This discussion is from an RV board and it shows the difference in ratings different mfg have* to rate their engines.
It is applicable to boats as engines can vary from industrial diesels to lawn implement marinizations.
--- In email@example.com
, "Jimmy Dee" <mrlimbo@...> wrote:
> I get confused when you guys start talking 5.9L cummings. Are you talking about using the motor from a Dodge Ram pickup or the 5.9 from a motorcoach? *
NO! You are absolutely correct. We (I anyway) are NOT talking about the engine as found in Dodge pickup truck. The engine shares the SAME block and decorative goodies as any Cummins "B" block (the terminology given to this particular engine design) but the innards are all different. *I have spoken on this forum several times about engine ratings, HP, speed, torque, etc. and one of the least understood terms is one called duty cycle rating.*
You MAY be aware of this rating type as it appears on welders or other heat producing appliances. The "power output" is given by the manufacturer (or rated) as say 300 amps. But the small print says 10% duty rating. This means that the welder will actually produce 300 amps of welding power but only for a small amount of time. In the case of a 10% rating, for ONE minute on and TEN minutes OFF.
In the arena of engine ratings, engineering provides for much the same type of rating but it is not stated as such. A particular engine sold to an OEM is sold with the understanding of it being able to perform a particular job . This "job" is understood to be expressed in an automotive rating such as found on the door jam of a truck or car. The vehicle is "rated" at 8501 lbs. or 18000 lbs or 26,000 lbs or 80,000 lbs.*
Once the OEM chassis builder has determined the requirements of the product he is building, the "engine" is then specced from the manufacturer to do that job. It is at this juncture that all of the BS starts to enter the picture. In the realm of engine production there are performance platforms (just like there are car platforms) that the engine manufacture creates at the design level. Take a Detroit Diesel 3-53 as an example. It may be "rated" at 55HP for industrial purposes. An industrial rating will permit it to operate at the advertised rating continuously and the engine will live up to its billing. But, because of the toughness of its platform, it MIGHT be given an automotive rating of 95 HP. SAME engine, different fueling schedule. What is the difference? An automotive rating presumes that the application will only operated the engine for 25% of the time at the highest rated HP advertised. This is the nature of an automotive application. It can start an operate a load needing 95 HP but it only requires it for a small percent of the time, 25% in the automotive rating.
You will NEVER see cross breeding between truck diesel applications (25% duty cycle rating) and automotive engine ratings as the engine cost factor is way out of line.BUT, in the case of the Cummins 5.9L "B" block there IS such cross breeding. The engine was designed from the ground up for use in industrial front end loaders by the J.I. Case company. The project was eventually taken over in early R&D by Cummins Engine Company. They saw the benifits of the small engine envelope and high torque capabilities being built into the engine platform. They felt that they could develop the engine into the market for long life diesel power in the medium duty commercial chassis line ala motorhomes and delivery trucks like the F-500-650-750 Ford. Eventually they had engine ratings in this market at upwards of 275 HP.
THEN came along the Chrylser Corp. and the light duty 8501 lb rated D250-350 pickup. They had been effectively shut out of the light duty diesel market by exclusivity contracts between Ford and IHC (6.9L-7.3L V-8) and the spec built Detroit Diesel 6.2L-6.5L V-8) They approached Cummins with the problem and amazingly (OR NOT) they turns them down. The primary reason was the fact that the price point on the engine HAD to be X and no more if Chrysler was to *be competitive. But the OTHER reason was diesel snobbery. Cummins DID NOT see their marketing setup as being compatible with the "car market". They couldn't meet the price point (and didn't want to) and they could not support the product with the current Cummins Distributor/Dealer network and they had NO intension of expanding or tinkering with what was considered a well oiled machine.
Then after SOME reconsideration, Cummins was shown the light on the marketing value of putting one of their engines into a pickup truck. I WILL concede, with their ongoing contracts (at the time) with Ford for the medium duty market and the fact that Ford was in bed with Cummins to the tune of 20% stock ownership (rumor had it that the two were going to combine and become known as FoCum Inc.) the move seems to risk alienation of their relationship but Ford too thought the venture ( a Cummins in a Dodge) to be folly and even IF they thought otherwise, was locked into an engine purchase contract with Navistar until 1995. *Ford was in NO position to complain about the side bibniz Cummins was getting into.
HOW did they do it? To meet the price point and do it on the Cummins existing line, numbers HAD to come up. I dod not remember the initial quantity Chrysler guaranteed them but it was enough to make Cumins some money on the project. But the REAL secret of this success was the fact that with EVERY Cummins engine built they build the do so with a unique personality. This personality is known in the trade and to Cummins support people as *a CPL number. EVERY engine serial number has a CPL (Controlled Parts List) which dictates HOW the engine is built. Since the discussion revolves around duty cycle and HP ratings it is quite obvious that one engine rated industrial or GEN Set application will have different parts (more heavy duty) than one rated for automotive applications.*
All 5.9L "B" blocks start off with the same block but there the differences start to pile up. Since Cummins had to meet a price point with the Chrysler project they had to completely re-engineer the engine to shed this cost. *Since the light duty needs of the 8501 GVWR (Gross Vehicle Weight Rating) of the Dodge truck were so undemanding Cummins could install much lighter duty (pronounced CHEAPER) operating components. That pricey Bosch Injection Pump that gave the "B" block such great low end torque got pitched and replace by the much less sophisticated (and FAR cheaper) V Series pump. Pistons no longer had to be hammer forged to withstand high fuel injection shock. Consequently, less stiff connecting rods were required as were less demanding connecting rod bearings, crankshafts and cylinder head designs were severely cutback on their ruggedness. All of this just so The Saturday Driveway Diesel Pickup Crowd could say they had a diesel in their truck. (truth be told, even with the severely derated engine they had more diesel in their truck then either Ford or GM).
They are NOT the same engine even though they share the same block. They cannot perform the same job as their heftier brethren in the medium truck field and putting one INTO a larger format (weight) vehicle will only result in premature engine failure.*