Rather interesting test on the E34 for the past week

[BMW4LIFE]

So I have been driving to santa barabra a couple times a week and did a little test on the MPG

Couple things I noticed...now let me remind you that the times of the drive and the weather conditions were pretty much the same for all trials...there were no stops or presses on the breaks and the MPG averages were started once the car was on the freeway and on cruise control till the off ramp at my destination

I noticed that @ 65MPH I got 31.1 MPG but interesting enough at 75MPH I got only 26.3MPG

now this might be no biggie but I found it rather interesting how only an increase 10MPH can decrease fuel consumption by some much

[ArnZ!]

The faster you go the more energy you'll need.

[Morgenster]

The faster you go the more energy you'll need.

by cube factor 'x to the third'

[Kibokojoe]

Its a BMW who cares about fuel consumption :). I drive my Honda if I want to get there cheap. I drive my Bimmer for image........

[repenttokyo]

our cars are about as aerodynamic as a brick.

[Tiger]

All cars runs optimally at certain speed have you tried to see what your fuel mileage is at 55MPH? I am wondering if you might get 35MPG at 55MPH.

On a long run I did long ago... I got 24.4MPG average on a 800 miles run... but that got stops... and went into city a bit and back out... could have been about 25 or so if all highway and this is on a 540l. I guess the average speed for the trip was around 70 MPH.

[philbyil]

Mixed mileage is in the 24's.
I average 26.7mpg driving 70/80mph on TX roads!
Now, If I drop the cruise down to 60 I get 29/30 and if I drop it down to 55 I get 31!

The gas mileage on the GQ has been consistent since I've owned it!










So I have been driving to santa barabra a couple times a week and did a little test on the MPG

Couple things I noticed...now let me remind you that the times of the drive and the weather conditions were pretty much the same for all trials...there were no stops or presses on the breaks and the MPG averages were started once the car was on the freeway and on cruise control till the off ramp at my destination

I noticed that @ 65MPH I got 31.1 MPG but interesting enough at 75MPH I got only 26.3MPG

now this might be no biggie but I found it rather interesting how only an increase 10MPH can decrease fuel consumption by some much

[ryan roopnarine]

My EAT chipped 525i with autotrans has done between 35 and 36 US MPG at 55mph before. I don't remember if it was because I had put 87octane in, but wouldn't be surprised if that was the case.

[genphreak]

"our cars are about as aerodynamic as a brick"

This is the case. The drag coefficient of an e34 is 0.30 or 0.32 (can't remember which), that is damn low, as they have a decent tail-design, flush windows and the rest is very neatly done to meet the wind tunnel tests when they were the main vogue.

[Russell]

"our cars are about as aerodynamic as a brick"

this is the case. The drag coefficient of an e34 is 0.30 or 0.32 (can't remember which), that is damn low, as they have a decent tail-design, flush windows and the rest is very neatly done to meet the wind tunnel tests when they were the main vogue.
+1

[Russell]

Its a BMW who cares about fuel consumption :). I drive my Honda if I want to get there cheap. I drive my Bimmer for image........
We all care about fuel economy. I drive a BMW and have done so since 1976 becasue I like quality cars, not image.

[Dave M]

Mixed mileage is in the 24's.
I average 26.7mpg driving 70/80mph on TX roads!
Now, If I drop the cruise down to 60 I get 29/30 and if I drop it down to 55 I get 31!

The gas mileage on the GQ has been consistent since I've owned it!

No complaints about the 31 mpg the 525 gets at 90-100 km/h. This seems to be pretty standard for te M50.

Philbyil, you've got the museum piece version of my car at 51k miles?!?! Should last for another few decades.

Dave

[philbyil]

Hi Dave,

You bet it is and I'm still enjoying this car (the GQ). She just turned over 55,555 miles on the odo this week!

The only option the car didn't have on the build sheet (besides being special ordered with a manual transmission) was the BMW telephone. Still have the original window sticker and owners docs on file, along with all receipts and service history etc.

Since I bought the car, I installed extra's such as sheepskin seat, armrest and headrest covers together with upgrades such as a JC chip, Euro headrests and a Hartge/VDO gauge package (and associated adapters), Ate Powerdiscs on the front and EBC Redstuff's all round (which greatly improved the braking). Other than a couple of warranty issues, I've never taken it to a dealer for any work and did all the regular maintenance on the GQ including improvements such as a new metal impeller water pump and alloy thermostat housing.

Regular servicing includes new plugs and air filter every 10k, brake fluid and coolant R&R every 2 years, 5k or 6 month Mobil1 15w50 oil and filter changes and tranny/diff fluid R&R every 10k or 2 years. Anality rules :D

Preventative maintenance such as new hoses, belts and tensioners was done at 40k. And, so far, the only suspension parts R&R'd have been the dog bones due to external rubber seals torn...everything else is nice and tight.

She drives like new! Great cars the E34's and the M50tuB25 motor is pretty much bulletproof!

