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2006 E320 CDI, 2009 ML320 Bluetec, 2009 GL320 Bluetec
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Discussion Starter · #1 ·

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drivbiwire said:
Keep in mind that the CDI is designed for best performance and durability on the ULSD 15ppm sulfur fuels.DB
Will the CDI's attain better performance/mileage using the newer low sulfer fuel, or will they need to be retuned/adjusted to some extent to take advantage of it?

Lou
 

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Discussion Starter · #3 ·
No changes required at all for current owners. The Mercedes falls into a category often referred to as "HSDI" or High Speed Direct Injection diesel. These motors require fuels with higher cetane (49+ verses the current standard of 40) and 0-15ppm sulfur (Verses the current levels of 500ppm) for optimum performance. The ULSD once it hits the pumps will quiet our motors further and you will be able to hear the difference, this alone can be attributed to the increased Cetane standards taking effect with ULSD. The higher Cetane allows for smoother pressure rises within the cylinder by virtue of faster ignition of the fuel and the increase in time between pilot and primary injection events.

Sulfur increases wear in our motor by virtue of higher levels of Particulate matter in the current EGR systems, retarded injection timing, increased acid formation in the oil, and increased soot/particulate related wear in the cylinders. Reducing sulfur from 500ppm to 15ppm allows the oils we use to work without having to disperse the previous high levels of soot formed during combustion. This will allow us to have greater reserves of the additives which work to protect our motors over the course of an oil change. This also results in reduced wear within the motor not to mention significant reductions in visible smoke output such as cold starts and full power runs down the highway...(not that we ever exceed the speedlimits).

Oil manufacturers will maintain high standards for fuel lubricity despite the reductions in sulfur. This eliminates all the concerns for reliability and stems from the previous reductions in sulfur.

Regarding higher fuel economy, for the most part fuel economy will not be affected on diesel engines built prior to the 2007 model year. However engines produced with systems like SCR will have a slight advantage in that they can be tuned to run more efficiently becase of exhaust after treatment for NOx verses utilization of EGR and injection timing which decrease the engine efficiency to meet US Emissions (Thank California for that one). The SCR system equipped motors will more than likely trade the improved emissions for more power and still be able to provide modest increases in fuel economy approaching 40mpg for the E320 in terms of routine economy numbers.

To sum up the benefits of ULSD, current owners will benefit by virtue of improved engine durability, lower maintenance costs, quieter engine operation and lower tailpipe emissions. 2007+ owners will get modest gains in fuel economy but significant gains in power along with all previously stated benefits.

DB
 

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DB,
I was watching mythbuster's the other night and they were experimenting with fuel. They started off busting the acetone myth as a fuel additive as well as the magnets and the 100mpg carburetor. What was interesting is when they got an old 300D to run on straight used cooking oil with a three mpg loss. What's the drawback to using cooking oil as an alternative to diesel. How about late models vs. early models performance, engine damage etc.?
 

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Actually, that was a 300SD they used. The used WVO, and they did some things wrong such as not boiling the water out of the grease they used as fuel. The reason it got three mpg less is that WVO, SVO, and biodiesel have lower BTU content than regular diesel fuel does. Some drawbacks of using WVO are... higher suspectibility to coked fuel injectors, gels easy at low temps, sometimes all the fats are not gotten rid of and can lead to engine damage. With WVO, you've really got to be on top of preventative maintainence, like more frequent oil changes, and keeping a closer eye on the fuel system. When I think of the CDI, I don't really think of WVO or SVO as a fuel source. Right now since we're on alternative fuels and MBs, I'd like to point out that DaimlerChrysler recommends using B5 blends of biodiesel at the highest in diesel MBs until further testing is done to make sure their cars can handle higher blends, but the older models have been known to run B100 without problems.
 

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Discussion Starter · #6 ·
100% agreement with you H-TownBenzoboy.

