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Old 06-18-2009, 06:02 PM   #6 (permalink)
RobertSmalls
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Join Date: Aug 2008
Location: Buffalo, NY, USA
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Prius C - '12 Toyota Prius C
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Quote:
Originally Posted by ziddey View Post
Hell, performance and economy should go hand in hand, discounting driving habits.
Mods that result in increased engine efficiency give you more horsepower OR better fuel economy: you choose with your right foot. Better driving habits are more effective than any mod.

When it was time for new plugs, I took a few measurements. My fuel consumption at idle and at 3000 rpm in neutral was unchanged when I swapped out the Autolite copper plugs with 40kmi on them for Denso copper plugs.

Denso came out with the Denso Platinium TT, and their ads boast about a 0.54% improvement in fuel economy, from 36.8 to 37.0mpg, versus "Competitor A". They don't say under what conditions, so you can't draw any conclusion other than that Plug A vs Plug B isn't going to make more than a 0.54% difference in power or economy. Utterly invisible to your butt-o-meter, and almost certain to be drowned out by noise in the data at the pump.

The manufacturer of your engine spent hundreds of engineering hours (I hope) optimizing the ignition system. If you believe it was optimized for performance/economy instead of cost, then I wouldn't mess with it.

The best place to test different gaps and different plugs is a bench dyno, but since I don't have one of those in my garage either, I'd be happy to read any data you collect on the road or in the driveway.
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