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Old 02-08-2010, 05:27 PM   #11 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,532

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

MPGiata - '90 Mazda Miata
90 day: 54.46 mpg (US)

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

Appliance car Mirage - '14 Mitsubishi Mirage ES (base)
90 day: 62.14 mpg (US)
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Quote:
Originally Posted by SentraSE-R View Post
1200 rpm is probably too low an engine speed for cruising. Your engine's BSFC graph should point you to where you want to be. Usually, your best efficiency is between about 1500 and 2200 rpm for 2 liter class engines.
True, but potentially misleading. (It needs qualification.)

Your best efficiency might be in that RPM range when accelerating/climbing and you want high load. But it's not correct to say you'll get better fuel economy cruising at that RPM when you could use a higher gear.

(I realize you then went on to describe pulse & glide, but I just wanted to bring this up in case someone doesn't make the connection.)

For someone who doesn't want to pulse and glide, driving with load (DWL) at low engine RPM is a good alternative.

I'd have no problem cruising at 1200 RPM provided the engine will do it without complaining (and by that I mean physically juddering). Bestclimb's post above describes lugging nicely.

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