Good Sam Club Open Roads Forum: Cummins/Tula dDSF (diesel Dynamic Skip Fire)
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Tow Vehicles

Open Roads Forum  >  Tow Vehicles

 > Cummins/Tula dDSF (diesel Dynamic Skip Fire)

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 2  
Next
ShinerBock

LVTX

Senior Member

Joined: 02/22/2015

View Profile



Posted: 04/15/21 06:26am Link  |  Quote  |  Print  |  Notify Moderator

I have been watching this study for a while along with the Cummins ETREE project that replaced an ISB 6.7L with an ISB 4.5L hooked up to a 130kW generator pushing a 175kW motor that netted over 60% better fuel economy without any sacrifices to performance. The dDSF project was a partnership with Tula Technology which basically uses special algorithms in the ECM to skip injector firing events based on different loads.

It is sort of like variable displacement systems in gas engines, but more dynamic since it uses an array of different firing densities(up to 30) versus just 8 to 4 cylinder deactivation. The firing density will depend on torque demand. This study was done on a class 8 truck that is rarely unloaded like our pickups so the instances of low torque demand would be more frequent in our trucks and could possibly increase fuel economy, even more, when unloaded.

The best part is that not only does it not add more mechanical complexity (other than an ECM that can handle more data at a faster rate), but it also lowers emissions so current EGR/SCR systems will not be used as much while increasing fuel economy by about 20%(in a class 8 truck). I was told by some of my contacts at Cummins that this will likely be implemented into the larger medium/heavy-duty engines first and then the light-duty commercial market shortly thereafter. It would be interesting to see it work if it is eventually implemented in our pickups.

A 20% increase on the average combined fuel economy of 15.5 mpg in the current Cummins diesel pickups is an additional 3 mpg.

Cummins and Tula study of Diesel Dynamic Skip Fire

[image]

* This post was edited 04/15/21 06:35am by ShinerBock *

BurbMan

Noblesville, IN

Senior Member

Joined: 09/20/2001

View Profile



Good Sam RV Club Member


Posted: 04/15/21 06:53am Link  |  Quote  |  Print  |  Notify Moderator

Definitely cool tech! Fuel injection in gas engines has been doing this for 20 years, where the the PCM varies injector pulse width based on power required. Longer injector open time = more fuel delivered into the cylinder. The fuel pump operates at a constant flow, and whatever fuel isn't used by the engine gets returned to the tank via the return line. Now some mfrs are using variable-speed fuel pumps to eliminate the return line to the tank.

Hopefully this technology in a diesel application will deliver good emissions performance without the EGR and other problematic components.


2015 Ram 3500 SRW 4x4 Laramie Crew Cab Long Box, Cummins diesel
2002 Lance 811 Slide-In Camper
SOLD: 2008 Terry 34' TT
SOLD: 2001 K2500LT 8.1L Suburban

Lance 811 Renovation Story!
Project Complete!
Maiden Voyage!


Groover

Pulaski, TN

Senior Member

Joined: 10/17/2007

View Profile


Offline
Posted: 04/15/21 07:17am Link  |  Quote  |  Print  |  Notify Moderator

A 4.5l in a class 8?! Or have mixed in information from different tests? Either way, I like the concept for a motorhome if the 4.5l can be made quiet enough to be acceptable for use a generator in a campground. Having separate engines for propulsion and generator in a motorhome complicates a lot of things and adds a lot of weight.

I spoke with a high level person at Thor recently and he told me that there was something like this in the works.

The article doesn't mention use a hybrid but could add a lot to the versatility of the drivetrain.

I don't understand how they increased fuel economy 20% but only reduced CO2 emissions 5% though.

ShinerBock

LVTX

Senior Member

Joined: 02/22/2015

View Profile



Posted: 04/15/21 07:38am Link  |  Quote  |  Print  |  Notify Moderator

Groover wrote:

A 4.5l in a class 8?! Or have mixed in information from different tests? Either way, I like the concept for a motorhome if the 4.5l can be made quiet enough to be acceptable for use a generator in a campground. Having separate engines for propulsion and generator in a motorhome complicates a lot of things and adds a lot of weight.

I spoke with a high level person at Thor recently and he told me that there was something like this in the works.

