Project Low-Buck SR20DE, Part 2

Track-driven SRs abuse their bearings if the oil level is allowed to drop one bit below the full mark on the dipstick, it's common to see the oil pressure fluctuate in hard corners with a car modified with good suspension and sticky R-compound tires. This makes it very temping for an SR owner to slightly overfill the crankcase to reduce the chances of this happening. This is also bad. A crankcase that's even slightly overfilled helps create a maelstrom of windage around the spinning crankshaft that both saps power and overheats the oil enough to torture the bearings. If you can imagine riding a bike underwater, this is what your crank experiences. This is the main reason why track-driven SRs run such high sump temps. When experimenting on the dyno, overfilling the crankcase by a measly half a quart caused a drop of 6 whp on an SR20. Having piston coolers that shower the crank with hot oil dropping from the pistons simply adds to the problem.

To help reduce the engine's sensitivity to oil level, gain power, and reduce sump temperatures, we installed a crank scraper and windage tray from Ken Johnson at Ishihara-Johnson Crank Scrapers. The crank scraper made of sheetmetal and cut to closely follow the contours of the crankshaft. It bolts to the main girdle. The crank scrapers job is to strip oil off of the rotating crank assembly so it can be retuned to the pan instead of flying around in a dense cloud, getting hotter and more aerated. We opted for the full-race scraper, which includes a Teflon insert that can be adjusted until it's actually in light contact with the crank so that it does the best job of stripping the oil cloud.

We also opted to run the full-race windage tray. A windage tray is a louvered plate designed to capture oil from the windage cloud that surrounds the rotating crank, and return it to the sump before it gets hot and frothy. The full-race windage tray goes completely across the engine's bottom end to strip as much windage from the crank as possible. However, the full-race windage tray requires some cutting and welding of the oil pan for clearance. Ishihara-Johnson also makes a three-quarter length street version of the windage tray that doesn't require pan modification.

The windage tray and crank scraper work together to greatly reduce the amount of windage in the crankcase. Eliminating the turbulence and oil mist generally gives a power increase of 5 to 6 whp and reduces the sump temperatures by 10 to 15 degrees. Oil with less entrapped air also does a much better job of lubricating the engine's innards. With less oil getting thrown around, the engine's oil consumption goes down and the rings aren't overcome by the volume of oil thrown on the cylinder walls. Although this part isn't absolutely necessary for a low-buck build, it's reasonably priced and gives a free gain in power, something that is hard to overlook in an all-motor build.

With our engine's bottom end details taken care of, we've still managed not to spend too much money. In our next edition of Project Low-Buck SR20DE, we'll massage our cylinder head and design some really cool headers for our budget build.