Torque: DMax vs Cummins HO

[KenW]

There has been some talk that the cummins has a broader and flatter torque curve than the DMax. I decided to examine torque curves for myself to see which was superior.

DMax: http://www.gm.com/automotive/gmpowertrain/engines_cartruck/diesel/66lb7_torque.htm



Cummins HO: http://www.cummins.com/na/pages/en/products/dodgeram/cummins24vturbodiesel.cfm#top



Max torque: HO 505 DMax: 520

The number in this table are approx from interpreting the charts.



RPM HO DMax

1000 360 340

1500 500 500

2000 505 515

2500 485 510

3000 410 505



80% of Max torque: HO 404 DMax: 416



RPM range of 80% or more of max torque: approx from chart

HO: 1100 - 3000(3100?) RPM

DMax: 1100 - 3200(3400?) RPM



My conclusion: Yes cummins has flatter curve and starts out with a little more torque on low end. In the most usual RPM range it is just about a toss up and the Dmax holds onto its torque better as RPMS go up. For towing Ho has slight edge and for drag racing DMax has small edge.



YMMV



Ken

 

[RustyJC]

Ken,



I'm amazed they're that close. Of course, plug in a minor fueling box such as the EZ and the advantage goes to the Cummins, big time. Wonder what the DuraMax guys have now or will have to compare/compete with the EZ?



(Speaking as a 5ver tower [torque], not a drag racer [BHP]).



Rusty

 

[Mark_Kendrick]

the question should be what is the Dmax capable of not how do they have it programmed. .



check this out for the ISB 260 rv engine...

http://www.cummins.com/na/pdf/en/products/truck/specsheet/4000102.pdf



It makes tons of torque for a wide range over above 500 ftlb. heck, the entire curve shown bottoms out at 520 ftlb I think this curve can be extended in both direcrions w/more tweaking.



too bad for those pesky emissions laws:-laf:-laf

 

[HiPerf360]

I never pull with my truck below 1500rpm so the Duramax would be better... . if my truck was stock

 

[Mark_Kendrick]

If you had the Dmax you'd be stuck w/stock because the transmission would freak.

 

[Breck]

If you pulled the numbers from an advertisement, those numbers are at the crank.



The true test would be on the road or a chassis dyno. If you look at the chassis dyno, the Dmax does not start making much torque until above 2100 Rpm’s.



I have noticed that the Dmax's do not "lug" down very well, at least the ones I have run across.

 

[Mark_Kendrick]

I still love my CTD . . I can leave it in 6th all the time as long as I don't drop below 30 mph.



The D-max just ain't for me. I want a brute, loud, rude and menacing. not a slip by like a gasser type.



I like having to kill the engine at the drive through



Half of the fun is the bombing and you just can't do that to the D-max/allison

 

[joesoot]

The HO will in most cases put more torque to the ground than the D/A.

 

[Rattler]

The Dmax might have it on paper, but not on the pavement. A couple of weeks ago i was headed home from a road-trip and a Dmax wanted to play. I am sorry but i could not turn him down . From a 70 mile an hour punch, i ran away from him, and my truck was still stock then.

 

[KennyM]

Here is a link to the real numbers, these are from the EDGE web site.



http://www.edgeproductsinc.com/chart_dura.html



The D-Dud has proof it's a DUD.



Ken

 

[Mark_Kendrick]

WOW. . They lose a full 20% before the rear wheels!!!#ad

 

[KKaiser]

And they make no HP or torque below 2250 rpm!!!! With an EZ my sedate little ETC/Auto makes more peak HP and Torque AND 750 rpm earlier!!!! I think I made the right choice, still!



Kent

 

[KenW]

That's very interesting how a torque curve from an unbiased source paints an entirely different and not pretty picture of the Dmax. Real torque starts about 800 RPM later than GM would lead you to believe. GM mislead potential customers?? NEVER







Ken

 

[DarrellB]

I knew that

Buddy of mine pulled his 2001 regular cab 2500 4x4 Dmax at the local truck pull last year and you can really tell they don't build any torque on the bottom end. His little Dmax got out pulled by all the gasser trucks including another freind's new supercrew Ford. :-laf :-laf. the poor guy still gets teased about that one.



Drivin the torque monsterOo. Oo.

Big D

 

[Alan Reagan]

Maybe the Dmax is building torque but not getting it through to the rear wheels efficiently. In other words, maybe the transmission loss is not linear but the loss decreases as RPMs increase. Don't know. Do know I like my HO. I've been towing on the Interstate, got into a passing situation with a Dmax and heard the engine pitch change when it downshifted trying to maintain speed. I had a Ford gasser that downshifted everytime it saw a hill coming if I was towing. I found that very irritating on long trips. With my HO, I don't have that problem. I pull the long hills in with the transmission in the big hole (6th gear).

 

[Mark_Kendrick]

Alan,

There's nothin' like weighing 21K and runnin in 6th for 150+mi at a time:--)

 

[KenW]

The lack of low end torque in the Dmax explains why when pulling a load the allison won't stay in overdrive when it tries to accelerate, at highway cruising speeds it is out of the torque band.



Ken

 

[Alan Reagan]

Mark Kendrick, You are right. I can load my flatbed and run up to NE Georgia and only have to change gears when I go through a small town or if someone pulls out in front of me. Otherwise, this truck pulls strong and I stay in 6th all the time. Also, my EGT isn't excessive so I'm in good shape on the towing end.

 

[HiPerf360]

Originally posted by Rattler

The Dmax might have it on paper, but not on the pavement. A couple of weeks ago i was headed home from a road-trip and a Dmax wanted to play. I am sorry but i could not turn him down . From a 70 mile an hour punch, i ran away from him, and my truck was still stock then.

B. S. I have raced a Duramax on the highway and i had to turn the Bluechip box on to beat him. Even then it wasn't a bad race... and I have more power than 90% of the people on this board!

 

[HiPerf360]

Originally posted by KenW

The lack of low end torque in the Dmax explains why when pulling a load the allison won't stay in overdrive when it tries to accelerate, at highway cruising speeds it is out of the torque band.



Ken

Who cares if it won't stay in overdrive? That is why you get an automatic. The computer that controls he Allison transmission is one of the most advanced automotive computers there is. This new style of computer uses "Fuzzy Logic," it is a system that allows the computer to make decisions on its own. The Fuzzy Logic computers don't use a standard table of numbers like the older style computers have, Like ours.



You guys need to quit bashing the Duramax and respect it for what it is, The most advanced diesel in the truck market today.