News:

www.W116.org - The #1 resource for our W116! Established 2004

Main Menu

280 SE fuel consumption

Started by carl888, 09 September 2006, 08:25 AM

carl888

Hello w116's,

Although this is relevant to my w126 and I posted on a w126 forum, I thought you Australian w116 280 SE drivers might be interested in my findings today regarding ignition timing.  Do any you have any experience that mirrors mine?


Oh, and I know I betrayed you all, you can see my new car here:

http://s115.photobucket.com/albums/n281/carl308888/280%20SE/




<<Well,

My 629 km round trip yesterday resulted in the 208 SE consuming a pathetic 22 mpg or about 13L/100 kms! OK, there were short bursts of 160, but really, that's not acceptable. Even more so, I've done that same trip regularly in quite a few other cars and can report the following consumption figures:

1984 BMW M528i
34mpg

1997 Porsche 911 Carrera
32mpg

Mum's new 2006 Citroen C5 Diesel
51 mpg!

Brothers 1994 C-180
36 mpg

1976 Ferrari 308 GTB
27 mpg

In other words, the Mercedes is dreadful. Even a carburettored 3.0 Litre Ferrari engine with 40mm of choke for each cylinder easily manages 27mpg. I know the 280's it's a bit short on gearing but the Cd is pretty low and with the cruise control on, well, it just should be better.

Luckily, yesterday a M110 workshop manual arrived in the post so I sat down this morning to see what could be done. Well, the first thing to catch my eye was the ignition timing. I noticed that the idle ignition timing (Vacuum hoses connected) for the USA, Japanese and Australian cars is 2 degrees AFTER TDC. That's ridiculous especially after seeing the advance curve. So what's happening to our Australian cars, is half the fuel is heading out the tailpipe, and being consumed by secondary combustion in the manifolds thanks to the smog pump....except at idle, which what the ADR27 directive is trying to reduce, idle emissions at the expense of everything else.

Armed with the timing light and the tank full of BP 95 octane, I began to advance the ignition. I started with the European timing specification which is 2 degrees BEFORE TDC. I took it for a drive, tools and timing light with me. The difference in the way the engine responded was not subtle. From 1500 rpm the car had increased torque and on the freeway, I noticed the vacuum gauge was about 4-5mm closer towards the "Economy" end and I was using less throttle. Higher up the rev range the power kept coming on whereas before it felt pretty strained about 4,000 rpm. I found a hill and dropped it to third and floored the throttle, excellent, no detonation up to 6,400 rpm. I then pulled over and advanced the ignition to another degree to 3 degrees BTDC. I repeated the experiment and still no detonation. Then I tried 7 degrees BTDC and in third gear at 5,000 rpm I could just heard slight signs of pinging so I instantly backed off, pulled over and reset the timing back to 3 degrees BTDC. I drove the car another 40 kms on the freeway and the fact that I was using less pedal was very obvious. I really look forward to checking the fuel consumption again when I do a run but I think it should be reduced somewhat. I would really like to plot some power and torque curves on the dyno too so that I have some hard data. The funniest thing, was, the car now idled at 1,400 rpm, so I had to re-set that of course.

I am concerned that I may be running too much advance under high load, high ambient temperature conditions and I'd really hate to burn a hole in a piston.......... I'll keep the timing light in the car with the tools just in case but I am only running 1 degree more than the European specification for these tests so I think I'll be OK. At the very least, I see no reason why you couldn't run the European 2 degrees BTDC setting. I am confident that at these ignition settings, the car will not run on 91 RON fuel.

Tomorrow I will run some gas analysis tests with the EGR and Air injection both in circuit and removed, I wonder what the result of that will be?

I'm really happy the way the car responded to a little tweaking today and I can't wait to check the consumption on my next run.

Of course I'm curious to know what the other 280 drivers are getting fuel consumption wise?

Regards,

Carl.>>

Denis

Hi Carl and friends

I hate to tell you this but it is a fact that most of the time, the M110 uses nearly as much fuel as an M116.

