My ML350 2003
 

So i have this car that i was going to sell for a diesel which can be modified a bit better but it appears i may be stuck with it.

It already has LPG and currently my fuel cost is comparable to a modern gasoline car so it is not too bad to own.

What mods do you recommend doing on it to make it more economical?

Will water injection play nice with LPG?

I also plan on deleting the mirrors which are slightly broken at the moment.
I also plan on putting full grill blocks. I can spray the radiator with water to reduce the need for the fan as it can suck quite a bit of energy when it is activated.

Hot air intake, would that have any negative effect on using it with LPG?

What else can you guys think of? I know it is not the most economical to begin with.

This is what it looks like:
http://cdcssl.ibsrv.net/autodata/ima....jpg&width=390

http://deckerkoepp.com/vehicle-photo...benz-ml350.jpg

What is your typical commute / driving like? City or highway?

Typical commute is mostly city with traffic ( i live in Istanbul with 20 million other people who clog up the highways). I know in traffic nothing much can be done for fuel economy besides getting a smaller car. But i do frequently go on longer trips. For daily commute i try to use my motorbike as much as possible.

welcome!
you could increase the psi in the tires to 40+. that would help on the trips.
I have a KIA Sportage and it adds a couple of MPG when I take trips.

LPG is already quite cold, at least when it's aspirated in a liquid phase. IIRC most of the LPG conversions require the vehicle to start on gasoline and then switch to LPG when there is enough heat in the coolant to exchange with the LPG at the vaporizer.


Are you sure a water spraying would be so much less energy-intensive than a regular electric fan? There is also the weight of a water tank, pump and nozzles. Even though it's already used in a handful of high-performance applications such as hill-climbing vehicles that run at Pikes Peak, I'm not sure if it would be a good idea into a regular road-going vehicle.


A warm air intake is unlikely to have negative effects with LPG. BTW some earlier dedicated-ethanol vehicles in my country had an adjustable air intake which allowed a more precise temperature trimming from a colder intake to use in summer to a warmer one more suitable to use during winter in order to prevent carburettor icing. Pretty much the same feature is still used in small piston-powered aircraft.

It is injected in gas form, it does have an heat exchanger-vaporizer to boil the LPG.

I would have thought that direct injecting it would be beneficial for performance as it also cools the intake charge and should be easily controllable. Not sure why they prefer gas injection.

If it helps at all, the gasoline version of your car is EPA rated for 14 mpg city, 17 mpg highway.

Actually, in traffic and city driving is where you can get the most significant improvement in fuel economy. Look ahead as far as you can to anticipate traffic conditions ahead, try to look through windows or around the car in front of you. You know, the usual stuff. Check out the 100+ hypermiling tips at the top of the page and see what techniques you can use.

Remove any unnecessary weight, like unused seats, or misc junk. I don't risk removing my spare, but I also don't have an inflater/plug kit to patch a tire. Only you can decide what you are comfortable with. Pump the tires up more, try to maintain the correct pressure bias if there is one. For example, my accord specifies 32 PSI front, 29 PSI rear, so I set it to 51 front, and 47 rear.

Regarding your water spraying idea, that is actually a really cool idea. Make sure you monitor your engine temperature with those grill blocks, the idiot gauge is not a suitable replacement.

I had an idea for what you could do to optimize the water sprayer. Place a large water tank in the front of the car and connect a thin rubber hose above the grill block opening. You could either drill really small holes all around the hose, or you could use drip irrigation hoses. Also, install a closeable valve before the hose so you can turn the water supply on before a trip, and off when you are done. With this setup, you wouldn't need a pump and the associated electrical draw.
Attachment 21213

If you are going to do this, consider using distilled water in the water supply, less chance of things rusting.

Another idea I just had: Position the tank at about the same level, or lower than the supply hose. Have the end of the hose open and hanging in the wind. As you increase speed, the air flowing by may suck the water up the tube, supplying more water at higher speeds. I made a diagram of what I am explaining.
Attachment 21214

I already try to do that as much as possible. But it is bumper to bumper mostly.

I will pump up the tires to the sidewall pressures. I was already running 45psi.

