Effect of Low Fuel Volatility On Cold Driveability
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The Clean Air Act of 1990 required that fuel volatility of gasoline sold at retail be reduced at summer months (June through September 15). In 1992, the EPA implemented Phase II requirement which further lowered the acceptable vapor pressure to 9.0 psi. In some areas, the regulation requires vapor pressure be no greater than 7.8 psi. Volatility is the term used to describe the fuel's ability to vaporize, or change from a liquid to a vapor. Low volatility gasoline helps reduce hydrocarbon emissions from evaporated fuel. "RVP" is the abbreviation for "Reid Vapor Pressure", a method used to measure fuel vapor pressure. This requirement is needed to protect our environment and improve air quality.
The downside of this regulation is its effect on engine cold starting and cold drive away during summer months. This complaint only occurs for a very short period after start-up and does not severely hamper the driveability. It is important that our customers are aware of the availability of these low RVP fuels and their effect. The few moments of engine roughness are a small inconvenience when the overall improvement of the atmosphere is considered. We all have an obligation to improve air quality and we are sure that Subaru customers wish to share in this endeavor to improve our air quality.
Our investigation has proven that there is variation in fuel quality and vapor pressure among retail gasoline supplies. In many cases, the cold start complaint can be reduced or eliminated by changing fuel brands or stations.
In the interest of customer satisfaction, we have developed a ROM for the ECU of 1992 Legacy automatic transmission and SVX vehicles whose owners cannot accept the effects of low RVP fuel. Installation of the ROM should only be performed after explanation of the above to the owner and after trying a different brand of fuel.
This ROM will not totally alleviate the complaint. Also, there is no countermeasure available for manual transmission Legacy or other models. Our experience shows that these vehicles have few complaints and they can be resolved using a different brand of fuel.
Naturally, you must confirm that the engine is operating properly by basic checks of mechanical and fuel management systems prior to installing the ROM.
This ROM will also help reduce the occurrence of source detonation or "pinging" on 92MY Legacys.
ROM INSTALLATION PROCEDURES
These ROMs are available in limited supply through your RDC.
Flat Rate Information
This operation can be claimed under the Subaru Limited Warranty, if applicable, using the following information: