Engine/Transmission (1994 - 1998) right gear ratio?

[HBarlow]

You should recheck your facts. Torque curves for the various engines used to be published on the Cummins website and in Dodge truck brochures every model year.

All 24 valve engines used in Dodge Rams produce maximum torque from 1600 to 2700 rpm in a wide flat band.

All HPCR engines used in Dodge Rams produce peak torque from 1600 to 2700 rpm.

All ISB6. 7 Dodge Ram pickup engines rated at 350 hp /650 tq produce peak torque from 1500 rpm to 2700 rpm.

ISB6. 7 engines of the 305 hp version used Dodge Ram cab and chassis trucks produce peak torque from 1600 to 2700 rpm.

You are mistaken. They absolutely DO pull hard at 1600 rpm, that is where peak torque first occurs.

I've never owned a 12 valve engine and am not certain about where their torque band begins and ends but I do know it is much narrower than 24 valve engines. I think it begins at 1500 or 1600 rpm but tapers off by around 2400 rpm.

Electronic engines which are all 24 valve and HPCR engines do not have a torque PEAK as you stated. Their maximum torque is produced in a wide flat band from 1600 (or 1500) rpm up to 2700 rpm because 24 valve engines breathe better at higher rpm and because the magic of computers allows the control of fuel and air to maintain a flat torque platform.

 

[AClayton]

I think the harmonics are certainly there and something every Cummins owner needs to be aware of. In stock form... . as what Harvey is most likely referring to,the Cummins does indeed pull hard and will do it for long periods of time. If the slightest bit of timing is added by a box other than the Smarty is where you can have unbelievable drivetrain stress. Automatics require rpm to keep pressures up and that is why our trucks require a TC and VB upgrade right off the showroom... ... in 12 and 24V form. I tow with no problems in the 1650 to 2200rpm range and use no timing other than the Smarty software. I have mine set 'weak' on timing to sort of settle it down some. My little 6k trailer offers no trouble at all but my heavy RV is where I have to reduce power output to be able to tow comfortably. Every truck is set-up differently and we all need to be careful with blanket statements. In Harvey's defense, the Cummins in stock form will indeed do as he stated and it is written in the literature right on their website.



It would take an unskilled driver months to figure out the power curves of these engines and all their habits at different rpm's. A Duramax or Powerstroke owner simply drive their rigs as if a gas motor was under the hood. In my opinion,it takes much more understanding of our trucks to drive them safely and to prevent pre-mature failures of our drivetrains. I have been guilty of it myself... ... . I learned from reading all the material on the pages of this site. You cannot expect a novice driver that is used to just driving to work or picking up groceries to hop in a dump-truck and go to town. These engines are medium-duty truck engines and need to be driven and maintained as such.



Alan

 

[cerberusiam]

You should recheck your facts. Torque curves for the various engines used to be published on the Cummins website and in Dodge truck brochures every model year.

What facts would those be? The marketing hype pulled from literature or the undeniable proof generated by multiple dyno pulls as installed in the truck?



Marketing literature is engine specific with no weight given to installed and tuned form. It makes good talking points but is less than adequate when applied to actually driving the truck.



TQ peak on a jerk pump runs 1900-2100 with a definite form. Its also well down once the rpm's go beyond 2500. A single event, aside from massive over fueling, will NOT produce TQ curves that are flat out to 2900 rpms.



TQ peak on a CR is right at 2500 rpms on every dyno sheet I have ever seen on stock fueling. The TQ curve is pretty flat all the way from 1700-2900 but a definite peak exists as described. Thats all multiple event and electronic control though, it can be manipulated by playing with the TQ management to produce a peak in the normal range of 1900-2100 rpms. A CR engine in stock form is almost 50% defueled by the time rpms drop to 1600, good luck getting it to pull under those conditions. :-laf



Bottom line is, WOT throttle and loosing rpm is on the wrong side of the TQ peak and every one of these trucks exhibits that exact behaviour when the rpms drop down under 1800. There is no conceivable reason to pull rpms that low under a load. Shift it, your transmission will thank you.

 

[HBarlow]

I guess that if I have a choice whether to believe the printed literature published by the manufacturer or the opinions stated by someone who appears determined to win an argument by sheer stubborness I'll believe Cummins.

 

[hsmith]

I don't know why folks even try to argue with HBarlow. I have never seen where he admits maybe being a bit wrong.

 

[HBarlow]

Show me where I am wrong and watch.

Opinions don't defeat facts regardless of how important some believe their opinions are.

