RoyJ wrote:
And THIS is why you have to be careful cherry-picking quotes to only suit your agenda Shiner. Did YOU read the entire article you posted?
Yes,it mirrors exactly what I have been stating, but also talks about multiple displacements being better suited for certain applications and duty cycles.
RoyJ wrote:
Read that very clearly - what word did he use? Duty Cycle
And that is exactly one of the things I said effects the longevity of an engine. You can have the same power output for an application, but two different duty cycles in those applications. You can have two applications that need 400hp to tow the same 50k at 65 mph, but one duty cycle is constant grades while the other is mostly flat land. A larger displacement 350hp engine is needed for the one pulling grades because it will run at a lower rpm, while the smaller displacement is probably better for the flat land because its fuel cost will be lower especially since it will not be at full load all the time.
RoyJ wrote:
Why does he advise you to select the LOWEST hp, only to up-rate it later for resale? It's because it affects engine life at high duty cycle, despite them all being "emissions certified".
To save on upfront costs of having to pay for added drivetrain components to handle the higher power and to keep their drivers from tearing up the driveline. We have fleets that do this all the time where they spec the minimum hp allowable for their application and the turn it up to the highest they can for resale since higher power figures are more desirable to used truck buyers. I have personally reprogrammed many CAT engines to higher power levels for resale.
However, you only have a certain emission certified power levels you can increase the truck to depending on application. Some applications may not allow the engine to be programmed at the highest possible power level, but can be programmed at a higher level that it currently is. You need to register the ESN to get the tune from the engine manufacturer and they will let you know the highest power level you can go.
RoyJ wrote:
Notice above a GCW he made a cut-off based on DISPLACEMENT? We know the upper end of the 13L rating (485hp) overlaps with the lower end of the ISX15 rating (400hp, EPA13). Why didn't he simply say: beyond 130k lbs, use a 450+ hp engine?
Because a 485hp 12.9L has lower longevity that an ISX15 @ 485hp.
Actually if you read, it is based on application and duty cycle. A 485hp 12.9L may be great in a flat land application duty cycle, but it does not produce enough torque in an application with a lot of grades pulling heavy loads. Similar to how a lower power level 6.7L does not produce enough torque and will not last long in an application meant for a higher power level. The less power/less torque engines will be at max load almost more often than higher horsepower/higher torque/higher displacement engine won't in these applications.
Also, higher the displacement engines make peak horsepower and torque at lower rpms. Generally, the higher displacement, the lower the peak power/torque. This alone allows bigger displacement engines to last longer because they don't have to work as hard/turn as many rpms to do the same work as an equally power rated smaller displacement engine. However, in certain applications where you are not loaded heavy all the time like fuel truck, a smaller displacement engine with the same power level is ideal since it is more efficient and lighter.
RoyJ wrote:
He explains that with such duty cycles, “higher displacement is an advantage when it comes to fuel economy. The larger engine size enables broader power and torque curves so the engine can be operated at lower rpms than smaller engines for improved fuel economy. Given that as well as the proven longevity of these engines, we simply do not see the 15L market declining.”
He specifically talks about LONGEVITY of the "15L market".
Again, based on application and is due to the fact that higher displacement engine make power at lower rpms than smaller engines. In most heavy haul applications with a lot of hills, a smaller displacement engine will not last long and will be very inefficient because it will have to be at much higher rpms than a larger displacement engine.
Same goes with a lower power engine of the same displacement in an application meant for a higher power engine.
RoyJ wrote:
Again, there's hp overlap between and ISL/ISM(ISX12)/ISX15. I've shown you before an ISL can be up-rated to 450hp for fire/emergency/RV applications.
The reason for the overlap is due to what I stated above. Yes, they are making the same power, but they are all spinning at different rpms to do it. The larger engine will spin at lower rpms due to their power band. It's like pulling up a grade with a N/A V6 of the same horsepower as a V8 that makes more torque at lower rpm.
RoyJ wrote:
Why don't they spec a 450hp ISL for a 160,000lbs B-train? Because it won't have the desirable service life of a 450hp ISX15. And before you say it, yes, both engines will be operating "flat out WOT", so emissions efficiency is not a concern...
Again, because the make power/torque at different rpms. A 450 ISL or L9 only makes 1,250 lb ft of torque at 1,400 rpms (and is only available in medium duty applications) while a 450 X15 makes 1,850 lb-ft at 1,000 rpm. You will not be at as high of an rpm in the ISX15. The ISX15 also reaching peak hp at a lower rpm as well which inherently makes it last longer in that application since it would not be working as hard. That is if the ISL could move the load with 600 lb-ft less. Oh, and before you say just add shorter gears, if you do that then it will not be able to run at highway speeds.