In fact, if you have the original Mercedes-benz owner manual, there is an interesting graph in it that shows fuel consumption of the M110, M116 and M117 (at least in my booklet).

What is shown ?

That the M117 generally uses almost a litre per 100 more fuel than the M116 - noticeable on a long vacation trip like we take in France (not to mention some wild aussie cross-country run  8) ).

And that the M110, while not doing much better than the M116, uses MORE fuel than the M116 between 190-200 kph. And this is not a mistake.

The 2.8 litre engine is too small for the mass of these cars. While fuel consumption is related to engine size, all engines (especially of that era) are at their peak efficiency in only a narrow rpm band, usually at medium rpm and around the maximum torque speed.

Under the substantial weight of these S classes, the M110 is more often outside that band than the M116.

Guess why I selected an M116 engine for my W116 car after this 8)

There are many known cases of this situation - the seventies Ford capri 2000 consumed LESS fuel than the 1600.

You can try to improve it a bit by tuning but don't expect miracles.

IMHO, the M110 is best suited to a 280CE 5-speed which is significantly lighter and where it easily matches the performance of the 350 Euro and almost matches the M117 Euro.

BTW, the great gain of the W126 with an M110 is being 50kg lighter  ::) than the equivalent W116 - not a great success IMHO.

Cheers

Denis

Paris, France

116.025

#2
Quote from: Carl Jones link=topic=768.msg6017#msg6017
My 629 km round trip yesterday resulted in the 208 SE consuming a pathetic 22 mpg or about 13L/100 kms!

Having driven Euro W116 280SEL and 280SE for the past several years, I'm impressed you managed 22 MPG!  For an M110, I'm afraid this is quite respectable. 

Thanks for your information on the timing, I'm now curious to check mine and see where it is and if I can get a little more pep out of my Hemi engine :)

oscar

Interesting.

Don't know if this'll make you feel better Carl, on my 1600km trip to Sydney etc I av 15.7 L/100km.  Bigger engine I know ie 3.5L V8 however at the time my motor was effectively a 2.6L V6. You may have heard about my engine problems somewhere :P ::)

Anyway, I wondered whether the fuel consumption may turn out less due to those two redundant cylinders and no injection activity. Boy I was wrong! Would've been interesting to pull the plugs to reduce the compression strokes.  But this wasn't a voluntary test and I don't want to repeat it.

It's good to see that some tweaks are providing improvements. 13L/100km i suppose isn't crash hot these days but unless I read a post like this I doubt I would've questioned it.  Good info.

If you can do gas analysis I'm assuming then you'll be able to change CO adjustment or mixture or something along those lines, is that right?
1973 350SE, my first & fave

fatherpierre

I remember getting an average of 17mpg in my 1979 280SE doing London driving, and I could squeeze 24mpg on runs.  My car was in dire need of a service.

My 'new' 350 gives a very similar set of figures so far.  I did 100 miles to work and back (85%) motorway and at 70mph. 

My last 280SE (126) gave a good 5mpg over the 116 and was much more responsive but had the same box, engine and running gear.

Perhaps it's down to weight and overall health of the whole beast....

When cars get old there's a whole multitude of factors that can cause problems. 

Denis

BTW carl

Don't you have the Euro engine in Oz ? With the 9 to 1 compression, you should set it at Euro specs ( I would even put in  several degrees more) and do exactly what you did listening for ping. But also adjust the overall mixture with a screwdriver at the top of the FI distributor. If you break the 12 litre/100 barrier, let us know  :P

To really save fuel : remove the spare tire, the carpets and sound deadening insulation, install manual window cranks, remove the air conditioning, install a small battery,, use only small tyres (195 s low friction Michelin) on alloy wheels, drive with a half empty fuel tank and ultimately get on a diet  ;D

You can also install an aluminium bonnet, boot and doorskins but you will not cover your expenses with the money saved.

The ultimate solution is to put an OM617 in there...

