Improving poor fuel economy - W124 multivalve diesel

[skemball]

O.K working on the basis that it is NOT water getting into the engine have you checked the brake fluid level or gearbox oil levels - This assumes they both have a vacumn take-off from the manifold (im not familiar with the 300D) If they dont then ignore my suggestion.

Many years ago i seem to remember a car that was sucking 'fluid' from the auto box into the engine - the vacumn take off was for kick down.

 

[grober]

O.K working on the basis that it is NOT water getting into the engine have you checked the brake fluid level or gearbox oil levels - This assumes they both have a vacumn take-off from the manifold (im not familiar with the 300D) If they dont then ignore my suggestion.

Many years ago i seem to remember a car that was sucking 'fluid' from the auto box into the engine - the vacumn take off was for kick down.

wrong thread??

 

[defector]

Ok, i realise this is an old thread, but here are my observations.
My E300d 94 estate with 220k miles which i put back on the road a month ago, a full tank brimmed to empty - literally as i ran it dry to check my low fuel light (which came on 1, yes 1 mile before the fuel ran out) - i achieved 575 miles.
The mileage consisted of 375 miles of motorway driving at speeds between 70 and 80 (with cruise where possible), and the rest in both urban and semi rural environment.
This gives me a consumption figure of just over 36mpg. I'm pleased
Otherwise, in urban and semi rural driving i'm getting about 32-33 mpg which again i'm pleased with.
Figures based on 1,900 miles since the car was back on the road.

My maintenance prior to putting back on the road was:
New pump seals
Cleaning out gunge from manifold
Cleaning out EGR and then blocking off EGR to manifold.
Removing ALL spindles/valves from manifold.
Using Diesel Purge to clean out injection system as i was getting smoke and bad idle/missing from cold - at least one bad injector- which has helped but engine is not as smooth as i would expect compared to a previous 300d, and this is summer so i expect it to be worse in winter so i will have to get the injectors done by then.

Lots of little things to do, and one or two major as well ( i think the suspension spheres definitely need replacing)

 

[Marko300d]

I do an 80 mile daily commute in my 93 218k miler S124 4speed auto
My journey is 70 miles of motorways and 10 Of 30 mph urban streets
I get 39-42 mpg
That's driving at between 60-70mph on the motorway and driving with a very light right foot ( but keeping up with the flow)
I get 550-80 out of a tank
I've just sold my 2.0 190D which l commuted in for the last 3.75 years and did 90k miles in
That did 47-50 mpg on the same commute

Mark

 

[Dieselman]

Mercedes multivalve diesels are under-geared, so cannot give exceptional economy. A higher axle ratio would improve things noticeably.

 

[mejermy]

I'm presently returning a gnats over 30mpg in mixed running, but I drive like a granny. E300DT OM606 auto. Looking at NumberCruncher's old (2008) post, does the team think that removing the cross over pipe altogether, removing the 3/6 flap and blocking any holes, and by passing the MB air filter by bolting a K&N type filter directly onto the manifold inlet (with adapter as appropriate) would simplify the airflow path? The mixing chamber would have to remain in place, EGR blocked already.

Dieselman's point re: gearing is well made, but I think one needs the engine to be 100% before moving onto further mods. Bolide's observations about higher revs are true, but it has to be a blues and twos emergency before I go much over 2000rpm.

 

[grober]

At High speed aerodynamics are vital. Make sure that engine undertray is still in place and in good nick. Using a slightly more modern engine oil 5w30 might help likewise a Dexron 3 rather then Dexron 2 gearbox fluid. A couple more psi in the tyres and low rolling resistance ones the next time you change. Vital also is car "attitude" -- a nose down car is more efficient than a nose up one. So no sagging back suspension please. Perhaps a diesel Cetane enhancer such as MILLERS DIESEL POWER ECOMAX Fuel Additive | Performance Additive | DIESEL POWER ECOMAX Folks think that increased fuel efficiency has a single magic bullet- in most cases its simply lots of little improvements/ Optimisations which together can make a difference.

 

[mejermy]

Grober - valid suggestions, as usual thanks. Both trays are in place and correctly attached. Pitch trim is correct. I use 10w40 as recommended for these older engines, but will consider going to something lighter. There are forum concerns about provoking leaks with more modern stuff. I put 300ml of 2 stroke in each tank (with my S211 220cdi and E250DT as well) and find it gives a smoother sounding engine, although no great consumption improvement. When I did the fuel filters I ran a filter full of pure Forte diesel injector cleaner through when restarting. The box oil is newish from the PO, but I will consider your suggestion when I do a change. Regarding my post, I just think all the 'high tech' obstructions in the intake manifold must give very little advantage even when new. The swirl flaps are out of the 211 for example, and it's better for it.

 

[Dieselman]

I'm presently returning a gnats over 30mpg in mixed running, but I drive like a granny. E300DT OM606 auto.

Is it definitely engaging top gear?