 

[cerberusiam]

I guess that if I have a choice whether to believe the printed literature published by the manufacturer or the opinions stated by someone who appears determined to win an argument by sheer stubborness I'll believe Cummins.

LMAO!!! Harvey, WHY do you do this to yourself time after time. Any disagreement and you can turn a phrase to make yourself come off as a total jerk. :-laf I gotta ask, do you have to work at it or does it come naturally?

Show me where I am wrong and watch.



Opinions don't defeat facts regardless of how important some believe their opinions are.

Opinion - subjective emotional response based on unsubstantiated information



Just exactly what substantiated, objective information have you posted that supports YOUR opinions? What have you offered other than a flawed marketing blurb? Really, and you call me stubborn for offering up facts instead of conjecture based on some one else opinion? Excuse me while I laugh myself silly at the irony. :-laf:-laf



Ok Harvey, you want proof and I have it. The question begs, what will you accept? Will you stipulate the dyno sheets I post are substantiated proof of facts?



Ball is in your court buddy. I have dyno sheets on a 12V and a CR that definitively prove what I am saying, jerk pump vs CR and their TQ curves in black and white.

 

[HBarlow]

Cummins Every Time - Ram - 6. 7L Turbo Diesel

Like I said above, I choose to believe the specifications published by the engine manufacturer who has designed and built the engines for a very long time. Their specs are for factory original equipment engines tested on engine dynamometer at the flywheel.

Individual results for one engine on one dynamometer, both of unknown condition, may mean something for that engine and that test but mean little when making a statement about all Cummins engines.

The chart above is for the current ISB6. 7 engines. Cummins has posted similar torque curve graphs for the current engines at least since I began driving one in 2001 but they drop off the website when no longer current.

The identical information has been published in every Dodge Ram brochure I've seen.

 

[cerberusiam]

Like I said above, I choose to believe the specifications published by the engine manufacturer who has designed and built the engines for a very long time. Their specs are for factory original equipment engines tested on engine dynamometer at the flywheel.

So whats wrong with this picture? How about 6. 7 and engine dynamometer, does that maybe not tell you something?



Point one, a 6. 7 CR curve is significantly different than a 5. 9 CR and radically different from a jerk pump.



Point two, engine dynamometer curves are NOT representative of a chassis curve. Those dyno sheets are putting the engine in the best light possible under the best conditions possible. Remember what I said about marketing blurbs not reflecting reality? Want to know how much tweaking was done to get that pretty picture, LOTS!!! :-laf



You are basing your opinions on data that is NOT representative of "as installed" conditions that exist. Do you really drive the engine around like that? How does the power get to the ground without wheels? Where do you sit? C'mon Harvey your smarter than that!!



You weaseling on me Harvey, I got money on you being a stand up guy that can admit his mistakes and you are not engendering much confidence I was right. Tell me, was this statement, "Show me where I am wrong and watch", just for the benefit of the peanut gallery?



Again, will you accept chassis dyno sheets as valid facts that prove you are off base?

 

[HBarlow]

You jumped into this discussion and told me I was wrong about something I wrote. I posted evidence above to prove I was not. All you have offered to support your opinions is more opinions which are simply not very valuable to me.

I learned long ago that anyone who tries as hard as you are trying to win an argument offering more and more opinions that wander around and still produces no facts or evidence to back his argument probably doesn't have an argument after all. So go ahead and spit and sputter if you choose, I'm through with the discussion.

 

[cerberusiam]

You jumped into this discussion and told me I was wrong about something I wrote. I posted evidence above to prove I was not. All you have offered to support your opinions is more opinions which are simply not very valuable to me.

I suspect not much of anything that wasn't derived in your world is of much use to you. This is an open forum, anybody can jump in and post info. You posted erroneous info I simply pointed out where you were mistaken.



As promised dyno sheetsthat are some hard facts not marketing materials pulled from a web site. When I round up my dyno sheets from the jerk pump will post them. Been on the road without access to the hard data.



Stock CR tune with the TQ peak right where I promised. Might want to do a better job of checking facts before posting opinons based on erroneous info. When you get done absorbing you can address "Show me where I am wrong and watch".



#ad






12V TQ curves are radically different and peak in the 1900-2000 rpm range tailing off quickly. As everyone knows best efficiency is obtained at peak TQ slightly above. Doesn't work as well with a CR running those rpms so we remap fuel curves, change cams, etc, to get that back down around 2000. Makes a big difference. Luckily the 12V's and VP trucks don't need that work to put the TQ where needed, one just has to drive to its strengths.

 

[HBarlow]

You are obviously a guy who is accustomed to winning arguments with a lot of bluff and bluster, noise if you will.

The only word I wrote about 12 valve engines is the fact that I have never owned one, am not familiar with them, and don't know what the torque curve of a 12 valve engine looks like on a graph. I did say that I know it is much more narrow than the torque curve of a 24 valve. You know that very well but are trying to win an argument by arguing another point which was not under discussion.

If you doubt me, go back and read my earlier post on the subject.

Again, for the record, I posted about 24 valve, HPCR, and ISB6. 7 engines. The torque curve of those engines begins at an an inital peak of 1600 rpm (1500 rpm on current ISB6. 7 engine rated at 350hp) and remains flat in a wide band to 2700 rpm. The Cummins torque curve for those engines is provided in my post above.

I am writing about 24 valve engines. I have not seen you post any evidence to prove your claims about 24 valve engines. Your experience with one 12 valve engine on a chassis dyno doesn't prove anything to me.

I went back to your graph above and scanned as hard as my old eyes permit and now see the fine line across the top. I am chuckling to myself.

What your own graph shows is an essentially flat line from 1600 rpm up to about 2700 rpm where it tapers off and then declines. Nobody is naive enough to believe that an engine produces a precise 650 ft. lbs. of torque in a perfectly flat line as indicated in the Cummins graph I posted. The graph you posted doesn't vary more than about 40 or 50 ft. lbs. , perhaps only 30 to 40 ft. lbs. from beginning of the flat portion to the end where it declines. For all practical purposes that is a flat torque curve except to someone who just wants to argue.

Thanks for proving my argument. Perhaps you don't understand the argument?

 

[NIsaacs]

I have had all my trucks on the dyno here local and have enjoyed the company of a diesel truck crowd. It is always fun to see the different brands, models and set ups. However, I really don't understand how they work or arrive at the numbers.



Years ago, I was a mechanic for an Allis Chalmers equipment dealer and worked on/rebuilt all types of tractors. When I finished one I would hook it up to a large PTO dyno and break the engine in. This dyno was capable of pulling the engine down to any RPM at WOT. After several hard pulls I would set it for maximum HP and let it pull for an hour.



When I first installed the Cummins in my Ford I had it on the Dyno at the Cummins shop in Phoenix. They did the same thing. They started it out at WOT and slowly put the screws to the dyno and forced the engine down to 1600 RPM.



I don't understand how the pickup dynos work by letting the engine run wide open for about 10 seconds?? Keeping in mind this in a controlled environment. Set temperature, clean surroundings, set elevation with optional cooling fans. How does this equate to driving for hours on end, in all environments and pulling the guts out on a 6-7 percent grade with a heavy load for ten miles, toping out at 10,000 ft. elevation??



Nick

 

[BigEasy]

All this pi$$ing between you two is making a real mess on the floor...

 

[HBarlow]

Yep, a little mess on the floor is often the result of a disagreement but the advantage of an occasional discussion, even one that involves disagreement about engine operating characteristics and other factors is that factual information is presented and learning occurs.

 

[cerberusiam]

All this pi$$ing between you two is making a real mess on the floor...

Huh?



This is just a friendly disagreement over the interpretation of data, no peeing is involved. We are just poking fun at each other. :-laf



Harvey is 100% correct, knowledge will ensue as usual. Just gotta pay attention.

 

[cerberusiam]

Again, for the record, I posted about 24 valve, HPCR, and ISB6. 7 engines. The torque curve of those engines begins at an an inital peak of 1600 rpm (1500 rpm on current ISB6. 7 engine rated at 350hp) and remains flat in a wide band to 2700 rpm. The Cummins torque curve for those engines is provided in my post above.

Yes you did, in a 12V forum. Sooo who's not on track here?



You lumped 24V in, am guessing you mean VP powered, in with the HPCR emissions motors and construed that the TQ and power curves are comparable. I am telling you a jerk pump TQ curve is NOT comparable to a CR, does not peak at 1600, is not flat all the way to 2700 rpms. All the jerk pumps, VE-VP-P1700, are comparable in the TQ curves and that will be peaking at 1900-2000 rpms and sharply dropping after the peak. Thats easily verified by a quick search here.

I am writing about 24 valve engines. I have not seen you post any evidence to prove your claims about 24 valve engines. Your experience with one 12 valve engine on a chassis dyno doesn't prove anything to me.

Excuse me? All CR's are 24V so how does it not apply? The number valves has nothing to do with the power curves. Thats all driven by timing, cam profile, and injection event sizing. Jerk pumps have a single injection event with all the fuel delivered in a single time frame, CR's run multiple events across the time frame and are tuned to control emissions. You CANNOT compare and expect the same results.



