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Torotrak to present extreme engine downsizing solution at Dresden supercharging conference

At the 21st Supercharging Conference in Dresden next week, Torotrak Group will present results from engine testing that verify previous claims for V-Charge, a variable drive mechanical supercharger.

In comparison with the incumbent fixed-ratio positive-displacement supercharger on a 1.0L GTDI engine, V-Charge achieved improved BSFC (brake specific fuel consumption), better transient performance and a maximum BMEP (brake mean effective pressure) of 31 bar.

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V-Charge system with mechanical variable drive outperforms conventional boosting methods on downsized gasoline engine. Click to enlarge.

In a paper entitled “Simulation and Verification of V-Charge Variable Drive Supercharger Performance on a 1.0l GTDI Engine” on the second day of the conference, Tobias Knichel, Torotrak Group’s Business Development Director, will share details of the development program. These will include simulation using a GT-Power model and engine dynamometer testing which was carried out at the University of Bath Powertrain and Vehicle Research Centre (PVRC). The presentation includes full load, part load and transient test results.

The V-Charge equipped 1.0L 3-cylinder Ecoboost engine has similar performance to a 1.5L 4-cylinder version, combined with improved driveability, despite a 33% reduction in displacement. This signals the potential for a new level of downsizing, enabling the industry to further reduce the CO2 output of high volume vehicles without compromising driver satisfaction.

The ability to control compressor speed on V-Charge independently of engine speed, allows parasitic losses to be reduced and the need to de-clutch is decreased. The use of a centrifugal compressor, instead of a positive displacement Roots-type blower, reduces power consumption, improves efficiency and requires less package space.

Packaging is also simplified by the quiet operation of V-Charge, dispensing with the need for soundproofing. Test results for NVH show the sound pressure of a V-Charge installation is up to 15.9dB(A) lower than a similar Eaton system with encapsulation, and 19.7 dB(A) lower than the similar Eaton system without encapsulation.

The paper concludes by indicating that V-Charge is well placed to satisfy the first stage of boosting on the most aggressively downsized engines because it has a continuous air power capability of up to 17kW. It can also provide a flexible handover to the turbocharger at any engine speed, enabling simpler boost control. Though tested on a gasoline application, Torotrak anticipates that V-Charge will achieve similar gains on a downsized diesel engine.

Comments

Brian P

Hmmm ... Torotrak has been kicking around for quite a few years.

If this really was an "Ecoboost" engine then the "incumbent" forced-induction device is a conventional exhaust-driven turbocharger, not a mechanically-driven positive-displacement supercharger.

I gather that they are proposing to use this as part of a twin-charging scheme, as a supplement to a turbocharger to help out with low-end torque.

The inability to fully convert remaining exhaust pressure into crankshaft torque by overexpansion (e.g. Atkinson cycle) does not act in favor of a boosted downsized engine, particularly when it's running under heavier load (on boost).

Call me skeptical; our family's real-world experience with boosted gasoline engines has been that they are not more efficient in the real world than a bigger, but less highly tuned, normally aspirated engine ... If someone can figure out a way to get them to run under load on boost without enrichment and without melting themselves down, that would help. Cue Bosch's water-injection system ...

SJC

This is a way to get more output from smaller displacement, nothing new. Five and Six cycle designs can do the same without blowing the engine up.

Trees

The device looks expensive and takes engine power to operate. I'm guessing Ford has crunched the numbers and have a good cost effective system with the turbine. Sure, they have to compromise upon optimal solutions, but the people shopping for value are more attracted to their solution.

I don't know the limits of turbine boost (psi) for such small engines, but they could stack compressor or serial boost the pressure. The hybrid turbine boost/charger is extremely effective for low end engine speed per the mild hybrid design. Best bang for the dollar efficiency gain.

Don't forget the heat gain from exhaust turbo. They will probably add an air cooler for higher boosts.

Better fuel would help. The high blend ethanol is extremely efficient for cooling. Injecting within compression cycle will improve efficiency. I can't imagine the octane need or cooling past high blend ethanol, but they always have hydrous.

SJC

"The use of a centrifugal compressor..."
A centrifugal with CVT would be interesting, but cost is the big issue. You don't get much better mileage with this, a 6 cycle gives better mileage and more power.

Brian P

Spark-ignition premixed-combustion engines on standard pump gasoline become knock limited very easily. Add more boost, and you have to drop compression ratio down or delay ignition timing or add lots of enrichment. It's not necessary to stack boosting devices in series to reach these limits! Thermal loading on pistons and exhaust valves (and catalytic converters) is a big issue.

Direct-injection can help with knock control but they all run premixed-combustion under load which limits how far this can be taken. Diesel-style injection late in the compression stroke is resistant to detonation but not good for emissions. (same PM and NOx issues as diesel has)

Yes, higher octane fuel (including ethanol) would help with this! It addresses the knock, but not necessarily the thermal loading. You can still melt a piston or an exhaust valve without detonation, although detonation makes it happen a whole lot sooner and faster.

As mentioned above, I am quite sure that Ford crunched the numbers and did the simulations, and ended up with an exhaust-driven turbocharger on the Ecoboost for good reason. Use of a turbocharger is still compatible with running cam timing that emulates the Atkinson cycle at part load, to divvy up the energy in the exhaust between the pistons (turning the crankshaft) and the exhaust turbine (turning the turbo compressor).

Yes, the supercharger will give more boost right off idle ... where detonation is at its worst. Or you can just change into the right gear when you need power, instead of lugging the poor thing ...

dursun

An electric driven compressor/turbo addresses the problem in simpler way.

Kumar Paran

May 2016 - Chris Brace, Professor of Automotive Propulsion, University of Bath

"The results of our on-engine dynamometer testing and analysis confirm that V-Charge can match or exceed the performance of other advanced boosting systems over a broad range of performance attributes. We believe that the technology offers a UNIQUE, purely mechanical solution, to engine boosting systems and is a key enabler for engine downsizing, a critical element of OEMs roadmaps to meet the challenging emissions targets whilst maintaining vehicle performance and driveability." - Unquote

goldalf

It is "boiled down" to the Super Metal, Compacted Graphite Iron

Compacted Graphite Iron (CGI) provides at least 75% higher tensile, 40% higher stiffness and approximately double the fatigue strength of conventional grey cast iron or aluminium alloys. The fatigue strength of CGI is up to five times higher than that of aluminium at elevated temperatures. In comparison to ductile iron, CGI provides superior castability, thermal conductivity and machinability. These combined properties of CGI offer cost-effective solutions for complex components that are subjected to mechanical and/or thermal loading

SJC

I agree that an electric supercharger probably make more sense.

ai_vin

I too agree that an electric supercharger makes more sense. And it reminds me that I have had this link - http://www.cpowert.com/ - in my favorites menu for a few years. Glad to share now.

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