Displacement on demand

[NoDOHC]

So today I was waiting for some parts, so I decided to test a theory that I have had for a while.

My theory is that if I am pulling 45 kPA of vacuum in my intake manifold while driving down the road I either need new gearing or some other technique for increasing the load on the engine (so that less energy is wasted pumping air across the throttle plates). The engine only pulls 71 kPA of vacuum to stay at 2,700 RPM (cruising speed).

Due to the complete lack of taller gearing for my transmission and/or differential. I opted to test plan B - Displacement on Demand (DOD).

I did my before testing on the same stretch of road about 2 hours earlier in the day and datalogged the trip to compute fuel economy.

My test setup was somewhat simple - I simply turned the idle up to 1600 rpm and then unplugged the power wires to the coil packs for the front rotor. This resulted in an immediate drop to about 900 RPM idle (which was fine).

My testing began at this point. I put my gauge page up on my computer, plugged in the inverter and went for a drive.

After about 10 miles on the interstate (+6 miles to get there), I decided to switch which rotor I was running on, so I pulled over, plugged in the front rotor coil packs and unplugged the rear rotor coil packs. I drove the 10 miles back home on the interstate and decided that all was good, so I plugged the rear rotor back in and drove the 6 miles home.

I had two problems: The first was in the driveway while adjusting the idle - the engine stalled on the first try (rotaries don't start as easily on one rotor as they do on 2). The second was that I was idling at a stop sign and my electric fan kicked on, causing the engine to stall (equally annoying to get running again).

Obviously, for this test I got terrible fuel economy, because I was still pumping fuel through the unfiring rotor, but the numbers listed below are indicative of instantaneous fuel economy at steady-state as calculated from injector energized duration (Assuming that the fuel was not flowing to the inactive rotor).

Baseline Average:
Traveling East: 35.3 mpg instantaneous
Traveling West: 29.0 mpg instantaneous

With DOD:
Traveling East: 45.2 mpg instantaneous (ran about 70 mph consistently)
Traveling West: 37 mpg instantaneous (I lost speed on a couple hills with the headwind)

My vacuum levels were:
Baseline Average:
Traveling East: -53 kPA Average
Traveling West: -38 kPA Average

With DOD:
Traveling East: -25 kPA Average
Traveling West -5 kPA Average

Now I am thinking about building an external controller that switches between the rotor at approximately a 30 second per rotor rate with a controlled transition. DOD mode would be activated by the throttle being below a certain level for 15 seconds or so. I would need some idle logic too (otherwise the e-fan kills the engine).

What do you all think?