New Induction System Bumps Efficiency By 10 MPG

Edward Niedermeyer
by Edward Niedermeyer
new induction system bumps efficiency by 10 mpg

We've argued for some time that OEMs should respond to high fuel prices by improving and lightening existing models and drivelines, rather than developing moon-shot, "game-changing" technologies. Et voila! Green Car Congress reports on the Pintle Regulated Venturi (PRV) induction system, developed by PRV Performance. The PRV-9 induction system is a bolt-on replacement for stock intake manifolds. By inducting air through a venturi throat, the doo-hickey burns a high-velocity homogeneous fuel-air blend more efficiently than standard induction; eliminating throttling losses and improving fuel vaporizing, precluding cylinder wall stratification. [You can read all the gory technical details at Green Car Congress] PRV Performance tested its intake on a JDM D15B SOHC-equipped Honda Civic, driving it at a steady 65 mph on a hilly 203-mile test run. The Civic achieved a reported 52 mpg, up from 41.7 on an unmodified Civic, with similar reductions in pollutant emissions. The EPA has tested an earlier prototype at 48 mpg, and will test this newer system later this year. PRV Performance claims that the technology is hybrid-compatible.

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  • Cdotson Cdotson on Jun 26, 2008

    A throttle valve is a generic device that is used to control the mass flow rate of the working fluid. In the case of automobiles the working fluid is air and by restricting the mass flow rate of air to each cylinder you limit the quantity of gasoline that is required and therefore the resultant power output. Throttling loss is the pressure lost as a result of restricting the mass flow rate. The pressure lost and the "pumping losses" the engine experiences is a function of *how* the MAF is limited and not purely by virtue of the fact that it has been limited. Venturis are the most efficient of throttling devices that I encountered during my days in engineering school and IIRC are capable of almost complete pressure recovery at full flow. In FormulaSAE competitions engine intake is restricted by a single 19mm diameter restriction for a 600cc engine. Everyone uses venturis with a 19mm throat diameter to maximize the pressure recovery and minimize the power reduction. I see no reason this system shouldn't work; y'all are just a real tough crowd. I'm cautiously optimistic and maintain healthy scepticism but again see no reason it shouldn't work. It's a good approach to seek significant but incremental improvements rather than delay any advancement at all until a paradigm-shifting change hits. It makes sense that the most gains are seen during highway driving as opposed to city cycle since the pintle will function more like a true venturi at WOT or high load cruise. Idling and light-throttle situations will restrict airflow to the donut-shaped area surrounding a close interface between the pintle and venturi inlet since it will be lower in area than the venturi throat. I think this hasn't been practiced by automakers because other methods are cheaper. This requires a complex shape interfacing with a separate complex shape with an individual actuator for each cylinder of the engine. This is much more expensive than a single throttle body fuel efficiency be damned (typical automaker mentality, right?). This is much more typical of slide-carburetors on 4cyl sport bikes which is probably the market that would be initially interested in this new pintle-venturi technology.

  • M0jumb0 M0jumb0 on Jun 26, 2008

    cdotson, I also see how it could work, but my problem was with the vague explanation. It looks like a great way to optimize velocity for different RPM, and the dyno graph seems promising. It adds a lot of complexity and expense to a relatively cheap piece, though. Race teams would have the cash to purchase and maintain something like this, but they operate in such a narrow power band I don't think it would have much appeal. If they could demonstrate a 30% increase in torque on other, more modern engines as well, then I could see OEMs picking up on this. Fuel efficiency is all the rage right now, so who knows.

  • Highvelcty Highvelcty on Jun 30, 2008

    Here is what I find good about this: - the minimal efficiency loss of using the venturi shape as a throttle - the pintle should allow laminar flow at all throttle positions - injection of fuel at the throat where pressure is the lowest should maximize atomization/mixing - the possibility of water injection at the throat as a means to control NOx problems forseen: - for proper mixing/atomization, the pintle/venturi must be a specific shape (intake diameter, venturi diameter, exit diamter, etc...) and with this specific shape, sonic velocity in the throat will be reached at low engine speeds. It seems that by pressurizing the intake system, one could flow more air at a given velocity, as a solution to this issue. On a side note, does anyone know if the pumping losses are less in a pressurized intake system?

  • Jmeyer99 Jmeyer99 on Jul 06, 2008

    PRV Respiration Here is a simple exercise to illustrate the PRV pumping loss reduction concept: 1. With your thumb and forefinger, partially pinch your nose and inhale deeply. Your diaphragm represents the piston and your lungs represent the cylinder. The sensation on your diaphragm is the pumping loss of a piston pulling on a partial pressure manifold. Your nasal passage represents the intake valve pressure drop 2. Repeat without pinching you nose at first, then a slight pinch at the end of the inhale cycle. This exercise represents PRV draw-down from a Venturi starting from full atmospheric pressure. 3. Note that your lungs pulled the same number of air molecules. It was much easier without the vacuum induced by your fingers. At the bottom of the piston cycle, the same number of molecules are pulled into the cylinder, given the same engine load, whether PRV or conventional throttle. This is because at the end of intake cycle, intake pressure – the pressure just immediately upstream of the intake valve -- must be the same for the same amount of air (and fuel). So, for the last millimeter of piston pull, pumping loss is identical...but PRV facilitates flow at the beginning where full atmospheric intake valve pressure is available. As intake valve pressure draw-down continues, the Venturi effect is applied but diminished until the last molecule of air is ingested. Note that the plenum pressure into the Venturi is always fully atmospheric and pressure reduction occurs only ahead of the intake valve. The overall effect is reduced cumulative pumping loss, and consequently, improved engine efficiency.