Update on race plugs and pump gas
05-25-06, 07:25 PM
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Update on race plugs and pump gas
After 8K miles I pulled all 4 of my 10.5 heat range NGK racing plugs from my TO4S powered 13 BRE with HKS Twin Power during my last 2K mile oil change. These miles included no serious track racing, just street use, with a nice mix of stop and go short trips, long highway cruising, and several runs I did after the first 1K mile break in on the new engine that saw speeds over 140 mph on several miles of deserted highway. This was during the peak of winter, with starting intake temps of as low as 4 deg C and most ambient temps in the high teens to mid 20's deg C, using pump 91 gas from California. Also using Wolf 3d as aftermarket computer, omp still in use, along with 1 to 2 oz's of Redline synthetic 2 stroke smokeless premix depending upon whether I was topping up the tank or just filling it half way due to not having enough cash on hand to do a fill up.
I'm happy to report that the plugs did quite well. The leadings have no fouling, and their color is that of a dry medium brown. The trailings were a bit fouled as is usual with trailings due to the fact they are so shrouded from the combustion chamber in the housings, but only slightly more so than I've seen using stock trailing plugs. Chris Greene of Wolf USA examined them and said....normal. He only noticed very slight degradation of the 'tine' on the leading #2 rotor plug (the back plug), which he also says is normal due to the back rotor usually running slightly leaner (we are adding some tweaks to the rear injector settings to smooth that out).
So, I've put these plugs back in their box and installed 11 heat range plugs. My actual plan is to order and install some 9's for trailing, to give them a bit of extra heat to self-clean, and not waste the good 11s since there is little difference between my old 9s and the 10.5's in the trailing, it would seem, it's all in the leading. I will run the 11s until the winter, then pull them and reinstall the 10.5s (but I'll put the old trailings into the leading ports and vice verse, like rotating tires for wear). Assuming the 11's do well over the summer, I will order 11.5's for next summer and continue this process until I either get to the 13 range plugs (the coolest available from Mazdacomp), or I get fouling, in which case I will know 'how low I can go' in spark plug limbo.
AFRs are 10.5 to 11 under boost, 15 under cruise, per Innovate wideband logging.
First autocross using 103 VP unleaded will be in a couple of weeks.......
One item of note - normally when I have installed new plugs in the past there is a noticeable difference in smoothness and ease of starting with the new plugs. Not so this time - I could feel no difference between the 8K mile 10.5's and the brand new 11's on startup. Very encouraging.
Beast
I'm happy to report that the plugs did quite well. The leadings have no fouling, and their color is that of a dry medium brown. The trailings were a bit fouled as is usual with trailings due to the fact they are so shrouded from the combustion chamber in the housings, but only slightly more so than I've seen using stock trailing plugs. Chris Greene of Wolf USA examined them and said....normal. He only noticed very slight degradation of the 'tine' on the leading #2 rotor plug (the back plug), which he also says is normal due to the back rotor usually running slightly leaner (we are adding some tweaks to the rear injector settings to smooth that out).
So, I've put these plugs back in their box and installed 11 heat range plugs. My actual plan is to order and install some 9's for trailing, to give them a bit of extra heat to self-clean, and not waste the good 11s since there is little difference between my old 9s and the 10.5's in the trailing, it would seem, it's all in the leading. I will run the 11s until the winter, then pull them and reinstall the 10.5s (but I'll put the old trailings into the leading ports and vice verse, like rotating tires for wear). Assuming the 11's do well over the summer, I will order 11.5's for next summer and continue this process until I either get to the 13 range plugs (the coolest available from Mazdacomp), or I get fouling, in which case I will know 'how low I can go' in spark plug limbo.
AFRs are 10.5 to 11 under boost, 15 under cruise, per Innovate wideband logging.
First autocross using 103 VP unleaded will be in a couple of weeks.......
One item of note - normally when I have installed new plugs in the past there is a noticeable difference in smoothness and ease of starting with the new plugs. Not so this time - I could feel no difference between the 8K mile 10.5's and the brand new 11's on startup. Very encouraging.
Beast
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