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Fallbrook Technologies Inc. developing variable speed supercharger drive using its CVP technology

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Performance of supercharged Mustang with and without NuVinci CVP; variable ratio vs. 1:1. Source: Fallbrook. Click to enlarge.

Fallbrook Technologies Inc. is developing a variable speed supercharger utilizing its NuVinci continuously variable planetary (CVP) technology. (Earlier post.) Fallbrook has targeted and is soliciting select automotive OEMs for such a variable speed automotive supercharger.

Fallbrook says it has been working closely with a tier one automotive equipment supplier on the development of the device. Test results from that supplier have demonstrated potential fuel-saving, engine down-sizing and/or down-speeding opportunities without adversely affecting performance and drivability.

The NuVinci CVP uses a set of rotating and tilting balls positioned between the input and output components of a transmission that tilt to vary the speed of the transmission. Tilting the balls changes their contact diameters and varies the speed ratio.

Performance gains result from boost optimization over a wider power band, particularly at low engine speeds. NuVinci prototypes designed for use in an OEM application have also passed automotive class durability testing by the tier one supplier.

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Schematic of variable speed supercharger drive. Click to enlarge.   Prototype variable speed supercharger drive. Click to enlarge.

Fallbrook believes, based on testing and independent analysis, that vehicle manufacturers can utilize smaller, more efficient engines with no loss in performance or drivability, thanks to the capability to tailor supercharger boost to driver demand offered by a NuVinci-enabled supercharger.

By controlling supercharger speed independent of engine speed, the NuVinci CVP enables ingestion of only the airflow required by the engine with little to no bypassing, thereby minimizing bypass losses and their associated NVH issues.

In light of the successful test results, Fallbrook and the tier one manufacturer are currently in discussions with potential OEM customers for the NuVinci supercharger drive. Fallbrook believes the drive can be packaged easily, as the current prototype is designed to mate with an existing supercharger line of products.

Fallbrook initially demonstrated its development of a variable speed supercharger drive by designing and building a prototype system coupling a NuVinci CVP with an aftermarket supercharger.

The demonstration car is a 2008 Mustang Bullitt, equipped with a ProCharger supercharger, and a NuVinci DeltaSeries continuously variable speed drive. With assistance in tuning by Lingenfelter Performance Engineering, it demonstrates considerable performance increases at lower engine speeds, when the variable speed drive is activated. The Bullitt prototype has logged more than 3,000 demonstration miles, and remains operational today for regular demonstrations.

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Simulated performance of downsized 2.0L I4 with Fallbrook supercharger drive. Click to enlarge.

Using an SUV equipped with a 3.6L V6 engine as a baseline, Fallbrook has also simulated the use of a downsized 2.0L I4 engine which has been supercharged in production. In the graph at left, engine torque is depicted on the Y axis, and engine speed on the X axis. The blue dashed curve represents torque from the standard 3.6L V6 engine.

A normally aspirated 2.0L I4 engine would result in the lower curve, producing about 175 N·m peak. By supercharging this engine (grey curve), more than 330 N·m can be produced, approaching the 350 N·m capacity of the larger engine. However, this peak output only comes at the top end of the engine speed range; the vehicle remains underpowered throughout most of the range.

The green area is the chart represents the increased low-end torque generated by a downsized gasoline engine, as compared with the same engine without the supercharger. The red line indicates that the smaller NuVinci supercharger-equipped engine performs on a par with a larger engine.

The NuVinci supercharger drive is part of the NuVinci DeltaSeries line of accessory drive solutions. The NuVinci DeltaSeries line eliminates the compromise of fixed ratio accessory drives by de-coupling accessory RPM from engine RPM. Other DeltaSeries drives in development include applications for HD vehicle cooling fans, high output alternators, AC compressors, and engine crank-mount units, which control the speed of the entire accessory beltline.

Comments

HarveyD

This could become another way to further downsize ICEs from 2.0 L to 1.2 L or so.

Nick Lyons

Don't modern variable-pitch turbochargers do the same thing, only more efficiently, since they use some of the exhaust waste heat instead of adding load to the engine? E.g. Ford's Ecoboost engines.

This is cool tech, but I think ICEs are moving more towards electrification of accessories and away from belt drives altogether.

kelly

Where were all these ICE gains before EVs hit the market with 100+mpge..