[Dash01]

Correction: Our cars are about as aerodynamic as a brick with its edges rounded off. The rounded edge thing makes more difference than you might imagine.

And, per tests done on the Ecomodders website, our (or most any) cars might benefit substantially from mods such as smooth belly pans, fairings to streamline the wheels, or perhaps lip spoilers. The worse the original shape, the more potential for improvement.

Belly pans made of Coroplast (the stuff realtors and politicians yard signs are made of) are cheap. light, stiff enough, and easy to work with, to pretty much cover the entire underside of the car. Exhaust pipe heat much less a problem than you may think, and that portion can be covered by taught aluminum mesh used for window screens, to vent the heat and still smooth the airflow. Makes the car very quiet, too, with less turbulence drumming on the floor pans, and more road noise reflected away rather than absorbed into the cabin. Keeps salt spray and crud off the underside, too, so less corrosion.

Wheels make a big difference. Attractive as some of our favorite wheels are, they generate lots of drag, since they are in effect crude turbines throwing a column of turbulent air laterally out into the slipstream, effectively increasing the frontal area of the car and buggering airflow around it. Better aerodynamically to go with smooth wheels, flush covers being about the best. Wheels like the Porsche "bowling ball" or "sewer lid" type are aerodynamically quite good, but unattractive to my eye, sorry to say.

Mirrors are also a significant source of drag, in the order of 5-6% of the total. Some on Ecomodders have gone with removal of external mirrors, replaced with fisheye ones inside the door windows and so out of the fast, turbulent, and therefore draggy flow that whips over the fender and around the windshield.

Ecomodders also reports worthwhile benefits from blocking the upper grill intake--the lower section down near the aerodynamic stagnation point at the nose of the car is adequate for cooling airflow--and a smooth cover for the upper grill (where airflow is pretty fast and so draggy) has significant benefits.

Most of us in the Bimmer crowd are averse to such mods for aesthetic reasons. That said, the belly pan idea still has merit, since that part of the car is out of sight. Worth considering, and certainly worth perusing the Ecomodder website for such ideas. Also, consider some of the almost un-noticeable mods made in recent Mercedes cars, such as small fairings to divert under-car airflow around the wheels, and/or allow trapped under-car turbulent air to escape more efficiently. This also helps reduce cooling drag, which is a very large portion of total drag.

[Tiger]

My MB E300 diesel got a full belly fairing all the way back to middle of the car. Comes off in two pieces.

[632 Regal]

So I have been driving to santa barabra a couple times a week and did a little test on the MPG

Couple things I noticed...now let me remind you that the times of the drive and the weather conditions were pretty much the same for all trials...there were no stops or presses on the breaks and the MPG averages were started once the car was on the freeway and on cruise control till the off ramp at my destination

I noticed that @ 65MPH I got 31.1 MPG but interesting enough at 75MPH I got only 26.3MPG

now this might be no biggie but I found it rather interesting how only an increase 10MPH can decrease fuel consumption by some much

Umm your forgetting 1 huge factor, ground cover per gallon. So you coverage is 31.1 @ 65 but 26.3 @ 75... I am NOT a mathamagician but from running them numbers through my head its about equil for ground covered.

Am I way off missing some grand desigh here?

Heh... didn't think so.

:D

Then again I rebooted and maybe I am way far off from reality.

[jofusfarr]

Huh?



Umm your forgetting 1 huge factor, ground cover per gallon. So you coverage is 31.1 @ 65 but 26.3 @ 75... I am NOT a mathamagician but from running them numbers through my head its about equil for ground covered.

Am I way off missing some grand desigh here?

Heh... didn't think so.

:D

Then again I rebooted and maybe I am way far off from reality.

[Bob in San Jose]

Lets see, ground cover equals miles?
As in Mpg where M equals miles.
I think your logic is illogical

[Dave M]

Jeff's been inhaling again ;)

[whiskychaser]

I am NOT a mathamagician but from running them numbers through my head its about equil for ground covered.

Comparing % increase in speed with % increase in distance covered, I reckon you get a net 3% improvement in ground covered by going 10 mph faster;)

[Bill R.]

Tiger, MB does that to catch all the oil thats leaking and keep it off of the driveway...:)

Only semi joking, i've had more than one customers car where i pulled that belly pan off and had to dodge the pool of oil that spilled out.. That lip around the pan holds a quart or 2 on the leakers.


My MB E300 diesel got a full belly fairing all the way back to middle of the car. Comes off in two pieces.

[Tiger]

LOL If you don't see a drainhole, drill a hole to make sure... LOL

[mzarifkar]

our drag cooefficient is .31 according to bently, which is the same as a porsche 997

another method for keeping track of consumption is l/h on the OBC, is you press 1000 and 10 at the same time, then enter test 7 SR (press 1 7 times) it will display your fuel flow in liters per hour. coupled with test 9, which shows your fuel capacity in liters, and your speed, you can spend away several miles with mental calculations