 

[kth286]

Nobody has mentioned brake drag in this thread.

It can make a big difference to fuel economy.

In my experience brake pads are not removed on a regular basis to be greased on their edges where they slide, so subsequently stay stuck against the disc in many cases.

Jack up and spin the wheels to determine.

 

[sspeed]

I put 300ml of 2 stroke in each tank (with my S211 220cdi and E250DT as well) and find it gives a smoother sounding engine, although no great consumption improvement. .

I too put 2 stroke oil in my V6 Diesel..
I thought the V6 Diesel was as smooth as its possible to get for a Diesel.....
Until I put the 2 stroke in..
I have been doing this for over 4000 miles now and the difference is quite considerable..
I haven't done it for fuel consumption reasons.. I did it for High pressure pump / Injector protection.
I did loads and loads of research from all over the web before I started doing it..

 

[Druk]

My recent diesel conversion of a 606 turbo into an R107 has now done 1600 miles and returned 36.7mpg over that distance. This is with standard turbo, straight thru 60mm pipe exhaust system, egr delete, no cat, no aircon compressor and manual gearbox driving thru a 2.47:1 diff. 70mph equates to approx 2500rpm in 5th.
Grobers comments on 'head-up' attitude might be very relevant to a possible further improvement as the thing has an up-at-the-front stance which is on the cards to be corrected. It seems the 606+manual box is considerably lighter than the old M110+autobox that came out.
Custom undertrays might have added benefit as well although a 107 is perhaps not the worlds most aerodynamic thing to start with.

 

[mejermy]

Is it definitely engaging top gear?

I'm quite sure that it gets there in a timely manner. I do count the shifts. I've had the car for a year, but only around 2000 miles as it's a 'spare', so research and refining is ongoing.

I too put 2 stroke oil in my V6 Diesel.

Thank goodness I'm not the only one. The Land Rover site went on at some length and seems full of the converted. The MB sites seem full of infidels who won't give it a go!! I posted on another thread about my experiences and data over 15000 miles, but in short it's all good.

Nobody has mentioned brake drag in this thread.

I do check for this at stops, such as lights, to see that the car rolls freely after braking,a nd there's no suggestion otherwise. I'm alert to this as my wife's W169 is a bugger for brake binding, and I'm in there (the W169) regularly to sort it.

Druk's ratios are interesting. I think I'm at 33kph per 1000rpm, or 62mph ish at 3000 rpm, which is muich higher. This from memory though, and based on data from the E250DT

 

[joecash]

What temperature is your thermostat meant to maintain? If it is running "cool" your mpg will be down

 

[Dieselman]

driving thru a 2.47:1 diff. 70mph equates to approx 2500rpm in 5th.

You could do with a higher ratio. In that body an OM606-turbo should be able to pull about 2000rpm at 70mph.

Any more news on your conversion now it's finished, it sounds great.

 

[Dieselman]

62mph ish at 3000 rpm, which is muich higher.

No wonder the economy is poor, that's 1.6 litre petrol type gearing.

 

[mejermy]

Just checked on the EPC and the diff should be 3.07:1. Was under there only yesterday changing the diff oil; should have checked on the flange. Next time then. This equates according to my calcs to 66.86 mph at 3000 rpm, assuming a 23" wheel diameter (allowing 4" x 2 on top of the 15" rim) and 1:1 in the box in top. Can't be ****d to go out and measure the wheels. So yes; not far from my earlier figure which relates to an OM605 and clearly low geared.

 

[Druk]

You could do with a higher ratio. In that body an OM606-turbo should be able to pull about 2000rpm at 70mph.

Any more news on your conversion now it's finished, it sounds great.

Possibly it would in top but changing the diff for say a 2.28:1 from a 500 would make the intermediate gears too high. The one big drawback is first is high which results in clutch protest pulling away on any form of gradient. It's still a heavy car to get moving. 2nd, 3rd and 4th are a delight to drive trundling round lanes and B roads which is what the car's for after all. I have an overheat problem when it's pulling hard up a long incline, which may be pump timing but I'm more inclined to think it's lean mixture. Max displayed boost is 0.7 bar and there's no real way of knowing if the ALDA is working commensurate with this boost. Because of the rapid rate of temp rise I'm thinking EGT's are going way high. Other than that it's a delight. Really pleasing to drive.

Some less pressing mods include a centre 'cherrybomb' silencer to try and alleviate the exhaust drone at 70+mph, and a custom airbox/filter. The current K&N filter lets too much of the high pitched turbo whistle escape. Annoying after a while.




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[Dieselman]

If it's not smokey, the EGT won't be high. Lack of fuel would also make the boost pressure low.

 

[Druk]

It's definitely not smoking, I've had it followed and it's clean, even under load. Are you saying that too much fuel would cause EGT to raise? I presumed it would be the opposite with it running lean. I'm also going to remove a section of the intercooler which, at present, blanks off most of the top section of the rad and is nearly twice as large a surface area as the original 210 one.




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