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

[John Mcrain]

*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?

 

[Baluncore]

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.

 

[jack action]

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

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.

 

[John Mcrain]

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.

 

[Baluncore]

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.

 

[John Mcrain]

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.

 

[Baluncore]

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.