bully dog box

[Garry Verheyden]

My 12 valve had no problems towing 23,000# at below 2000 rpm also, but I will never tow at below 2000 rpm anymore unless it is on flat ground with no headwind. If it is on flat ground, you could tow 50,000# all day. But not on hills. I agree with Kieth about it being hard on things below 2000 rpm. I towed 23K up a hill with no problem at 1850 rpm in 4th gear until I snapped my input shaft in the middle of the hill 30-40 seconds later. Had a nice towing bill for my truck and 35' 5th wheel 250 miles from home.

Garry.

 

[KLockliear]

I think you missed that I gave the 1800rpm range as the low end for these engines. I was making references to lugging in response to the 1200-2000rpm normal driving range... 80% of that range is too low for decent power.



The 12v's were known to make power lower in the band, but not a 24v. Not a fair comparison.

 

[PCline]

Garry... how do you attribute low rpms to snapping your input shaft? Do you think the low rpms were causing heat that weakened the shaft? Or maybe you're saying that if you would have been in a lower gear (higher rpm) you would have been driving less torque through the shaft?



At any rate, I think shafts break from torque not rpms. I do agree to some extent that lower rpms produce less of a hydrostatic oil bearing and could wear things a little faster, but I don't the difference between even 1200 rpm and 2800 rpm is diddly in that respect. Lugging the engine is a different story. I don't lug the engine at any speed.

 

[Garry Verheyden]

PCline,

Exactly what you said. The torque ouput was way too high at that rpm. I know these engines can put out way too much torque at low rpms than what the drive train is designed for. What I am saying is if exhaust temps. could be maintained reasonably at higher rpms, I would rather look for power increases at above 2000 rpm where you have less chance of drivetrain carnage.

Garry

 

[tpicard]

I'm a little confused on this. What is the definition of lugging? I was taught that lugging occurs when unit under load is losing rpm's, so if you are not holding RPM or gaining RPM you are lugging. I maybe mistaken it's been years since I was in school. Hence I do lug mine slightly but only to shift point.

 

[91W350]

I must be lost too. Almost all of the drive train parts I ever broke was from shock or high engine rpm abuse. My experience with the Cummins is low, but my big block Chevrolets claimed a lot of parts over the years. Usually it was lack of lubrication or compromised lubricant, high rpm stresses, or shock factors like trying to rock out of a mud hole or dropping the hammer at 5000 rpm. In pulling applications I can see where low rpm and high drive train stress might cause low transmission lubrication for the load friction at hand. As far as engine parts, oil is supposed to be the load bearing, as long as the pulling is not below normal oil pressure, what does it hurt?

 

[RSnaith]

Originally posted by KLockliear

I think you missed that I gave the 1800rpm range as the low end for these engines. I was making references to lugging in response to the 1200-2000rpm normal driving range... 80% of that range is too low for decent power.



The 12v's were known to make power lower in the band, but not a 24v. Not a fair comparison.

Actually, you had mentioned 2000 RPM, but thats neither here nor there. I was simply pointing out that Matt's driving style kept him in the 1200 - 2000 RPM range, and that he was looking for something that would make usuable power within the range that he wished to drive in. Its awful tough to make power at 1200 RPM with these smaller engines, but I don't think its impossible to make enough torque at 1600 - 1700 RPM to tow decent loads without lugging, thereby reducing engine wear and driver fatigue. Of course, as the load weight goes up, you either need even more torque or you have rev higher.



As for the 12 valve reference, it was simply to point out that it is indeed possible to build a small displacement engine that is capable of generating usuable low RPM torque. A VP44 equipped 24 valve can't get as low as the old 12 valve, but I think the CP3 equipped 24s will approach the low RPM power of the old trucks.

 

[Garry Verheyden]

Mathew said he would like to see a big improvement in the torque at the lower rpms, which is what I have on my 12 valve. I have enough torque at the lower rpms to tow, but I will slip my clutch at below 1800 rpm, I've broke an input shaft at about that rpm and destroyed 3 clutches at less than 1800 rpm(I was a slow learner) but at least I was a learner. Even if the clutch doesn't slip at below 1800 rpm, the engine does make more groaning type sounds if I step on it under heavy loads. It doesn't sound good for it. (engine is 400+ hp)

When I tow my 15K 5th wheel now, I bring the rpms up to about 3500 rpm before shifting on hills etc. This driving habit has made it possible to keep my dual friction clutch for the last 2 1/2yrs with no problems.

