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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(Your mileage may vary…)
Being a gearhead, and savvy on intake physics, I’d say B.S. The presssure drop (ambient to a vacuum), ensures a homogeneous mixture, since it boils at that pressure. Regardless of velocity from a restriction.
So let’s see some data on a V-10 Excursion. That’s where the gains should be most dramatic, or well received. Large SUV’s.
Oh wait, what was I thinking, that’s exactly what GM was thinking with their Two Mode Hybrid in a Tahoe!!
So, it’s like a more complicated tornado “air management system”.
moveable venturi throat?
Welcome to 1905 and the SU carb
Sounds like one of those ripoff “turbonators”.
John
awaiting emissions test results with baited breath
It may not be a fraud…
burns a high-velocity homogeneous fuel-air blend more efficiently than standard induction; eliminating throttling losses and improving fuel vaporizing, precluding cylinder wall stratification.
…but physics teaches that there is no free lunch. What is given up in the name of more efficient combustion? Torque? RPM?
The trade-out may not be worth the fuel gain.
Being that it eliminates the current intake manifold I’d say that it is nothing like those tornado things.
I too would like to see more real world data before jumping to an opinion one way or the other.
I call BS for two reasons:
1. This idea of having the injector on the venturi is a step backward when you consider the performance and economy gains of Direct Injection.
Or put in simple terms, Port Fuel Injection is so 1982.
2. Pintle regulated venturi sizes: how is this better than the variable induction intakes used on cars back in the 80-90s? I’ll assume that pintles are more efficient than butterfly valves, but I’m still not buying this.
Always beware of so called “new” technology from a company looking for “Interested investment partners” at the bottom of their webpage.
This is completely different than the “tornado”. Those gimmics claim to “speed up” air by spinning it. The venturi effect is real. In this case they use the pressure drop to acheive a more homogeneous air/fuel mixture. Apparenly the gains in MPG and torque come from reducing one of the engine’s inefficiencies (i.e. standard throttle body/injector system). If thats the case the only trade off would be a more complicated intake manifold.
I’ll give these guys a chance to develop their technology before dismissing it. EVERY company that focuses on developing new technology needs investors. R&D costs money and startups rarely have enough of it.
gawdodirt –
Not necessarily. Fuel injection, intake, and exhaust are all anisotropic, especially for a SOHC engine. Even at high number there’s got to be reduced mixing near the cylinder wall because of the short time scale.
If the fuel/air mixing is done separately in a Venturi, the dimensionless mixing time : residence time is effectively increased.
SO…maybe not a total crock, but certainly not a revolution (so to speak) in engine technology.
If I’m not mistaken, the D15 has dual port fuel injection fired in batch mode. So I would imagine that by changing the intake manifold and adding 2 more injectors, they would also have to do some tricks with the the ecu programming. This is a late 80s/early 90s engine, so there is probably a lot to be gained by adding injectors and changing the fuel/air maps. I don’t doubt that the shape of the intake manifold had something to do with the gains as well, but this would be more impressive if they did it on a state of the art K series engine instead of what is basically 1st or 2nd gen EFI tech.
Also, doing the test at a constant speed, and thus constant RPM makes me a little suspicious, because you can make a lot of compromises when designing engine “breathing apparatus” for a certain RPM. Favoring velocity over volume, helps torque in the lower rev range, while favoring volume helps in the higher revs. Let’s see a before and after dyno graph to see what’s really going on here.
@JT: I think you slightly misunderstand the implications of the physics. This process presumably improves combustion efficiency, meaning (1) higher pressure after combustion, and (2) less energy remaining in the exhaust gases (more water vapor and carbon dioxide, less NOx, unburned hydrocarbons, etc.). If this is then used to increase fuel economy, that means the vehicle is geared to use the additional energy released in combustion to propel the car at a given speed at a lower RPM, rather than to increase power. That’s your tradeoff, but either way you still end up ahead.
This analysis is contingent on the device in question not being, as other commenters put it, “BS.”
Update: I agree with m0jumb0 above–dyno charts will tell the tale.
Every time the piston pulls downward against a vacuum, engine efficiency is lost. This concept is known as pumping loss. All throttle plate designs have substantial pumping losses. The vintage 80s slide plate incurrs the same pumping losses.
PRV induction recovers pressure regardless of engine load because of the integrated throttle (pintle) and the Venturi effect.
Dyno comparisons have been on the website for a year, showing the substantial gains in torque.
James Meyer, PRV Performance. http://www.prvperformance.com
Also, doing the test at a constant speed, and thus constant RPM makes me a little suspicious,
They said the course had hills. (Our author described it as “hilly,” which may not have the same connotation.) Depending on how gentle those hills are or are not, RPM may have varied.
awaiting emissions test results with baited breath
They have some “emission test” PDFs on their website.
But I’m highly suspicious because their website is an appeal to investors, not to customers. They don’t even pretend.
(The website is poorly constructed, with images shrunk in-browser, but that’s okay if they’re a bunch of mechanical engineers.)
Six Fuel-Saving Technologies to Help Hit 35 mpg Soon by Paul Weissler in Popular Mechanics on April 29, 2008:
1. Multistage Oil Pump
2. Shortened Cylinder Head
3. Variable Compression Ratio
4. Guided-Spray Turbo
5. Electromagnetic Valve Actuators
6. Hydraulic Power Electrification
from the website
How does a PRV work?
Air enters the contoured Venturi via an air filter.
Fuel vaporizes and expands in the low pressure throat.
Fuel vaporization induces air flow into the Venturi entrance.
Fuel vaporization in confined space thrusts mixed charge into the engine.
Charge is always homogeneously mixed and cooled because the pintle regulates air flow at the confluence of fuel and air.
why you want it to expand? surely a standard injector does a good job of mixing the air and the fuel. In fact a standard toyota injector(from a 2002 avensis with a 1ZZ-FE) managed to hit Lambda 1.001 the other day on its MOT. now if thats not a nearly perfect combustion then I don’t know what is.
so its not a way of getting a stoichiometric. So it must eliminate the throttle some way.
oh wait no thats still there just its now called a pintle. This just looks like an SU carb for the new century.Only problem being that most manufacturers are going toward direct injection and away from port injection.
and the website is woefully short on details.
If it is exactly as advertised PRV could sell these manifold as after market too. Just like Holley/ Edelbrock in the old days, we can go to a shop buy one & slap it on.
Once they mass manufacure them the price should come down, especially the price of fuel. Lots of folks with older cars will buy these too.
SU carbs’ plunger are not exactly operating in the same direction, their plunger are perpendicular ( 90 degrees) dont think it has same effect.
Wow, why doesn’t this come in cars already?
Oh, most likely becuase of the “new physics” involved, like Bernoulli’s principle.
The only way there can be anything to this is if an advanced fluid simulation uncovered a heretofore unknown aspect of fluid dynamics.
I hope I’m wrong, of course.
Sean,
By saying “ansiotropic” do you mean “LAMINAR?”
Definition is related to computer graphics terminology.
In the real world, turbulence, or swirl, in the chamber is actually benefical right up to the point where it zaps energy from the actual kinetic momvment. Like previously stated, there is no free lunch.
“PRV Induction” Recovers Throttle.”
Like a foot on the accererator pedal?
I’m having a difficult time seeing how an engine can function at part throttle without pulling a vacuum. The intake stroke is going to pull a vacuum if there is a restriction in the intake manifold, otherwise you have no throttle.
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.
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.
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?
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.