Low RPM-high torque vs High RPM-low torque -- durability?

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In summary: Turbo diesel engines offer greater power and efficiency than a standard diesel, but they can be more expensive to buy and maintain. They also tend to require more frequent maintenance, including oil changes and tune-ups. Turbo diesel engines offer greater power and efficiency than a standard diesel, but they can be more expensive to buy and maintain. They also tend to require more frequent maintenance, including oil changes and tune-ups.
  • #1
John Mcrain
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*Comparation of diesel vs petrol engine with equal power
*Why all heavy duty-long last engines are low RPM?
*Is low RPM main reason why diesel last longer then petrol engines?If does,why high RPM engines "kill" engine faster?
*What are pros/cons for diesel and petrol in term of durability?
 
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  • #2
John Mcrain said:
What are pros/cons for diesel and petrol in term of durability?
Higher compression ratio gives diesel better economy, but requires heavier construction.
Heavier construction permits higher torque = lower RPM for same HP.
Low RPM is associated with low piston velocity.
Diesel is a better lubricant than petrol.
 
  • #3
John Mcrain said:
Is low RPM main reason why diesel last longer then petrol engines?
No, it's low piston speed. Piston speed depends on RPM, but also on stroke. More on Wikipedia and HPWizard
John Mcrain said:
If does,why high RPM engines "kill" engine faster?
With higher piston [sliding] speed comes higher wear rate. (Archard wear equation)

Also, a piston can easily do 0-100-0 km/h from top to bottom and vice versa. Those accelerations put stresses on the parts that are compressed and extended on each stroke. The higher the piston speed, the higher the acceleration, the higher the stresses that can fatigue the material.
 
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  • #4
jack action said:
No, it's low piston speed. Piston speed depends on RPM, but also on stroke. More on Wikipedia and HPWizard

With higher piston [sliding] speed comes higher wear rate. (Archard wear equation)

Also, a piston can easily do 0-100-0 km/h from top to bottom and vice versa. Those accelerations put stresses on the parts that are compressed and extended on each stroke. The higher the piston speed, the higher the acceleration, the higher the stresses that can fatigue the material.
Yes piston speed is function of RPM and stroke.
But at same RPM ,piston speed is faster at long stroke then short stroke.
 
  • #5
John Mcrain said:
What are pros/cons for diesel and petrol in term of durability?
Petrol engines wear with a step and taper at the top of the cylinder where ring pressures are greatest immediately after the spark. That taper flexes the rings, which wear the grooves and ring surfaces. Sudden high RPM can break the upper ring.

The slower injection and smooth combustion of a diesel reduces wear at the top of the cylinder so there is less flexing and breakage of rings, which gives longer engine life.
 
  • #6
Baluncore said:
Petrol engines wear with a step and taper at the top of the cylinder where ring pressures are greatest immediately after the spark. That taper flexes the rings, which wear the grooves and ring surfaces. Sudden high RPM can break the upper ring.

The slower injection and smooth combustion of a diesel reduces wear at the top of the cylinder so there is less flexing and breakage of rings, which gives longer engine life.
Diesel vs turbo diesel,durability?What do you think.
 
  • #7
John Mcrain said:
Diesel vs turbo diesel,durability?What do you think.
There are no hard and fast rules.
Obviously a turbo diesel is more complex and can have higher RPM.
 

1. What is the difference between low RPM-high torque and high RPM-low torque?

Low RPM-high torque refers to an engine that produces a high amount of rotational force at a low speed, while high RPM-low torque refers to an engine that produces a lower amount of rotational force at a high speed.

2. Which is better for durability, low RPM-high torque or high RPM-low torque?

It depends on the specific application and design of the engine. In general, low RPM-high torque engines are better for heavy-duty tasks and have a longer lifespan, while high RPM-low torque engines are better for high-speed performance but may have a shorter lifespan.

3. How does the choice of RPM and torque affect the durability of an engine?

The choice of RPM and torque can affect the durability of an engine in several ways. Higher RPMs can put more stress on the engine components, potentially leading to wear and tear over time. On the other hand, high torque can also put stress on the engine, but it can also provide more power for heavy-duty tasks.

4. Are there any other factors besides RPM and torque that impact engine durability?

Yes, there are several other factors that can impact engine durability, such as the quality of materials used, maintenance and care, and the overall design and construction of the engine.

5. How can I determine the best RPM and torque for my specific needs?

The best RPM and torque for your needs will depend on the specific application and requirements. It is important to consult with a professional or do thorough research to determine the most suitable engine specifications for your needs.

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