Thread: degree of hardness of a turbo motor

this is some thing i have always wondered about , when the built a motor pre turbo's they harden the metal to a certain degree of hardness , block , con rods, valves , pistons , etc etc now with engines that are built to run with turbos etc are they made with an highe degree of hardness to allow for the extra pressure that a turbo places on every thing ??

Originally Posted by richard4u2

this is some thing i have always wondered about , when the built a motor pre turbo's they harden the metal to a certain degree of hardness , block , con rods, valves , pistons , etc etc now with engines that are built to run with turbos etc are they made with an highe degree of hardness to allow for the extra pressure that a turbo places on every thing ??

One of the mechanical properties of metal is hardness - the resistance to indentation.

Hardness as such is primarily of interest for wear, but with steels (not necessarily other metals) it is sometimes used as a measure of strength, because it is possible to relate the two and testing hardness is much simpler than testing tensile strength.

The loads on engine components are only affected a small amount when an engine is turbo charged.

To understand this you need to understand how, why and when the loads are induced in the various components.

Major loads are caused by inertia when the parts are accelerated - the Newtonian Law force = mass time acceleration.

As the engine rotates at constant speed, the velocity of the reciprocating parts (piston, etc.) is constantly changing i.e. they are being accelerated/decelerated. The highest acceleration rates occur at top dead centre and bottom dead centre - when the piston changes direction. At maximum engine rpm's, this is when high loads are induced in the reciprocating parts and engine bottom end.

The higher the rpm, the higher the acceleration of reciprocating components, and the higher the loads in those components.

Without turbo charging, the main method of increasing engine power is to increase the rpm.

With turbo charging, the engine power is increased without increasing rpm. In fact power will be higher at reduced rpm.

Now the turbo does increase the pressure in the cylinder, acting on the piston. But it is very important to understand when the increased pressure is applied to the piston and how the load induced by this pressure combines with the inertial loads.

It turns out that the loads from the pressure due to turbo charging act in the opposite direction to the inertial loads at top dead centre and they are partly cancelled.

So the answer to the second question is no.