I went on a quest to find out how to get more power and better mileage out of my 2008 ML-320 CDI. What I found was how complex the problem is, and in the end - not worth the pursuit.
The short answer without reading all below is - the easiest method is to simply buy a new Ad-Blue engined vehicle. It will have better fuel economy and power both - about 20% - for what is otherwise the same engine. Now for the long explanation.
I spent quite a bit of money (frankly nothing better to do) looking for a so-called tuner. There is one reputable one - Carlsson. They will charge you about $2500 - and to accomplish their process, you either need to send them the ECU or use their add-on module that slips between the ECU and harness and intercepts signals.
All those other so called tuners who will fix your car for $500 or less are messing for the most part with two primary things - the throttle map - so the car "feels" better, and modifying the "smoke" map - which is actually a calculated limit of fuel vs. intake air mass at stoichiometric ratio. What virtually all tuners do is move the limits / map - which makes the throttle feel better but does not actually produce any more power (but does lower fuel mileage) - or it adds fuel but it also certainly raises emissions by huge amounts. Some of these guys are brighter than the average, and they remove EGR and / or remove the DPF regen function by changing some maps. As you will read below, both are problematic and the wrong way to go about things - and if you take out DPF without actually taking out the DPF - the back pressure will stop you cold in a thousand miles or so.
I went straight to the sources - Motorola Freescale that builds the CPU (not ECU) and tools to program it, and Bosch (who builds the ECU). There are things they would talk about, and things they would not. My background helped fill in some blanks. But not a single tuner I was able to exchange emails with has a clue as to what actually happens in the engine - at least no one who I could find. Most talk about torque limits (categorically there is NO such map in the controller), or EGR maps, or DPF maps. Truth be known, I learned there is a single byte which turns on / off EGR, and another single byte that turns on / off the DPF regen. But to do it, you need access to the very specific address locations (varying quite a bit by model / engine), and then either have to open your ECU (not possible to reseal to anywhere near the factory seal), or you have to crack the ECU encryption / checksums via OBD-2 to modify the switches. Can it be done - yes, but not by anyone out there I could determine. All the real "maps" in the ECU are related to air mass & fuel injection quantity vs. crank angle - and more maps to make adjustments to those basic ones dependent on temps (ambient, boost, engine), EGR opening, and limits to fuel to effect control over boost or to limit smoke (map of actual air-mass vs. theoretical fuel burned). Presuming you gain access to the EPROM flash, and can locate the maps, you still need lots of dollars invested in software tools (i.e. Motorola Freescale Code Warrior plus the BDM module), and some method to compute the new checksum - which if wrong - bricks the ECU until it's fixed. There is no such thing as permanently bricking an ECU - it's only a question of what needs to be done to reprogram it back to live conditions. TANSTAAFL - "there ain't no such thing as a free lunch".
How did I learn all this - I bought all the tools (fully licensed almost $10K), a development board from Freescale, and a complete ECU from Mercedes. I took them all apart, I made changes - I put it on an engine on a dyno (yes I have one), bricked a few things - in other words - the old traditional "hacker" - someone who wants to figure out how to do things - especially when someone tells me I'm not allowed to or can't possibly.
Something about me before you read on - I'm someone who seriously modded my ML - adding things like Distronic and Keyless Go after the fact, and installed an S-class wheel in a car not programmed for it. To accomplish these things I've built circuit boards, written code, and the like. I have had my entire car interior disassembled to add heated / ventilated front seats - just for the heck of it - and I'm a programmer of 40 years (retired), who worked on ECUs for GM back in the '80s. I added a CAN bus and put in an electronically controlled engine (OM-606) and trans (5 speed) into my 1993 S-Class diesel - just because. I tell you this so you will understand that I was trying to get power and still control emissions on my ML - and this post is a result of what I found.
So onwards ...
A diesel operates in an air-rich environment, with air-fuel ratios ranging from about 17:1 to 145:1 or even more lean. This is far different from a gasoline engined car which runs close to 14:1 at all times. The diesel rarely operates fuel-rich with modern controls - and if it ever does - that's when "smoke" happens.
A lean engine produces very few HC and CO emissions. Internal to the engine (prior to exhaust gas treatments) a diesel of equal power produces 1/10 the total emissions of a gasoline engine. The HC and CO emissions are very easily dealt with via very small catalyst. But lean, hot, efficient operations produce a lot of NO and NO2 - and that's the rub.
Conversion of CO and HC is an oxygenation process - add oxygen to the CO and HC - and you get water (H2O) and carbon dioxide (CO2). If you start oxygen rich - the catalyst process is trivial.
Conversion of NO and NO2 pollutants is a reduction process - strip the oxygen from the NO and NO2 resulting in free oxygen and nitrogen. The very toxic NO / NO2 pollutants revert to non-toxic gases Oxygen and Nitrogen.
The above two reactions are mutually incompatible - one is oxygenation, the other is reduction.
Back to the diesel, the leaner the engine runs, the higher the combustion temperatures, and the higher the NO and NO2 emissions. A 3-way catalyst of a gasoline engine does control NO/NO2 emissions in an environment where the amount of oxygen in the exhaust is strictly regulated - first using up the remnant oxygen to take care of CO and HC, then in a depleted environment clean up the NO and NO2. That is not possible on a diesel - in the oxygen rich environment (diesel exhaust is at least 15% oxygen) the chemical reaction necessary to split the O from NO & NO2 won't function - you need the aforementioned oxygen depleted environment.
How do you get an oxygen depleted environment ? In gross terms - you add more fuel late in the cycle, which consumes the oxygen without producing combustion heat - thus no useful power for the fuel burned. Incidentally it does produce more soot, but you do now have an oxygen depleted gas which allows you to chemically reduce / strip the O from NO and NO2. Alternatively you can get an oxygen depleted environment by adding EGR in the engine, which reduces the oxygen levels by providing less oxygen in the combustion air in the first place and also has the effect of lowering the combustion temps which produces less NO and NO2. Either / both of these processes causes a diesel to become less efficient, using more fuel to produce the same amount of power because the fuel is being used to "deplete" oxygen, not produce power. And to top it off, you need a larger Diesel Particulate Filter to trap additional soot, and a heating cycle (more fuel being burned) to burn off the accumulated soot, thus even more wasted fuel.
The other modern alternative - use Selective Catalytic Reduction via an intermediate compound (ammonia) where very active Hydrogen is added to the exhaust stream and preferentially strips the Oxygen from the NO / NO2 to form water, free oxygen, and nitrogen - all benign.
SCR allows the need for EGR to either diminish or go away entirely, the fuel previously burned to deplete oxygen is no longer used. Reducing EGR allows the combustion process to run hotter, using the fuel more efficiently, and the NO / NO2 produced in the hotter combustion is fixed up after the fact via SCR. There is less soot, and so while the DPF continues to exist, it is smaller, and is regenerated (burned off) less often affecting mileage less.
Voila - less fuel wasted for non-power operations, and for any given fuel quantity, more power from hotter combustion and thus more mileage. The effect is about 20% overall - though as they always say - your mileage may vary.
Now ... can you fix the older non-SCR engine to have SCR, and have more power and economy. Yes - if you want to spend a LOT of time and money. Basically you have to duplicate the efforts to add ad-blue, then expend huge efforts to change the ECU maps to reduce EGR, remove the post-injection, and advance the injection timing to get the hotter process.
And guess what - the EPA won't accept your results without a lot of tests - they don't care that you end up with a clean engine - you just "tampered" with an emissions system ... good luck with that argument.
You do have one easy legal method - re-engine the older vehicle with a newer engine complete with all it's controls and systems. But that's where buying a complete new car is probably the easier answer.
So there you have it - the 3.0L Mercedes diesel in the latest generation cars has more HP, Torque, and better mileage because with SCR (ad-blue) the engine is tuned for power, and the emissions are handled primarily without burning more fuel. You don't need to be an engineer or serious hobbyist, but rather can buy it with full warranty and no hassles.
There's another benefit from Ad-Blue - now you can have a yet smaller diesel engine with as much or more power than a gasoline engine - hence the new E and GLK 4-cyl diesels.
