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Sturman Industries Developing New “Distributed Rail” High Pressure Fuel Injection System

The Sturman Environmental Injector (bottom) vs. a common rail system (top). Click to enlarge.

Sturman Industries—the digital valve company—is developing what it calls the Environmental Injector: a new fuel injection system that combines the benefits of current high pressure common rail injector technology (flexible timing, flexible injection pressure and multiple injection events) with the additional benefits of Sturman’s hydraulic intensified injector (higher injection pressures, improved safety and alternative fuel usage).

Sturman has been working on applying its digital valve technology to intensify fuel systems for more than a decade. The hydraulic intensified injector uses a portion of the fuel as a working fluid to increase the pressure of the charge prior to injection. The current S1 intensified injector supports an injection pressure of 2,400 bar (a 3,000-bar version is in development) and supports variable injection timing, pressure and duration, along with multiple events, small quantity control and low dwell.

The intensified injector has the disadvantages of increased parasitic losses and pressure spikes in the nozzle. The Environmental Injector addresses these by moving the fuel accumulator volume from the fuel rail to the injector nozzle itself, with delivery from a low pressure fuel pump, and using a hydraulic fluid delivered by a low-to-medium pressure oil rail to intensify the pressure in the injector.

The Environmental Injector is similar to a common rail injector in that the injection of high pressure fuel, contained in a variable high pressure chamber, is controlled by a needle control valve, providing the benefits of flexible timing, flexible pressure and multiple injection events. Sturman has previously shown that its digital needle control valve provides performance equal to current common rail systems.

The Environmental Injector (EI) is fed by low pressure (4 bar) fuel and <300 bar hydraulic fluid, rather than high pressure fuel. The EI acts as its own high pressure fuel pump, intensifying the pressure of the hydraulic fluid to provide high pressure fuel in the bottom of the injector when the intensifier control valve is actuated.

Unlike Sturman’s current hydraulic intensified injector, the intensifier piston charges a volume in the bottom of the injector. The volume in each injector is large enough to maintain desired pressure during an injection event. Sturman refers to the total fuel volume in all of the injectors as a “distributed rail”, replacing the accumulator rail in the common rail system.

Proposed benefits of the Environmental Injector include:

  • Increased injection pressure. Pressure spikes in the nozzle are reduced by the compliance offered by the large fuel volume in the nozzle. This allows the mean injection pressure to be increased without exceeding the allowable stress levels in the nozzle. This in turn enables increased injection pressure capability beyond the previous limits of both common rail injectors and hydraulic intensified injectors.

  • Alternative fuel capability. Both the intensifier control valve and the needle control valve operate in medium pressure hydraulic fluid, allowing the system to be more adaptable to alternative fuels than if the fuel itself was used as a working fluid. In 2001, Sturman collaborated with AVL on a paper that examined the use of hydraulically intensified fuel injectors driven by oil in a common-rail concept using digital valve technology for a DME-fueled compression ignition engine.

  • Reduced parasitic loss. Since all of the pressurized fluid in contained in the EI, the energy penalty normally associated with a hydraulic intensified injector (venting of high pressure) is significantly reduced.

  • Reduced cost. Replacing a high pressure fuel pump with a low-medium pressure hydraulic pump and a low pressure fuel pump offers reduced cost.

  • Improved safety. Medium pressure hydraulic rail and lines replace the high pressure fuel rail and supply lines.

  • Eliminates an engine failure mode. In the event of nozzle failure, the intensifier control valve will not be activated, and only the volume of fluid contained in the injector can be injected. This eliminates an engine failure mode and provides individual shut off for a “limp home” capability.

  • Flexibility of the hydraulic rail. The hydraulic rail could be used in multiple applications, including ride control, accessory drives, and engine valves.

Joe Vollman, Sturman’s VP of Business Development, presented a poster session on the Environmental Injector at the Diesel Engine-Efficiency and Emissions Research (DEER) conference in Dearborn, Michigan this week.


  • Denis Gill, Herwig Ofner, Eddie Sturman, John Carpenter, Marc Wolverton (2001) Production Feasible DME Technology for Direct-Injection CI Engines (SAE 2001-01-2015)


Why is it named Environmental Injector? What it does to the environment??


presumably higher injection pressure and finer control of injection events will lead to lower emissions, at least that has been the case so far, hence "environmental".

Henry Gibson

Considering just the carbon dioxide releases, diesel engines are the highest efficiency automotive engines available. Their efficiency approaches that of the best operational fuel cells at much lower cost. One aspect of their efficiency, that is not widely considered, is that diesel fuel can be made from crude oil at lower energy cost than gasoline. Thus the well-to-wheels energy expense is lower than other fuels further reducing CO2 releases.

Diesel does not evaporate as fast as or as easy as gasoline which reduces hydrocarbon pollution. Exhaust filters and catalysts can reduce particulates and NOX levels to that of gasoline engines.

Compressed natural gas can be mixed with the intake air in diesel engines and can replace as much as 80% of the diesel fuel. The new injectors may allow even less diesel being used. Propane and butane can also replace diesel in the same way. Methane is a very easy to produce biofuel and can be produced from all forms of biomass.

Plug-In-Hybrid cars with diesel engines are likely to be the lowest fuel cost, lowest CO2 releasing, automobile at much lower cost than fuel cells. ..HG..


Well put, Henry Gibson.

As much as I like the idea of an all electric car, the range vs cost issue will not go away so easy.

A compact single cylinder diesel generator equipped series hybrid will likely be a very competitive strategy, with good range, performance, low cost, reliability...


"A compact single cylinder diesel generator equipped series hybrid will likely be a very competitive strategy, with good range, performance, low cost, reliability... "

only problem is it will not meet American emissions regulations (T2B5). still, all the better for us in Europe!

our refinerys are set up to make gasoline this is why diesel is 4.75 a gallon and gas 3.8 high global diesel demand is driving our refiners to ship diesel overseas where they can maximise profits. Then again using a plasmatron to gassify octane to syngas and feed that syngas to a high compression engine like a diesel is a good idea less emmissions too. currently MIT has a 700 watt hour plasmatron that can gassify 16 kilowatt hours worth of fuel to be feed in to an engine or 4.3% penalty in energy, but since a diesel is at least 25% more thermal efficent than a otto cycle you end up with 21% inprovement and a plasmatron cares not what liquid you feed it , ethanol, butanol. vegoil, fastpyrolosis liquids, algaeoil, if it is liquid has carbon, hydrogen and or oxygen atoms a plasmatron shreads it all in to CO +H2 syngas.


Sure the current refineries produce a mix of products as per requirements. I would expect that the economics of that mix determines the cost (and volume) of production.
If it were more profitable to produce a greater percentage of diesel, they would.

For multiple injections and hence max control/efficiencies. This is near twice commonly used pressures ?
I wonder how far to go before the injectors start exploding?

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