fuel economy

[ronnie 0]

Hi people,

With gas prices going through the roof and everyone ( well, most of us) getting concerned about our planet, I thought it'd be interesting to start a thread on fuel economy.

Anyone have any ideas on how to re-tune a 328i for better economy?

occasionally I read about chips that improve economy and power. has any tried one that really works? I dont tend to trust advertising blurb all that much.

Is it possible to reprogramme a stock chip to do this?

Any other ideas out there? fuel mixing? best tire pressures? different air filters?

Cheers!

Ronnie

[JiB 0]

Tall and skinny tyres with 40psi in them will help.

But simpler stuff like:

-Correct tyre pressures (I guess you could go one or two psi up, this yielded less gas consumption in dad's 4x4)

-Correct Alignment

-Take out all unecessary weight

-Don't stick things out the window

-Drive with the windows up and no a/c (if you have no interior like me the drive tunnel = insta heater )

-Make sure the motor is always doing the least work possible

So less weight+less resistance=less gas.

My 2c

[tibbs.james 1]

I found that all those things above made a good enough diffierence to economy for me.

Driving smoothly & keeping it under 3k rpm helped most for me.

Also i wont use my car unless it runs long enough to get up to temperature properly.

Thats what feet/mountain bike are for ( short trips )

[ronnie 0]

yep your on the right track.

those things will make a minor difference.

Driving style makes a bigger difference too. I saw an economy comparison in a BMW magazine between the auto writer, a BMW driving instructor and Seb Vettel. Believe it or not Seb won. He turned of all fans, radios, air con (in the middle of summer too!) and drove like such a snail that he was passed frequently by a lot of irate people... you can try drafting trucks, dont accelerate uphill, coast downhill, etc.

But what I'm after is something that will make a bigger difference without having to drive like a nana.

currently I can get between 9.5L/100km and 13L/100km, depending on how I drive. I'm trying to see if there's something that can regularly keep a big engine car under the 10L/100km, as a daily commute car.

not that I consider a 2.8L all that big... I was born in Canada and anything under 5L is tiny...hehehe

[ducatiss 1]

other than what others have already said, I dont think there is anything else that you can do other than keeping your maintenance up to date. It sounds as if the km/l that you are getting are pretty right for the 328i.

[Cale 36]

I read (and hear) things like:

Only fill your car in the morning when its cold and the fuel density is higher.

Never let your fuel tank fall to sub 1/2 full, as the more fuel the less air is in there, therefore less evaporation.

Don't know how much of a difference these would make- if they're even measurable.

I reckon that once the gauge reaches under 1/4 it goes down way faster than if it were above 1/4. Maybe its my imagination.

[Jeddy 0]

Never let your fuel tank fall to sub 1/2 full, as the more fuel the less air is in there, therefore less evaporation

But if you've got more fuel in your tank you car will be quite a bit heavier.

I've just been keeping it under 3k rpm or so and i get maybe an extra 50-80k's out of an e30 tank

[Mark 178]

There are no magic "fuel economy" fixes.... the 2.5/2.8 BMW engines were never made for fuel economy.... they're made for storming long distance trips. I've been driving my car like a nana with a fear of speed and I've still only managed to wring 450 k's from 57 litres of 95 octane!

Thankfully I live in the city, so I walk to work and try to only use my car on the weekends.

[Fothers 5]

I decided to do an economy test in my E46 328 & with the cruise control on 105, and Frank Sinatra on the CD player, I managed 7.6l/100k on a trip from the Nth Shore to Cambridge and back. That's 37.1 mpg in old terms which I thought was bloody good. Avoided all the plain clothers coppers (Maximi, Camry etc) by Hampton downs too!

Edited June 1, 2008 by Fothers

[elmarco 56]

I've had the 330 down to showing less than 7l/100km on cruise control on the open road (no hills). On average I think it is more like 7.5 - 8.5 (which is still 10% better than the VR6 I had before) and about 10 - 10.5 around town.

I don't think that's too bad really considering it is a 3 litre in a relatively heavy RWD car. It's never going to be down there with a Polo diesel, but then a Polo diesel is never going to keep up with me if I flex the right foot....

