Reputable links for horsepower from windage tray/crank scraper

[Stew Meat]

I know this thread is old, But I slogged through much of it, not all. My 2 cents about the cloud of droplets following the crankshaft around is only another series questions: Would oil exiting the main bearings be scraped off the crank journal by the air surrounding it as it spins? And if so, would it come off at the trailing edge of the crank and be suspended in the lower air pressure behind the trailing edge? And at some point of crankshaft speed it would just be a target for the leading edge to hit it again? In my mind, the way to get rid of it would be to design a crank shape that would cut through the air without leaving a low pressure area at the trailing edge. Perhaps taking a 28 oz imbalance 302 crank and rounding the lead edge and knifing the trailing edge and balancing it for use in a 50 oz block?

[Kevin Johnson]

I know this thread is old, But I slogged through much of it, not all. My 2 cents about the cloud of droplets following the crankshaft around is only another series questions: Would oil exiting the main bearings be scraped off the crank journal by the air surrounding it as it spins? ...

"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/ilass ... RS/097.pdf

... And if so, would it come off at the trailing edge of the crank and be suspended in the lower air pressure behind the trailing edge? ...

Yes. The technical term is 'entrained.'

... And at some point of crankshaft speed it would just be a target for the leading edge to hit it again? ...

Yes. The impact generates a parasitic loss and the friction heats the oil.

... In my mind, the way to get rid of it would be to design a crank shape that would cut through the air without leaving a low pressure area at the trailing edge. Perhaps taking a 28 oz imbalance 302 crank and rounding the lead edge and knifing the trailing edge and balancing it for use in a 50 oz block?

Seventeen years ago David Vizard ran a series of careful dyno tests investigating an aerodynamic leading edge and a lipophobic coating as well.

The August issue of Circle Track magazine has an article by David Vizard on crank profile and coatings. The first test compares 3 3/4" stroke square face and aero counterweight Scat cranks in a wet sump motor. The aero counterweights were good for 3.5 hp at 5,500 rpm, up to 9.9 hp at 7,250 rpm. This motor had a peak hp of 470 at 6,250 rpm.

The next test is a teflon based coating on a dry sump motor crankshaft, with a 3 3/4" stroke.The coating was worth 8 hp at 7,500 rpm, but gains were not seen until about 5,000 rpm. This motor had a peak hp of 570 at 7,250 rpm.

[Stew Meat]

Wow. Thanks for that reply. This is all fascinating stuff. 10 hp from managing air/oil movements around rotating parts, as well as the gains from keeping oil cooler and less beat up. At the end of the day, I will probably just modify my oil pan and call it good for my purposes, but I think I finally understand the problem. DV has talked about rounding the bottom edge of cylinders to enable air exchange to happen easier...perhaps a modification that cannot be overlooked for the general easiness compared to crankshaft work. I must emphasize How thankful I am to have access to studied people like you and DV, and ptuomov. I think the same curiosity that drove your careers drives our hobbies, and we are blessed to have access to what you all have learned.