View Single Post
Old 02-23-2013, 12:41 AM   #48 (permalink)
EcoModding Lurker
Join Date: Jan 2013
Location: Oregon, US
Posts: 43

ZoomFreakingZoom - '88 Mazda RX7 Convertible
90 day: 19.02 mpg (US)

Geo - '96 Geo Prizm Base
90 day: 32.42 mpg (US)
Thanks: 2
Thanked 2 Times in 2 Posts
Originally Posted by Christ View Post
Everyone forgot about the pumping loss reduction from WAI. Warmer air = thinner and easier to compress. It also reduces the effective compression of the engine because there's just less air being pumped in, meaning less force on the piston required to reach TDC on compression, so less bearing/ring friction, etc.
I thought higher compression generally meant better efficiency? Or is it just that a higher compression, smaller displacement engine is more efficient than an equivalently powerful larger displacement engine with less compression?

Piston and bearing friction shouldn't be affected by compression, it's kinda like how there is the same rolling resistance from your tires if your going up a hill versus going on flat ground, at least that's how I see it. If it was effected, I suspect the difference would be very small.
1988 rx7 convertible. Streetported, racing beat header and presilencer replacing all 3 catalytic converters. Atkins 6 port sleeves. K&N cone filter intake. 22mpg average, 27mpg max. Spreadsheet (updated regularly):
  Reply With Quote