Say, I've just about had it with my cut back truck and I want someone to crank it up because everyone and their dog passes me on the Interstates. I'm a company driver who has no clue and want someone in Effingham IL to take care of this for me - I've had enough.
Well, bucko, it's a little more involved than that. I figure it's a driver for some huge company - Freightliner Columbias are the choice of fleet managers everywhere. Owner operators, not so much. Lots of those companies have decided the only way they'll make money is to turn down the engine power, force shifts at certain rpms, and limit top speed to, oh, say sixty two miles per hour (as an example) to save fuel costs.
I also figure this driver has no clue because it doesn't make a rat's behind what the brand of truck happens to be - it's the engine, stupid. A Detroit Diesel isn't gonna have the same diagnostic hookups, computers, engine management systems and so on as a Caterpillar, Cummins, Volvo or a Mercedes - which are found in Freightliners.
The engine must be hooked up to a dealer's diagnostic computer, and there might even be a password required from the factory - which might be provided through the dealer's 'puter hooked to the internet. Engines must have the necessary parts to have the power turned up above their original rating. Most of our motors are factory 475 hp Cats, but they were ordered with the proper injectors, pistons, and so on to allow them to be cranked up to 550 hp. Of course, a 475 horse motor can be cranked back and basically castrated as far as power and shifting points go. Top ends can be limited, too. Mine is limited to 80 mph with my foot to the floor, and 78 on cruise.
All of this costs money and will void the warranty. There are a lot of 550 Cats out there with 475 tags on 'em - most owners buy the cheaper 475, run the warranty out, then have it set up as a 550. Our motors don't have any other limitations other than the top speed - and a few of our trucks don't even have that. They'll go as fast as the gearing and power will allow - in the vicinity of triple digits.
In the good ol' days before ECMs and so on, you might find a Diesel Doctor at a truck stop with some pump goodies to crank up the power on the old "manual" motors. Cummins were really simple - it just took a different "button" with some stronger fuel return springs and some other adjustments to make them scream. Cummins used a "common rail" injection system where the fuel was pumped to a certain pressure and the injector controlled the fuel timing and duration. If you cranked up the fuel pressure, the injector would then pump in more fuel. Also, by changing the allowed rpms - the fuel curve would be moved "up" the range, so at the same rpms - now you could have more power.
But, it took a discriminating driver to keep from burning a motor out doing that. If the motor was subjected to a hard pull, the exhaust temperature would get pretty high - measured by a pyrometer. Turbos could burn out, cylinders could score (the oil protecting the cylinders from the piston rings could burn out and leave no friction protection), holes could be burned in pistons, or heads crack. The usual cutoff of 2100 rpms could be bumped up to well over 2500 - but those motors were not designed to run that hard, and that was a good way to break connecting rods and ventilate blocks were they really didn't need that hole knocked out the side.
So, if you wanted your 855 Cummins to run, you could do all this. However, you kept an eagle eye on the pyrometer in a pull, and watched the water and oil temperatures very, very closely.
This sort of controlled mayhem was certainly not what a fleet manager wanted. They wanted their motors to cater to the lowest common denominator so that the engines might survive some gear jammin' idjut. A lot of truck jockeys would back off the aneroid valve. This was an early pollution control mechanism. When the operator stomped on the loud pedal, the fuel was restricted until a certain level of boost from the turbo kicked in. This kept the truck from blowing black smoke when it was suddenly floored. Backing it off would "free" the motor the operator could accelerate more quickly. The motor didn't actually make more power, but it allowed the power at hand to be applied more quickly.
Where the throttle arm came out of the pump was shielded by a small fitted plate held in place with some pins and sealed with a wire tie off. Just about any used fleet truck I ever saw showed evidence of tampering - the seal would be gone and the plate pried back so the aneroid valve could be accessed.
The old Cats used a different injection system - their pumps controlled the fuel pressure and duration. They needed a different approach - but there were plenty who knew how to crank them up as well. Caterpillars were relatively expensive to repair partly because of the complex fuel pumps. Detroits could also be turned up, but since I hated the old two strokers, I didn't and still don't care about cranking one of them up. Boat anchors, all of 'em.
So, the advent of computerized engine management systems were solving several problems - reducing pollution through finer control of the fuel injection - which meant more torque and better fuel utilization as time went on. Being able to set the operating parameters was a big plus for the fleet types.
Even with all the proprietary 'puter hardware hot rodders have managed to hack into the ECMs to make the electronic motors really scream - but they suffer badly in the hands of fools just as in the past. Plus, any mods made are immediately apparent when a factory tech hooks his laptop to the motor.
