New Chevrolet 1/2T diesels on the way

[RustyJC]

Originally Posted by Uncle Dave

Your calks are missing the mileage penalty the DPF regeneration imposes on the diesel rigs. The harder you drive and tow them the more time they spend in regen mode.

Actually, it's the other way around. A modern diesel that's "working" (towing our 5th wheel, for instance) seldom goes into a forced regeneration. That's because the exhaust temperatures are high enough to passively regenerate the DPF when pulling grades, etc. The modern diesel pays the regeneration penalty when it's in "mall cruiser" mode, subject to extended periods of idling and other light duty service. In this operating mode, the supplemental diesel fuel is necessary to raise exhaust temperature to the point that the captured carbon in the DPF is burned off. The mileage penalty associated with regeneration when in towing service is minimal compared to the lightly-loaded, just cruising around town fuel mileage.

Rusty

[Uncle Dave]

Originally Posted by RustyJC

The gas 3.5L ecoboost has superior BHP and similar torque when compared to the 3.0L turbodiesel. Since BHP is a product of torque x RPM (divided by 5252, in US units of measure), the gas engine's ability to rev higher due to lighter weight components, time requirements for diesel combustion, etc. translate to higher BHPs. Diesels generally will produce their torque at a lower RPM than comparable gas engines, however.

Let's wait to see some real world results for towing performance and towing fuel mileage for comparable trucks towing comparable trailers. Ram's marketing strategy for the 3.0L turbodiesel is really pretty simple - to offer trailer tow ratings very close to the 5.7L Hemi while offering equal or better EPA fuel economy than the 25 MPG highway rating of the 3.6L Pentastar V6.

Rusty

Jury is already in on the towing- of course none of these are standardized j2807 numbers but the 4x4 1/2 ton diesel is way off what an ecoboost is. (never followed the hemi ram closely)

7450 for the dodge in 4x4 trim vs 11K for the ecoboost.

I tested out an ecoboost from a friend a while back- extremely impressive.

My medium weight towed rig is this boat:

Ecoboost trip - YouTube

I have little use for a 4x2 truck and the dodge is already at the limit of my "light" load.

Its not going to to "do it" for me.

Uncle Dave

[Uncle Dave]

Originally Posted by RustyJC

Actually, it's the other way around. A modern diesel that's "working" (towing our 5th wheel, for instance) seldom goes into a forced regeneration. That's because the exhaust temperatures are high enough to passively regenerate the DPF when pulling grades, etc. The modern diesel pays the regeneration penalty when it's in "mall cruiser" mode, subject to extended periods of idling and other light duty service. In this operating mode, the supplemental diesel fuel is necessary to raise exhaust temperature to the point that the captured carbon in the DPF is burned off. The mileage penalty associated with regeneration when in towing service is minimal compared to the lightly-loaded, just cruising around town fuel mileage.

Rusty

Thats not the experience I have in my Sprinter.

The easier I drive it the less it regens.
The harder I drive it the more it regens.

Straight up.

Regardless - an 08 pays no regen penalty.

UD

[RustyJC]

Glad you're happy with your Ford. You've made your choice, but alternatives in the market for others who don't care to tow 11K lbs with a 1/2 ton truck are always a good thing. As far as the 3.0L Ram turbodiesel offering is concerned, the marketplace will ultimately decide its success or failure.

Rusty

[Uncle Dave]

Originally Posted by RustyJC

Glad you're happy with your Ford. You've made your choice, but alternatives in the market for others who don't care to tow 11K lbs with a 1/2 ton truck are always a good thing. As far as the 3.0L Ram turbodiesel offering is concerned, the marketplace will ultimately decide its success or failure.

Rusty

I do not own a Ford.

UD

[RustyJC]

Originally Posted by Uncle Dave

Thats not the experience I have in my Sprinter.

The easier I drive it the less it regens.
The harder I drive it the more it regens.

Straight up.