Take it all in - Mercedes has done a wonderful job - though perhaps has not explained it all to the public.
The short answer without reading all below is - the easiest method is to simply buy a new Ad-Blue engined vehicle. It will have better fuel economy and power both - about 20% - for what is otherwise the same engine. Now for the long explanation.
I spent quite a bit of money (frankly nothing better to do) looking for a so-called tuner. There is one reputable one - Carlsson. They will charge you about $2500 - and to accomplish their process, you either need to send them the ECU or use their add-on module that slips between the ECU and harness and intercepts signals.
All those other so called tuners who will fix your car for $500 or less are messing for the most part with two primary things - the throttle map - so the car "feels" better, and modifying the "smoke" map - which is actually a calculated limit of fuel vs. intake air mass at stoichiometric ratio. What virtually all tuners do is move the limits / map - which makes the throttle feel better but does not actually produce any more power (but does lower fuel mileage) - or it adds fuel but it also certainly raises emissions by huge amounts. Some of these guys are brighter than the average, and they remove EGR and / or remove the DPF regen function by changing some maps. As you will read below, both are problematic and the wrong way to go about things - and if you take out DPF without actually taking out the DPF - the back pressure will stop you cold in a thousand miles or so.
I went straight to the sources - Motorola Freescale that builds the CPU (not ECU) and tools to program it, and Bosch (who builds the ECU). There are things they would talk about, and things they would not. My background helped fill in some blanks. But not a single tuner I was able to exchange emails with has a clue as to what actually happens in the engine - at least no one who I could find. Most talk about torque limits (categorically there is NO such map in the controller), or EGR maps, or DPF maps. Truth be known, I learned there is a single byte which turns on / off EGR, and another single byte that turns on / off the DPF regen. But to do it, you need access to the very specific address locations (varying quite a bit by model / engine), and then either have to open your ECU (not possible to reseal to anywhere near the factory seal), or you have to crack the ECU encryption / checksums via OBD-2 to modify the switches. Can it be done - yes, but not by anyone out there I could determine. All the real "maps" in the ECU are related to air mass & fuel injection quantity vs. crank angle - and more maps to make adjustments to those basic ones dependent on temps (ambient, boost, engine), EGR opening, and limits to fuel to effect control over boost or to limit smoke (map of actual air-mass vs. theoretical fuel burned). Presuming you gain access to the EPROM flash, and can locate the maps, you still need lots of dollars invested in software tools (i.e. Motorola Freescale Code Warrior plus the BDM module), and some method to compute the new checksum - which if wrong - bricks the ECU until it's fixed. There is no such thing as permanently bricking an ECU - it's only a question of what needs to be done to reprogram it back to live conditions. TANSTAAFL - "there ain't no such thing as a free lunch".
How did I learn all this - I bought all the tools (fully licensed almost $10K), a development board from Freescale, and a complete ECU from Mercedes. I took them all apart, I made changes - I put it on an engine on a dyno (yes I have one), bricked a few things - in other words - the old traditional "hacker" - someone who wants to figure out how to do things - especially when someone tells me I'm not allowed to or can't possibly.
Something about me before you read on - I'm someone who seriously modded my ML - adding things like Distronic and Keyless Go after the fact, and installed an S-class wheel in a car not programmed for it. To accomplish these things I've built circuit boards, written code, and the like. I have had my entire car interior disassembled to add heated / ventilated front seats - just for the heck of it - and I'm a programmer of 40 years (retired), who worked on ECUs for GM back in the '80s. I added a CAN bus and put in an electronically controlled engine (OM-606) and trans (5 speed) into my 1993 S-Class diesel - just because. I tell you this so you will understand that I was trying to get power and still control emissions on my ML - and this post is a result of what I found.
So onwards ...
A diesel operates in an air-rich environment, with air-fuel ratios ranging from about 17:1 to 145:1 or even more lean. This is far different from a gasoline engined car which runs close to 14:1 at all times. The diesel rarely operates fuel-rich with modern controls - and if it ever does - that's when "smoke" happens.
