View Single Post
Old 02-01-2009, 10:43 AM   #1 (permalink)
MetroMPG
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,513

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.71 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 60.16 mpg (US)
Thanks: 4,058
Thanked 6,957 Times in 3,602 Posts
Lighter valve springs - an OEM efficiency tactic

I was sure this topic was discussed before, but couldn't turn it up in a search.

Anyone who's ever worked on a head for the first time may have been surprised at the amount of pressure valve springs exert on the cam. Try turning a lubricated cam in a head - there's an unexpected amount of resistance!

The idea of going with valve springs with less resistance was suggested - as something that would likely return a very small improvement in efficiency.

I happened across a reference that suggests using lighter springs is actually a tactic automakers have used to reduce fuel consumption:

Quote:
Pulling the engine from the Altima meant adopting some of that car's bias toward fuel economy, smoothness and torque. That's the excuse for a rev limiter that smacks you in the face on every shift. Super-light valve springs designed to get that last fraction of a mile from every gallon of gas mean no more revs until you buy 16 more springs and an ECU.
Source is a discussion of putting an Altima engine in a Sentra (and then building/tuning it for more power).

2002 Nissan Sentra SE-R Spec-V - Sport Compact Car Magazine

Not that this is particularly useful info. How are you going to get lighter valve springs? Or decide "how light is too light?"

__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote