JG26_Irish

First a question: What is the difference between Euro spec Diesel fuel and USA spec Diesel fuel? I know the USA fuel is low sulphur content when compared to previous USA spec fuels but how is the Euro spec fuel "Better"? and how does that translate into more power output? I thought the higher output in the Euro diesels was only due to the more relaxed emissions regs which allowed them to tune the engines for higher boost (more NOx) and possibly richer FA ratios? Maybe not. Please educate me on this.

As for the 4 cylinder twin turbo 2.1 liter diesel in use today? It seems to be performing well. A colleague of mine owns a E250 Bluetec and reports that it is capable of 41 mpg at 80 mph along the same stretch of interstate highway that I drive in my daily commute. When I run the same speeds on the same roads in my older E320 Bluetec, I get between 29 and 33 MPG averaging about 31. If I lower the speed to 77 mph or lower, I can increase this to about 32-33 mpg on the same run (got 33 yesterday). This is not level highway and has a bunch of up and down mountain pulls. On level ground, I can do 34 mpg as long as I keep my speeds below 78 mph. But alas, I am a lead foot, lol. Running 82 mph steady drops the mileage to about 28-29. However for some weird reason (higher average manifold pressure?), this goes up to about 30-31 mpg running 95-100. Sadly, I can only run those speeds for long periods of time when I drive in Mexico. The Polizei seem to frown on it in parts of the USA, My colleague is not inclined to go faster than 80ish in his car but he clearly is getting at least 10 mpg better on average. That is significant. The I4 is not slow either. The twin turbo system lets it spool the smaller turbo fast for low rpm response and efficiency and the 2nd unit kicks in to provide more air flow for higher rpm power and a broader total range of useable operation. This is a nice feature. My old V6 single turbo system may be simpler and less stressed but it also starts to wheeze above 4k rpm. It accellerates faster at half throttle than at full throttle. I like the easy torque output (400 ft-lbs), but I do wish it had better WFO output. But it is a minor complaint. I have 120k on the clock and it is stone reliable so far. The much smaller 4 banger is able to put out almost as much HP and torque from its 1/3rd smaller displacement but is also able to rev to a higher range and still generate good power making it very flexible. My car only runs 2k rpm at 80mph. Not sure what the E250 runs at the same speed. Maybe one of the owners can chime it or I can ask my colleague next time I see him. I have driven the older inline six cylinder diesels as well and almost bought one same for the SBC system.. They get better mileage by a small margin but the performance and feel is similar to my V6. The sound is different. Honestly, I like my car but if they did not have the wonky SBC I would have bought an older model as I liked the simplicity of the older inline engine.

Irish

kajtek1

Diesel has cetane rating, what is comparable to gasoline octane.
More cetane- more HP you can squeeze from the same amount of fuel.
Some things are also cultural. In Europe owners don't hesitate to chip their engine as high-speed city traffic calls for good acceleration. In US the 300 hp cars take 15 seconds to roll via intersection and nobody honks on them
Higher HP= less reliability and when European don't mind to repair their engines - in US you'd have class action suit in days.
At 80 mph on flat roads my E250 will make much better than 40 mpg, but where I drive, flat roads are almost non-existent.
Our V6 Bluetec is in W211 and 6 years apart very likely is having different transmission programs, even on paper it is the same transmission.
The first impression when I got 4-banger was how much smoother the car drives. V6 has brutal torque at low rpm and when that can be nice for passing, it also shows on lower speed gear changes.

Tschuss_Bill

US minimum Cetane is 40, in Europe, it is 51. Quite a difference.

JG26_Irish

I am not a diesel expert but I did stay at a Holiday Inn Express recently, lol (I am a professional engineer with significant US based refinery design experience) but some of the statements may need to be clarified regarding the claims made of the higher cetane Euro spec fuels. Per Cheveron Global's technical review of Diesel fuels:

Cetane Number Increasing the cetane number improves fuel combustion, reduces white smoke on startup, and tends to reduce NOx and PM emissions. NOx seems to be reduced in all engines, while PM reductions are engine-dependent. These cetane number effects also tend to be non-linear in the sense that increasing the cetane number produces the greatest benefit when starting with a relatively low cetane number fuel.

