v8440

LBZ, you're right about the cummins guys making excuses. I've pointed that out myself a few times before. To boot, I'm a cummins guy myself. The thing is, you went over the line and got rude towards mouseguy. It's plain to me from his posts that mouseguy knows what he's talking about, at least when it comes to dynos and such. You would probably have been better served staying civil and not posting the first shot into rudeness: "Mooseguy,
Try looking at a Dyno reading for an LBZ it will reinforce your obvious lack of knowledege about the truck. Nice try though"

That didn't help your case in this argument at all, and tends to label you as just another ford or chevy troublemaker trying to stir up trouble, even when that is not the case.

Me personally, after carefully looking over the claims you are both making, I think you both would actually agree on the physics behind all this if you sat down and discussed it point by point to nail everything down. It's just that you two disagree on what's the most important factor, namely how quickly the turbo spools up on what truck.

I have no experience with a duramax at all-I've never pulled with one. Just a couple of weeks ago I pulled a fairly heavy load with my '06 SRW 3500 dodge. It has the auto with 3.73's, and is STONE stock, down to the original air filter element. I pulled my dually from LA back to AL after the transmission finally went out in the dually at 270k. Before unloading anything, I took the truck and trailer combo across a set of scales at our local farmer's market. It weighed 18,160 lbs with me and my passenger. The tow truck weighs about 7k empty. If I understand right, this is fairly close to the rated capacity of the truck. It was a slug from standing starts until boost came up, and several times it would downshift out of OD on the cruise control when we encountered long and moderate steep hills. Once it downshifted, it picked speed up without any problem, but it was definitely working to do it. Incidently, this is all at 65-70 mph. Would a stock '06 duramax have out accelerated it? Quite possibly so, I don't know. A number of dodge guys will immediately point out that my truck only has 3.73's, the 1st gear in the dodge isn't nearly as deep as in the allison, the converter is way too loose, etc. These things are true. They are also irrelevant. Nobody put a gun to dodge's head and made them put a poorly matched automatic transmission in these trucks. Same with the gearing-I could have selected 4.10's when I ordered the truck. Boo hoo. If a duramax-equipped truck can outpull it as a result of these things, then, as Bruce Hornsby would say "That's just the way it is".

Now, the truck that was being towed against your garden variety duramax...that would be a different story!

So, in summation, let's all put down our crack pipes and back away slowly. It'll be alright-the sun will rise tomorrow and 6.0 powerstrokes will still be breaking down.

mouseguy

The thing that bugs me about all the bragging that goes on with the PSD and the Duramax is that its always how well they do at the drags or on the inertia dyno. I could really care less about that.

What I care about is pulling trailers. And how that works is the truck is running at about 70MPH on a flat highway and we come to a hill. What I want the truck to do is hold 60-65 MPH without downshifting. And I want to get good fuel economy. I don't give a darn how fast it accelerates. I'm not racing it !

The stock PSD and the Duramax accelerate faster. OK. But as soon as the PSD sees a hill its downshifting ! And if you look at the Ford torque curve, its peaks at 570 ftlbs and falls off from there. At 2000 RPM its only making about 520 ftlbs of torque. My Cummins is making 600 foot pound of torque, maybe more with the timing advanced. Almost 20% more than a PSD. So the PSD drops a gear and revs its brains out and then the fan cuts in too yet and the fuel economy goes down the crapper. That is not what I want.

I thought the Duramax was going to be better in this regard, but my cousins truck didn't seem so. I guess it was only one truck. The torque converter seemed to unlock in it because the RPMs seemed to climb when it was on hills. Now if you got this strong torquey engine, why the heck would it do that ? Why not let the engine torque its way up the hill like a real truck would ?

I guess at this point I should say I hate automatic transmissions.

Anyway, that is my take why I think the Cummins is a great pulling engine.

XLR8R

I have a couple of dyno graphs for bone stock CTDs - a '98 and '05 - but I don't have a way to upload them.
I'll just speak to the '05, since it's more relevant.
The '06 LBZ and the '05 CTD dyno graphs are remarkably similiar in appearance, and these are my observations:

First, I don't know what happened to the LBZ, but it fell into a hole for a couple of hundred RPM down low - especially in the torque department.

At 1200 RPM (the beginning of the LBZ graph), it made 360 ft-lbs & 75HP while the CTD produced 500ft-lbs & 120HP.

At idle(800 RPM), the CTD made 380 ft-lbs & 60HP.

The LBZ peaked at 570 ft-lbs @ 1800 RPM, while the CTD reached 610 ft-lbs by 1600 RPM.

The LBZ gradually dropped to 500 ft-lbs @ 3200 RPM, where it died. The CTD's torque curve was almost dead flat, staying at 600 ft-lbs until 2900 RPM, where it layed down.

The LBZ's HP rose steadily to 310 @ 3200 RPM, and the CTD's rose steadily to 325HP @ 2600 RPM. Both engines just fell on their faces after reaching their peak HP.

Even though the LBZ's HP & torque fell off after peak more quickly than the CTD's did - it definitely has more "top end" (if you can call 3000 RPM that! ).

The dyno curves are similiar in shape, but with significant differences. Just from looking at the graphs, the LBZ would make a better drag engine, and the CTD would make a better pulling engine. Both engines are capable of doing either duty, but one must factor in their durability, expense of modding, etc.

XLR8R

I agree - I think the CTD is the benchmark standard of workhorse engines, and I can't stand slushboxes either unless they've been modded to work much more like a manual!

