Search Results

ORVR (Onboard Refueling Vapor Recovery) canisters trap vapors during normal operations of a vehicle's engine, and during refueling. This study evaluates the relative risks involved should a canister rupture in a crash. A canister impactor was developed to simulate real-world impacts and to evaluate the canisters' rupture characteristics. Numerous performance aspects of canisters were evaluated: the energy required to rupture a canister; the spread of carbon particles following rupture; the ease of ignition of vapor-laden particles; the vapor concentration in the area of ruptured, vapor-laden canisters; and the potential of crashes to rupture and ignite canisters. Results from these five items were combined into a risk analysis.

Simultaneous tests of emissions and driveability conducted at 4.4°C on a chassis dynamometer using 10 late model vehicles showed a strong correlation between degraded driveability and increased tailpipe hydrocarbon emissions. Other regulated emissions were uncorrelated to driveability, or were small in magnitude. The 24 test gasolines were systematically varied in front-end, mid-range, and tail-end volatility and so spanned much of the moderate and high DI (driveability index) fuel region. Splash blends of 10%.vol ethanol and 15%vol MTBE blended gasolines were tested in addition to hydrocarbon gasolines.

The Coordinating Research Council (CRC) volatility group has issued a new cold-start and warm-up driveability test designed to improve the resolution of volatility effects on MPFI vehicles. Additionally a new demerit weighting procedure is now available to use with the new test. The weighting procedure was developed through an intermediate-temperature cold-start and warm-up driveability program conducted in the fall of 1994. The program also evaluated the effects of MTBE and volatility (driveability index) in late-model vehicles. The new test procedure and demerit calculation ordered fuels by volatility and generally generated higher average demerit levels for MPFI vehicles than the procedure used in previous cold-start programs. As in previous programs, driveability was a nonlinear function of DI and the presence of MTBE was not found to be a statistically significant effect. A volatility index based on percent evaporated was generated.

Simultaneous measurements of cold-start/warm-up driveability and tailpipe emissions on a chassis dynamometer were made at 5°C using four late-model vehicles. Two fuels wore used: a low driveability index (DI) fuel containing 11% MTBE and 29% aromatics, and a high DI fuel with no MTBE and 43% aromatics. Tailpipe hydrocarbon emissions and total weighted driveability demerits (TWDs) both correlated with the fuel used; both increased significantly when high-DI / no-MTBE fuel was used. A strong linear relation exists between TWDs and simultaneously measured tailpipe hydrocarbon emissions. CO and NOx emissions did not correlate with fuel composition.

Fuel alcohols, such as M85 (a blend of 85 percent by volume methanol with hydrocarbons) and Ed85 (a blend of 85 percent by volume denatured ethanol with hydrocarbons), are inherently involatile at low temperatures and may contain soluble or insoluble contaminants. We explored the adequacy of existing specifications for M85 and Ed85 by studying fuel effects on cold starting and vapor flammability, and fuel contaminant effects on materials compatibility and filter plugging. These studies demonstrated deficiencies in existing specifications. Therefore, we developed General Motors specifications for M85 and Ed85 to improve vehicle performance and durability. Key features include a Cold Starting Performance Index to improve wintertime starting, a conductivity and chloride ion specification to reduce corrosion, and a particulate contamination limit to reduce filter plugging.

A two-phase test program designed to investigate the effects of Reid vapor pressure, T50, and oxygenates on hot-start and driveability performance of vehicles operated at high and low altitude in high and intermediate ambient temperature ranges was conducted during July and August of 1992. Twenty 1983 - 1992 model-year vehicles were tested on a set of eighteen fuels which included six hydrocarbon-only fuels, six gasoline-ethanol blends, and six gasoline-MTBE blends. Fuel-injected vehicles showed very few demerits and were insensitive, in most cases, to the fuel variables studied. By comparison, carbureted vehicle's demerit levels were three times the level associated with fuel injected vehicles. Statistically significant degradation of driveability was demonstrated in these vehicles when tested on fuels with low T50 and low RVP. Driveability problems related to low T50 fuels were frequently symptomatic of vapor lock.

We have developed and validated a simple, quick, in-expensive method for determining the methanol or hydrocarbon content of a methanol blend fuel (a mixture of methanol and gasoline). The method exploits the insolubility of water in hydrocarbons. Briefly, 50 mL of fuel is mixed with a like amount of water and allowed to settle; the volume of the upper phase is directly correlated to the amount of hydrocarbon in the fuel. Equations and graphs are provided which translate between the hydrocarbon volume measured and the methanol content or the hydrocarbon content of the fuel. This method and the graphs and equations in this report are valid for methanol fuels made with any gasoline or virtually any hydrocarbon mixture, provided there are not oxygenates such as ethanol or MTBE present in the hydrocarbon fraction. The accuracy and precision of the method are excellent, for mixtures of dry methanol and oxygenate free gasoline.

The UPS292sc, a late injection DISC (direct-injection stratified-charge) engine, has demonstrated extraordinary multifuel and cold starting capabilities. In this paper in-cylinder measurements of gas temperatures and pressures during & cold start are reported. Analysis of the results clearly indicates that the traditional description of the ignition process does not adequately explain cold starting in a late injection DISC engine. Alcohol droplets directed onto an operating spark plug at -20 °C were observed to ignite. It is believed that ignition proceeds via energy transmission from the alternating current spark, independent of the compressive heating. Ignition is therefore virtually independent of ambient temperature or fuel volatility.