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BMW Diesel Owners / Enthusiasts
Do you own a diesel powered BMW? Maybe a 335d or a BMW x35d? Come and talk about what makes your car great!

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  #1  
Old 02-09-2013, 05:37 PM
Thomv Thomv is offline
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Improving fuel economy

Re-tuning the computer has been discussed for more power, but has anyone looked at it purely to increased mileage. I am starting a 110 mile round trip commute with my 35d which gets excellent mileage. (28 on the road). But why not be greedy? Can it be better. Got plenty of power.

Thks in advance.
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  #2  
Old 02-10-2013, 07:11 AM
KeithS KeithS is offline
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Carefully watching cause and effect for well over a year, I believe I have a handle on what impacts MPG of the 335D. Using highway driving under optimum conditions (flat roads, less than 75 MPH, ambient temp about 70 but NO AC usage), I achieve 40 MPG. These are the factors that reduce that amount.

The EGR program update lost 2MPG (That has been fixed with a later update)
A/C uses 2 MPG
Each 10 degree drop in ambient temp temp loses 1 MPG
18" wheels may lose 1 MPG or so (I have 17's so cannot verify)

As far as reducing power, just make believe there is an egg between your right foot and the power pedal!

Last edited by KeithS; 02-12-2013 at 03:43 AM.
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  #3  
Old 02-10-2013, 07:19 AM
d geek d geek is offline
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Quote:
Originally Posted by KeithS View Post
.... just make believe there is an egg between your right foot and the power pedal!
^^^This is the most effective mod for maximizing fuel economy in any car
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  #4  
Old 02-10-2013, 09:53 AM
GreekboyD GreekboyD is offline
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Leave the extra weight of the wife and kids at home.
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  #5  
Old 02-10-2013, 09:00 PM
Snipe656 Snipe656 is offline
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Lighter wheels and tires might help. I know a lot of people claim increases in mpg with their winter tire setups.
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  #6  
Old 02-11-2013, 06:26 AM
ChasR ChasR is offline
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Mein Auto: 335d, E28 M5, Clubman S
The Evolve folks claim a 10% improvement in fuel efficiency with their tune. If so, with the miles I drive, the tune will pay for its self in a couple of years. I'll know later this week.
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  #7  
Old 02-11-2013, 06:48 AM
BMWTurboDzl BMWTurboDzl is offline
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Program engine to run as a 4cyl while on hwy.? I6 engine mated with 6spd. The 335d is the best you'll get out of that.configuration.

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  #8  
Old 02-12-2013, 02:47 AM
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Axel61 Axel61 is offline
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better yet, STOP flooring the bastard on the road and drive like Grandma!!! LOL
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  #9  
Old 02-13-2013, 12:18 PM
kungpao kungpao is offline
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Mein Auto: 2009 X5 35D
but... but.. it's fun to flog it!

Driving like a Grandma didn't help in my x5. I found that driving normally for me got better mileage than trying to watch the gauge. Course it helps that my daily commute averages between 55-65mph so i get the higher range of the fuel economy rating
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  #10  
Old 02-23-2013, 05:27 PM
robster10 robster10 is offline
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Do most of you check tire pressure? Although some use nitrogen, if you use reg air tire pressure can make a difference. Keep it at specs. I'm in Canada so outside temps fluctuate with the season, so even with runflats they may look ok but if low will create more rolling resistance. Experimented with higher pressure & got better mileage but if you put in too much handling characteristics change.

Last edited by robster10; 02-23-2013 at 05:30 PM.
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  #11  
Old 02-24-2013, 06:27 AM
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BB_cuda BB_cuda is offline
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Electrical loads play a role

I have experimented with the seat warmers and rear defogger while cruising on a 300 mile trip home. The trip normally yields me ~38 mpg going 70 mph. Using these devices for about 50 miles, i saw some drop off but guessing it was about 1-2 mpg. The alternator produces this current needed and think of it as a higher load on the alternator requiring a little more torque (on the pulley itself) to produce the higher current. I have heard that NASCAR racers shut down the alternator at the end of a race and run off the battery to get that little extra uumph. I thought it befitting to mention this on opening day of the season . DAYTONA 500
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  #12  
Old 02-24-2013, 06:52 AM
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Flyingman Flyingman is offline
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Quote:
Originally Posted by Thomv View Post
Re-tuning the computer has been discussed for more power, but has anyone looked at it purely to increased mileage. I am starting a 110 mile round trip commute with my 35d which gets excellent mileage. (28 on the road). But why not be greedy? Can it be better. Got plenty of power.

Thks in advance.
Thomv, I recall when looking into some tunes that they had different maps you could choose from. Some were for better economy vs power. You could tweak it all over the place (or map).