A lean engine produces very few HC and CO emissions. Internal to the engine (prior to exhaust gas treatments) a diesel of equal power produces 1/10 the total emissions of a gasoline engine. The HC and CO emissions are very easily dealt with via very small catalyst. But lean, hot, efficient operations produce a lot of NO and NO2 - and that's the rub.
Conversion of CO and HC is an oxygenation process - add oxygen to the CO and HC - and you get water (H2O) and carbon dioxide (CO2). If you start oxygen rich - the catalyst process is trivial.
Conversion of NO and NO2 pollutants is a reduction process - strip the oxygen from the NO and NO2 resulting in free oxygen and nitrogen. The very toxic NO / NO2 pollutants revert to non-toxic gases Oxygen and Nitrogen.
The above two reactions are mutually incompatible - one is oxygenation, the other is reduction.
Back to the diesel, the leaner the engine runs, the higher the combustion temperatures, and the higher the NO and NO2 emissions. A 3-way catalyst of a gasoline engine does control NO/NO2 emissions in an environment where the amount of oxygen in the exhaust is strictly regulated - first using up the remnant oxygen to take care of CO and HC, then in a depleted environment clean up the NO and NO2. That is not possible on a diesel - in the oxygen rich environment (diesel exhaust is at least 15% oxygen) the chemical reaction necessary to split the O from NO & NO2 won't function - you need the aforementioned oxygen depleted environment.
How do you get an oxygen depleted environment ? In gross terms - you add more fuel late in the cycle, which consumes the oxygen without producing combustion heat - thus no useful power for the fuel burned. Incidentally it does produce more soot, but you do now have an oxygen depleted gas which allows you to chemically reduce / strip the O from NO and NO2. Alternatively you can get an oxygen depleted environment by adding EGR in the engine, which reduces the oxygen levels by providing less oxygen in the combustion air in the first place and also has the effect of lowering the combustion temps which produces less NO and NO2. Either / both of these processes causes a diesel to become less efficient, using more fuel to produce the same amount of power because the fuel is being used to "deplete" oxygen, not produce power. And to top it off, you need a larger Diesel Particulate Filter to trap additional soot, and a heating cycle (more fuel being burned) to burn off the accumulated soot, thus even more wasted fuel.
The other modern alternative - use Selective Catalytic Reduction via an intermediate compound (ammonia) where very active Hydrogen is added to the exhaust stream and preferentially strips the Oxygen from the NO / NO2 to form water, free oxygen, and nitrogen - all benign.
SCR allows the need for EGR to either diminish or go away entirely, the fuel previously burned to deplete oxygen is no longer used. Reducing EGR allows the combustion process to run hotter, using the fuel more efficiently, and the NO / NO2 produced in the hotter combustion is fixed up after the fact via SCR. There is less soot, and so while the DPF continues to exist, it is smaller, and is regenerated (burned off) less often affecting mileage less.
Voila - less fuel wasted for non-power operations, and for any given fuel quantity, more power from hotter combustion and thus more mileage. The effect is about 20% overall - though as they always say - your mileage may vary.
Now ... can you fix the older non-SCR engine to have SCR, and have more power and economy. Yes - if you want to spend a LOT of time and money. Basically you have to duplicate the efforts to add ad-blue, then expend huge efforts to change the ECU maps to reduce EGR, remove the post-injection, and advance the injection timing to get the hotter process.
And guess what - the EPA won't accept your results without a lot of tests - they don't care that you end up with a clean engine - you just "tampered" with an emissions system ... good luck with that argument.
You do have one easy legal method - re-engine the older vehicle with a newer engine complete with all it's controls and systems. But that's where buying a complete new car is probably the easier answer.
So there you have it - the 3.0L Mercedes diesel in the latest generation cars has more HP, Torque, and better mileage because with SCR (ad-blue) the engine is tuned for power, and the emissions are handled primarily without burning more fuel. You don't need to be an engineer or serious hobbyist, but rather can buy it with full warranty and no hassles.
There's another benefit from Ad-Blue - now you can have a yet smaller diesel engine with as much or more power than a gasoline engine - hence the new E and GLK 4-cyl diesels.
Take it all in - Mercedes has done a wonderful job - though perhaps has not explained it all to the public.
