Crank Scraper
Until I started doing my rod bearing replacement job, I did not know what a crank scraper was. When I was doing my research for "what else to replace while I'm down there," I ran across many people saying to install a crank scraper. I bought a Ishihara-Johnson crank scraper for around $100 after reading many forum posts about how it is something of a necessity for 944s due to their habit of not having the best oil circulation on the track. I don't plan to turn my car into a race car, but since I had the oil pan off, it was something rather simple to install.
Here is what Ishihara-Johnson says about crank scrapers:
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 the windage cloud
· Helps reduce engine damaging oil-foaming
· 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 or becomes entrained in a cloud surrounding the spinning bottom end.
This oil eats up horsepower your engine is making by increasing the rotating mass and also creating parasitic drag. A crank scraper mechanically strips off excess oil by coming close to, but not touching*, the moving crankshaft and rods. It also interferes with the pressure differential that draws oil into the so-called windage cloud. Here is a short video clip made by one of our customers showing a rotating assembly and crank scraper from a Mitsubishi 4G54.
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. Here is a pictorial of the crank scraper installation on the earlier scraper for the Suzuki G10 engine. Here is a pictorial of an installation on an AMC V8 -- very typical of two piece scrapers.
Do they really work?
Yes! Crank scrapers in various forms have been in use in stock passenger car engines for at least 45 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.
As you can see. They're something that you should add if you have the pan off already.
Ishihara-Johnson makes a variety of crank scrapers for the Porsche 944. Check out their web page. I opted with the cheapest, most simple, crank scraper. However, if I were to do it again, I would buy the teflon lined crank scraper
For this write up, I will skip the step by step installation, as the Ishihara-Johnson scraper kit comes with excellent detailed instructions. I am just going to go over the general installation. It's not overly hard, but rather time consuming. You need to use a hand file and file the crank scraper down to 1mm clarence around your entire rotating assembly. I spent about 45 minutes per cylinder. However, I didn't have a very aggressive file.
After spending that amount of time, on your back, filing back and forth with a hand file, it can get rather tedious. This is why I say that if I were to do it again, I would have spent the extra money and gotten the Teflon lined crank scraper.
The crank scraper comes with the crank scraper, detailed instructions, new machined washers (for specific thickness) for the main caps, spare bolts, and a paper clip. The paper clip is used as a feeler gauge to make sure you have the 1mm clearance between the crank scraper and all rotating components. This is a close up of the actual scraper. You can see the holes that go on the main bearing cap studs, the flat part is near the crank lobes, and the radius curved and pointy part goes around the connecting rods. To install it, you'll have to remove the main bearing caps and the oil pickup tube. Then install the crank scraper. Rotate the engine by hand and check clearance between the crank scraper and the crank rotating assembly. Here you can see mine installed and clearance.
At the time of this write up, I have not yet started up my engine to compare performance and oil pressure readings. I will update this page when the time comes.
