Quote:
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Originally Posted by Dodge2Dub
Quote:
Originally Posted by BMRLVR
It is less about the RPM you shift at than the percentage of throttle opening! I try to never use more than 25% throttle until the engine is at operating temperature. 50% - 100% throttle, but still shifting at low RPM's will hurt the engine just as much as spinning it 7 or 8K cold at low throttle openings.
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Why is the throttle position that important at low RPM when the engine isn't spinning quickly and the stress levels are low? |
Engine speed is an issue, but load is also an issue. High load puts more stress on the bearings since higher throttle openings cause the engine to make more torque. More torque = higher BMEP. Higher BMEP = more force exerted on the pistons, rods, crank and ultimately the bearings. When the engine is not at operating temperature the hydrodynamic lubrication in the bearing is not fully developed so you can have metal on metal contact!