I think variable geometery turbos would prove to be the most beneficial. You also need to understand that these cars are tuned to produce the lowest emissions, which may conflict with most efficient or best power out.
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Last edited by Flyingman; 02-24-2013 at 06:58 AM.
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  #13  
Old 02-24-2013, 07:19 AM
335dFan 335dFan is offline
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VAC Motorsports Intelligent Diesel Control Module (335d / 535d/ X6d / X5d etc)

VAC Motorsports has a piggyback unit VAC - Intelligent Diesel Control Module (335d / 535d/ X6d / X5d etc) that you can order either as increased performance or increased MPG. I do not own one, but am considering it as an alternative to the JBD, although it is more expensive.

http://store.vacmotorsports.com/vac-...etc-p2081.aspx
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  #14  
Old 02-24-2013, 07:23 AM
Snipe656 Snipe656 is offline
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According to a user on here the VAC does increase the mpg some as per their pen and paper calculations. I have a used JBD that I will be putting up for sale soon, once I get around to taking a picture of it. I never used it but don't think from reading on here or from way back when I talked to the original owner that it increases your mpg any.
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  #15  
Old 02-24-2013, 02:24 PM
robster10 robster10 is offline
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Quote:
Originally Posted by BB_cuda View Post
I have experimented with the seat warmers and rear defogger while cruising on a 300 mile trip home. The trip normally yields me ~38 mpg going 70 mph. Using these devices for about 50 miles, i saw some drop off but guessing it was about 1-2 mpg. The alternator produces this current needed and think of it as a higher load on the alternator requiring a little more torque (on the pulley itself) to produce the higher current. I have heard that NASCAR racers shut down the alternator at the end of a race and run off the battery to get that little extra uumph. I thought it befitting to mention this on opening day of the season . DAYTONA 500
Unlike the A.C. compressor I believe the alternator always spins no torque change. The compressor has a clutch on it and when not on just spins the pully (friction loss) but when A.C. is turned on clutch engages and creates an additional load on motor reducing mileage. As for nascar thay may have something that disengages the pulley line completely. I know they sell underdrive pulleys witch spin components at a different rotation level wich creates more hp/torque but not really it just reduces the drag on the motor.

Last edited by robster10; 02-24-2013 at 02:25 PM. Reason: ...
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  #16  
Old 02-24-2013, 03:20 PM
d geek d geek is offline
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Quote:
Originally Posted by robster10 View Post
Unlike the A.C. compressor I believe the alternator always spins no torque change. ....
Sure it does. The higher the electrical load the more force it will take to turn the alternator. Especially after a cold start when the starter and glow plugs have depleted the battery and it is sucking down the current. No work is done for free
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  #17  
Old 02-25-2013, 03:36 AM
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Flyingman Flyingman is offline
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Quote:
Originally Posted by robster10 View Post
Unlike the A.C. compressor I believe the alternator always spins no torque change. The compressor has a clutch on it and when not on just spins the pully (friction loss) but when A.C. is turned on clutch engages and creates an additional load on motor reducing mileage. As for nascar thay may have something that disengages the pulley line completely. I know they sell underdrive pulleys witch spin components at a different rotation level wich creates more hp/torque but not really it just reduces the drag on the motor.
Don't you wish! The more current produced the more torque translated onto the generator rotor which is in turn driven by the pulley and fan belt. It will definietly cost you some MPG to run more electrical equipment, but it would not be nearly as much as the A/C compressor.
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  #18  
Old 02-25-2013, 05:30 AM
Pierre Louis Pierre Louis is offline
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I believe higher cetane fuel may improve fuel economy. I don't know if putting in aftermarket additive for this would be a good idea only because of side effects on the rest of the engine/pollution control system. BMW is on record not recommending aftermarket additives.

It might be a good thing to try different sources of fuel to see which will give the best economy, since apparently higher cetane also produces less soot and will cause less depletion of the DEF.

PL
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  #19  
Old 02-25-2013, 02:44 PM
robster10 robster10 is offline
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better mileage.

Quote:
Originally Posted by Flyingman View Post
Don't you wish! The more current produced the more torque translated onto the generator rotor which is in turn driven by the pulley and fan belt. It will definietly cost you some MPG to run more electrical equipment, but it would not be nearly as much as the A/C compressor.
At idle & in park turn on your rear defogger & heated seats, try this again seperately by turning on the AC. Watch as the rpms drops for the later. There's more current drawn for the first two than most other equipment in the car, but very insignificant change of torque draw. That is why some makes also dropped pulley style water pumps for electric motor driven water pumps, no torque drawn away from crank pulley.
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  #20  
Old 02-25-2013, 02:50 PM
Snipe656 Snipe656 is offline
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That does not disprove what the others are saying in that some added fuel consumption happens with added load to the electric system but nothing to the level of adde fuel consumption a belt driven compressor does.