HarveyD

Very good question Kelly. They were in neutral.

Engineer-Poet

Even a variable-geometry turbocharger requires a certain amount of airflow and time to spool up.  A supercharger doesn't have that (though I think electric may be better than mechanical drive).

It's certain that a supercharged engine wastes a lot of energy as exhaust pulses.  A compounding turbine can capture that and feed it back using e.g. BAS-type motors, and I believe we've seen some concepts with all of those elements.

Nick Lyons

@E-P: I don't think responsiveness is much of a problem with the latest turbo designs, while energy-efficiency has become the overriding concern. This CVT/supercharger enables downsizing, which has efficiency benefits; I just think it's likely to be too little to late. Electric supercharger/turbocharger combos are another way to address any turbo-lag/low RPM issue with turbos. Also, anything relying accessory belt drive is likely to be a short term solution, IMHO--I think belts are on the way out.

Nick Lyons

@E-P: I don't think responsiveness is much of a problem with the latest turbo designs, while energy-efficiency has become the overriding concern. This CVT/supercharger enables downsizing, which has efficiency benefits; I just think it's likely to be too little to late. Electric supercharger/turbocharger combos are another way to address any turbo-lag/low RPM issue with turbos. Also, anything relying accessory belt drive is likely to be a short term solution, IMHO--I think belts are on the way out.

ToppaTom

Where were all these EVs before "EVs hit the market with 100+mpge"?

Engineer-Poet

Nick, I think you're right about belts; the electric bus, whether 13.8 V, 42 V or higher seems to be the target.

The question is what's going to wind up on it, and how.  A battery or ultracap plus BAS can make up for turbo lag, which would allow a supercharger/TIGERS combo to be replaced by a much smaller turbocharger.  VVT implementing the Miller cycle recovers the exhaust energy recycled to supercharging as crankshaft work.  The question is, how much does it cost vs. rolling balls?

The one thing we can know for certain is that the answer changes over time.

Roger Pham

Too little too late, Nick?
How about considering this: A NuVinci on one end controlling the supercharger, and another NuVinci on the other end moderating the exhaust compounding turbine, feeding excess exhaust energy back to the engine? No need for energy-wasting "waste gate."

The cost and weight of this set up will be a lot less than an analogous electric setup with electric motor/generator pair, allowing higher market penetration and more fuel saving potential. There may be a modest gain in efficiency as well when electrical losses are avoided with this totally-mechanical setup.

I'm real excited to see this concept demonstrated successfully on a highly-functional, high-performance prototype. I wish the best for their success.

Peter_XX

@Roger
I fully agree with your analysis! This would be an interesting concept. The only comment I would like to add is that you may need a two-stage turbine setup. The reason is that with a very high level of turbocharging, the pressure drop over the turbine would be too high to get high efficiency in only one stage. Recall that a conventional turbocompound engine has one turbine in the turbocharger and one “power” turbine, i.e. two turbine stages. The ideal two-stage “power” turbine could be a radial turbine in the first stage and an axial turbine in the second stage.

Roger Pham

Agree, Peter.
Two-stage turbocompounding in an Otto-Diesel cycle engine is more efficient at part-load than a Miller cycle engine with a single turbocompounder, while the Otto-Diesel engine has higher power density.

joe.vanni

Replace an 3.6 with a 2.0 engine means roughly halve weight and cost of the engine.
It 's amazing the constant torque at 350 Nm in the range between 2000 and 5000 RPM.
Excellent solution as a range extender especially for trucks. The engine designers are playing theirs final trump and is better for them to do so now, before it is too late..

kelly

"Where were all these EVs before "EVs hit the market with 100+mpge"?"

Like the enabling NiMH EV battery patent, sitting on a oil/auto shelf.

Face it, as with average auto mpg being in the twenties for a hundred years, big auto/oil, especially US, are happy with the poorest gas mileage the traffic will bear.

Directly, or indirectly, electric vehicles are responsible for the 20% increase in mpg during the last four years.

Peter_XX

@Kelly
EVs are not necessarily better than HEVs in a well-to-tank comparison. With US electricity mix, they could even be worse than HEVs. Look at page 116 in the report below. Electricity via plug-in HEVs seems to be the most efficient way to substitute fossil fuels.

http://web.mit.edu/sloan-auto-lab/research/beforeh2/files/kromer_electric_powertrains.pdf

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