Denis

Paris, France

chazchuzzlewitt

I've found all the MB engines I've driven deliver their power in a similar fashion- adequate up to the mid-rev band then between 2500-5000rpm they really wake up. This of course doesn't help the fuel economy running auto cars at motorway speeds, but tho power and control for high-speed driving is better. I don't think the 110 engine is underpowered in the 116- it seems plenty peppy and powerful enough from what I've experienced to propel this tank along as well as the 350 I had before..

I thought the 103 engine that succeded it felt more underpowered moving the 124 around, and this car really needed the 104 24v engine before it really moved.

Denis

Hi fellows

Styria is hinting that his big displacement is not that bad...It is unfortunate that Daimler-Benz did not create a fuel consumption curve for the M100 because I suspect that at 110 kph, it would not be that much higher than an M117 for the same reasons as the M116 is not much worse than the M110.

If I were to dream, I would wonder what the M110 would get with 10 to 1 compression and a modern engine management system (like a megasquirt kit) but I would venture to see that 11 litres/100 would be reachable.

Cheers

Denis

Paris, France

s class

I've driven my 280SE for 10 years and over 200 000km personally, and I have done all the maintenance and tune-ups myself.  The best it ever gets is about 13l/100km crusing at 120km/h, with not much load on the largely downhill run from Johannesburg to Durban (580km).  Generally, I would expect more like 14,5l/100km on the open road at sensible speeds.  (I could tune it slightly more economical, but then performance suffers and it tends to ping over 4000 rpm.  If I drive it at 4500rpm on the open road, consumption is more like 15,5l/100km or even more.  Sorry, that's just how it is. 

My engine is a euro spec in excellent condition (full engine rebuild with OEM spares, new injectors, new fuel distributor, new pump).  Also, suspension is rebuilt front and rear, so no extra drag from alignement issues.  I don't expect I'll get it better than this. 

Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

carl888

Hi Denis,

Thanks for your reply, but I don't think some of the things you say are true I'm sorry.  Remember, I am speaking about steady state fuel consumption.  My car needs about 30 HP to cruise at 110 km/h on a level surface with tyres pumped up and alignment correct.  Now it needs that power irrespective of the size of the engine, all it needs is 30HP.  The weight of the car makes absolutely no difference unless we are accellerating.  Remember our friend Newton, he knew about accelleration, therefore F=MA (Force = Mass x Acceleration), that's something we can't change....but we are not taking about accelleration!   All we are worried about at 110 km/h is friction and air drag.

Back to the M110, at a steady 110 km/h, my car is supposed to consume 10.3L/100 kms.  NOT 13!!  I am not going to stop on this project until my car consumes what the factory claims!  Actually, that's not quite true, I am prepared to accept 11 L/100 kms because the Australian cars have a 8.0:1 compression ratio engine not the 9.0:1 European one.  I must admit, when I had the head off my car, I was very tempted to shave it.  I might still do that, but I'd take it to 10.0:1.  That's for later.

I think you might be surprised if you weighed a W123 BTW.  My W126 280 SE weighs 1720 kgs.  My mums W123 300 TD weighs 1,747kg!  Both cars full of fuel, no driver.  I have a friend with a 280 CE, next time we pass our local weighbridge I will weigh it.

Oscar....yes, the gas analysis and mixture adjustment.  I am halfway though playing around with the injection, with the EGR and air injection both connected and disconnected.  My initial tests suggest that with the current ignition timing, 98 RON fuel and the pollution gear removed, the car will still pass ADR27!!!  If so, had we been able the purchase 98 RON fuel back in 1982, they car would not have needed all that rubbish in the first place.  I will confirm this later.

fatherpierre:  That's more like it, I see no reason why I can't get to 25 mpg minimum on a trip.

Styria:  Yes, now you can see why I gave up on finding a w116.  That car is not yet how I would like one to be, but it's closer than all the other 57 cars I looked at.  Unfortunately I have not yet been able to do enough miles in the 280 to confirm the fuel consumption, hopefully later in the week.  It is looking good though after 180 kms so far.

More to come!

Regards,

Carl.


Denis

Hey carl, you said:

QuoteMy 629 km round trip yesterday resulted in the 208 SE consuming a pathetic 22 mpg or about 13L/100 kms! OK, there were short bursts of 160, but really, that's not acceptable.

But now you are into "steady state fuel consumption", OK... you changed the rules so it is not so much that "some of the things I say are not true" but that we are using different criterion now.

This is what i said:

http://gallery.w116.org/v/show_room/350SE/conso_DBZ.jpg.html?g2_enterAlbum=0

Now looking at the 280SE, it is around 11.2 l/100 at 110 kph and given the advantages of the W126 10.5l/100 is a possibility but you had better be very vigilant : one slip of the toe and you are right out of your target  :(

And for that matter, my M116 is supposed to be just about as good as the M110 , at about 11.5l/100 which I know to be a pipe dream.

Let's face it : a track, perfect weather and a bit of luck will get you those figures but I wouldn't expect them day in day out. What is more important are the relationships between these curves.

As I said, I wish the M100 graph would be there, who knows, it might only use  14l/100 at 110 kph  :P

But who would believe...that is the reason for the DIN 70 030 standard which has been used for a long time in Germany as the "realistic" figure.

BTW - my "theory" of the small engine using more fuel than the bigger one is known to engineers and I last discussed this with a master mechanic/trainer working for Jaguar in the UK.

But I wish you luck on that project and do tell us the results but it would be nice to also get "real world" values as the DIN 70 030 standard (roughly defined as 110kph +100% fuel consumption).

Cheers

Denis

Paris, France

oscar

Re the fuel curves and consumption posted by MB versus real world consumption figures.  You all know this I'm sure but isn't it unrealistic to compare both when the "city" and "highway" figures are obtained in a static environment.  For example, on a dyno and measuring air volume and vacuum to determine fuel usage not emptying a tank and finding the nearest bowser. Something like that.  It's not necessarily the manufacturers fault as a way of promoting these figures, instead perhaps a more uniform method of testing all cars.

I'm not knocking anyone's attempt to experiment or improve fuel consumption, it's just that I read a long time ago that factory posted figures are for comparison to other models/brands etc and are usually lower than what one would experience themselves.  Having said that, there's no harm in trying to break records and I once boasted here about 10.8l/100km, 22USmpg, 26UKmpg in my 350.  Not surprisingly, I'm yet to substantiate that figure :P
1973 350SE, my first & fave

robertd

Hi Carl,
I have had a good look at the pics of your 280SE, looks in fine condition. I must admit that I am a sucker for most mercs, and I would probably own a good W126 as well. The only thing is, I love the effortless surge of the big V8's. Today for example I had to teach a young buck in a V8 holden ute a lesson in manners. He had been tail gating me through the township of Drysdale in a 60km zone. I waited until the large round about at the edge of town where the road widens to double lanes. At this point as predicted this hoon blasted past ( or should I say tried to ) He didn't know there was a bigger hoon ( me) Just waiting to give the big 6.9 a tramp. I couldn't wipe the smile off my face for half the day. Thats what I call satisfaction.
Carl, when are you going to come down th coast and play cars with me?
Regards Robert
116   1978 450SEL 6.9 #  4848
116   1979 450SEL  6.9 # 5884
116   1979 450SEL  6.9 # 6225  SOLD
116   1978 450SEL  6.9 # 5128  SOLD
116   1979 450SEL  6.9 # 5884  SOLD
116   1974 450SEL  DJet

carl888

OK guys, here we go.

Today I was finally able to do another run in the 280 SE.  After experimenting with timing and mixture during the week, I arrived at the following set up before the run.

timing:
4 degrees BTDC
95 RON fuel
mixture:
lambda 1.0 @ idle of 825 rpm, vacuum connected.
tyres:
34 psi all round

The run was not under the same conditions as the last one where I managed a crazy 22 mpg.  The ambient temperature was 8 degrees centigrade hotter and I had 4 people all up this time compared with 2 before.  I ran the air conditioning for 50% of the trip whereas last time I did not run the A/C at all.  Finally, the average speed was up from 109 km/h to 116 km/h for the duration of the test.

The car managed 11.50 l/100 kms or 24.5 mpg.  Needless to say, I am very happy that I managed to better the pervious run consumption by 2.5 mpg with the air con for some of the way with a 7 km/h higher average speed.  Had I kept the speed to 109 km/h average of the first test, I might have cracked 26 mpg with the air con off.  I will certainly try this later!

Anyway, I just goes to show that with a little tweaking and common sense, the is room for improvement with these cars with a few basic workshop tools.  Anyway, I've done all the hard work for you, now you can try it for yourself.

My car is coming up to it's 80,000 kms service so I will certainly shout it some synthetic oil, a valve adjustment and some plugs amongst other things, maybe I can squeeze a bit more out of it yet!

Thanks for the all the replies to my message earlier, I'll repy to them all later when time permits.

Regards,

Carl.



carl888

Hi Styria,

Yes, the high average speed :)  I hope you understand but I would prefer not to disclose the location, at least until I've had a chance to check the mail box over the next few weeks!   I will go far as to say it was a Melbourne to South Gippsland run, on some of the back roads.  Average speed calculated with a friends GPS after correcting my odometer (1% over reading, speedo 4% over reading)

I think you might be confusing Lambda with CO.  A lambda reading of 1.0 refers to an AFR (Air fuel ratio) of 14.7:1.  Another term is Stoichiometric or "Ideal" mixture for this reading of 1.0.  A Lambda reading of greater than one means it's running lean, a Lambda reading less than one means it running rich.  Note, although we try to aim for a Lambda of 1.0, this is a compromise setting between economy and power although it does guarantee a complete burn of the mixture.  Maximum power is achieved with a Lambda of 0.86 (AFR of 12.60:1) and maximum economy is a Lambda of 1.05 (AFR 15.4:1).  I managed to get the CO down to just over 1% which I'm happy with.

I have uploaded some pics of the gas analysis, you can see them here:

http://s115.photobucket.com/albums/n281/carl308888/280%20SE/

The first pic shows the analyser with the two tools needed to perform the job, the long screw driver for idle speed and the special long INHEX screwdriver for adjusting the mixture.  On the display you can just make out the Lambda being displayed.  The second pic shows the probe up the exhaust.

I have been measuring the urban consumption however I am uncomfortable posting the results just yet.  For what ever reason, I seem have improved the urban fuel consumption by over 25%.  I personally do not believe this is possible so I am going to average the results over three tank fills which is what I did to measure the consumption pre "Fiddling."

On a side note, I believe and engine really should never wear out now.  With modern lubricants the car body should rust away before the engine wears out!  300,000 is not a big mileage unless you want to sell it.

Allow me to answer the other questions from others:

Robert..yes, I'll visit soon, though I have a trip coming up so it will have to be late October.  I know what you mean about your 6.9, and I would like one, in fact, that is what I originally wanted, but all the cars I looked at were of an unsatisfactory condition and I bought the W126 because it was a peach, you can see for yourself soon.  As for dragging off hoons, you know I have other things for that :)

Oscar..Good point about the fuel consumption figures though it's pretty easy to replicate the steady state ones. 

Styria, I seriously thought about shaving the head, but I thought a nicer way to do it would be to buy a complete second hand head and rebuild it myself, so if the worst happened, I could put the original one back on.  To get it to about 10:1 only a bit over a mm would need to come off from what I calculated.

Denis...not really, and I don't want an argument about semantics, but I really think you need to try a little fiddling for yourself.  I covered 629 kms with a few busts of 160, that's about as steady state as you can get in the real world and also quite realistic when one does a trip.  It's all very well to have a theory, but it's better to back it up with experience IMO.  I've received a lot of comments about my tests (Mainly how I was wasting my time, not on this forum I might ad) but not ONE person had EVER tried what I did!  I reckon I can crack 10.50 L/100 kms if I stick to 110 km/h :)

Just curious about Paris, some of my Italian friends are really angry about the discrimination against non catalysed cars in the cities.  It looks like the banning of older cars in cities is already about to spread to Germany too.  Is this a possibility for France?  I hope not, and that you can enjoy your car for many years to come.

Regards,

Carl.