Spark Plugs & AFR changes

NoDOHC · 03-01-2011, 10:59 PM

So the hotter type plug does a worse job. Interesting... I will have to think about why this might be.

For clarification:
Were you running Water injection?
Was this completely under boost, or did it exhibit the same behavior under vacuum/idle?

I have seen mileage improve by changing heat ranges, but I thought I went to a hotter plug to improve the economy. I apologize - unlike your awesome data acquisition systems, I have to rely on my ever-more-sketchy memory.

I will think about what would cause this and post again if I can think of something.

RICE RACING · 03-02-2011, 12:00 AM

On my system when I have checked it the hotter plug seems to be burning better (not misfiring as much).

In the small scale stuff you can run an engine much richer on a hotter plug v's a cold plug (cold plug needs to be set leaner) to stop misfiring....

Anyway its an interesting thing I noted, am repeating experiment with full CDI ignition system and see what that shows.

j9fd3s · 03-31-2011, 04:21 PM

interesting. since fuel and air volume are close enough to the same, does that mean a richer AFR = more complete combustion, or is it the other way around?

ive noticed differences too, i'm currently playing with a 12A PP with a 48IDA, and i've tried a few different plugs in the "tuning the carb" phase.

in the idle/low speed range the rx8 plugs actually wanted more fuel than the autolites.

the W/b on a p port is kind of a slippery slope, its on there...

RICE RACING · 04-01-2011, 08:06 PM

Quote:

Originally Posted by j9fd3s

interesting. since fuel and air volume are close enough to the same, does that mean a richer AFR = more complete combustion, or is it the other way around?

ive noticed differences too, i'm currently playing with a 12A PP with a 48IDA, and i've tried a few different plugs in the "tuning the carb" phase.

in the idle/low speed range the rx8 plugs actually wanted more fuel than the autolites.

the W/b on a p port is kind of a slippery slope, its on there...

Yep, it's common. Surprised more people don't notice this.

03-01-2011, 10:59 PM	#1
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 18	So the hotter type plug does a worse job. Interesting... I will have to think about why this might be. For clarification: Were you running Water injection? Was this completely under boost, or did it exhibit the same behavior under vacuum/idle? I have seen mileage improve by changing heat ranges, but I thought I went to a hotter plug to improve the economy. I apologize - unlike your awesome data acquisition systems, I have to rely on my ever-more-sketchy memory. I will think about what would cause this and post again if I can think of something. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)

03-02-2011, 12:00 AM	#2
RICE RACING Don Mega Join Date: Dec 2008 Location: Utopia Posts: 1,688 Rep Power: 18	On my system when I have checked it the hotter plug seems to be burning better (not misfiring as much). In the small scale stuff you can run an engine much richer on a hotter plug v's a cold plug (cold plug needs to be set leaner) to stop misfiring.... Anyway its an interesting thing I noted, am repeating experiment with full CDI ignition system and see what that shows. __________________ www.riceracing.com.au Worlds best Apex Seals Coil on Plug Water Injection ECU Calibration

03-31-2011, 04:21 PM	#3
j9fd3s Rotary Fanatic Join Date: Mar 2008 Posts: 123 Rep Power: 18	interesting. since fuel and air volume are close enough to the same, does that mean a richer AFR = more complete combustion, or is it the other way around? ive noticed differences too, i'm currently playing with a 12A PP with a 48IDA, and i've tried a few different plugs in the "tuning the carb" phase. in the idle/low speed range the rx8 plugs actually wanted more fuel than the autolites. the W/b on a p port is kind of a slippery slope, its on there... Last edited by j9fd3s; 03-31-2011 at 04:24 PM.