The article doesn't mention use a hybrid but could add a lot to the versatility of the drivetrain.

I don't understand how they increased fuel economy 20% but only reduced CO2 emissions 5% though.


The ISB 4.5L was in a class 6 cab-over truck. You can find more info on that study here.

Cummins ETREE Final Report

Diesel engines already emit less Co2 than an equivalent gas engine even without emissions equipment so I doubt you will see much improvement there. It is NOx that they emit more of and cannot be reduced with a catalytic converter like a gas engine due to a diesel's lean air/fuel ratios. It would ruin a catalytic converter very quickly.

Groover

Pulaski, TN

Senior Member

Joined: 10/17/2007

View Profile


Offline
Posted: 04/15/21 09:05am Link  |  Quote  |  Print  |  Notify Moderator

"Diesel engines already emit less Co2 than an equivalent gas engine"

Regardless of the fuel there should be a strong correlation between fuel consumption(or savings) and CO2 output. Those statements may have come from different trucks too.

If the 4.5l engine is expected to do the work of a 6.7l it will be interesting to read what they did to ensure long life.

ShinerBock

LVTX

Senior Member

Joined: 02/22/2015

View Profile



Posted: 04/15/21 09:32am Link  |  Quote  |  Print  |  Notify Moderator

Groover wrote:


If the 4.5l engine is expected to do the work of a 6.7l it will be interesting to read what they did to ensure long life.


The 4.5L is pushing a 175kW(234 mechanical horsepower) electric motor in a hybrid setup so it is not primarily the diesel engine that is doing the work. Very similar to a diesel-electric train setup.

RoyJ

Vancouver, BC

Senior Member

Joined: 10/19/2006

View Profile


Offline
Posted: 04/15/21 02:43pm Link  |  Quote  |  Print  |  Notify Moderator

Both real exciting technologies in the diesel front. The Skip Fire is almost like PWM for electric motors, and may be the big step we're waiting for in in-cylinder emissions control vs relying solely on after-treatment. Hopefully 1 day we can look back at the past 15 years as a "interim" emissions phase, much like gas engines of the 70s and 80s.

I've been saying for years we should look at series hybrids used on trains (GE's AC-AC drives can hit 90+% efficiency). It's much easier to optimize your prime mover for a few set-points, than a 3-D map of rpm vs throttle position.

With a battery, we can't use pure AC-AC of course. But a battery is also necessary because unlike a locomotive, we need more than 8 throttle settings, and also need instant response. The extra reserve capacity of the battery should make up for the rectification / inversion losses of AC-DC-AC.

spoon059

Just north of D.C.

Senior Member

Joined: 10/03/2010

View Profile



Good Sam RV Club Member

Offline
Posted: 04/15/21 05:17pm Link  |  Quote  |  Print  |  Notify Moderator

I don't understand the majority of what you wrote, but I like the idea of a smaller engine, similar power and better fuel economy.


2015 Ram CTD
2015 Jayco 29QBS

garyp4951

TN

Senior Member

Joined: 12/06/2010

View Profile


Offline
Posted: 04/16/21 06:28am Link  |  Quote  |  Print  |  Notify Moderator

Maybe power your house too when it goes out[emoticon]

Groover

Pulaski, TN

Senior Member

Joined: 10/17/2007

View Profile


Offline
Posted: 04/16/21 10:46am Link  |  Quote  |  Print  |  Notify Moderator

ShinerBock wrote:

Groover wrote:


If the 4.5l engine is expected to do the work of a 6.7l it will be interesting to read what they did to ensure long life.


The 4.5L is pushing a 175kW(234 mechanical horsepower) electric motor in a hybrid setup so it is not primarily the diesel engine that is doing the work. Very similar to a diesel-electric train setup.


But all of the power still originates with the diesel engine unless there is a plug in battery pack that I am missing.

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 2  
Next

Open Roads Forum  >  Tow Vehicles

 > Cummins/Tula dDSF (diesel Dynamic Skip Fire)
Search:   Advanced Search

Search only in Tow Vehicles


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:




© 2021 CWI, Inc. © 2021 Good Sam Enterprises, LLC. All Rights Reserved.