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Old 02-01-2012, 05:31 PM   #24 (permalink)
COcyclist
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TDi - '04 VW Golf
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Quote:
Originally Posted by viio View Post
First two fill-ups have given me 55mpg and 58 mpg (UK) - both are short on the 61.8mpg combined that the factory suggests. I've been carrying a fair bit of weight around but as it's mostly long motorway journeys I'm surprised it isn't higher.

I wonder if I ought to reconnect my cold-air feed to see if the engine is starved of oxygen. I have a feeling I'm having to work the engine quite hard to get it to climb hills etc and the cold air feed might help with that.
Everything I have read and experienced about diesels says to supply the engine intake with as much cool air as possible. Block the radiator because they are so efficient they don't generate much heat but I would keep the cold-air intake in place and free flowing. Warm-Air Intake mods may work in gas (petrol) vehicles because they are fighting against the throttle plate at low load situations. The warmer air is less dense and allows gas engines to run with the throttle a little more open and operate more efficiently at hypermiler cruising speeds. It hurts their power too but some people may get a few mpg out of it. Not for diesels though. Diesels don't have a throttle and can work at very lean injection rates.
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Quote:
Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
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