In several forms of racing, they preheat the engine oil and coolant so as to preheat the engine and it’s components as well. For many of these applications it is said to be critical to go through this process to insure longevity and performance from the engine. I’ve been around a few of these engines, both in race situations and on the engine dyno, and can tell you that it’s a pain. Regardless of what you have or don’t have to do the actual heating, the whole process just ads to the time, energy, and staff that is required to run a car. Whether it is worth it or not is not what this video is about, but rather what the heating does to the engine itself.
Engines that require preheating often do because the clearances present are so tight as to require heating in order to avoid damage. Sometimes it is just to keep the oil clean and well circulated prior to running.
Regardless of the reason, knowing just how much a component or clearance will change due to heat is interesting and offers a glimpse into why preheating might be done on some combos.
Check it out.
But how much does the crankshaft journal grow from cold to hot? It is unrealistic to assume the crank journals do not expand when heated.
The major cause of heat is due to oil swirl in the bearings, this absorbs power and heats up both the crank and the bearing. As long as the clearances do not go out of tolerance the overall clearances should stay pretty much the same from cold to hot. The primary function of the oil is to move the heat away from the bearings, the lubrication is a secondary consideration.
More oil flow is preferable to more pressure as it is the oil which takes the heat away from the bearings. As long as the pressure is sufficient to provide adequate oil flow there should not be a problem.