280 SE fuel consumption

[Denis]

Hi carl and other creatures of this great site

Actually, I have "tuned" a lot of cars for power and economy and the best results always come from the lighter cars.

I do not understand why you think that weight has nothing to do with steady state fuel consumption, if true a W116 made of feathers would use as much fuel as one made of lead ? F=MA is true enough but there are other forces acting on a moving vehicule.

You correctly note that drag (a horizontal vector opposing the motive force vector) is important but also friction, and the rolling resistance friction is related to the weight of the vehicule itself, it is the downward vertical force vector that contradicts the horizontal force vector of motive force. It applies resistance to bearings and tyres that is proportional to the weight of the vehicule. Reduced rolling friction is a very big deal for tyre manufacturers.

On the positive side of weight we do have the kinetic energy of the mass in motion but unfortunately the best fuel economy usually turns out to be at around 50 kph 

Wher your theory does apply much better is with airplanes in steady flight but car unfortunately do not benefit from an airfoil support...hmmm...maybe ...noooo...

In the end, "tuning" for better fuel economy often yields a 10% improvement but getting much more means bigger changes. For an M110 with K-jet, even the ones with a lambda computer, there are definite limits.

In your game, I would also consider an engine management system mod that could be tuned for a lean AFR up to 16.5 to 1 on a flat road, at steady speed. That is what I plan to try with my 350SE and Megasquirt setup. This device can also control ignition timing. I only wish it were economical to modify the engine from 9:1 to 10.5:1 compression but that is not economically recuperable.

Insofar as the catalyst law stuff for our older Eurocars, we all hide behind the "collector" status of our old Benzes here. At age 33, my 350SE has no problems and Paris has yet to face the "no cat equals dirty car" rules, in fact the city is just making car access more and more difficult. I also admit that driving a W116 in Paris is nice but parking it is a nightmare as even the underground parkings have tight turns that a 350SE barely deals with. A longer wheelbase W116 may be a bit too much !

These cars belong on the highways and excellent secondary roads in France. In the end, we may all have to park our older cars at the outskirts of town but that is really a good idea


However, I must protest the banning of the Fiat 500 "yoghourt pot" cars from the fifties in the city of Rome, it is a national outrage, an insult to Italian traditions 

Cheers

Denis


Paris, France

[NAS_878]

Here's some figure about my 1979 4 Speed Automatic 280SE fuel consumption.

Engine : M110.989
Static Timing : 15 BTDC
Differential : 3.69 to 1
Tire Pressure (cold) : 32 psi (front) , 36 psi (rear)
Max speed : 90 km/h
Avg speed : 70 ~ 80 km/h
Loading : 4 adult passengers (70kg+75kg+72kg+95kg=312kg) and empty bonnet (spare tyre in place)

Case #1: almost non-stopping driving (with 2-3 traffic light stop)

Distance Traveled : 114km
Fuel Used : 12.015L
Fuel Consumption : 9.487 km/L or 10.540L/100km

[ I am very close to the factory graphs on fuel consumption. ]

Case #2: average city driving, bad traffic jamm

Distance Traveled : 505km
Fuel Used : 70.83L
Fuel Consumption : 7.129 km/L or 14.025L/100km

Seems like the 280 fuel consumption is the best when doing non-stop suburban driving. (comfortable too)

[Andrew280SEL]

H

Seems like the 280 fuel consumption is the best when doing non-stop suburban driving. (comfortable too)

Yes, seems so. May or may not have something to do with the fact that the 280 always starts off in 2nd instead of 1st in Drive, I'm not entirely sure.

But know this: The M-110 motor is certainly going to yield better results when in the higher rev range, i.e it's power curve. I have noticed, and I swear it, my 280 will always be better fuel consumption when doing 100-110 than when I'm doing 80 kms. Reason being, obviously, the M-110 in my car is really starting to bring the power on around 110 kms, whereas around 80 in 4th it's in the lower rev range and the engine's not "comfortable".

