Interesting SG2 observations.
 

My car is stick, to clear up any confusion.

My MAP reading is usually 3.9-4.1 when I'm idling at a red light in neutral with the foot on the brake. GPH is 0.2

My MAP reading is 3.6-3.9 when I am idling at a red light in neutral with no foot on any pedal. GPH is 0.2

My MAP reading is 3.6-3.9 when I'm idling at a red light in neutral with the clutch pedal pressed and no other pedal pressed. GPH is 0.2

My MAP reading is 3.5-3.3 when I'm idling at a red light with the clutch pedal pressed in and the stick into 1st gear and no other pedal pushed in. GPH bounced back and forth between 0.1-0.2

The lower the MAP and GPH reading the more gas you save. Any comments or observations you guys see?

According to wikipedia, the source of all knowledge in the known universe. MAP = BAP - Manifold Vacuum. So when you hit the brake, you're bleeding a bit of the manifold vacuum, and the MAP reading is higher than in N w/ no foot on any pedal, but since engine speed is the same, idle fuel consumption is the same. What's funny is that the clutched being pushing in w/ the car in first does something. I wonder, does engine speed change at all when the car's put into first w/ the clutch in? If Honda had the ECU drop the idle speed just a bit when first was selected, that might explain why MAP/gph drops.

The engine speed drops from 650+ to around 615~625. You guys have anymore interesting observations?

brake light loads the alternator and MAP is higher without load and or engine braking and lower with throttle - it is a vacuum measurement higher vacuum means engine is trying to take more air in than the throttle opening will allow resulting in less gas being burned. Clutch in releases the transmission input shaft load on the engine but puts a throwout bearing load on the engine and end bearing crank load.

That must be it then. Clutch in plus first gear results in the ECU dropping engine speed. It's kinda interesting, because it also implies that like JanGeo said, when the clutch is in and input shaft disconnected, there isn't any change in fuel consumption. So, when you're not powering anything, fuel consumption at idle seem to be directly proportional to idle speed. :thumbup:

now use this to your advantage.

I know a lot people on here have SG2's. You guys haven't dscovered anything?

Mine drinks gas no matter what I do :D Then again the Jeeps ECU is rather stupid