With ever increasing fuel prices and more strict emissions regulations, could it be interesting for EMUs to incorporate some optional fuel saving strategies?
I know I’d like to be able to go cruising without breaking the bank, and without compromising performance when it matters.
Dynamic Skip Fire seems like a particularly well-suited strategy for this. The ECU decides whether to cut spark and fuel to whichever cylinder is set to fire next; based on engine harmonics, load, optimal cylinder pressure, optimal throttle angle, EGT, etc.
DSF generally leads to 7-15% reduced fuel consumption and emissions on production vehicles already built for efficiency.
The primary reason for this increased efficiency, is reduction of “active” engine displacement in conditions where full power isn’t required. This in turn reduces pumping losses in the throttle body which is normally almost shut at low load.
On our vehicles built for power, with throttle bodies, combustion chambers or turbos which are massively oversized for cruising and “low-load” conditions; efficiency gains with DSF may be quite a lot higher than for ordinary road vehicles. No performance is sacrificed (in theory), because the DSF algorithm instantly scales “active” engine displacement in response to requested torque. At WOT the ECU requests ignition for 100% of regularly possible ignition events.
I’ve seen in docs that DSF works for V8, V6, straight-6, straight-4 and straight-3. It might work for other configurations as well. Efficiency gain increases with the number of cylinders. Getting harmonics and balance right is a matter of finding an appropriate algorithm.
The technique works for both gasoline and diesel engines.
One major caveat is that DSF basically requires individually deactivatable intake+exhaust valves (like MIVEC-MD, FreeValve, ACT, etc). There are aftermarket options to convert regular OHV and OHC (with rocker arms, mind you) valvetrains to get this function.
ps. EMU support for FreeValve-like systems would also be neat, as that would let engine builders delete camshafts and get complete control of valves as well 