Quote:
Originally Posted by psalt
The best way to make that decision is to measure your AFR's under load with a wide band O2 sensor (before the cat). My experience is that most lambda SC's run a little lean under WOT which is one reason they can't tolerate much ignition advance. Optimum advance for a wide VIA hemi like the 911 is in the mid to high 30's BTDC, but the factory chose to limit the advance to 25 BTDC. If you have the octane, you can usually run more advance with AFR's in the low 13's. When you set the dwell to 25-35 you are really only effecting the WOT and cold mixture, because the system pulls the average mixture back to stoich when in closed loop.
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Good stuff in this post... So what you're saying is that while trying to tune to 50% may be what the factory recommends for optimum emissions for cold starting, some benefit may be gained by tuning to 25/35% to ensure you don't go lean at WOT? And you might be able to get more advance out of it too? I'd never heard that before but it makes sense.