Just shows how fast automotive development moves these days.

[CamB 48]

I dream of 10l. Actually not really, I don't bother trying since it'll never happen.

I get 12.5l/100km in mixed driving, about 14l around the city and its about 9l-10l at 100km/hr air con on, in 6th. I figure if you want the performance, you have to pay. Mind you, mine's 3.2 litres and the little devil wants me to rev it.

On other cars I've tested aircon at slightly under 1 litre/100km - easily the biggest impact other than driving style and auto vs manual.

I reckon there's no magic way to get more - if there was BMW would already be doing it as fuel economy sells. This is the main reason I disbelieve Fuelstar's 10-15% economy improvement claim.

Actually interestingly the old 2002 gets better fuel economy - a 2 litre 8v with a (very - 4.27) short diff gets easily under 10l/100km on the open road. I think it's about 8l/100km.

Edited June 1, 2008 by CamB

[Grant 4]

Actually wrong, the M52 engine was designed with economy in mind and does significantly better than the earlier M50 engines

And if yuo run it on 98 you should see at least 520 km from 55 litres - I get as much as 570 and I dont drive like a nana best range for an M52 is 2,000 to 3,500 RPM - if you do the maths that means it is MORE economical than running it on 95

I'm exactly the same. In my manual E36 328i, I generally get around 600km's to a tank. That is probably 60% open road driving and 40% city driving. I don't exactly thrash my car, but then again I don't drive like a nanna either.

All open road, I have got 650km's easily enough too.

I 90% use BP 98 petrol.

Cheers

Grant

[lidistick 70]

E36 328i auto.

Town = 12.5~13l/100kms

Long distance = 9l/100kms, kissing the redline multiple times

98% BP Ultimate

2% Gull Force 10.

I think Gull has slightly higher octane as the car feels friskier. 95 octane is terrible. Never tried 91.

[ronnie 0]

its a good discussion we have going here.

Interesting to note no-ones really mentioned engine re-mapping yet though. no computer wizzkids in here? It really does work...

Someone else also mentioned gear ratios, which is extremely effective. You can actually plan the ratios around what type of driving you do as well, if your a real fanatic. tends to be an expensive way to go though... but even an auto can be driven economically similar to a manual. The new auto boxes arent slush boxes anymore and using the "manual" section lets you get to a higher gear faster. Lower rpm's = less fuel consumption.

Personally I think the biggest contributor to poor fuel economy, in NZ especially, is the idiots who design the traffic light systems here. They dont design traffic to flow, you bounce from one red light to the next, to the next, to the next... you get the idea. and whoever thought it was a good idea to put 7 traffic lights along 2km stretch of road with that type of system?

It was kind of amusing to notice that there was much less traffic backed up when the light at a motorway onramp wasnt working...

They just dont seem to understand that traffic simply behaves like water. If you have two streams joining into one, you have to do one of two things to keep water flowing and not backing up. Either increase the speed of the larger flow, or make it wider to increase capacity so the speed can stay the same.

Having said all this, while its fun to go through all this as a brain teaser as well as do our bit to save the planet, I thoroughly enjoyed turning traction control off in the wet last night, putting the hammer down and listening to Pirelli P6000's try and hang on! (and still got 8.2L/100km on the trip from Howick to city!) Oh the Joy! Almost rivals Beethoven's 9th Symphony....

Dont worry guys, fuel prices will drop again!! either that or we all buy scooters...

[pjay 8]

E36 328i - 15L/km on the motorway anywhere between 80 - 120kph. 8L/km in town sitting under 60kph. Full tank = 450kph driving hard, 550 driving softish. Have never been a full tank without at least one flooring, and have never ran the tank dry.

[Mark 178]

From the above comments it seems I need to get me an M52!

[tonylauno1 7]

yep your on the right track.

those things will make a minor difference.

Driving style makes a bigger difference too. I saw an economy comparison in a BMW magazine between the auto writer, a BMW driving instructor and Seb Vettel. Believe it or not Seb won. He turned of all fans, radios, air con (in the middle of summer too!) and drove like such a snail that he was passed frequently by a lot of irate people... you can try drafting trucks, dont accelerate uphill, coast downhill, etc.

