RoyJ wrote:
All you manged to show was the correlation between hp level and emissions - that's not "backup" to your statement that hp has no correlation to engine life.
What I said was a lower hp will effectively enhance engine life. You failed to prove otherwise.
Start a new thread and I'll show you plenty of industry evidence. There's nothing magical about "MD trucks" - every engine on earth, steam turbine, lawn mower, ship engine, jet engine, bulldozer, behave the same way. Increase power output, and down goes the life expectancy. It's comical you even try to deny that.
It is clear that you didn't read any of the links I posted. They all stated what i have been saying that the reason for multiple power levels in medium duty trucks is due to emissions, application, and cost. Not one of them say anything about how higher power levels not lasting longer unless it is the wrong power for the application where a higher power level in an application where a lower power level will do will have a lower return on investment due to the increased up front costs, and a low hp engine will not last long in an application meant for a high hp engine because it has to work to harder. You are not taking real world applications into account in this fantasy land where all engine run at a constant speed.
I don't see how it is that hard for you to understand given all of the links and information I posted even though you have failed to provide one link proving otherwise. You have absolutely zero experience with modern medium/heavy duty diesel engines and you are trying to tell me and all of the experts in the industry in the links I have provided that we are wrong.
Here are some more links. Please read them because they back up exactly what I am saying.
This one also goes into having the right displacement for right application as well as power level, but it also backs up what I am saying.
"According to David McKenna, director of powertrain sales & marketing for Mack Trucks, truck engines have in the past several years evolved rapidly with new technologies to deliver greater efficiencies to meet customer expectations.
He says there now is a trend to smaller-displacement diesels for certain applications.
“At one time,” he relates, “it was a given that going to a smaller engine that produced higher horsepower would result in the trade-off of shorter longevity. And that was acceptable to some customers running ultra-light operations. But fast forward 20 or 25 years to today, and now we have the technology—including the materials the engines are built from—to make them lighter without sacrificing performance or longevity.”
McKenna adds that by one mark engines have changed markedly in the past 30 or more years. “Back in the ’70s,” he points out, “the average power density for highway diesels was 25 hp. per liter. In the ’80s and ’90s, that measure rose to between 29 and 31 and now it ranges from 36 up to 39 hp. per liter. So the size and weight once needed to get 350 hp. from an engine can now deliver 400 hp.”Sizing the engine"If you’re spec’ing a Class 6 or 7 truck, engine selection becomes more complicated. For example, the Isuzu Diesel 6H 7.8L in the Chevrolet Kodiak C-7500 offers five different horsepower and torque options, ranging from 215 hp and 560 ft.-lb. torque to 300 hp and 860 ft.-lb. torque, with 230 hp and 260 hp in between. The approximate cost difference between the lowest and highest hp ratings, factoring in a heavier transmission required for the 300 hp engine, is as much as $8,500. This variance in engine hp/torque availability and cost is common across all Class 6 and 7 truck OEMs.
Matching the right hp and torque ratings to your application. How do you choose among hp and torque options? An underspec’d engine presents performance and potential premature maintenance issues. If you over-spec, you pay a much higher cost per unit without a corresponding return on investment. How do you strike the right balance?"All About Medium-Duty Work Truck Engines"Consider where your trucks will do the majority of their hauling – whether it’s in the city, the highway or in suburban areas will determine how they should be geared. Trucks properly spec’d for city applications have higher axle ratios and lower speeds.
Trucks spec’d for highway or suburban runs have a lower rear axle ratio for higher speeds and better fuel economy. Running city spec’ed trucks on the highway will eat away at your profit line through increased fuel consumption and piston crown and bearing failures in the engine."Medium-duty spec’ing tips