CETANE NUMBER The cetane number is a measure of how readily the fuel starts to burn (autoignites) under diesel engine conditions. A fuel with a high cetane number starts to burn shortly after it is injected into the cylinder; therefore, it has a short ignition delay period. Conversely, a fuel with a low cetane number resists autoignition and has a longer ignition delay period. Although the cetane number of a fuel is assumed to predict its ignition delay in any engine, the actual delay represented by the cetane number is valid only for the single cylinder engine in which it was measured. The fuel’s performance in other engines may differ. A fuel’s ignition delay is determined by its chemistry. In a warm engine, the delay is independent of the physical characteristics, such as volatility and viscosity of the fuel. Cetane Index correlations use density and distillation temperature properties to estimate the cetane number. However, these physical properties are used as indirect indicators of chemical properties.) Cetane number measurement applies only to diesel fuel grades No. 1-D and No. 2-D. It is not measured for fuels containing petroleum resid (e.g., marine fuels).

CETANE NUMBER AND OCTANE NUMBER Cetane number (diesel fuel) and octane number (gasoline) both measure the tendency of the fuel to ignite spontaneously. In the cetane number scale, high values represent fuels that readily ignite and, therefore, perform better in a diesel engine. In the octane number scale, high values represent fuels that resist spontaneous ignition and, therefore, have less tendency to knock in a gasoline engine. Because both scales were developed so that the higher numbers represent higher quality for the respective use, high cetane number fuels have low octane numbers and vice versa.

Clarification: I am not seeing any clear evidence of higher cetane content automatically resulting in higher HP or higher specific output. The European Union's goals for its Diesel spec are to maximize efficiency, and reduce greenhouse gas emissions. The higher cetane increases the volatility of the fuel making it ignite faster and burn more completely resulting in less unburned carbon and better cold weather starting properties during the very cold European winters. This may enable a euro owner to chip his Diesel to increase the manifold pressure and fuel flow more before black smoke and high unburned carbon in the exhaust results when compared to the US owner who must make do with the lower cetane spec fuels which ignite slightly slower thus having less time to burn can only tolerate so much before the same black smoke and PM emissions result. The US Diesel spec goals were different. We were seeking lower NOx and particulates emissions in addition to the SOx reductions that both regions sought to obtain. Those smog producing emissions required lower combustion temps and/or additions of SCR cats with urea injection. Since the average winter temps in the USA are somewhat warmer than most of Europe (hard to tell this winter), the need for the better cold ambient cold engine start properties were less desirable. Since the Euros were less concerned with NOx emissions they accept higher combustion temps which result from higher boost pressures or higher compression ratios and the higher efficiencies which are gained from each. If you raise the boost on the engine all things being equal, you will generate a corresponding increase in torque and HP. But the higher temps result in higher NOx. My point is that if you raise the boost on your US based engine using US spec fuel you will see a similar increase in output an a similar increase in NOx. The lower cetane spec fuel may begin to smoke more at a lower boost level than the more rapidly burning Euro spec fuel and the US spec fuel will likely have a slightly lower efficiency for the same reason. My long winded point is that to say that higher Cetane content equates to higher quality and more HP is a blanket statement on a highly technical subject and without some qualification it is not necessarily true. It depends on one's goals. The same blanket statement that premium high octane gasoline is better fuel and results in higher HP is similarly misleading. Both can be true but if I put high octane fuel into my low compression family car that needs only regular grade gasoline, I will not get higher hp and will get lower fuel mileage due to the lower BTU content of high octane fuel. If I put the same high octane gas into my turbo-charged race car and then dial up the boost, I can increase the specific output and may or may not improve the efficiency. I suspect the same to be true of high cetane content diesel. If I put it into my US spec Dodge Ram Diesel pickup, and do nothing else, it is likely to do nothing. It might get slightly better fuel economy but that will depend on the state of tune. If I turned up the boost it might smoke slightly less on the upper end of that spectrum. I would be interested in other's perspectives on this subject and I am still learning about this one.

Irish

Tschuss_Bill

Very thorough, thanks for that. Here's another read on the subject.

http://www.trucktrend.com/how-to/exp...ts-your-truck/

I think the net net, you want higher cetane. One of the things I was reading about recently was the coking intake port issues on BMW diesel engines. California mandates a minimum cetane of 53, the BMW coking problems on Calif vehicles is far less than the rest of the US.

kajtek1

Interesting point about CA diesel having higher cetane.
Our E250 is popping DPF code from time to time. On Nevada fuel that happens about every 40 miles (I am getting ready to do DPF purge) but lately DW took the trip to California and codes vanished for like 600 miles.
I know CA beside different cetane usually also have more detergents and other environmental stuff in the fuel, but the difference in particles seems to be pretty obvious.
That experience contradicts the theory Irish presented, but who says life choices are easy?