So I'm wondering if I'm doing 80kms, perhaps I should try cruising in 3rd instead. Not sure, haven't tried it yet but it'd be interesting as the engine would be working less hard.

Sorry if i've stated the obvious guys...but at my age it's new interesting stuff to me 


EDIT: Sorry, should've read Styria's post, I've basically just repeated what he said 

[NAS_878]

I can only say that my W126 280SE uses sometimes MORE fuel than the W126 560SEL and they are both tuned properly.

Sad...

But here in Malaysia, we have to pay road tax every year and it's based on the displacement of the engine.

My JDM 1986 Honda Accord 2.0Si (B20A) [1928cc] is around MYR 380 per year.
My 1979 280SE W116 [2800cc] is around MYR 1500 per year.

I guess if you are living here your 560SEL would be around MYR 13000~15000 per year.

For W116 450SEL 6.9 that would be around MYR 20000 per year. [You have to be VERY RICH to keep this car]

I would say it's ok for the W126 280SE to use more fuel than the W126 560SEL if both cars are in Malaysia.

I LOVE the 6.9 but it's impossible for me to own one here.

All 6.9 owners in this forum sure touched by an angel... 

[carl888]

So I'm wondering if I'm doing 80kms, perhaps I should try cruising in 3rd instead. Not sure, haven't tried it yet but it'd be interesting as the engine would be working less hard.

Sorry if i've stated the obvious guys...but at my age it's new interesting stuff to me 


EDIT: Sorry, should've read Styria's post, I've basically just repeated what he said 

H

Seems like the 280 fuel consumption is the best when doing non-stop suburban driving. (comfortable too)

Yes, seems so. May or may not have something to do with the fact that the 280 always starts off in 2nd instead of 1st in Drive, I'm not entirely sure.

But know this: The M-110 motor is certainly going to yield better results when in the higher rev range, i.e it's power curve. I have noticed, and I swear it, my 280 will always be better fuel consumption when doing 100-110 than when I'm doing 80 kms. Reason being, obviously, the M-110 in my car is really starting to bring the power on around 110 kms, whereas around 80 in 4th it's in the lower rev range and the engine's not "comfortable".


Hi Andrew,

The M110 engine produce more power higher up the rev range, but there will be a corresponding increase in fuel consumption too, so your car will consume about 20% more fuel at 80km/h in 3rd as opposed to 4th gear at the same speed.  If you want to check what your car should be consuming in fuel vs. speed, have a look in the owners manual, the facyory fuel consumptions charts are plotted in the back and from my experience, are surprisingly accurate.

Regards,

Carl.

[Andrew280SEL]

Hey Carl,
Thanks for that, I had a look and yeah, they do sound pretty accurate. I have learned something new   

[huck280]

I'm impressed - I had a w123 280e with the 4 speed box, and once managed 22mpg on a long run averaging about 58. That was the best I ever got.

On my 450sel, I get about 15mpg, and about 19.5 on a long run (240 miles) oscillating between 60 and 85 mph, with a fair few traffic jams. I was really pleased with that - that's almost factory claims!

Leif

[NAS_878]

I wish I can try the fuel consumption at 110km/h.

I think I need to change my differential... because if I go higher than 90km/h... the rear of the car will start to vibrate... that's not good... but I did give 120km/h a try... although only a few second. This is where the fun of driving a W116 280SE starts.

[johnnyw116]

i find the fuel consumption of my W116 not important 

[johnnyw116]

thank you for the compliment  but i drive my W116 more than my daily car its almost the other way around  it is in the shop for a new paint job now a friend of mine gonna give it a new paintjob he's verry good , i had some litlle rust things at my sunroof and scratches around my car not verry visible on the pictures gonna make a new picture when he has his new paint job i am verry happy with this W116 becouse he has much options in holland 280's have almost no options mostly the options are sunroof and automatic but mine has almost full options rare for holland 280's