I've driven some souped up Cats and Cummins over the years. I never burned one up, either. I wouldn't work for someone who didn't trust me enough to drive their truck without being a nanny about it. I can live with the 80 mph restriction - I'm for thinking that's fast enough for a truck these days. But, forcing me to short shift each and every time, even when climbing a mountain or some other demand for high horsepower would piss me off. I'll do my best to make mileage, but when I need power, I'd better have it on tap.
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Do modern tractors have an OBD-II port so you could hook up a programmer, like in the diesel pickups?
I know they've gone to computer controlled engine management systems, but whether or not an OBD-II connector would hook up - got no idea. The last tractor I ran was made in the pre 'puter days.
Trucks have a circular port protected by a twist off cap, usually on the bottom of the dash near the steering wheel. The connector plugs in and uses a twist on sleeve to hold it in place. The cable is pretty long, because it's part of a squid that hooks up to other various ports on the motor - albeit with different style connectors. I'm pretty sure that tractors have the same setup.
Okay, now my memory has been jarred. If you look at this picture - from this post about my neighbor's 9400JD. If you look to the right of the hydraulic control panel, you'll see two connectors below the cigarette lighter receptacle.
Your brief allusion to two-strokers tingled my curiosity. Has two-stroke diesel ever been popular in trucks in the US? what about in other heavy mahinery? And wat is the most popular engine configuration in big trucks today? I'm from Europe so I know little to nothing about US trucks, only that they look awesome.
steisan:
The vast majority of diesel powerplants in class 8 trucks (I'm sure in the lighter classes as well) are four strokes these days. However, before Detroit Diesel came out with their Series 60 line, they made a wide variety of two stroke engines. I can't think of a two stroke Cat or Cummins -doesn't mean they didn't make one or two, just that I never ran into one.
Inline four and six cylinder, plus V-8s were manufactured. In order for them to run properly, they required "blowers" to charge the cylinders - I'm sure it's because of the relatively high compression ratios. I'm familiar with the V-8s, which were designated by their individual cylinder displacements. An 8V71 would be a V-8 with each cylinder displacing 71 cubic inches. The "naturally aspirated" (remember, they had a blower - mounted between the cylinder banks) variant was known as the 318. It was rated for 318 horsepower. The 350 (hp) 8V71 had a turbo as well. Maybe you've heard of "Jimmy" (GMC - which almost exclusively used Detroit power) blowers for drag racers - their motors use blowers that owe their beginnings to the old 6v and 8v Detroit blowers scavenged from a junk diesel motor.
Later motors increased the displacement to 92 cubic inches. I drove what was called a "Silver 92" - an 8V92 rated at 475HP. Fresh out of the box, it would scream. However, Detroits had a bad and well deserved reputation for being short lived motors. 150k miles seemed to be about the time they'd puke something up and require a major overhaul. The motors also had no low end torque - one had to "keep one on the boil" all the time. I hated them, particularly after I drove some other brands that actually had some usable low end torque. Ya didn't have to be concentrating on winding the living crap out of the motor just to get up a hill or started from a light.
Most of the old diesel buses had a Detroit - a lot of people after hearing one in a big truck would often comment on how they sounded just like a bus. They do. The bus motors were never under the strain that a big rig would put them under, so they tended to last longer in that application. Detroits also made very good stationary power supplies - if they ran at a constant rpm, they tended to last. So, generators, agricultural apps like tub hay grinders and irrigation motors were really more suited to the strength of their design.
I was always told by the old time truckers that the proper way to drive a Detroit motor was to open the door of the truck, put one hand in the door jamb, and slam the door on your hand. The pain would piss you off enough to want to abuse the motor properly, so off you'd go, winding the tar out of the thing. The Series 60 motors are light years ahead of the old two strokers as far as low end torque is concerned, but they don't have it compared to Cats and Cummins motors even today. One still has to have a Detroit wound up close to the cut off at 2100rpm to make the best power and torque, where a Cat or Cummins might be 1400 to 1600rpm. So the other brands have a lot more flexibility in the usable power ranges, and you don't have to feel like you're trying to kill the damn thing just to go down the road. Have I mentioned how I hate Detroits? Heh.
Thanks for this great insight. I think blowers were needed becasue with the dependability ne needs from a truck engine and the large C/R ratio (as you mention), the usual two-troke lubrication isn't just enough, so they had to use a conventional bottom end and lubrication and use a blower as a source for fresh air.
I've seen a couple of two-stroker Caterpillar bulldozers in my neck of the woods, they really sound strange and are used at very fixed (and high) rpm (at least, that's how they sound).
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