JG26_Irish

Actually, your experience would seem to confirm most of what I said or implied. High 53 cetane fuel should ignite sooner and burn faster and more completely and thus cleaner when compared to a 40 cetane number of most US Diesel fuels. The higher cetane rated fuel should experience less PM emissions and thus less clogging of the DPF as well as less carbon build up in all of the usual places. What I said was that the US emissions goals were more focused on NOx, SOx and particulates than efficiency or extreme cold starting abilities and our fuel spec allowed lower cetane mainly because we did not need it to meet those goals. They are being met by low sulphur fuel, and the addition of the SCR cats with urea injection to meet NOx emissions goals and the DPF to meet PM goals. Based on what I have learned so far, the higher Cetane content fuels should burn cleaner. What I was not convinced of was that it would also result in more HP without also making other mods to the engine state of tune. I do think under certain conditions the high cetane fuels could make more peak hp at max throttle if it enables better combustion and less unburned fuel to escape, That however, is highly speculative and until I saw back to back dyno runs to support it, I would be skeptical.

For those owners who regularly cross back and forth in and out of Calif, I would be interested in your MPG averages when running on the Cali spec Diesel versus the Nev/AZ/OR spec lower cetane fuel. Do you consistently get better mileage on the high cetane fuel? If so, how much? I did not own a Diesel when I lived in Los Angeles and the Cali spec high octane fuel was only 91 octane and led to the early death of my little turbo-charged Ferrari killer causing me to have to replace the engine when I returned to KY. I did not even pay attention to the Diesel available out there. I have been looking as some of the premium Diesel options offered in some regions. They appear to mimic the Cali spec of higher cetane and increased detergent additives, etc. I was wondering which parts of the country offer these fuels and what your experiences have been with them as well?

Question: What is your normal day to day driving route like? Is it lots of city, stop and go driving or mostly highway? If it is lots of city driving it could only be that a long run of fast highway driving was all you needed to burn most of the deposits out of your DPF. My daily drive loop is 50 miles of interstate and 12 miles of local highway with only the last 3 miles being stop and go, 35mph city driving. All the rest are at speeds of 55-80 and mostly on the upper end of that. So far, that has prevented any clogging. I do not have the urea injection on mine since it was an older car but those as far as I know do not make the DPF clog worse.

Irish

JG26_Irish

This morning I was traveling to work on my usual commute route of 50 miles of interstate highway. Due to the snowy road conditions I was running much slower than I normally would. Averaged only 45mph for that loop. But, the old V6 diesel was able to churn out 39.3 mpg for the same loop at those sedate speeds. So, If I wanted to troll along at a snails pace all the time like Mr. Magoo, I could almost reach 40mpg. I think I will pass. I will say "Thank God for ESP". Saved my bacon more than once.

Irish

kajtek1

The 250 delivers 60 mpg easy at low speeds, but I had no patience to test it for long.
Main problem at 50 mph is that it doesn't want to stay on 7th gear and normally driving on lower gear cuts the economy. Looks like its "sweet spot" is in 55-60 mph.
We took another long trip to California and this time higher cetane did not help with DPF showing the codes, so the above theory did not confirm. Kind of strange why code sometimes comes after 15 miles and sometimes after 300.

arto_wa

You both are probably talking about the instrument panel's computer reading?

If so, driving whole tankful and manually checking would give you pretty realistic reading - EPA ratings are usually not too far off.

I got 34 mpg for over 30,000 miles by manual method on 2008 E320 BlueTec.
The only thing I miss about my 2010 Jetta Sportwagen TDI 6 sp manual is the fuel usage....

kajtek1

I just add fuelly link to my signature showing the hard-calculated mpg.Computer shows about 5% difference.
Years ago I had a project that require 600 miles "commute" and over 2 years period I made about 20 of those trips.
Started with 2008 VW Jetta diesel wagon and after several trips bought 2005 E320cdi.
The same route, the same speeds generated exactly the same mpg on both cars.(32)
Actually in Mercedes I was making the 8hr trip about 20 minutes faster due to better acceleration.

arto_wa

I was getting 43 - 44 mpg with the above Jetta, but oh boy it was costly to maintain due to the emission s**t...

kajtek1

It is lot about the speed. .
Some owners claim that 1981 VW diesels were making 45-50 mpg and I knew such guy personally.
For me the gas pedal in the truck was either on the floor for driving, or up for braking. Making that 35 mpg.

JG26_Irish

I straight up agree. I like to accelerate hard to get away from traffic and then run quick pace so that I am passing most of the other traffic (old street bike rider survival tactic). It is so ingrained into me that no mater what I ride or drive, I want to be slowing passing the other vehicles all the time. My numbers for 50 or 60 mile runs on a given day or speed are just that, a snapshot. My long term everything mileage is more like 29.x consistently. Some days it is really bad if I am feeling it.

Irish