I would disagree that we should concentrate on improving the low rpm horsepower instead of the higher rpm horsepower. SOME more power could be improved at the lower rpm, but I would like to see the majority of the horsepower to be improved at or above 2000 rpm.

Garry.

 

[RSnaith]

Originally posted by Garry Verheyden

I would disagree that we should concentrate on improving the low rpm horsepower instead of the higher rpm horsepower. SOME more power could be improved at the lower rpm, but I would like to see the majority of the horsepower to be improved at or above 2000 rpm.

<chuckle> From the days I spent trucking, this is a debate that has no winner I've seen as many light and heavy duty trucks tore up by high RPM heavy pulling as I've seen tore up by low RPM lugging. For myself, my 01 spent most of its days down at 1700 - 1800 RPM while pulling 30K+ loads. When getting into hills, I did bring RPMs up to the 2000 - 2100 mark, but only because I didn't build the engine to have enough beef in the low RPMs. A good set of EDMs, a quick spooling turbo, and a fueling box that brought in power earlier than my Drag COMP would have helped me and my driving style a great deal.

 

[Mathew Clausen]

Jeez - haven't looked for a couple of days - such a simple question - all sorts of answers!



First - let me say I do not tow anything. My max load is usually 1000 lbs (couple of motorcycles and two passengers). I also do not hot rod or race anyone. But I enjoy an engine that will feel more lively than the '03 does stock. Maybe I mis-stated my request for "big torque gains" at low RPM. All I really want is for the engine to really feel like the claimed numbers that show peak torque at 1400 rpm. Instead - in stock form - it definitely feels like peak torque is around 2000 rpm (which the dyno charts seem to back up). My 2001 HO felt similar stock - but after adding a DD TTPM (same as edge ez I think) the peak torque felt like 1500 or so. This was perfect for me and made it much more enjoyable for normal driving. I am looking for something similar for my '03. So far - the "pressure" boxes do not look to be helping the lower end that much. And again - I am not looking for huge numbers - if it would just have the same torque at 1500 that it does at 2000 I would be happy.



Regarding "lugging". With an engine that has a claimed peak torque rating at 1400 rpm - I would hope that I can daily drive it empty in that rpm range without fear of hurting anything. Surely these engines have spent thousands of hours on a dyno at Cummins at 1400 rpm at full load. All this talk about huge con rods and huge bearings - and then worry about running under 2000 rpm????? That is why I bought a Cummins vs PS or Dmax. The few seconds that I run it there while accelerating is not going to hurt the bearings or anything else. The exhaust temp would be my biggest worry at the lower RPMS and large loads - which is why I have a pyro.



Would I change my driving style if towing huge trailer while turned up to over 400hp- yes. That is a different situation that puts things much more on the ragged edge.



So - Let me revise my original question - I am looking for an upgrade that provides a boost in performance and driveability empty in the 1500rpm range that is similar to the increase seen with DD TTPM / Edge EZ boxes on a 2001 HO. I do not plan on any other mods - except possibly a larger air filter.



Thanks for all the input previously.



Mathew

 

[Jeff Kelderman]

in other words, you are like me. you want something that hauls a$$.

 

[Garry Verheyden]

Mathew,

I thought you meant lower rpm HP gains that would be high enough to tow decent loads at the lower rpms. But if you were just taling about 2-3000 lb loads at below 1800 rpm, I'm sure it wouldn't hurt the engine or drivetrain and it would be nice to have some improvement at the lower rpms.

I was talking about turning the HP up high enough to tow big 5th wheels etc. at lower rpms (this has resulted in plenty of damage in the past for myself)

Garry.

 

[jimnance]

I had the same thought. Up the HP/Torque so I could go up the hills at lower RPM. Since installing the big BFG's on mine I've decided this engine really is happiest and gets best fuel economy between 1800 - 2200 RPM.



I'm about 1700 RPM at 62 MPH with the BFG's and on the flat all is fine. However, at the first sign of ANY kind of grade it's time to reach for fifth gear. I think the idea of upping the HP to help on the hills has merit, but I think the engine will be happier up in the 2200-2500 RPM range when pulling BIG loads in the hills.



Stock, I let the engine pull down to 1800 RPM before pulling another gear, but I wouldn't want to go lower than that on the hills. The engine just doesn't "feel" right.

 

[CATCRACKER]

i spin mine to 3400 rpms everyday. i feel confident that this hurts nothing. if i had to i would stand on the trottle all day long at 3400rpms in stock form of course. i was topping my truck out the other day and held it at red line 120mph for 2minutes no probs. dont be scared it is better to over rev than to lug. i shift 1500-2000rpms when cruising. W/o much accleration i will leave it in 6th as low as 1300. but i would rather leave in 5th at 1900 rpms rather than going down to 1300 in 6, it just depends how i feel. there is not that much d/f b/t 5th at 1900rpms and 6 at 1300 as far as mpg. just my driving style. i suspect alot of you guys drive like this. when i am towing i keep rpms high shift 1700-2500. dont be scared to spin this motor.



i spin it everyday to 3400 rpms



oh yea my buddy (400hp) broke his crank in an 01($4500 rebuild) blew his 6speed(whole new unit)



it is possible to kill a Cummins and 6spd, it is just rare!



i have never heard of anyone else twisting a crank other than him.

 

[Jeff Kelderman]

where are you able to run 120mph? Talledega?

 

[pecandude1]

the speed limiter kicks in at 109. what did you do cut some wires ?Oo.

 

[Vaughn MacKenzie]

Due to the high compression, long stroke and high amount of power generated by each power stroke of the diesel engine, running hard at lower RPM such as below 1600 can transmit harmonics from the crankshaft through the driveline. Your power pulses are further apart and can lead to harmful vibes/oscillation.



General rule of thumb. . . the greater the load the higher RPM you should operate at to minimize engine stress and maximize efficiency. Running the boulevard at an easy pace? 1400rpm is great. Want to mash it? Drop down a gear first!



Got a big load climbing a grade? Sure, it may hold 65 in OD and you've only got it half way to the floor at 1900rpm, but you're better off dropping down a gear and running 2500rpm. Spread the amount of work your engine needs to do over more power pulses, instead of hitting hard on fewer power strokes.



High RPM generally causes more wear, but running the engine slower than adequate when under load puts much greater pressures on pistons, cylinder walls and bearings. While you may have the torque & power to get the heavy work done at low RPM, the laws of physics are still at play on your engine's internals.



Vaughn

 

[krabman]

Vaughn, I work in AK, left in January got home yesterday. Before I left I remember reading your posts and saying to myself " he's gonna buy an 03" and sure enough hehe... . Anyhow I long ago stopped keeping track of how many logged hours of diesel operation I have but I just added 6000 odd hours to it in the last three months if that gives you any idea. Its a lot of engines and a lot of hours. In general I can tell you that the concept of flogging a diesel within in an inch of its life because thats what they were designed for just isnt true. This will reduce longevity and increase costs every time. The same holds true for engines that receive inadequate loading. An engine that gets lugged fairly often will need bearings rolled sooner than one that does not. Knowing these things I dont lug my truck, when I start bogging I grab a new gear. I dont baby it, I work it hard. I dont flog it. As far as the concept of increasing power to lower RPMs, this is a sound idea as long as your just looking to move the RPM a small amount. A little moderation and common sense should see you through many happy miles.

 

[jimnance]

I agree Krabman. These engines are designed to work best at an RPM somewhere between peak torque and peak Horsepower. Where in between will depend upon the load, grade, and even engine design. Running almost any engine at max rated RPM's will reduce engine life. Some industrial engines are designed to work at a specific RPM, but most automotive engines have to have a broader range due to the varying conditions they will be operating in.



Working an engine hard can be good for it. Getting oil temps up just a bit and even EGT's will reduce carbon build up and the tendency for oil to build up acids due to moisture build up.



I guarantee you if you run a 5. 9 cummins at 3,000 RPM day and night you'll cut it's life in half, maybe more.



Ask any Marine user of a Cummins B engine and they'll tell you they run 'em at 1800-2000 RPM to extend engine life and conserve fuel.

Originally posted by krabman

Vaughn, I work in AK, left in January got home yesterday. Before I left I remember reading your posts and saying to myself " he's gonna buy an 03" and sure enough hehe... . Anyhow I long ago stopped keeping track of how many logged hours of diesel operation I have but I just added 6000 odd hours to it in the last three months if that gives you any idea. Its a lot of engines and a lot of hours. In general I can tell you that the concept of flogging a diesel within in an inch of its life because thats what they were designed for just isnt true. This will reduce longevity and increase costs every time. The same holds true for engines that receive inadequate loading. An engine that gets lugged fairly often will need bearings rolled sooner than one that does not. Knowing these things I dont lug my truck, when I start bogging I grab a new gear. I dont baby it, I work it hard. I dont flog it. As far as the concept of increasing power to lower RPMs, this is a sound idea as long as your just looking to move the RPM a small amount. A little moderation and common sense should see you through many happy miles.