Leaner engine operation…higher operating and component temps…decreased CO emissions…higher idle speeds…increased NOx emissions…erratic operation…complete stalls with E15 and E20 gasoline blends. Look for more details upcoming here on poweretblog and in the Jan/Feb. issue of Power Equipment Trade, but I’ve just gotten my hands on the impressively titled “Effects of Intermediate Ethanol Blends on Legacy Vehicles and Small Non-Road Engines, Report 1,” a study prepared by the National Renewable Energy Laboratory for the U.S. Dept. of Energy, and want to share some of the results.

First—this is a looooong 136-page report, complete with a serious number of eye-glazing charts and graphs that would put all but the most avid small engine technophiles into deep slumber. No, I haven’t read every word of it—probably never will—but managed to read the summaries of the small engine section and also the scope of the study and some of the charts, basically hitting the high points. (If you want your own copy, you can download it here.) So let’s go:

The study, which began in late summer 2007, tested E0 (unblended), E10, E15 and E20 ethanol gasoline blends in a “pilot study” to identify emissions levels and any specific, immediate operational problems with each fuel blend, followed by a “full-life” study in which the engines were run for extended periods of time on each fuel blend. The study is just that—not a comparison, but a chance to view engine operation in a controlled environment with higher ethanol blends and observe the results. Products tested were Honda, Briggs & Stratton and Kohler generators, a Briggs power washer, Poulan blower, Stihl residential grade trimmer, Weed Eater blower and a Stihl commercial grade trimmer.

EDITOR’S NOTE: The following test result information reflects product performance in a completely new fuel environment under rigorous conditions. Each product tested has fared well in the marketplace under previous and current fuel formulations—and in fact the products were selected for their high sales volume and widespread use by end users in the marketplace. Knowing the competitive nature of the industry, I could see how some are liable to use these results to slam competitors. But before you do, all you wide-eyed product managers out there, let’s pour some E15 or E20 into your fuel tank and see how your product fares during 24 or more hours of constant operation! This is basic research in a completely new fuel environment, of utmost importance to the small engine industry, and the results should be viewed as breaking new ground, not a reflection of conventional product performance.

According to the report, “Performance varied considerably among the engines tested, regardless of the fuel used. Therefore, it is not possible to completely isolate the effects of ethanol on operability. However, a few observations are noteworthy:”

• As ethanol levels increased, leaner engine operation was observed in all of the tested engines, as indicated by decreased CO emissions.
• Temperatures of both the exhaust and engine components increased as ethanol levels increased.
• HC emissions generally decreased with increasing ethanol, although increases in HC emissions occurred in some engines.
• NOX emissions increased with higher levels of ethanol in all engines; however, combined NOX + HC emissions (which are regulated as such) were tempered by decreasing HC emissions in most cases. Net changes of HC+NOX with increasing ethanol ranged from –36% to +41% and were engine-specific.
• CO emissions decreased with higher levels of ethanol.
• With greater ethanol content, three handheld trimmers demonstrated higher idle speed and experienced unintentional clutch engagement. The increased speed was again caused by the fuel:air mixture enleanment, which can be adjusted and mitigated in some engines.
• Residential and Commercial Class I and Class IV engines were aged to full life. The residential Class I as well as the commercial engines exhibited no sensitivity to ethanol from a durability perspective in the short duration of this project. The effect of ethanol on the durability of the residential Class IV engines was not clear given that a number of these engines failed during full- life aging regardless of fuel type.
• No materials compatibility issues were observed in the short duration of this project, but they were not specifically characterized as part of this study.

Another section of the study looked at specific products and engine operation:

• In the pilot study, the Briggs generator began losing power on E20 at full load, leading to an interesting discussion of whether some of the plastic carb components had swollen due to ethanol exposure and restricted fuel flow. Tests with other blends were “without incident.”
• The Poulan leaf blower, in the pilot study, began to “run poorly during aging with E15 at about 34 hrs. The engine ran very poorly during the final E20 phase.”
• In the Stihl FS 90 trimmer’s pilot study, “The (unit) ran poorly on E20, and high idle speed on E15 and E20 led to clutch engagement at idle.” The report notes that during the full-life study, the problem was corrected by altering carburetor settings and reducing idle speed.
• The Honda EB3000c generator’s full-life study noted that with E20, the engine was “‘bouncing off the governor’ at light loads when testing began…However, after 250 and then 500 hours of aging on E20, the engine ran normally at all loads.”

Again, what’s posted here is just a very, very small slice of the overall report, and what I thought readers would find interesting. This is also just a small first step in a lot of research and work for the small engine industry to adapt to new fuel blends in the marketplace. Look for more developments and comments from industry officials in future poweretblog posts and in Power Equipment Trade magazine.