WVO/SVO simply cannot work in the CDI under any circumstance. The main issue is the viscosity of the oil in conjunction with the higher pressures of the CDI fuel system. Older Mercedes engines used low pressure fuel systems in the order of 1900-2600 psi. The CDI is running in excess of 23,500psi. Attempting to pump a thick oil such as SVO/WVO which has 4 times the viscosity of diesel when heated to 190F will destroy the fuel system.

One issue with Biodiesel is the latest SCR catalysts are not compatible with Biodiesel due to different types of contamination from the bio fuels. The SCR systems were designed for petroleum based byproducts, the bio fuels present different types of by-products which the catalyst must burn off. YES it is possible to make current engines run on and meet emissions with 100% biodiesel but the car makers are working towards systems that function on either type of fuel in any ratio...this is the issue currently being addressed.

DB
 

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Discussion Starter · #7 · (Edited)
Your idea of current information was probably written before I was concieved, so it's no surprise you are still living in the dark ages of diesel injection systems.

If you want to read about the current model year CDI's specs check out the MBUSA website:
http://www.mbusa.com/campaigns/e320cdi/index.do

CDI fuel system pressures are old news, in fact the Current CDI engine fuel system pressures are being increased further for the 2007 model year to exceed 27,000 psi.

CDI Fuel plunger:


CR3 which is currently in use uses a new style of variable displacement 3 plunger high stage pump. Incoming fuel is varied in volume so that the rail is maintained at 23,500 psi, as a back up to the pumps internal regulation the CR3 system uses a spill off valve(in the rail) to prevent over pressure and fine regulation of the rails pressure. This allows pilot and primary injection to get full rated system pressure at any engine rpm which helps to achieve optimum injection timing control and to a lesser extent fuel atomization at low engine rpms where other systems cannot make full rated pressures.

Fuel pressure are key due to the design criteria of HSDI engines like the Mercedes CDI, the reason is the CDI only has in most cases at 3500 rpm a 3 milisecond window for injection, injection delay and combustion of the fuel. Compared to an F1 engine running at 17,500 rpm they have upwards of 5 miliseconds to achieve the same thing! Higher fuel pressures allow faster injection of the fuel as well as a resulting lengthening of the period of time for that fuel to burn which to a certain extent also allows for more power to be produced by the motor without a resultant increase in emissions.

Currently in testing Bosch is using a 35,000 psi CRI system at Bosch and Siemens both coupled with ultra high speed piezo injectors. The goal is to eventually top 45,000 psi but there is a way to go yet before they get the systems reliability up to where diesel customers expect.

FYI, Other production diesel engines use a system called Pumpe-Duese, these systems operate at momentary 2,000 bar or 30,000 psi fuel pressures, which prevents the addition of fuel to trigger catalytic burn off cycles post combustion...the end is near for these systems. This current production year incorporated Piezo activation to increase injection window periods and this increased engine output of the 2.0l engine to over 180hp and nearly 380 ft-lbs of torque while achieving 40+ mpg...

The other key factor to the shift to high pressure CRI systems is when coupled to Piezo activation the injection pressures can be controlled to produce extremely smooth rise of the cylinder gas pressures by virtue of 5-10 injections per combustion stroke! This lends itself heavily to the luxury car market due to the refinement and quietness of the motors while producing greater drivability and fuel economy.

And yes you are correct about the pressures of the fuel sytems creating heat...LOTS of heat! Most diesel fuel sytems have an additional fuel radiator/cooling grid which cools the fuel once it leaves the engine. Fuel temperatures often exceed 200F after a single pass throught the fuel pump. The break down of the fuels are a key reason why Bosch, Siemens and MB are concerned about running "Bio" based fuels. It has already shown issues resulting from the bio-fuels breaking down within the injectors and high stage fuel pumps, another topic for another day.

