ShinerBock wrote:
4x4ord wrote:
ShinerBock wrote:
4x4ord wrote:
This is the torque curve for the PACCAR MX 13 that’s Peterbilt uses in their medium duty truck
Looks like PACCAR is unaware of the 1800 rpm fuel saving rule.
I think you are a little confused as to what that 1,800 rpm rule is. It is the rpm at which diesel burns most efficiently and completely and there for will generally have the highest thermal efficiency for the amount of power it is creating around that rpm. Basically, it is the point at which you get the most out of a drop of diesel fuel. This is not to be mistaken for the spot at which an engine is using the least amount fuel or the different rpm ranges to make power for different applications, industry needs, or rpm limitations due to engine size.
I might be a little confused. This quote from your original post in this thread:
Knowing all this, manufacturers of diesel engines, turbochargers, fuel injection systems and engine control systems have all directed their efforts at producing engines that make the most of this 1,800-rpm phenomenon. So, drive your diesel at or near to 1,800 rpm if you’re looking for the very best in both engine torque and fuel economy."
has me understanding that engine manufacturers would be designing their diesel engines to be used at 1800 rpm to make best use of the “rule”. The PACCAR 13 litre totally misses out as it won’t even rev to 1800. Would you expect the PACCAR 13 litre to be more fuel efficient at 1700 than 1100 rpm?
Re-read the sentence above especially the part in red. In order to create more horsepower within reliability and emissions specs, you have to go big. The bigger you go, the more you are limited on rpm.
I believe you are your own worst enemy here.
That’s not helping. We have 2017 emissions compliant 12.5 litre Cat engines that work all day long at a constant speed of 2100 rpm. Our application requires high power being transmitted with belts and pulleys so higher rpm is desirable. PACCAR has designed their 13 litre to be used in medium duty truck applications and I would have thought fuel economy would be a high priority.