Direct injection doesn't really cool the intake charge, since it doesn't vaporize at the intake manifold and is injected directly to the combustion chamber at the liquid phase instead. But if LPG was fed in the liquid phase through a regular port-injection it would freeze the intake manifold. Some older Fiat engines and dedicated-ethanol ones from other manufacturers featured a heated intake manifold which had some ducts where the engine coolant would pass in order to avoid the risk of freezing due to a similar effect while running on ethanol. Anyway, LPG is not road-legal in my country, allowed only for special machinery such as forklifts and some tractors, but most of the illegal conversions that I have already seen were based either on dedicated-ethanol or Fiat engines exactly due to the intake heating provisions.

My lpg is manifold injected not port injected.

I suppose this is good for economy.

I assume you're talking about a positive-pressure (multipoint) setup instead of a closed-loop (throttle-body or single-point injection), but even though the LPG would go a shorter distance across the manifold compared to a throttle-body injection, trying to get it injected in the liquid phase could still increase the risk of getting the intake manifold frozen.

I have been researching LPG and water injection lately.

LPG burns slower at slower RPMs and it burns faster at faster RMPs. Some tuning needs to be done for LPG converted vehicles. And from what I hear, it is usually a compromise (if dual fuel ability is to be maintained).

On the other hand, when water is injected the burn rate of the fuel slows down. Which could theoretically bring LPG closer to gasoline.

So after some study, if i can get LPG to behave like gasoline, my standard tune for the car would work very well in my opinion. That is what i would like my current goal to be.


I am adding some articles that i find to this thread mainly so that I can find them later on.
https://www.omicsonline.org/scientif...AME-SR-591.pdf

I'm more used to CNG than LPG, but since the LPG is vaporized prior to the injection it does sound quite odd that you would at a first stage have to add some heat to the fuel and then cool down the intake stream with a water injection.

I have the opportunity to get bigger rims and tires. But they will be wider. Will i lose or gain mileage?

Most likely lose, the more tire on the road, the more resistance.

I have hooked up torque and have been trying the pulse and glide. I am trying to keep load at %80 but the car accelerates pretty fast and i seem to prefer %70, less chance of the automatic transmission lowering gears.

Obviously it is like a brick and slows down fairly quickly. The cruise control (which is actually just a speed limiter) is fairly nice for pulse and glide.

Best tank of lpg so far:
207 km with 38L. (18.3L/100km) 12.8 mpg

When i started this thread I was at 180 km per 38L (21.1L/100km) 11.14 mpg

Well ****, if it was any worse, i would be in single digit territory.

I shall do further upgrades and fixes. The abs and the egr has to be fixed. Will report back how that improves mpg. (Note lpg has less energy per liter tha gasoline and diesel).

I want to do a radiator and oil flush.

For the oil, i want to run it with ATF for 15 minutes. Then fill with 0-40 mobil 1.

For the coolant, i want to do a flush with a bit of vinegar, the with a bit of soap followed by distilled water and finally the coolant.

Do you guys recommend anything else? Or will I corrode the aluminium block with the vinegar?

I've seen kerosene being used for oil flush, but have never seen anybody using ATF for that.

ML350 ecomod
 

Well, you certainly have your work cut out for you, but any improvement will or should be noticeable. Being a heavy vehicle reducing friction and drag will make a big difference. I second pumping up the tire pressures that will offer the quickest/easiest thing to do. On your coasting, moving the shift lever into neutral should help some as Mercedes tend to use a lot of engine braking, ( I have several and service many others), far more than our previous Toyota Highlander or my Prius. Next, I would look for at an oil change to the differentials checking the factory specs and ensuring I had the lightest weight synthetic lubricant the met MB specs in those to lower friction. The engine in this vehicle is pretty efficient, but is burdened with carrying a heavy load. Trying to lighten throttle application on take-off will yield a lot of improvement. Look for ways to unload the engine, A/C, alternator and other electrical loads to further improve mileage. Your weather might not permit that.

At some point i will try externally charging the battery all the time to see if i can get the alternator to cut off.

Can you recommend any oils? The spec only lists a single weight. What I have in there is pretty old and I should change it soon.


I have to use the AC. But i try to switch it on only while engine braking. Damn i wish the ecu's for these were open source.

