Author Topic: Tips for Improving Mileage, Most of Which Simple  (Read 36202 times)

DesktopDave

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Tips for Improving Mileage, Most of Which Simple
« Reply #135 on: October 31, 2010, 05:59:20 PM »
My mileage is always better with cruise, but it's hard to isolate it from all the other variables...it's not a huge difference regardless.  Running the numbers indicated less than 10% for me, but the seasonal fuel mix and route variables were really difficult to compensate for.

Driving slower made far more difference from what I could determine.  Drafting semis and driving slower was worth an easy 25%.
'08 Karmesinrot 128i 6MT
'86 Zinnoberrot 635CSi (M30B32/G265/3.46 torsen LSD)

Sold: '97 Montrealblau 318iS, '91 Brilliantrot 318i, '91 Brilliantrot 318iS

longtallsally

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Tips for Improving Mileage, Most of Which Simple
« Reply #136 on: November 01, 2010, 12:06:18 AM »
Quote from: ///m42 sport;98158
^^Does fuel economy improve with cruise control or without?  I've noticed the opposite.

I've noticed that on highway cruising at 65 with the cruise control, and 410lsd, I get about 26mpg on the obc. But if I turn it off I can get somewhat better mpg.  

Anyone else notice this?


I use the cruise more for speed camera avoidance over here, but the primary benefit it offers in terms of fuel economy is going to be the consistency.  Your foot may think you need "x" amount of pressure (throttle opening) whereas the cruise controller realizes you only need "y" of pressure and thus can help a good bit.

Admittedly it is more of a convenience thing for me.

I will say that although you are right at what OEM states for mileage, I'd say that is a bit low.  I think mine is low and I'm at 29 in autobahn conditions which means I generally keep it around 80 mph.

In mixed, I'm now getting 26-28.

Biggest punches in the tank that I've found:
- roof rack (kills the mileage and I lose from 2-4 mpg)
- rabbit starts (drop 1 mpg with 3-5 of them on a tank)

Things that don't matter (much) in my experience:
- AC (I might lose 1 mpg, but I wasn't using it constantly last summer- when I get home to CA, I'll have more accurate data on this)
- Going freeway speed (I actually get better economy cruising at a constant 65+ than a constant 25-35 which is more frequent than you think over here)

Biggest assistants (just from driving style)
- coasting on hills
- short shifting (this one is HUGE as I generally keep the revs below 3k)

I've posted to a couple of these threads at varying stages of my just over a year and 10k miles since I bought the car.  It now has just a bit over 194k miles on the clock.  I still have not replaced the air filter or spark plugs and I'm getting that mileage.  Perhaps this week I'll do that and clean the AFM and see if I get an improvement.  Aside from my eventual rebuild, I'll be doing the COP conversion, electric fan, and low temp T stat to try to help more.

rabidroco

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Tips for Improving Mileage, Most of Which Simple
« Reply #137 on: March 01, 2011, 09:52:17 PM »
Quote from: 318/6;76590
In an effort to maximize fuel efficiency while keeping performance relatively high, we made a few adjustments to our 318is.

Engine build:
Rebuilt bottomend using 86mm slugs from '95 M3
Machined valve cutouts to drop static c/r slightly in order to use 87oct
Special rods to save rotating mass of over 900 grams
All pistons and rods balanced to within .25g
Very loosely built bottomend
Intake cam advanced xx-degrees
12 pound flywheel (soon to be swapped to 7 pound unit)
stock 4.10 gearing for now, s3.91 in the garage
Weight: 2460 with full stock trim and full tank
Fuel economy over 975 miles:  3 passengers and a loaded trunk -- 37mpg @ 74-76mph.  
Should do 40mpg easily running solo.  Oh yea, and it's as fast as a 25i.  :D



This sounds amazing. Do you have an update?
Did you consider using an M44 block for the better low-end = mpg?

rabidroco

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Tips for Improving Mileage, Most of Which Simple
« Reply #138 on: March 01, 2011, 09:55:30 PM »
Quote from: 318/6;76590
In an effort to maximize fuel efficiency while keeping performance relatively high, we made a few adjustments to our 318is.

Engine build:
Rebuilt bottomend using 86mm slugs from '95 M3
Machined valve cutouts to drop static c/r slightly in order to use 87oct
Special rods to save rotating mass of over 900 grams
All pistons and rods balanced to within .25g
Very loosely built bottomend
Intake cam advanced xx-degrees
12 pound flywheel (soon to be swapped to 7 pound unit)
stock 4.10 gearing for now, s3.91 in the garage
Weight: 2460 with full stock trim and full tank
Fuel economy over 975 miles:  3 passengers and a loaded trunk -- 37mpg @ 74-76mph.  
Should do 40mpg easily running solo.  Oh yea, and it's as fast as a 25i.  :D


This sounds amazing. Do you have an update?
Did you consider using the M44 block for better low-end and therefore mpg?