Tula Eliminates Cylinders to Improve Fuel Economy

Cylinder deactivation is not new at all in the automotive world as it has been used for decades. A revolutionary system known as Dynamic Skip Fire from Tula Technologies takes this concept into a new dimension, but with huge fuel economy gains as a result particularly in heavy-duty applications.

In a document presented to this year’s SAE World Congress, Tula explained in detail its DSF technology and the testing process used to validate it. Tests were performed utilizing a 6.2L V8 gasoline engine from GM—an engine that typically resides in everything from muscle cars to commercial vans and heavy-duty pickup trucks. Results showed Tula with 18 percent fuel economy savings through the use of DSF versus the engine with factory deactivation.

The current cylinder deactivation, heavily employed by GM, cylinders are deactivated only when the transmission is in a specific gear and/or the engine runs at a steady RPM rate. With the deactivated cylinders always the same, most engines run deactivation in two cylinders at a time in fixed operation modes. Instead, the Tula system is activated on a cycle-by-cycle basis.

Running cycle-by-cycle suggests that the cylinders are deactivated inpidually, as required, and on the fly. In order to make up for the potential energy loss and noise increases, DSF increases air mass in firing cylinders to increase torque and reduce friction losses. This enables an array of firing pattern selections and minimizes overall wear on the engine as a whole.

The production L94 6.2L V8 has gone through modification to include the Tula Technology DSF and was mounted in a 2010 GMC Yukon Denali SUV. Meanwhile, hardware modifications included the addition of production lost-motion lifters on intake and exhaust valves, a new lifter oil manifold assembly with a solenoid system for directing oil to lost-motion lifters, and changes in oil routing to help facilitate lubrication of lost-motion lifters. Of these modifications, only the lifter oil manifold was not a stock GM part that had to be fabricated.

Findings were promising in independent laboratory testing. DSF led to the engine’s combustion stability enhancing over the stock GM cylinder deactivation, particularly in the lower load range where a V8 is proven at its weakest. The increase of air mass in active cylinders has paved the way for DSF to counter the intrinsic losses associated with deactivation at low loads and improved thermal efficiency. Furthermore, the DSF system enhanced heating of the catalyst in the catalytic converter, leading to lower NOx emissions in some conditions.

GM owns a stake in Tula; hence, can directly benefit from the cutting-edge Dynamic Skip Fire technology.