Regardless - an 08 pays no regen penalty.

UD

I'm not going to debate what you say you've experienced. I'm just telling you the theory behind diesel emissions control and operation of the DPF (and, yes, I'm an engineering manager for a manufacturer of large industrial diesel engines, so after 40 years here, I have a fair idea of how these things work).

Rusty

[Uncle Dave]

Originally Posted by RustyJC

I'm not going to debate what you say you've experienced. I'm just telling you the theory behind diesel emissions control and operation of the DPF (and, yes, I'm an engineering manager for a manufacturer of large industrial diesel engines, so after 40 years here, I have a fair idea of how these things work).

Rusty

Help me out Rusty,

In an 08 or earlier that isn't equipped with a Urea system or DPF.

When towing you get black smoke on hard throttle right?

(I did,do, and all my other diesels did)

If the EGT isn't high enough to burn off the black smoke when towing how can it be high enough to regen on its own?

UD

[RustyJC]

Black smoke (soot, actually) is composed of partially burned microscopic droplets of diesel fuel. It occurs because some of the injected fuel was in a region of the combustion chamber where there was insufficient oxygen to achieve complete combustion.

That's why the "bombed" diesel pickups can bury the whole street in a cloud of black smoke. The tuner (box or chip) allows the engine to fuel before sufficient air (boost pressure) is available for combustion, so the engine is spewing partially burned fuel out the tailpipe - the black smoke or soot. In short - too much fuel, not enough air.

Once the soot leaves the combustion chamber on an uncontrolled engine, combustion pretty well stops, so it makes it all the way out the tailpipe. Higher EGTs won't burn the soot in the tailpipe of an uncontrolled engine - there's insufficient free O2.

Regeneration of the soot trapped in the diesel particulate filter is another matter. The particles of soot are captured in the substrate of the filter media, and all that is necessary is sufficient free oxygen and heat to light it off. The ECM monitors O2 and post-DPF temperature and, when regeneration is required, can call for enough excess boost (O2) and heat to initiate combustion in the DPF. It only stands to reason that the higher the EGT is to begin with (high load operation), the less supplemental heat from regeneration fueling is required to launch this combustion process.

Rusty

[Uncle Dave]

Originally Posted by RustyJC

Black smoke (soot, actually) is composed of partially burned microscopic droplets of diesel fuel. It occurs because some of the injected fuel was in a region of the combustion chamber where there was insufficient oxygen to achieve complete combustion.

That's why the "bombed" diesel pickups can bury the whole street in a cloud of black smoke. The tuner (box or chip) allows the engine to fuel before sufficient air (boost pressure) is available for combustion, so the engine is spewing partially burned fuel out the tailpipe - the black smoke or soot. In short - too much fuel, not enough air.

Once the soot leaves the combustion chamber on an uncontrolled engine, combustion pretty well stops, so it makes it all the way out the tailpipe. Higher EGTs won't burn the soot in the tailpipe of an uncontrolled engine - there's insufficient free O2.

Regeneration of the soot trapped in the diesel particulate filter is another matter. The particles of soot are captured in the substrate of the filter media, and all that is necessary is sufficient free oxygen and heat to light it off. The ECM monitors O2 and post-DPF temperature and, when regeneration is required, can call for enough excess boost (O2) and heat to initiate combustion in the DPF. It only stands to reason that the higher the EGT is to begin with (high load operation), the less supplemental heat from regeneration fueling is required to launch this combustion process.

Rusty

If I extrapolate-

I want to understand where you are coming from.

You are saying a diesel under a higher load will use less fuel for the regen process because it doesnt have as far to raise the temp before burn off begins.

Doesnt a higher load mean more unburned hydrocarbons go to the DPF than a lower load to begin with?

My experience with the Sprinter is that higher output equals more particulate matter to burn off, and hence more frequent regens.

Either way - I wish I could go back to my pre DPF Dmax.

