Most of us know about windage trays, but what is their function and what exactly is “windage?” Simply put, windage is a force created on an object by friction when there is relative movement between air and the object. Windage loss is the reduction in efficiency due to windage forces.
As it pertains to internal combustion engines, windage is the power loss caused by the friction of the oil in the engine coming into non-lubrication contact with its internal moving parts. For the most part, this is oil splashing against the counterweights of the crank as it spins. If there is poor oil control inside a high performance engine, windage can cause a significant power loss. First, as rpm increases, the amount of power loss for a given amount of windage increases dramatically. As a liquid, it's the same concept as water in a swimming pool providing little resistance if you slowly dip your hand into it. The feeling of resistance becomes much different if you do a belly flop off the high dive into that same pool. Second, high-g turns, rapid acceleration and good old engine vibrations puts a lot more kinetic energy into the oil collected in the bottom of the pan. This makes oil control much more difficult.
A windage tray is a medal tray that is bolted to the main caps on the bottom of the engine that is designed to keep the engine oil from splashing up in the engine and stop the oil pump pick-up tube from sucking air instead of oil. It also stops the engine oil from foaming in the oil pan due to splashing. It is designed to prevent parasitic loss, from oil slapping onto the crankshaft, and to shield the sump oil pump from windage effects. Many trays also have scraper louvers built into them that strip away oil from the windage cloud.
In terms of pan designs and their quality, the standard oil pan, found on most passenger cars, is at the bottom of the evolutionary ladder (see photo, below). Narrow and rarely deep enough for adequate oil volume, a stock pan is typically little more than a bucket that holds oil at the bottom of the block. In the interest of keeping costs down, manufacturers rarely make an effort to control oil. That may be fine for “grocery getter” cars, but it's terrible for high performance and race cars. Car manufacturers have realized this fact and have been installing windage pans on their high performance models for decades.
Standard Oil Pan
Windage can affect an engine in a few different ways. When unchecked, windage can cause oil pressure and oil temperature problems, in addition to power loss.
At high RPMs the spinning crank can draw in and throw the oil draining from your engine back against the block similar to how a hurricane throws rain and debris around its center. This oil being splashed back against the block and into cylinder walls absorbs extra heat from all the additional contact with the bottom of the block. As a result engine oil temperatures increase.
Adding to the problem, the oil being spun and splashed around the crank tends to become aerated and can cause a frothing cloud around the rotating assembly. With air bubbles in your oil its ability to dissipate heat is reduced and the oil temperature issue is intensified. As these temperature and aeration issues accumulate they can gang up and have an effect on your oil pressure as well. The more aerated your oil becomes the more your oil pump will struggle to pump it. Combine this with your oil being particularly hot and thin, oil pressure starts to drop.
The third major issue created by windage is power loss. The thicker the atmosphere of air and oil is around the crank the more drag the crank will experience as it rotates through it. It can be hard to image, but the drag created by all this extra windage is not insignificant. Dyno testing show that the friction that it generates can rob an engine of 1-2 hp.
A windage tray keeps oil near the bottom near the pump during hard turns where g forces push oil up the sides. Since more oil creates more windage problems, modern Hemi engines, using 7 quarts of oil, make use windage pans.