat range. Can be done on the dyno as well.
Tblu92 is correct too.
That's why I said +/- 1 range from ideal is fine for driving around.
In my car, I've found it likes 12.0-12.2:1 at peak torque (4800-5000).....it's NA.
Didn't get far enough with the tuning to change the power enrichment at peak power which seems to be right around 6300.
I know if we got it too lean at peak torque, I got knock retard.
Of course different combos are different. We are striving to give the engine what it wants, the numbers will fall wherey will.
We are tuning on the dragstrip...so it takes a lot of runs. Just ran out of summer!
Fun topic.
Ron
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
Youre right Ron, every combo is different. My LS3 is making peak torque around 4500-4600rpm, almost 460ftlbs cam only. One of the highest Ive seen for the cam and mods I have. I have to look back at the log to see where the afr is at that rpm but its probably low to mid 12's then leans out to 12.8 up top, shift point is at 6500.
Last edited by C5Natie; Nov 2, 2012 at 02:36 AM.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Isn't it kind of pointless to "read plugs" on anythign but a dedicated drag car? If you make one hit, coast back to the pits, and pull them out, then yes it could tell you a lot of great information. After you DD it at 14.7 and light load, wouldn't the plug be seeing so many varying conditions that it would be unreadable, besides extreme cases?
(These are not rhetorical questions. I am genuinely asking.)
Jack
(These are not rhetorical questions. I am genuinely asking.)
Jack
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
You can still tell from the general conditions of a plug how the car is running though. I guess thats more what I meant when I said "reading" the plugs. Wot is what really matter though, that when you see the most load and when stuff breaks.
Burning Brakes
Joined: Jan 2008
Posts: 941
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From: Grand Rapids MI
Jack
Instructor
Joined: Nov 2011
Posts: 128
Likes: 21
From: Meridian ID
Old school racer here--- Can't really tell by these photos --however this is how I was taught a 100 years ago
1st to read timing on the plug:
You go to the plug strap--and look for-- where the color changes on the strap--very difficult to read old plugs-- best is to use new ones---I like to use NGK plugs as the cadium plating is there to burn off cleanly when 1st ran and it's very easy to see where the color changes-----
Ideally you want the color change to be on the CURVE of the starp
IF the color change is more towards the strap end--Needs more timing
IF the color change goes down towards or into the threads--too much timing
As far a fuel goes (rich/lean) you have to get a magnifying glass and look into the plug's core----
Again very difficult to read with any plug that has been run much
Ideally you would want some color to grow up from the bottom of the core porcelain apprx. 1/16" to 2/16"
More than 2/16" would make it on the RICH side
Less than 1/16" woud make it on the LEAN side
NO color would be VERY LEAN
Fuel additives make the plugs inaccurate to read this way beacuse the additives change the fuel burn
Best is to mix some race gas with premium fuel to raise octane
1st to read timing on the plug:
You go to the plug strap--and look for-- where the color changes on the strap--very difficult to read old plugs-- best is to use new ones---I like to use NGK plugs as the cadium plating is there to burn off cleanly when 1st ran and it's very easy to see where the color changes-----
Ideally you want the color change to be on the CURVE of the starp
IF the color change is more towards the strap end--Needs more timing
IF the color change goes down towards or into the threads--too much timing
As far a fuel goes (rich/lean) you have to get a magnifying glass and look into the plug's core----
Again very difficult to read with any plug that has been run much
Ideally you would want some color to grow up from the bottom of the core porcelain apprx. 1/16" to 2/16"
More than 2/16" would make it on the RICH side
Less than 1/16" woud make it on the LEAN side
NO color would be VERY LEAN
Fuel additives make the plugs inaccurate to read this way beacuse the additives change the fuel burn
Best is to mix some race gas with premium fuel to raise octane
Reading plugs is definitely becoming a lost skill!
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Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Can't see the center electrode down inside to see AFR
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
Could it be that my old spark plugs were ok, heat range wise, but the octane booster that was still in the tank when I first ran the motor turned them orange? And...now the new stock heat range plugs are too hot?
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
That's what I'd say. I always considered a light cinnamon brown color on the center electrode and ground lug to be an indication of proper heat range. Try some new plugs of the heat range you used before, but without any octane booster.
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
Thanks Z. I just ordered some Tr6's at autozone. I'll get them this afternoon. Those are the same heat range as the autolite 103 but ngk seems more popular with LS motors. Hope it helps.
Safety Car
Joined: Aug 2011
Posts: 4,454
Likes: 412
From: Portland OR
It takes a LOT of miles with unleaded fuel to get the light brown/tan color to the porcelan.
My guess is your TR6 will show heat about half way up the ground strap.
I believe the white you see is just the plating burning off.
I switched from the 5 to the 6 in the hope of avoiding KR and being able to run a degree or 2 more timing. Car really didn't care........
My guess is your TR6 will show heat about half way up the ground strap.
I believe the white you see is just the plating burning off.
I switched from the 5 to the 6 in the hope of avoiding KR and being able to run a degree or 2 more timing. Car really didn't care........
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
I started to think it may be the plating burning off as well. Anyway I figured the car ran good all this time with colder plugs so I threw the tr6's on. Im just think of when I go to the track and Im beating on the car with higher temps a cooler plug will help avoid any detonation.
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
Well guys heres what I found....first of all, the whitish color is from the plating on the tip. The nickel coating gives it that color. I hadnt seen that before with my autolites because they have a black coating, not nickel. What I did go off was the color band you can see on the ground strap. With the stock heat range they were close to the base, indicating it was on the hot side. With the ngk tr6's, the mark is now closer to the middle of the strap indicating a proper heat range. I noticed the car idles very well with the ngk's and seems to rev up smoother. Also less exhaust popping on decel. Only thing now is, I did a 3rd gear wot test on the fwy today while data logging. I figured it was warm and if I would see any detonation it would be then. I got no knock and the car felt great BUT the timing at wot was 31.9* when I had tuned it at 28*. Im guessing the ecu sees no knock and is advancing the timing? Iat' were low, 90's*, but I have that table tuned out anyway.
Safety Car
Joined: Aug 2011
Posts: 4,454
Likes: 412
From: Portland OR
How much different between your high and low octane spark tables?
Perhaps before, it was looking more at the low table?
Any time the car see KR, it begins shifting to the low table. It uses a blend depending on how much knock learn it sees. It is odd behavior for sure.
I gave up trying to tune at the dragstrip and made both tables the same, and always make sure to scan runs.
BTW....I saw the exact same behavior on the ground strap between the TR5 and TR6 plugs.
Ron
Perhaps before, it was looking more at the low table?
Any time the car see KR, it begins shifting to the low table. It uses a blend depending on how much knock learn it sees. It is odd behavior for sure.
I gave up trying to tune at the dragstrip and made both tables the same, and always make sure to scan runs.
BTW....I saw the exact same behavior on the ground strap between the TR5 and TR6 plugs.
Ron