But what I'm after is something that will make a bigger difference without having to drive like a nana.

currently I can get between 9.5L/100km and 13L/100km, depending on how I drive. I'm trying to see if there's something that can regularly keep a big engine car under the 10L/100km, as a daily commute car.

not that I consider a 2.8L all that big... I was born in Canada and anything under 5L is tiny...hehehe

Could be fairly difficult in keeping a heavy car with big engine under 10L/100km unless there are less red lights and traffic jam. Fuel consumption for these cars are pretty good for what they are, I have a e46 328ci. All depends on your route and driving style. The easiest way to keep fuel consumption down is

1) accelerate slowly away from traffic lights, 90% of cars are slow off the line anyway so I keep mine under

2500rpm to match the slow car next to me.

2) release gas pedal early when coming up to intersection, no point in keeping it on the gas and stomping on the brake pedal hard.

3) leave some gap between you and car in front so keep a constant speed to reduce acceleration.

ECU remapping, chipping usually cost alot and you probably need to drive for years to get those money back even if it does save fuel.

[tonylauno1 7]

I read (and hear) things like:

Only fill your car in the morning when its cold and the fuel density is higher.

Never let your fuel tank fall to sub 1/2 full, as the more fuel the less air is in there, therefore less evaporation.

Don't know how much of a difference these would make- if they're even measurable.

I reckon that once the gauge reaches under 1/4 it goes down way faster than if it were above 1/4. Maybe its my imagination.

I notice it too, the last 1/4 is used up much quicker than the first 1/4 but this happens on every single car I own. Maybe it's to do with the way the gauge is running or measuring???

Less fuel in tank creates more condensation but does that really matter?

Maybe less fuel in car (only fill up 1/4), lighter it is, better fuel consumption cos you have 45kg less in your car. Easiest way to reduce 45kg, I thought that petrol weights about 1kg per litre.

[tonylauno1 7]

I decided to do an economy test in my E46 328 & with the cruise control on 105, and Frank Sinatra on the CD player, I managed 7.6l/100k on a trip from the Nth Shore to Cambridge and back. That's 37.1 mpg in old terms which I thought was bloody good. Avoided all the plain clothers coppers (Maximi, Camry etc) by Hampton downs too!

7.6L/100km sounds about right on open road.

Mind you I have seen coppers in 03 XR6 Turbo, 02 Commodore SS, 99 540i. Got caught when the SS was pacing me after I overtook him.

[Nic325i 0]

I notice it too, the last 1/4 is used up much quicker than the first 1/4 but this happens on every single car I own. Maybe it's to do with the way the gauge is running or measuring???

Less fuel in tank creates more condensation but does that really matter?

Maybe less fuel in car (only fill up 1/4), lighter it is, better fuel consumption cos you have 45kg less in your car. Easiest way to reduce 45kg, I thought that petrol weights about 1kg per litre.

Petrol is only about 75% of the density of water - i.e. about 750g/litre

[Jammasterjames 0]

Here's how I lay it down:

328i Auto on BP 98

One week test wit my new Cold air box/cone filter:

11.54L/100km

Regular Pimpin' thru tha week, and a return trip from Albany to Puhoi -getting tha revs up high and "pwning" a Holden who was tryna chase me down on tha hills past Orewa...

[Antallica 15]

Mine's around the 12-15L/100km in town... turns to 15L/200km open road easy. I see Gull was offering '91 at lower than $2 last night.

[pjay 8]

Mine's around the 12-15L/100km in town... turns to 15L/200km open road easy. I see Gull was offering '91 at lower than $2 last night.

mmm $1.99, still wouldnt fill up there

[topcat 11]

the wife gets 9.5L/100k's regulary in the 3.5L e23.

and thats a combo of highway and town.dont know how she does it.the right pedal gets plenty use.lol

could the old school of engineering be at work....who knows

Edited June 11, 2008 by topcat

[speedyg 16]

1989 E30 325i manual with M20 2.8L.

I got 9.5L per 100kms on a trip from Chch to Blenheim.

But about 14L per 100kms around town.