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E90/E91/E92/E93 (2006 - 2013)
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  #26  
Old 07-11-2005, 03:53 PM
CC 330i CC 330i is offline
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Location: Central Coast of CA
 
Join Date: May 2005
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Mein Auto: 2006 330i SG with Blk Int
Quote:
Originally Posted by Mr. E
10 MPG is just crazy, if it continues like that you should learn to treat the gas pedal as something other than an on/off switch.

For comparison, my E46 M3 gets around 27 MPG highway (best case) and averages about 16-17 MPG around town. I don't baby it, either!
Yeah, this is funny! I call my friend who has a Z3 the "digital driver" because his gas pedal and brake pedal are either 100% on, or 100% off. He does not seem to know how to use the pedals any other way! Talk about jerky!
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  #27  
Old 07-11-2005, 03:59 PM
CC 330i CC 330i is offline
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Mein Auto: 2006 330i SG with Blk Int
Quote:
Originally Posted by jason_jm
OK, here goes
so far 880 miles on the clock, and 4 used tanks to get there - averaging around 15/16 MPG
Oh, by the way, my 1983 GTI which had a 1.8L inline 4 cylinder and 90 HP and weighed 2000 pounds got about 15 MPG when I drove around "hard". I got 25mpg on the freeway at 70 mph.

Another thing, if you only have 880 miles, DO NOT use the cruise control. Your engine is not broken in and you need to keep the tach needle moving. Shift between gears often, and vary your speed. Your fuel consumption will get better as the engine breaks in. You are about halfway there. You need 1250 to 1500 miles before you should keep a constant RPM long enough to use cruise control.

I went through about 3.5 tanks to 880 miles, so you are not doing that badly. Just take it easy until about 1500 miles, and don't use the cruise control (except for maybe a minute or two) until then.
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  #28  
Old 07-11-2005, 05:59 PM
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Wingboot Wingboot is offline
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Mein Auto: 330Cic
[QUOTE=dynosor]Modern fuel injected engines cut their fuel off completely when you lift you foot off the throttle until the revs drop to 1200 - 1500 RPM. If the car is in gear at speed the revs drop slowly. If you depress the clutch, the revs drop quickly. In either event, the ECU won't let the engine stall. Coasting in neutral requires fuel to keep the engine running, and will use more fuel than coasting in gear. The latter uses the momentum of the body to keep the engine running.[QUOTE=dynosor]

Right, coasting in gear is FREE. It uses less fuel than idle.
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  #29  
Old 07-11-2005, 06:03 PM
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Wingboot Wingboot is offline
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As for your question. That is not normal. Are you driving around town at full throttle? I have been driving E46's (328, 325, & 330) since 99 and have usually gotten 28-34 highway and 22-25 city. Even during the break in period.
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  #30  
Old 07-11-2005, 06:43 PM
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dynosor dynosor is offline
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No "compression" when throttle is closed

On a diesel engine the airflow is not restricted when you lift off the throttle, but with a gas engine at significant revs there is almost no airflow into the engine when you lift off the throttle and therfore little compression braking to speak of. There is friction that goes with agitating the little air that is in the engine.

You would not coast on a flat road and expect to maintain speed. You can coast down a hill in gear, maintain speed and use no fuel; or coast in neutral with an idling engine consuming some fuel, using the brakes to maintain speed.

It is more efficent to accelerate "hard" in 4rth gear from 2000 RPM to 3000 RPM and then coast back to 2000 RPM in gear than to maintain an even speed of 2500 RPM - the engine uses less fuel when breathing well because of higher effective compression, then uses no fuel as it slows down. Try it and report back.

Running this way between 4000 and 5000 RPM will probably not save fuel because of the extra fuel enrichment used to cool the engine, wide open at these speeds, and the higher air drag that comes with with reaching 100 MPH.

Quote:
Originally Posted by gesoffen
None of this takes into account the reduced coasting distances of idling in gear (manual trans.) due to compression braking.

Last edited by dynosor; 07-12-2005 at 01:13 AM.
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  #31  
Old 07-11-2005, 06:54 PM
1st time bimmer 1st time bimmer is offline
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Location: CA, USA
 
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Mein Auto: 2006 330i sport
I got 30-31 mpg on open freeway @ 80 mph and 19-20 mpg around town for my 06 330i step after 2200 miles.
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