|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.
|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.
|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.