You can clearly see from the dyno run the TQ peaks about 2500 rpms and the curve is relatively flat from 1700 out to 3000 rpms, just like I said. Without some manipulation of the tuning you will never see high TQ at 1600 as the engine dynos depict, as installed in the truck it doesn't work that way due the de-tuning that has been performed to save parts.



Back to the jerk pumps, watch what happens when you tune a CR to the fueling curves of a jerk pump. The form of the top line is almost indentical to what one would see with only a single massive event to inject the fuel. Back it down 200 rpms to get rid of the late valve timing in an emissions engine and that is what it would look like. Clearly a large peak and a tail, not the sharp ramp and flat curve of a stock CR.



Again to the OP's question, trying to pull rpms under peak TQ into the range he is talking about is out of the power band and hard on the engine. In addition the harmonics zone is much more pronounced in a jerk pump so running thru it constantly just accelerates wear. The failure you talk about is quite common when doing just exactly what you described, putting the load on the back side of the TQ curve.



This is not a new concept and is pretty well documented over the years of accumulated data right here. A search quickly turns reams of reading.



Here you can see the effects of removing the TQ management built into a CR and shaping an injection event to more closely match a jerk pump scenario. I think Marco has a pretty good grasp on what needs to be done to match them.



#ad

 

[HBarlow]

This is where our disagreement began:

That may be correct but it pulls a bit better and is easier on the drive train if you shift on the upside of the TQ peak and stay in front of it. Your numbers are off on the TQ peaks also, a stock CR will not pull well down to 1600 rpms when its peak is at 2500 rpms. Peak TQ on the 12 and 24V's shows right around 2000 rpms which is where the sweet spot is for towing. Under that its just needlessly lugging and rattling thru the harmonics band.

Auto, 5 speed, 6 speed, it doesn't matter, the harmonics kill EVERYTHING. :-laf

At that point both of us were clearly talking about HPCR engines.

You stated a Common Rail engine won't pull well down to 1600 rpm, that it's torque peak is developed at 2500 rpm. I posted a current graph provided by Cummins, Inc. showing a flat torque curve between 1500 and 2700 rpm.

Now you are posting endless crap about jerk pumps, whatever that is, apparently trying to confuse the issue.

Having a discussion with you is like having a discussion with a woman or child.

Why don't you address your original statement posted above?

 

[cerberusiam]

I clearly indicated 12V, 24V, and CR in the paragraph when I was referencing TQ curves. Go read it again. I specifically said Peak TQ on the 12 and 24V's shows right around 2000 rpms , not a lot to misunderstand there. I also clearly stated that your TQ figures are off on the CR's as the chassis dyno sheets prove. There is a reason these engines are not allowed to make full power at 1600 rpms in a Dodge truck, but thats another discussion.



Engine dyno specs are one thing, chassis dyno another. Chassis dyno sheets show exactly how the enigne is configured to run where it lives. Enigne dyno sheets show what is achievable under optimum conditions at the crank. They do NOT take into account gearing, transmission selection, and more to the point tuning for emissions. Cummins builds engines. Period. The reason they don't have chassis dyno info is they don't do chassis with ALL the pieces. Its not valid to use an engine dyno sheet to portray how it works as installed.



Look at the forum header, its the 94-98 forum. Thats a 12V jerk pump, or if you prefer single event, section. You broad brush stroked the 5. 9 from inception to end as having the SAME power curves, its just NOT true as I have shown and you can eaily find for yourself. The OP has a 12V P7100 truck. You brought up the VP and CR engines into the discussion, not me.



Since you don't understand the term jerk pump and how it fits into this discussion then we have an even larger semantics problem because your not understanding the basics that control the power curves. If you did and had driven/dynoed a 12V, early 24V, and a CR, like I have, you would understand what I am saying.



To the OP's original question, running the shift points down to 1600 rpm's under load is NOT a good idea for all the reasons I have pointed out. Shift points should be selected to keep the rpms at or above the TQ peak, in his truck 1900-2000 rpms depending on how the aneroid, injectors, turbo, and fuel pump is configured to deliver the power. The harmonics zone runs roughly 1700-1900 and less time spent in it the better. CAN they be run down to 1600? Sure, with the caveat its NOT the best practice.



Harvey, you have admitted no experience with a 12V. Why then would you go to such pains to try to dispute those that DO have that experience? That would indicate your the one with the overriding need to be right all the time.

 

[BigEasy]

Are you guys engineers or lawyers?