Is there such a circuit to put the brake light in series with the ac clutch?

for lubricants, Mercedes recommends Mobil 1 but any high performance synthetic would be great, Royal Purple for example.
Being a later model vehicle with computers managing things, it is difficult to get into circuits like the A/C clutch without risking back-feeding the computer and causing some otherwise strange results. I am sure it can be done, by looking through the schematic and then carefully measuring and understanding where to go into the circuit. You might consider placing a relay in the circuit so it is normally closed when not on the brakes and then opens when the brakes are applied thus not impacting the A/C system circuitry otherwise would be one idea.

Thanks for the tip.

Any idea how one can access the ecu's on these things?

I wish they were open source. Then i could program whatever algorithm i wanted in to them.

I had an idea. I do not really use the LOW setting on the transmission. Any possibility modifying it (flipping the gears?) to transform it to a HIGH setting? Currently at 120kph it is at 3000 rpm. Not good for such a big engine.

With my best efforts on the road i got 12.83 l/100km (18.3 mpg) on the highway. Driving mostly 80-100 km/h. Mostly closer to 80. This is with LPG.


If i energy adjust it i get 10.26 l/100km (22.9 mpg). Amount of energy i would have used if i were running on gasoline.

If i price correct it for gasoline just to feel better i get 6.93 l/100 km (33.84 mpg). Liters of gasoline i would have had to buy if I was paying for gasoline instead of LPG.

Last numbers are not too bad. But i think that i can still improve it. Adding a grille block and various other aero mods...

I've been looking around for an appropriate open-source ecu myself. There are a few around but none that really address 'lazy ecomodding' as far as I know.

I think what you are thinking of is something like an Injector-Controller that's customised for ecomodding useage.

Another option might be to drop a more modern engine into that Mercedes, say from a Mercedes A180. Those old Mercedes engines were pretty lethargic and the newer ones might have similar power just use a lot less fuel.

I live somewhere where engine swaps are a bureaucratic nightmare. And finding an engine would cost more than the car itself :(

From my experience and from the theory I know about it should work brilliantly, but I've never tried.

Do you want to try? I would be happy to assist you if you are interested.

I know that feeling... :mad:

But anyway, how hard would it be to get an used Sprinter of that dual-fuel petrol/CNG version from Germany to Turkey so you could drop its drivetrain into the ML350?

Not very hard.

Also, having been through this myself, "if an engine is already available on that type of car or series" then it all becomes much easier.

For example, my Renault Scenic had an econobox 2.0 originally. I just dropped in the 2.0 sports motor with ~30% more power but because it's a factory engine available on other models in the range there is no drama.

If you can show that the engine was available in Germany at some point earlier or later their ability to argue becomes less.

For example, if you put a 2010 tdi engine back in an older ML it becomes hard for them to argue it isn't right.

My engine swapped car feels more 'right' than whatever came from the factory. It feels like the car that the factory should have made.

You can also do things like put original intakes on to make it look totally stock if you need to know so that it isn't obvious what lurks beneath.

The problem is far beyond emissions compliance, since some countries still have displacement-based taxation schemes. I'm not sure how it works in Australia, but it doesn't seem to happen there.

Forgive me if I talk as a repeat tourist of Turkey, but they are known to have the worlds most expensive fuel.

To offset this, they have a Renault factory or too, and zoom around having fun. in usually 1.2L cars. If you don't really drive too far, an ML350 is ok.

VW tdi's are very common there as are the Renaults. :-)

1 gallon of gasoline is about 5.35 usd.

I just researched it and it seems quite a pita.

And a new engine would cost about 7k euros, considering the price of lpg, it will probably never pay for itself.

Turkey became a hub for many automakers, not just Renault. Fiat is also quite popular there. But anyway, their 1.2L cars might still fare better efficiency-wise than the 1.0L penalty boxes from Brazil :turtle:

Well, i just sold the car :(
I was sad to see it go, but the annual tax was close to 1000 usd, which would make any economod or hyper miling gains insignificant.

I believe i hyper miled it to the beso fo my abilities.


Now to find a suitable car and add a hitch to it.

Define "suitable" and which features from the ML350 you wouldn't be willing to just let go.

Right now i am in between a passat 1.6 tdi or a polo.

Polo has a 1.2 tdi and a 1.6 tdi. Also not quite decided about the dsg transmission in them either.

Those dual-clutch transmissions are not my cup of tea at all, but anyway, would you rather get a sedan or a wagon?