MILW CFA16-4 27C Editors Pick! Contributor's Pick!       
MILW CFA16-4 27C at Bensenville, Illinois on February 14, 1965, Kodachrome by Chuck Zeiler. Built in August 1951 (c/n 16L488), class 16-FF on the Milwaukee Road. It is seen smoking at the Milwaukee Road's Bensenville engine facility. According to Jim Boyd's book, Fairbanks-Morse Locomotives In Color (ISBN 1-878887-63-7), there are two possible explanations for the smoke. Unlike Alcos, which produced black smoke as a result of turbo-lag, the F-M's opposed piston (OP) diesels were normally aspired, using a Roots blower to pressurize the intake air.

While a properly maintained OP is a smooth and reliable engine, they tend to develop one distinctive characteristic: blue smoke on acceleration. This is the result of two potential causes, which are usually mixed to varying degrees. The first is lubricating oil. While the bottom crankshaft lives in an oil-filled crankcase (like an EMD), the top crankshaft is in a "dry sump", lubricated by pressurized internal passages and a surrounding spray of oil (like the top deck valve chamber of an EMD 567). When the OP idles or shuts down, some of the top sump lube oil will drip down the cylinder walls above the piston, and if the walls are scored or the piston rings are worn, the lube oil will get into the firing chamber and often pass unburned into the exhaust manifold, where it can ignite in a smoky pall when the engine is revved up. The other cause of smoke is the cooling water seeping into the cylinders from the seals where the injectors pass through the water jackets around the cylinder walls. This will also cause smoke. You could tell how well an OP is being maintained by its penchant for smoke upon acceleration.

Date: 2/14/1965 Location: Bensenville, IL   Map Show Bensenville on a rail map Views: 13416 Collection Of:   Chuck Zeiler
Locomotives: MILW 27C(CFA16-4)    Author:  Chuck Zeiler
MILW CFA16-4 27C
Picture Categories: Roster This picture is part of album:  Milwaukee Road
User Comments
Name Type Comments Date
Steve Young General If they used a Roots blower, then by definition they're not normally-aspirated. 6/27/2018 4:26:58 PM
Chuck Zeiler General Steve, I sort of agree with you, but the following is from the Wikipedia article about naturally aspired engines: As a two-stroke diesel engine is incapable of this natural aspiration, some method of charging the cylinders with scavenging air must be integrated into the engine design. This is usually achieved with a positive displacement blower driven by the crankshaft. The blower does not act as a supercharger in this application, as it is sized to produce a volume of air flow that is in direct proportion to engine's requirement for combustion, at a given power and speed. By the Society of Automotive Engineer's definition, a mechanically scavenged two-stroke diesel engine is considered to be naturally aspirated. 6/28/2018 11:36:03 AM
Steve Young General Far be it from me to argue with the SAE! Every day's a school day; mechanical scavenging is not the same as forced induction. Thanks! 6/28/2018 11:42:37 PM
Jack Petrof General My 2 cents would be the possibility of uncompletely burned fuel making white smoke.I once drove a KW semi-truck whose old Detroit 8V-71 smoked like the dickens when cold! 3/18/2019 1:05:37 PM
David Krebs General In any case it is a great shot! 4/15/2023 10:22:30 PM

Add a Comment:  
Please Log in to leave a Comment.  
Link to this page: