Ishihara-Johnson crank scrapers and other windage control products are a very simple but effective way to improve the performance of your engine!
What are some of the benefits?
· Less rotating mass for the engine to accelerate because of the removed oil
· Less loss of power because of excessive drag caused by oil droplets in the windage cloud
· Helps reduce engine damaging oil-foaming both on the surface and bubbles deeper within the oil
· Helps avoid oil starvation by keeping the oil in the pan during hard braking and turning as well as during off-road driving
· Helps to cool critical engine parts by quickly returning heated oil to the sump
· Helps to prevent the cylinder walls from being overloaded with oil
· Can help with fuel efficiency
During normal engine operation a significant amount of oil adheres to the rotating assembly or becomes entrained in a "windage" cloud surrounding it. It should be remembered that the particular characteristics of oil adhesion and/or oil-in-air entrainment vary depending on the engine rpm and what the vehicle is doing at the time. How the oil droplets are kept and drawn into the tornadic windage cloud is explained by the phenomenon known as the Tea Leaf Paradox, which was first described by Albert Einstein in 1926. It is counterintuitive that oil droplets would be kept and drawn into ("entrained") rather than completely expelled out of the windage cloud due to centrifugal force.
When a portion of the total droplets are small enough in physical size the predominate influence on their behavior switches. Rather than just their momentum due to being ejected from or impacted by the rotating assembly they are guided by the air currents in the windage cloud.* This droplet behavior in a gas atmosphere, which is a type of "fluid", in the confined volume of the crankcase is what the Tea Leaf Paradox addresses. The oil droplets have a greater density than the gas molecules.
Remember that an "equilibrium" of entrained oil is reached for the particular operating conditions. This means that not all the oil is held but rather that the amount rises until a certain point is reached and then the extra is not taken in or it swaps places with oil already in the cloud that is then released. Generally the higher the rpm, the more oil that is held because of the higher pressure differential. It is not unusual for a quart or more of oil to be suspended in the cloud at high rpms in many engines.
There are many alternate terms used for crank scrapers including -- but not limited to -- oil wipers, oil skimmers, and baffles.
* "High-speed video observation and phase Doppler anemometry measurements of oil break-up in a model engine crankcase" S. Begg, G. de Sercey, N. Miché and M. Heikal, Presented at ILASS - Europe 2010, 23rd Annual Conference on Liquid Atomization and Spray Systems, Brno, Czech Republic, September 2010. Full text available here: http://www.ilasseurope.org/ICLASS/ilass2010/FILES/FULL_PAPERS/097.pdf
This impacted and entrained oil eats up horsepower your engine is making by increasing the rotating mass and also creating parasitic drag. At low rpms and in extreme conditions where the rotating assembly is flooded by sump oil, the crank scraper mechanically strips off excess oil by coming close to, but not touching**, the moving crankshaft and rods. At high rpms it interferes with the pressure differential that draws oil into the windage cloud and allows a new lower equilibrium of entrained oil to be established.
Our crank scrapers are constructed from steel unless noted and include installation instructions. The scrapers are installed in a variety of positions but generally between the oil pan and engine block or along the main bearing caps. Some fitting to your individual engine may be required and the procedure for carefully checking this is explained in the installation instructions.
Do they really work?
Yes! The drysumped Merlin V12 aircraft engine from WWII had a rudimentary scraper directing oil to the scavenge pump. Crank scrapers in various forms have been in use in stock passenger car engines for about 90 years!*** More importantly, they are currently in use in a variety of OEM engines of both large and small displacement -- from relatively low RPM V8 engines to high RPM straight fours. Most auto enthusiasts are surprised to learn just how common they really are. In short, it is an extremely well-proven technology that is often simply not recognized. The modern trend is to have many more oil control devices in engines. Crank scraper technology is OEM equipment on various modern engines from Nissan, BMW, Chrysler, Ford, Mazda, Honda, Toyota, VW, Porsche, GM, Pontiac, Chevrolet, Mitsubishi, Mercedes and many other manufacturers.
[*** In 1923, Clair Smith applied for a patent for a device used in splash lubricated engines to reduce an overabundance of lubrication in some areas and redirect it to other areas receiving less lubrication. This design was a forerunner of the scrapers subsequently used in positive crankcase lubrication engines; patent 1,569,404.]
