Solutions to ECU going open loop?

[oldtamiyaphile]

My Renault has the annoying habit of going open loop for about 10 seconds each time the engine is started (bump or key).

I believe it's costing me up to 2L (~1/2 gal) per tank as if I drive normally the onboard fuel level (in litres to on decimal place) is basically spot on. Throw in a bunch of hypermiling, and the tank is dry with the display suggesting I still have 2L left. I'm assuming that the onboard fuel level doesn't correctly account for enrichment, causing the discrepancy. It follows that if I could stay away from this rich open loop mode, I could save nearly that amount.

So the question is, what can be to mitigate the problem?

Driving technique.

1. Bump starting early and letting the engine DFCO for ~10 seconds so it's in closed loop when it's time to go again. This is great for lights, turns and stops, but it's not practical for EOC.

2. Bump start and let the engine idle for ten seconds, before accelerating. This might work OK some of the time, like bumping knowing that a light is about to change/ waiting for the traffic to move at a newly green light

3. Keep the car in gear as long as possible. DFCO usually disengages at ~1200rpm, but if you key off at 1200rpm, you can force DFCO down to 800rpm or less, when you key back on, push the clutch in as soon as the tacho needle swings, the engine starts and stays in closed loop. The engine has practically no engine braking at ~800 so this technique actually works really well (especially loaded or towing) - if only I had taller gearing.

Car mods:

I don't really know, but considering #3 in driving techniques, I'm thinking it should be possible to emulate this state while EOC.

So what ideas do you guys have for closing the open loop gap?