|Cutaway rendering of the PRV system. Click to enlarge.
A Colorado company, PRV Performance, has developed a prototype Pintle-Regulated Venturi (PRV) induction system that replaces a conventional intake manifold with a Venturi for each cylinder of the engine; a fuel injector directly feeding into the throat of the Venturi; and a pintle, moving in and out of the Venturi, to throttle the air flow.
Fuel injection at the Venturi throat results in the effective mixture of fuel and air due to the high velocity and reduced pressure at the vapor-liquid contact region; pressure is recovered in the expansion section. Testing by the company has shown an improvement in fuel economy of up to 14% in city cycle and 25% in highway cycle driving.
|Dynamometer results. Baseline system in red, PRV system in blue. Click to enlarge.
Dynamometer testing also indicates an increase in torque and horsepower, compared to a conventional manifold baseline system. Use of the PRV system also shows a decrease in emissions of criteria pollutants, with a drop in HC of 7.3%; a drop in CO of 83%; and a drop in NOx of 18%.
The pintle positions are set by the throttle, with the movement of the pintles synchronized by linkage mechanisms. The fuel injectors are standard, and fuel injection timing is regulated by the electronic control unit as with a conventional manifold. Vaporization of the fuel occurs in the confined throat of the Venturi. The exit into the cylinder is contoured with an abrupt expansion ring.
With a properly designed pintle, the air flow can be regulated with the same flow characteristics as a throttle plate while facilitating the Venturi effect at all throttle positions, thereby enabling optimal air-fuel mixing throughout the operating range, according to the company.
The company has worked through eight generations of prototype, installed and tested in a Honda Civic with a JDM D15B single overhead cam engine.
The company will present a paper on the PRV system and the test results at the SAE World Congress in 2008.