For example, here are a couple quotations from a recent patent held by General Motors; click here for more information about Mr. Tom Bishop:
Some pictures of OEM crank scraper technology in passenger car engines...
Is a windage tray the same as a crank scraper?
No, a windage tray serves a different but related basic function. It is present to act as a physical barrier between the rotating assembly and the sump reservoir. A crank scraper actively removes excess oil and returns it to the sump. Some windage trays do have scraper technology built into them but even then a dedicated scraper will approach the moving parts much more closely.
There are all sorts of industry terms for parts that function as a windage tray (often in addition to other functions) such as baffle, deflector and so on. Many times multiple levels of windage trays are used. This is because the design requirements for windage trays in an engine under acceleration are often diametrically opposed. Care must be taken that a windage tray does not become a de facto second sump by sealing the actual sump well area off too effectively.
Above: Honda B-series engine showing an installed Teflon® scraper on the left and the factory windage tray covering the entire assembly on the right. The windage tray shields the rotating assembly from splashing sump oil while the scraper actively removes excess oil. Before 6000 RPM the standard steel version of this scraper returned a 1.5 % to 2 % hp gain and from 6000-8900 RPM the hp gains averaged 2.5 %. Remember that this was on a statically mounted engine already having a full windage tray as with the Suzuki G10 mentioned below.
A windage cloud will still form on a statically mounted engine with a full windage tray. For example, roller dyno testing of a scraper in the Suzuki 993 cc three-cylinder G10 engine with a full windage tray still showed an average 3 % hp increase (over four pulls data ranged from 2.4 % to 3.5 %). Power began growing at about 2750 rpm and peaked at 5300 rpm (the maximum for that economy cam). Here are the dyno charts. In a moving car the oil would be sloshing around and making at least partial contact with the rotating assembly creating larger windage losses -- consequently the gains would be greater when using a scraper.
Will my engine still get enough internal splash lubrication?
Yes. The rod and main bearing journals are constantly spraying large amounts of oil in all directions when the engine is operating. Much of this oil lands directly on the cylinder walls and other internal components which depend on splash lubrication. The scraper removes oil directly only from portions of the surface of the crankshaft and the rod big ends, neither of which depend upon lubrication of any sort. These components, as well as the pistons, do depend upon a flow of oil to cool them. By constantly removing oil that has contacted these hot surfaces and allowing fresh oil to re-wet and cool them the thermal efficiency of the engine is enhanced. Hopefully, too, the user is reassured by over four decades of the successful and dependable use of scrapers in OEM stock engines as well as competition engines of all sorts.
Many enthusiasts remember splash lubricated engines where the big ends of the rods dipped directly into the sump reservoir for lubrication. This is essentially pre-WWII technology and does not apply to modern engines with positive pressure bearing lubrication from an oil pump.
Can the retroactive application of this technology help solve longstanding problems with certain engines?
Yes. In 2005 we designed a complex system of scrapers, windage trays and baffles that allowed the wetsumped Porsche 928 to survive a full season of high rpm racing without the well-known 2/6 rod bearing failure. This was unprecedented in the history of this engine.
General answers: What is windage and what are the differences between an oil baffle versus a windage tray versus a crank scraper?
Some modern engines like the Ford Coyote introduce air flow near the central axis of rotation which at high rpms helps to reduce the pressure differential holding entrained oil droplets from within.
**** This video of raw data periodically shows how highly aerated oil drawn into an oil pump will emerge from cam bearings like shaving cream. http://www.youtube.com/watch?v=SmjQn3IBsP8
What about dry sumps: do they eliminate windage?
There are many levels of dry sump technology as well and windage is still an important issue in their design. Dry sumps are primarily intended to deliver an uninterrupted supply of quality oil to the bearings under all reasonable types of vehicle movement (aircraft systems are more complex). Oil aeration is reduced but not eliminated. The faster the engine spins the higher the quality of the oil supply needed and so in F1, for example, many more stages and/or scavenge points could be in use along with active versus passive oil deaerators. Mercedes engineers have remarked that up to 8% of the output of a passenger car engine can be lost to oil churning.***** Feedback from drag racers measuring ETs before and after oil control improvement suggest the percentage loss can easily exceed this.
***** See SAE 750051, page 5. http://papers.sae.org/750051/
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