Table 2. Typical emissions improvement seen on the FTP-75 test at 20 °C (1.8 L 4-cylinder vehicle).
Figure 8. Improvement with injector heating in THC and catalyst efficiency during Phase I of an EPA-75 test.
SUMMARY/CONCLUSIONS
Delphi has developed and integrated a world class, first-to- market, heated injector engine management system for E100 applications. This system has been optimized to achieve maximum efficiency of heater function, resulting in superior cold start performance and emissions reduction when compared to other competitive systems. Delphi has not only developed the heated tip injector but also the arrangement of the related heater circuit elements and accompanying engine calibrations for various applications.
The heated tip injector cold start simulation methodology for assessment of injector designs has been presented. The injector model has been validated by comparing bench test heater and fuel temperature measurements. The vaporization model assumes that the heated fuel from one injection mixes with the cold air required for one combustion event resulting in a mixture of air, fuel vapor and liquid fuel mixture at a uniform temperature. The resulting fuel vapor fraction is calculated and a successful cold start is considered to have occurred if at least six consecutive injections produce a fuel vapor fraction greater than approximately 6%, a value to some extent dependent on the engine particulars.
Vehicle tests have been performed demonstrating that Delphi's heated tip injector solutions are capable of enabling cold starts down to an ambient temperature of −5 °C for E100 applications. Starts with a total preheat and crank time of about 8 s (6 s preheat and 2 s cranking) were attained at −5 °C compared with about 25 s and an engine stall (16 s total preheat and 8 s total cranking with 1 s reaction time) with a competitive heated fuel rail system on a similar engine application. It was also shown that the injector preheating could be eliminated altogether in exchange for a longer cranking duration yielding a lesser overall start time (4 s vs. 7 s at 0 °C), while starting could not be achieved without preheating using the competitive heated fuel rail system under similar conditions.
Vehicle emissions improvements employing heated tip injectors have also been presented. During FTP-75 emissions tests using E22 and E100 fuel with heated tip injectors energized for the first 100 s of the test, reductions in total hydrocarbon (THC), carbon monoxide (CO) and non- methane hydrocarbons (NMHC) have been realized compared with testing when the injector heaters were not energized. Using heated tip injectors, THC and CO values were extended further below the acceptable proposed PROCONVE L6 limits. Additionally, the amount of NMHC was reduced from marginally acceptable limits to quantities less than the proposed PROCONVE L6 allowable values.
The Delphi heated injector system requires minimal engine hardware modifications and has been validated per the Brazilian E100 requirements. Rigorous quality assurance and warranty risk mitigation processes were used during product development to ensure reliability Production plans are slated for 2012 in the Brazilian market.