Well folks after I get my truck fixed next week I will be heading out of town and into Mexico with better and cheaper LSD (not the drug) that is about $1.80 a gallon next month.
Anyway I recall some people discussing some years ago about governors on the gas engines limiting the vehicles to 120 MPH. Even recall some lawsuit.
Anyway I am wondering if the cummins had it. I want to test the speed of the truck of the long straight roads of he autopistas. I have had it up to 100 for a very short time and it did it without even blinking.
I would prefer to do it on the Mexican autopista because speed limits are not enforced and its too expensive for the average Mexican to use so there is usually very light traffic on these things.
My last truck I had was the pathetic V6 w/5 speed. I took it for a test drive on the autopista and it struggled to get to 115. Bet Dodge did not put a governor on that model of truck ;-)
The 'Govener" you speak of was places on some models as a safety feature. It was controlled by the ECM and the "logic" behind it was to not let end user exceed the speed rating of the tires. Aftermarket programmers can defeat this limit and in the cause on a truck of mine I simply tell ECM that different tires are present and it changes the speed limit. Your vehicle may not have one since its top speed is mostly limited by gear rato and low engine RPM redline. A big gas engined vehicle can go a lot faster top end because of no low RPM redline.
My 04 CTD goes into fuel shut off around 3,100 RPM. For some unknown reason I'm hesitant to run it over 2,500 for long periods of time. Anyone know the maximum safe sustained RPM? BTW: My fuel mileage goes to hell over about
My 04 CTD goes into fuel shut off around 3,100 RPM. For some unknown reason I'm hesitant to run it over 2,500 for long periods of time. Anyone know the maximum safe sustained RPM? BTW: My fuel mileage goes to hell over about
It theory any RPM up to redline but as you have seen much above 2000 RPM in a cruise MPG can take a dump. This has to do with flame speed and increased pumping losses. Although I do not own a CTD I have driven many and I do agree that it just does not feel happy above 2300 RPM or so. Part of this reason is displacement because 5.9 is a pretty big six and there is a lot of mass in there to balance. THis is likely why GM and Ford stuck with V8 designs because they are easier to balance can have a smaller bore/stroke for same general displacement. In theory though your CTD should have the MPG edge because a engine with fewer cylinders with same general displacement has less heat loss due to a better volume to surface area relation (one reason they use big displacements in OTR trucks) The negative of this though is that they do not like to rev up much.
Once again, Snohead has it wrong. The ECM does govern engine speed, but its based on RPM, not road speed. IIRC, the ECM holds the Cummins to
3150-3200RPM while in gear, and 3250RPM while in neutral.
Changing tire size in the ECM does nothing to this, as the ECM on the ISB trucks is blissfully unaware of the res of the truck. The PCM controls the trans shifts and knows about road speed, but is unable to control the engine.
The ISBe (common rail) may be different, since at some point Dodge and Cummins agreed on common software etc, IIRC.
"Flame speed" in a diesel isn't an issue. The flame is propagated in the direct center of the piston on most, if not all, diesels. The Cummins 5.9 engines have been tuned to turn at over 4000 RPM, so flame speed down the cylinder at stock RPMs isn't an issue either. The loss of MPG at higher ground speeds can be directly attributed to the exponential increase in aerodynamic drag.
Mine feels great all the way to 2800 RPM, and I've pushed it to 3100 numerous times.
Interesting comment, considering the 5.9 is a SMALL inline six diesel, and the new one is 6.7 liters.
The inline six is inherently easier to balance than any V design. GM and Ford likely stuck with V8's for the following reasons:
1) Higher RPM ability, thus quicker acceleration when under no load.
2) Low hood line
3) Cummins was unavailable due to contractual obligation.
4) could be put into vans, not just trucks.
The inline six will deliver more torque at low RPM for any given displacement than a V8 will deliver. This is the reason for better efficiency.
Actually if you knew what you were talking about you would know that flame speed is a issue because as RPM increases the rate of expansion is not fast enough and the power output is overcome by increased power requirements to "pump" the engine through next compression and efficency drops off. Sure you can spin one up to 4000 RPM but torqie will be way down, it will be well past peak HP and efficency will be in the toilet so what have you proved? Nothing.
Maybe to you but I can tell when a engine is happy and not and it is not happy at 2800 and sounds strained.
Not at all. If you knew thoery you would understand why I said what I said and the dynamics behind it. Longer stokes are needed to obtain displacement on there is more mass to balance due to forces of heavy pistons on longer strokes and their inertia as they change direction of travel at each end of stoke. The longer the stroke and bigger the bore the more there is to overcome and balance out. For each doubling of RPM the inertia in pistons in increased 4 fold. BTW, the reason the new engine is a 6.7 is so they can lower boost to reduce NOx formation some. No be mystery here at all. Ford did same thing with 6.0 PS
Not so because as the size (bore/stroke) of it increased the dynamics of balancing the inertia forces in it become difficult. The mitigate this by reducing RPM when possible.
More to it than thay, it would have been a pain in the arse to thry to fit it in and then there is the issue of the 600 lbs more weight up front that many do not think matters. A 1200lb motor if fine in a 2 ton truck that can weight 10 or 12 K empty but not in a truck half that weight.
Again you do not understand why. The reason is because of longer stroke which improves piston to crank angularity for its displacement. If you have a big bore short stroke 6 with same displacement as a V8 it would offer no torque advantange over a V8. Your logic is wrong on the reason for efficency (you would know this too "IF" you had studied IC engine thermodynamic principles) is when you take the total surface area of a engines cylinders verse the displacement, the few cylinders for a given displacement the less surface area to volume and the less heat is lost to it and a engine be it gas or diesel is a heat engine in that the heat of combustion expanding the gasses in the cylinder drives piston down and this force is coupled to crank. The less heat that is lost to cylinder surface area the more of it is applied as force in the pressure of expanding gas because as mixture cools it contracts and you want the cooling to take place because it is expanding against piston travel not because of surface area contact.
One word: Bullshit. All of the above is BULLSHIT. Why? Because its a DIESEL. So long as you have oxygen, the fuel will burn, and the expansion of gases will continue. There is plenty of fuel injected to allow the engine to move at 3000 RPM under the rated load. When this ceases to be the case, such as when the truck is severely overloaded, the engine is "lugging". It is said to be lugging because there is not enough power to increase RPM despite increasing the amount of fuel injected. Then, and ONLY THEN, is your theory applicable. As stated, it takes being severely overloaded to make this happen.
As to your "increased power requirements to "pump" the engine through next compression" statement, that is simply a bunch of crap. Top fuel engines make enough power to overcome the decreasing pump efficiency despite similar compression and higher RPM than the Cummins. IOW, the decreasing pump efficiency isn't a noticable factor for higher RPM in the Cummins, as many drag racers can attest when tuning the Cummins for 4000RPM.
This is also false. Peak power levels depend on the fueling curve programed into the injection pump via the "plate" or the ECM. The most efficient RPM for the B5.9 series Cummins is at 1900 RPM, according to Cummins. However, also according to Cummins, peak power is found at 2800RPM, in factory trim.
Engines do not have emotions. Thus, despite the sound it makes, at 2800RPM, the Cummins is well within factory specified limits. It can not only be operated safely, but it will deliver power as specified all the way to the RPM limiter.
If you knew reality, you'd know that 5.9 litres displacement is SMALL. The next step up in Cummins line, (prior to the 6.7) was the C series at 8.3 litres. This doesn't even consider the larger N series, or any of the OTR diesles marketed by Cat, Cummins, or Navistar.
And yet, since the crankshaft is larger, there is more room for counterweights.
This is why the throws on the crank are spaced out at 120 degrees. Imagine that, perfectly equal throws for perfect balance.
SO? if all of them increase equally, they are all still equal, and thus.... still balanced.
Who cares? Thats not your original point, nor is it the point under contention.
More bullshit, which I've already addressed.
Huh?
I know why.
I gave no reason for the efficiency, I merely stated that the inline six IS more efficient.
Nice.... you've just proven one reason why you were wrong when you posted that the V8's were more efficent because the parts were smaller.
A govenor on a gas engine is one thing but on a diesel it's another. Diesels are governed by the engine manufacturers to prevent the rotating mass from totally grenading when the engine is spinning faster than it's designers intended it to. The larger the diesel engine displaces, the slower they turn for the shear amount of rotating mass. A gasoline engine will grenade when pushed past it's intended rpm limit just as a diesel will but usually at twice the rpms or more.
The 5.9 Dodge Cummins will run safely upto 2600-2800 rpms.. after that it's all total mechanical twilight zone and apt to break one. Govenors are not something Dodge installed on the engine. It's Cummins way of not having to replace broken engines because some knucklehead decided to push it past it's limits.
Better tell that to the competition pullers, who are turning their engines to 6,000RPM. Obviously, they do that for the reduced power that they get out of the engine.
Cummins seems to feel it's fine up to about 3,400RPM, as that's where the no-load electronic 'governor' kicks in. Heck, the engine's not even making peak HP (in stock form) until 2900RPM. And as in my post to SnoIdiot, with stronger valve springs, competition guys are turning 6,000RPMs from theirs.
In the 80s I drove a M1009 CUCV (Commercial Utility Cargo Vehicle) while in Germany. The militarized version of the Chevy Blazer. Though military regs limited speed to 50, driving that speed on the Autobahn was way too slow. I would usually drive it at 70 MPH. Making it the fastest tactical vehicle the military has, even to this day. Anything above 70 and the engine would start making a loud, terrible sound, though I have gotten it up to 80 to see how it would respond. Not very well.
It has the Detroit Diesel 6.2L v8 with a turbo 400 trans. only 150hp (135 w/kerosene). It had NO power. The truck had trouble even going up hills.
Due to my postion nobody really bothered to ask where I was at anytime. So me and a companion took our vehicles out for test drives. We were one of the first to get the M998 HWMMVs. Though the field officers did not want them because they liked their comfortable rides, while the HWMMV was very rough and noisy in comparison
This would be the first time I took both vehicles through serious off roading. While the other was driving the HWMMV, I had trouble keeping up with it. The M1009 just had no power even with it in 4L. We went up some serious hills where the vehicle would barely go, while the HWMMV had no problems.
After each highway run, I would have to hurry and run over and get it washed before the Motorpool Warrant Officer would see the condition of the vehicle. Every time after run of above 55, transmission fluid would get pushed out somewhere and end up splattered on the back of the vehicle.
The maximum safe RPM should be listed on the CPL tag on the engine. When towing heavy it's best to keep the RPM above the torque peak but below the max RPM. If you climb a steep grade, when the RPM falls to the torque peak you should downshift. It sounds wrong to me but that's what Cummins says. They made the engine so I believe them.
Driving technique recommended in the Cummins QuickServe Online ISB owner's manual:
Cautions: Do not operate the engine at full throttle operation below peak torque rpm (refer to engine dataplate for peak torque rpm) for more than 30 seconds. Operating the engine at full throttle below peak torque will shorten engine life to overhaul, can cause serious engine damage, and is considered engine abuse. Do not operate the engine beyond the maximum engine speed. Operating the engine beyond the maximum engine speed can cause severe engine damage. Use proper operating techniques for the vehicle, vessel, or equipment to prevent engine overspeed.
Technique: The engine produces maximum power at an rpm less than governed engine speed. To obtain optimum engine performance on a grade, allow the engine speed to load down to near peak torque before shifting. This will result in an engine operating speed in the maximum power zone after the shift is completed. Refer to the engine dataplate for peak torque rpm and governed speed rpm.
Safely these engines will run at 2600 rpms. Anything after that is twilight in terms of rotating mass. I maintain fleets of these engines. Typically they will last longer if they're unmodified and left to do the job they were intended for. They're not cheap to repair or replace. The only reason I can see for anybody defeating the mechanisms that keep these engines out of the twilight zone is an all day tree stump pulling marathon. They are fairly forgiving engines when pushed past their mechanical limits... but every diesel that I know of has a snapping point.. especially Cummins engines.
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