Switching to an electric water pump for added fuel economy makes sense. A belt driven always has a load and always runs. Electric only needs to run when needed and the added load to the alternator will also take less "engine power".

I personally find it surprising this could be measured via mpg. I'd think it would be very minimal.
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  #21  
Old 02-25-2013, 03:15 PM
ddeliber ddeliber is offline
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As a side note, I read on an MB forum recently that the "blue efficiency" system on their E-classes (not the Blue tech diesel) recently incorporated disengaging the alternator under low use situations. My point here being that Mercedes only recently introduced this feature (2012+ or 2013+ can't remember which). This does not say anything about BMW, just that MB is pretty good with their tech and pre 2012 cars did not have this feature.
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Old 02-25-2013, 03:39 PM
robster10 robster10 is offline
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But not a loss of 1-2 mpg as stated by using the heated seats & rear defogger by previous poster. My daily commute roundtrip is 260 km or 161 miles. Tried this with my D but no difference. As well no traffic stop & go to deal with so I believe that after a couple of fills was pretty accurate don't trust the computerized gauge check with fill up receipts. Same pump same station. Tried this on a gasser but different story, same commute distance etc. Gasser has electric ignition system, spark plugs etc. Our diesels don't. with the extra current load taken, may take some spark away from the plugs not getting full burn from fuel, but then again gassers aren't as efficient as diesels. As well didn't use A.C. or heating, even with the use of heating system (not seats or window defog) ac compressor engages taking away humidity in the cabin just as AC does when put on cold. I've always noticed a differnce in fuel consumption when in use. If as said above the alternator was disengaged with some sort of clutch sytem where just the pulley turns & not the internal windings or magnets I could see a gain in mpg, becuse the alternator is a rotating mass, but again this was in a gasser!

Last edited by robster10; 02-25-2013 at 03:51 PM. Reason: ...
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  #23  
Old 02-25-2013, 03:49 PM
Snipe656 Snipe656 is offline
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Originally Posted by robster10 View Post
But not a loss of 1-2 mpg as stated by using the heated seats & rear defogger by previous poster.
Agreed. I think it was a combination of other things.
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Old 02-25-2013, 06:17 PM
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Quote:
Originally Posted by Snipe656 View Post
That does not disprove what the others are saying in that some added fuel consumption happens with added load to the electric system but nothing to the level of adde fuel consumption a belt driven compressor does.

Switching to an electric water pump for added fuel economy makes sense. A belt driven always has a load and always runs. Electric only needs to run when needed and the added load to the alternator will also take less "engine power".

I personally find it surprising this could be measured via mpg. I'd think it would be very minimal.
Snipe, I already demonstrated this in the past with my Garmin Ecoroute Gauges. I have engine load at idle with and without A/C on. It is rather remarkable how much power the A/C takes from the engine.

Plus I have three (3) years of MPG and can track quite consistently that my MPG goes down in the warmer months and goes up in the cooler months, by about 1-2mpg. The only conclusion is the A/C.

Some say all of the attached rives (A/C, Power Steering, Alternator, Water Pump) may take as much as 25-40hp for a midsize vehicle. A/C is about 5HP and alternator was about the same. However, unless I misunderstand the basic mechanics, our A/C is either clutched on or off (determined by thermostat), so it is either fully compressing freon gas or free wheeling, whereas Alternator is only working against actual electric load.

If you do city driving these loads are going to be a larger % of your total fuel consumption, but if you are doing highway miles, it will be a lower %.

There is no debate about this.
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  #25  
Old 02-25-2013, 06:51 PM
Snipe656 Snipe656 is offline
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Quote:
Originally Posted by Flyingman View Post
Snipe, I already demonstrated this in the past with my Garmin Ecoroute Gauges. I have engine load at idle with and without A/C on. It is rather remarkable how much power the A/C takes from the engine.

Plus I have three (3) years of MPG and can track quite consistently that my MPG goes down in the warmer months and goes up in the cooler months, by about 1-2mpg. The only conclusion is the A/C.

Some say all of the attached rives (A/C, Power Steering, Alternator, Water Pump) may take as much as 25-40hp for a midsize vehicle. A/C is about 5HP and alternator was about the same. However, unless I misunderstand the basic mechanics, our A/C is either clutched on or off (determined by thermostat), so it is either fully compressing freon gas or free wheeling, whereas Alternator is only working against actual electric load.

If you do city driving these loads are going to be a larger % of your total fuel consumption, but if you are doing highway miles, it will be a lower %.

There is no debate about this.
I am not saying the AC would not cause for more usage. I am saying I highly doubt that the added load to the electrical system will result in any where near as measurable a fuel consumption rate as the AC system does. But I am admitting fully that the added load to the electrical system will cause for some small increase in fuel consumption.
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