LBZ Power

XLR8R,
so the 650ft/lb of the duramax made 570, and the Cummins 600ft/lbs made 600. Well, the fact that the Cummins has no drive line loss, and obviously chevy must falsely represent the actual power of the D'max must mean Cummins is better. Would have like to have seen a graph, but I'll take your word for it Cummins is better Duramax is weak. Thanks for clearing it all up.

XLR8R

Actually, the CTD made 610 ft-lbs, but now I'm sure there's a few of us wondering why the smart-aleck attitude on your part? I didn't make the dyno graphs - just reported my observations.

As someone posted earlier, any opinion or preference is fine, but when you're trying to make a case or a point - it doesn't serve you very well to post with a chip on your shoulder!

fredw

i have seen a cummins 06 graph, it starts around the 530lb/tq and goes up to 607 peak in standard

hp is around a high of 280hp, now if you put that on the same dyno graph as the Lbz you can see the difference, the cummins is more closer to the LLY second gen specs

there is many guys that have used the two trucks at work as well and the duramax pulls just as good if not BETTER

and looking at the dynos it just complements this info

its personal preference, and running them stock they both will do fine.. but we all know we dont run them stock..... What Does BEtter When Bombed is the real question

staarma

That is probably the true statement of this thread. I agree totally with it.

The little Cummins is outperforming the other two using less cubic inches to do it with and better mileage and costs several thousands less. I'm cool with that.

BTW, I'll post some graphs of my 600 on monday when I get back to work. They were done on a Dynojet inertia chassis dyno but they are good graphs. I'll try to scare up some LBZ graphs to post as well.

rustyshakelford

in my opinion everyone needs to get what they think will benefit them the most. if you like a duramax, get one. if you like the cummins, get one. i could care less if i make a few less hp/trq then another trucks making. if its what i wanted and i like it who cares. and if you dont like what you got, get something else. i think its great gm was able to get all the kinks worked out of the d-max, its a nice motor and mated to a good tranny, dodge is fixing to try something new w/ the 6.7 and ford w/ the 6.4. im sure there will be some hiccups but thats to be expected. all 3 really are pretty similar these days so you cant go wrong. why must it be so one sided?

brett

mr T

If I read that spec sheet correctly from a couple of pages ago..it said the manual 6 speed will get 610 torwue at 1400 rpms!!...good lord thats awesome! alot of semis get their peak torque at 1300rpms!...thats some serious down low tugging power....i dont even think an auto should be an option with this motor...just like the viper! NO AUTO!!...but this new tranny should be interesting...Ford knows that...thats why its trying hard to get their payload and GVWR up to steal some thunder cause they know that the only thing that you could really criticize the newer dodge cummins about is the 4 speeder

anni2VADER

dmax guys like fredw& lbzpower mention there allison trannies more than there motors, that speaks volumns.without the allison, the dmax is an average engine period.bottom line,6 forward gears,pathetic 245 series tires and a lighter weight truck, it better be faster!

rich

since i started this i'm gonna tell ya'll for sure which one does better going to run the same route with basically the same load so i will see which one does better. Their wont be anything but stock truck versus stock truck. the 07 has 1500 miles on it while the 06 had 11k thats the only difference between the 2. wont be any winter fuel crap exscuse or anything else. Like i said before i buy a truck for what it can do STOCK not what i have to spend after paying big $$$ for a truck and then having to spend more just to get to perform descent

XLR8R

That'll be a great comparison.

ASHNBAK

This gentleman is correct! It's only the tranny that makes the Dodge loose in the magazine tests. When pulling the grapevine going south from the San Juaquin valley, my buddies 03 Duramax out pulled me because his 3-4 split is closer than my 2-3 split. I had to slow down to grab 2nd and he kept going in his 3rd. Any hills that we pulled, from L.A. to Oregon, that we both stayed in a 1:1 final drive, our trucks were dead even. As a matter of fact, I ran up on him several times during the trip. Wait until the new 6 speed auto test are done and you "Cummins" guys can finally relax........you'll win.

JOHNBOY6.6

So my truck with a ZF 6 is average? Funny thing is none the CTD boys around me want to play anymore. My truck pulls a trailer just fine. In-laws use it to drag their horses around. I pull my tractor, haul cars, and some times help my buddy with light loads for his trucking bussiness. I drive it almost every day. It finished 3rd in DHRA Work Stock points. I had it at the drag strip Saturday ran 13.332 @ 98mph. That was not on weinie stock tires. Dynos you are all caught up on that one. Dynos are a tuning tool IMHO. Real world tests like Drag racing, Sled pulling, and Trailering are what will tell you what runs and what does not. This power band thing is funny to me. My truck on a Load Cell dyno made 475hp and 950tq. I made over 400hp form 2200rpm to 4200rpm. Tq is over 700flbs from 2000 to 3500rpm. I have seen several twined common rail CTD on the dyno that make 100hp more than me. But when I sled pulled against them I beat them both buy 25 feet. Why Narrow power band . Their horsepower graph looked like a radio tower. Went up quick and dropped quick. I got accussed of run N2O at that pull. They teched my truck and could not find anything. The tech guy said "I doubt he has N2O as his truck. It smoked the worst off any truck here today. N2O will clean up a lot of smoke."

I am not saying the the CTD Dodges are bad trucks. They are very good trucks. They are getting better to why. Because they have to or lose market share to GM. The Duramax is good running with whatever trans you get behind it. What you buy comes down feel IMHO. These two engines have different feel to them. The inline6 vs V8 thing. In the end it comes down to what you like.