Spark plugs vs Ignition timing
TECH Fanatic
Joined: Jan 2009
Posts: 1,063
Likes: 475
From: Bostwick, GA.
Gas or E85?
What's the AFR set to?
How's is it tracking vs commanded?
Snow white porcelain...
Cut the threads off and look at the fuel ring at the base of the porcelain.
Minimize the anti-seize
What's the AFR set to?
How's is it tracking vs commanded?
Snow white porcelain...
Cut the threads off and look at the fuel ring at the base of the porcelain.
Minimize the anti-seize
Thread Starter
TECH Fanatic
Joined: Jul 2022
Posts: 1,032
Likes: 389
From: Alaska
Thanks Buzzard: I am burning best available Unleaded 90octane
Observed AFR 11.5... Commanded about 11.9. PE is not as accurately responsive as I'd like.
Just started WMI system, adding a trickle of 70% methanol through a 6gph nozzle..
.
.Hopefully: a bunch of experienced old-school tuners will show up here, and we'll have an old fashioned "Here's how we did it back in the old days:" Spark-Plug reading expertise thread.
.
.
edit: The anti-sieze is remnant from long ago, previous owner was " Marine Mechanic " everything around saltwater got antisiezed.
Observed AFR 11.5... Commanded about 11.9. PE is not as accurately responsive as I'd like.
Just started WMI system, adding a trickle of 70% methanol through a 6gph nozzle..
.
.Hopefully: a bunch of experienced old-school tuners will show up here, and we'll have an old fashioned "Here's how we did it back in the old days:" Spark-Plug reading expertise thread.
.
.
edit: The anti-sieze is remnant from long ago, previous owner was " Marine Mechanic " everything around saltwater got antisiezed.
Last edited by Full Power; Jul 18, 2025 at 03:10 PM. Reason: clarity
What motor? Compression? Intercooled? Charge temps?
So like 9lbs of boost and 13* total timing? You aren't even burning the CAD plating off the plug yet. Its super cold. If you are on 70% methanol you can likely run around 25* or more to 4-5lb range. Then taper off to 13* by 20lbs and interpolate between the two for a nice even curve. I drop 1-2* around PK tq on the whole map. Then get a plug read, bump up a degree at a time from there until the plug reads about 1/4 to 1/2 way down strap and cleanly burns off the cad. Can also watch the threads. Shouldn't see heat getting into the 2nd thread ever.
So like 9lbs of boost and 13* total timing? You aren't even burning the CAD plating off the plug yet. Its super cold. If you are on 70% methanol you can likely run around 25* or more to 4-5lb range. Then taper off to 13* by 20lbs and interpolate between the two for a nice even curve. I drop 1-2* around PK tq on the whole map. Then get a plug read, bump up a degree at a time from there until the plug reads about 1/4 to 1/2 way down strap and cleanly burns off the cad. Can also watch the threads. Shouldn't see heat getting into the 2nd thread ever.
Thread Starter
TECH Fanatic
Joined: Jul 2022
Posts: 1,032
Likes: 389
From: Alaska
LM7 maybe 9.4 compression, 208/214 .550" Low-Lift VSR 78/7512 PSI manifold pressure, aftercooled IAT under 110 Fahrenheit
Bottom timing row ends at 1.2 G/Sec cylinder airmass. actual airmass runs 1.4 from 3000 rpm on up. We packing cold air in.
3600- 8 degrees
4000 - 9 degrees
4400 -10 degrees
4800 13 degrees
Tried 11 dgrees down low, and 15 degrees up top for very short time and had 2 to 2.4 KR all over. Had to go "Full Retard"
very poor quality 90 octane unleaded is primary fuel, thus the 70% methanol spray. Progressive controller begins 7PSI max at 14 PSI
Bottom timing row ends at 1.2 G/Sec cylinder airmass. actual airmass runs 1.4 from 3000 rpm on up. We packing cold air in.
3600- 8 degrees
4000 - 9 degrees
4400 -10 degrees
4800 13 degrees
Tried 11 dgrees down low, and 15 degrees up top for very short time and had 2 to 2.4 KR all over. Had to go "Full Retard"
very poor quality 90 octane unleaded is primary fuel, thus the 70% methanol spray. Progressive controller begins 7PSI max at 14 PSI
I misread your post. My fault. I'd leave it as is. I was under the impression you were on 70% methanol and 30% pump gas. Either way those plugs are very cold. (and clean porcelain for pump fuel).
Kinda wonder if its false knock you are seeing. Have anything hard mounted? Engine trans etc? Stock ECU? Either way that's a cold reading plug.
Kinda wonder if its false knock you are seeing. Have anything hard mounted? Engine trans etc? Stock ECU? Either way that's a cold reading plug.
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Thread Starter
TECH Fanatic
Joined: Jul 2022
Posts: 1,032
Likes: 389
From: Alaska
"
Kinda wonder if its false knock you are seeing?"
KR ALL Zeroes, all the way across when I pulled 2 degrees out.
2 degrees KR all over high airmass cells when I tried 11 degrees down low and 15 up top.
pretty sure it's legit KR.
Also, pretty sure our 90 Octane Pump gas is frequently splashed with some bit of 87.... or Jet-A
Fuel quality here is not consistent.
Used to run 10 % Toluene for Early/ initial tuning efforts. Burns clean, adds octane.
Kinda wonder if its false knock you are seeing?"
KR ALL Zeroes, all the way across when I pulled 2 degrees out.
2 degrees KR all over high airmass cells when I tried 11 degrees down low and 15 up top.
pretty sure it's legit KR.
Also, pretty sure our 90 Octane Pump gas is frequently splashed with some bit of 87.... or Jet-A
Fuel quality here is not consistent.
Used to run 10 % Toluene for Early/ initial tuning efforts. Burns clean, adds octane.
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