DENSO DEFENDS PORT FUEL INJECTION...

Gasoline direct injection engines currently provide about a 10% improvement in fuel

economy vs. those with a conventional port fuel injection system, according to Denso

Corp. But at last week's Global Powertrain Congress in Ann Arbor, Mich., the company

said PFI engines equipped with a variety of emerging technologies can match the perfor-

mance of GDI powerplants.

Not surprisingly, Denso already markets or is developing most of the new technolo-

gies it mentioned.

High costs have limited direct injection systems to only a handful of gasoline-powered

vehicles. Denso says most of these applications are in Japan, with Mitsubishi and Toyota

taking the lead in introducing the technology. By 2005, it projects that one-fifth of all gaso-

line-powered vehicles sold in Japan will feature direct injection.

High fuel costs also are driving European applications. But Denso doesn't expect

much increase in the U.S. market without some sort of major cost reduction and techno-

logical improvement to reduce oxides of nitrogen emissions, which are more difficult to

control in a GDI system.

…AND POINTS TO EMERGING PFI TECHNOLOGIES

Denso's vision was outlined in a paper presented at the Powertrain Congress by Doug

Patton, senior vice president of engineering customer support for Denso International

America Inc. He says the most promising technologies are variable valvetrain controls,

more sophisticated computer algorithms, advanced calibration systems, new air/fuel

sensors and a more efficient ceramic substrate design. By employing these technologies,

Patton says PFI engines will be able to meet upcoming emissions and fuel economy

standards in the U.S. and Europe.

Noting that independent variable valve timing and continuously variable valve lift

systems already are on the market, Patton says the next step is to integrate the two func-

tions. This will result in better control of intake and exhaust valves and reduce pumping

losses, which he says will yield "significant" improvements in fuel economy and torque as

well as in lowering emissions. But achieving those results will be a complex process that

involves optimizing tradeoffs in injection timing, spark timing and valve opening. Patton

envisions a camless electromagnetic valve control system but doesn't say when he

expects this to materialize.

Denso also is working to optimize the shape and placement of injector holes to

improve fuel atomization. But after experimenting with a higher number, the company

feels it already has the optimal number of injection holes: 12.

Patton touts Denso's linear air-to-fuel ratio sensor as a way to improve efficiency.

Unlike competitive switching units that only determine if an engine is running lean or rich,

the Denso system measures the exact ratio. This allows it to better control injection rates

and minimize oxides of nitrogen emissions, according to the company.

 

Further out, Patton says electric superchargers will be able to boost low-end perfor-

mance, allowing smaller engines to match larger ones in performance. But he doesn't

expect this to happen until the end of the decade