Fuel Saver Technology minimizes consumption, but does not hinder performance.
Awe-inspiring power and respectable fuel efficiency? That’s right, you get them both with the latest Charger, 300, Challenger and Grand Cherokee SRT® models. With a bigger 6.4-liter HEMI® V-8 under the hood, Fuel Saver Technology offers improved fuel mileage, with increased power over the previous-generation SRT powertrains.
Fuel Saver Technology – a torque-based system – deactivates four cylinders when full power is not required. One such common scenario would be while cruising at highway speeds. The even application of throttle during cruising tells the system that it can knock out four cylinders and start saving fuel. Each time the system activates, the same four cylinders are shut off. To keep the driver informed when the system is operating, an “Eco Lamp” is illuminated on the cluster.
“Fuel Saver Technology works electronically when the vehicle is at a steady-state position moving down the road,” said Marty Jagoda, Vehicle Integration Responsible, Chrysler 300 SRT/Charger SRT. “When a large amount of torque is not required to move the vehicle down the road, the system will deactivate four cylinders, and therefore start saving fuel and decreasing emissions as the vehicle is operating.”
Fuel Saver Technology is electronically calibrated to operate within a certain spectrum of both speed and engine RPM. The range of operating speed is from 20-80 mph. There is an RPM window that goes from 1,200 to 3,000 RPM, allowing Fuel Saver Technology to function in multiple gears within the transmission. When Fuel Saver Technology is in operation, cylinders one, four, six and seven deactivate. On the odd bank, those are the two outside cylinders, and on the even bank the two inside cylinders.
“The Fuel Saver Technology cylinders have unique lifters that are controlled by a solenoid valve,” said Jagoda. “The solenoid valves are located in the valley of the engine and with help from the Powertrain Control Module (PCM), determine if the engine runs as a V-8 or V-4. For V-8 Mode, the PCM controls the MDS solenoid to Voltage-X. When Voltage-X is applied, the solenoid valve is in the ‘open’ state, which allows oil to flow through the block, heads and into the lifters like any other pushrod V8 engine.
“For V-4 Mode, the PCM controls the MDS solenoid to Voltage-Y. When Voltage-Y is applied, the solenoid is in the ‘closed’ state, which forces oil to bypass the lifter. When the oil bypasses the lifter, the lifter will engage a lock-out pin and not operate, essentially turning the cylinder off. The engine will operate in this state (Fuel Saver Mode) until the PCM requests Voltage-X to the MDS solenoids and the process starts over again.”
When an SRT vehicle is in Fuel Saver mode, the engine is loaded up more than in V-8 mode. When dropping down to four cylinders, the throttle is opened up more and thus increases the mass flow in the engine needed to produce the level of torque that was being made in eight cylinder mode. The exhaust system was designed to account for this with minimal obtrusion to the driver.
“What’s being transmitted through the exhaust system is four cylinders that are running really nicely and four cylinders that aren’t running at all,” notes Jagoda. “That can create some level of undesirable NVH (noise, vibration and harshness) above and beyond if you were running an eight cylinder engine. The exhaust system has to have both of those aspects in mind. It was a multiple iteration development process, maximizing both V-8 exhaust note and the exhaust note in Fuel Saver Technology.”
The 6.4-liter HEMI engine puts out 45 more horsepower and 50 pound-feet more torque than its predecessor. The entire torque curve on the vehicle was changed to be more driver-friendly. At the same time, fuel efficiency has increased, with a large portion of that attributed to Fuel Saver Technology.
“What Fuel Saver Technology means in the SRT lineup is that we increased performance,” said Jagoda. “At SRT, we are Street and Racing Technology, so our number one goal is to bring race track technology to vehicles with license plates and put them on the street. We’ll never compromise performance or any aspect of performance for items such as Fuel Saver Technology.”
Fuel Saver Technology one of the many functional performance elements that have come to define SRT. It is only offered on current SRT vehicles equipped with automatic transmissions.