UD

[RustyJC]

You may want to check the air filter, wastegate function and anything else on your Sprinter that could affect airflow. The control systems on modern diesels are set up to not provide more fuel than air is available for combustion. These systems read absolute intake manifold pressure and intake manifold temperature and compute airflow (pounds of air per second); they will then adjust fuel flow proportionately. A modern diesel (even uncontrolled) should show minimal to no black smoke under sustained high loads - it should always have sufficient oxygen for good combustion. There's an example of that on another current thread - a poster's engine MAP sensor failed, and the 500 BHP engine suddenly would only produce an indicated 155 BHP maximum - the ECM couldn't measure airflow so it reduced fuel flow accordingly.

The exception would be on sudden "throttle" pedal application (diesel cycle engines by definition are unthrottled, or at least were until the use of EGR) - the engine development engineer has to balance the user's expectation of immediate throttle response with the lag inherent in spooling up the turbocharger to provide the required higher boost pressures required for complete combustion (although VGT turbochargers have reduced boost lag markedly). In these instances, the ECM will allow a brief "overfuel" so that the engine responds and accelerates while the boost pressure catches up - this can produce a brief light puff of soot that's visible out the tailpipe of an uncontrolled diesel.

Rusty

[Uncle Dave]

Originally Posted by RustyJC

You may want to check the air filter, wastegate function and anything else on your Sprinter that could affect airflow. The control systems on modern diesels are set up to not provide more fuel than air is available for combustion. These systems read absolute intake manifold pressure and intake manifold temperature and compute airflow; they will then adjust fuel flow proportionately. A modern diesel (even uncontrolled) should show minimal to no black smoke under sustained high loads - it should always have sufficient oxygen for good combustion.

The exception would be on sudden "throttle" pedal application (diesel cycle engines by definition are unthrottled, or at least were until the use of EGR) - the engine development engineer has to balance the user's expectation of immediate throttle response with the lag inherent in spooling up the turbocharger to provide the required higher boost pressures (although VGT turbochargers have reduced boost lag markedly). In these instances, the ECM will allow a brief "overfuel" so that the engine responds and accelerates while the boost pressure catches up - this can produce a brief light puff of soot that's visible out the tailpipe of an uncontrolled diesel.

Rusty

Never seen a wisp of smoke from the Sprinter.
Id better not for what it costs and its only got 9K miles on it.

I have a cat powered motorhome that runs quite clean with only the occasional puff on a uphill downshift.

Dads Motorhome has a c12 and it rarely puffs.

My old Dmax would puff pretty hard up the grapevine, but not like a chipped unit.

UD

[RustyJC]

OK, I guess I misinterpreted your comments. When you say the Sprinter produces more particulates under heavy load, I thought you were basing that observation on visible soot. Otherwise, how would one know?

Rusty

[Uncle Dave]

Originally Posted by RustyJC

OK, I guess I misinterpreted your comments. When you say the Sprinter produces more particulates under heavy load, I thought you were basing that observation on visible soot. Otherwise, how would one know?

Rusty

It regens more often.

Why else would it regen more often?

UD

[RustyJC]

I can't do an armchair diagnostic from here regarding your particular situation on your Mercedes diesel, but I can only state that the Cummins-powered Ram pickups regen far more frequently around town than they do when working on the open road. Consider that when the 6.7L was introduced on January 1, 2007, there was a period of perhaps a year when there were a lot of warranty claims for VGT turbochargers with stuck nozzle rings (the Holset VGT turbos used on Cummins engines use a moveable nozzle ring in the turbine section, not moveable vanes) or plugged EGR coolers due to carbon (soot) buildup. Guess which trucks had this problem? The mall cruisers that just loafed around town or were used for stop-and-go commuting. Seldom if ever did the dealers see a hotshot rig or a truck used exclusively to tow a large RV back in the shop. It was obvious which applications produced more soot - the lightly loaded ones.

Rusty