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California98Civic · 06-16-2020, 01:26 PM

I just bought a lightweight VMS Racing crank pulley for my Honda Civic engine. OEM diameter. Moderately lighter (weighing 2.6 lbs instead of something like 4 lbs or maybe a bit more). I already deleted both the AC and the PS and put the alt on an on/off switch. So, not much to under drive!

Even though 2 lbs reduction on a sock 6 or 8 inch diameter pulley size is maybe less than 1 HP up to 2500 RPM, I drive a 106 HP car. The relative effect is greater. Also, I drive mostly city, and even on the freeway I do a lot of pulse and glide driving, so I run the engine up to 2000 or 2500 far more often than most people. In the city, at a light, I store a bunch of energy in that rotating mass quite quickly in first gear and then maintain it through the subsequent shifts. Ultimately, in the city or the freeway, I put the clutch in to coast and waste all that energy. It is a small amount, but it is wasted over and over and over.

Next will be the flywheel, whenever I get into a transmission swap or service again. Somewhat bigger gains to be had there.

Here is a great discussion and calculator:
https://www.w8ji.com/rotating_mass_acceleration.htm

06-16-2020, 01:26 PM	#31 (permalink)
California98Civic Cyborg ECU Join Date: Mar 2011 Location: Coastal Southern California Posts: 6,299 Black and Green - '98 Honda Civic DX Coupe Team Honda 90 day: 66.42 mpg (US) Black and Red - '00 Nashbar Custom built eBike 90 day: 3671.43 mpg (US) Thanks: 2,373 Thanked 2,172 Times in 1,469 Posts	I just bought a lightweight VMS Racing crank pulley for my Honda Civic engine. OEM diameter. Moderately lighter (weighing 2.6 lbs instead of something like 4 lbs or maybe a bit more). I already deleted both the AC and the PS and put the alt on an on/off switch. So, not much to under drive! Even though 2 lbs reduction on a sock 6 or 8 inch diameter pulley size is maybe less than 1 HP up to 2500 RPM, I drive a 106 HP car. The relative effect is greater. Also, I drive mostly city, and even on the freeway I do a lot of pulse and glide driving, so I run the engine up to 2000 or 2500 far more often than most people. In the city, at a light, I store a bunch of energy in that rotating mass quite quickly in first gear and then maintain it through the subsequent shifts. Ultimately, in the city or the freeway, I put the clutch in to coast and waste all that energy. It is a small amount, but it is wasted over and over and over. Next will be the flywheel, whenever I get into a transmission swap or service again. Somewhat bigger gains to be had there. Here is a great discussion and calculator: https://www.w8ji.com/rotating_mass_acceleration.htm __________________ See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.