DB
 

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Discussion Starter · #9 ·
As I have mentioned quite a few times already filtration is extrememly critical. 2 micron absolute filtration is already in use, in fact CAT pioneered the filtration standard for use in their equipment and even built a production facility specifically for this system.

The Mercedes has a fuel filter which already comes close to the 2 micron standard and should be able to offer sufficient filtering to allow the components in the fuel system to excede 400,000-500,000 miles with the exception of the injectors. The injectors retain the same design concept that allows nozzle replacement to reduce servicing costs down the road. Nozzles for the 7 hole injectors will be about 1/3 the cost of a gasoline injector with about the same life time.

Add to the fact the CDI uses an incorporated water sensor the owners provided they follow the guidance of changing the fuel filter every 26,000 miles should have no problems with component life on these motors.

The high stage fuel pump based on reports I have seen (assuming 5-7 micron nominal) filtration should last anywhere from 15,000-20,000 hours of use. This includes the next generation of CDI. Its the generation after that where filtration will have to be stepped up to what CAT is using (2 micron absolute) to get pressures north of 30,000+, again no big deal.

DB
 

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Discussion Starter · #10 ·
lear31a driver said:
You are right in two of your points, I received my degree in engineering when your biggest concern was making the transition out of diapers. Further, my advancement in diesel systems has spanned your entire life. So rather than be an ass, and dispense cut and paste info, treat others in this forum with the professionalism they deserve. You remind me of two former co-pilots I knew. Both flew into the side of hillsides and perished. Both had the same overtones as you. Both were pretentious. I receive several PM’s regarding your statements, and I conclude them with similar endings. “Don’t expect professional advice from unprofessional people”
Your experience in diesels thus far has proven not only to be grossly misguided but lacks any value in terms of applicaton to modern equipment. It's guys like you that would tell people to change oil every 3,000 miles yet be unable to explain why other than "It looks dirty" then argue with people who actually know what they are talking about because you refuse to accept that it actually increases wear. You are in fact "Old School" when it comes to cars, you fail to look beyond the obvious.

You strike me as the type of guy who flies "Safe and maybe not legal" because of your vast experience in "F4's" you think the rules don't always apply because they appear counter to your "experience". I can't say that I have much small twin engine jet time since most of mine was in a single engine jet... So, I have always relied on strict adherence to well founded procedures to keep "me" safe and legal. I am not going to waste my time arguing over experience or background, I won't pretend to know what your experience level is in aircraft, but you repeatedly make a dangerous mistake by assuming you know my background when you do not... "ASSUME" is a dangerous thing which is why I fear for guys like you in the cockpit.

I come from a background where I don't make assumptions about what people know or don't know. If you think something is too basic for you don't read it, the other guy may find some value in it and thats what matters. I will give you all the building blocks needed so that you can make your own decisions and develope your own opinions especially when it comes to cars. It's no secret that the automotive industry is advancing at a rapid pace. What was current 6 months ago is now obsolete. When guys like you come along bragging about how they studied engineering 30 years ago, lets just say it does not mean much given the advancements in the past few years.

I know you have the ability to understand modern cars and you seem to make the connections as you did with the fuel and filtration, but that is old news to me since I worked with that over 5 years ago...But the majority of my posts are not geared towards you but rather the new owner who is getting their first exposure to a modern vehicle.

Getting back to cars since this is a car forum, You seem to have an issue with excerpts? Why is that? I have had a LOT of good feedback from people on the forums here that they appreciate reading the actual material which I often includ in posts. I have even sent the full documents to a few who have sent requests provided it was available in electronic format. My advice seems to run counter to yours and it rubs-you-raw for some reason. Rather than producing supporting documents you throw a few personal attacks followed by a typical "couldn't be a Colonel" tantrum. I have no doubt that I am younger than you (not sure how much) but I do continue to pay attention to modern advancements in the automotive industry. If I ever got out of aviation I'd be right back into automotive, currency has it's advantages.

Now, I must be on my way to Seoul.

DB
 
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