A while back I started this post looking for saturn specific parameters for dfco..
http://ecomodder.com/forum/showthrea...ers-26812.html
Turns out exact answers are non existant because the variables are so stinkin' high. I talked to an executive in advanced engine developement (from one of the domestic auto makers) about DFCO. I was probing for some more answers but left with more information but no actual answers. He said that there are thousands of lines of programming for DFCO alone in the cars ecu.
I struck out on my own to find some answers. I borrowed a listening device and hooked it to one of my fuel injectors. This thing is cool. It has long leads with clips on one end that plug into a small box in the car that also has headphones to listen with. It is often used to find a bad wheel bearing for example. You clip one lead near each wheel and can flip back and forth and listen for the offending item. I clicked it on a fuel injector so I could hear when it was pulsing (clicking) and when it was silent (not squirting the liquid gold we are all trying to conserve).
At first my ears were getting sore from the cheap heavy head phones until I discovered they had enough volume to hang from my rearview mirror and hear the clicking or lack of. I ran around for about the last ten days or so (which is three fill-ups, I drive a lot) with this thing cllicking away. Listening to the fuel injectors alone will get your foot out of the throttle. Learning the DFCO of my saturn was my main goal and I learned a lot but nothing super concrete. Here is the basics for my car. Yours will have its own parameters of course but you will get the idea.
It seemed to drop out of dfco at about 32 mph regardless of rpm
It dropped out in the 1500-1300 rpm range (a few times 1600 or 1200-ish)
If I backed off the throttle slowly it would not go into dfco (or not for a long time)
If I jumped off the throttle (fast tps closed reading) it jumped into dfco right away
If I wasn't fast enough on the closed throttle it would take 2-3 seconds (sometimes longer) before going into dfco.
If i got off the throttle quick enough and was in dfco but touched the throttle (even slightly for a second) it came out of dfco and would not go back in.
In 5th gear it would drop out from low rpm (usually about 1400-1500 rpm).
In 4th gear it would drop out from low vehicle speed (under about 32mph).
In 3rd gear it would drop out from low speed as well.
It was satisfying to be driving along at 55mph and jump off the gas and hear the annoying high speed ticking on my mirror go silent. I knew for certain that as I coasted down quietly that my fuel injectors were not shooting any gas. Another method for seeing this in action (aside from the listening tool or expensive instrumentation) would be to put a little led inline with one of your fuel injectors and watch the light blink or go off.
Another thought on DFCO that I have not read here is you go a little further than you think. I have heard mention about all that compression slowing you down. It is but not quite as much as you think. For compression to happen in the first place you need air to compress. With the throttle plate closed, very little air is entering the cylinder on each intake stroke. I absolutly know the value of EOC as referenced in my above mentioned post. I have avoided it on this car because the fuel pump is marginal and will leave me stranded someday I suppose if I don't replace it. I have driven over 3000 miles in the month I've had it and not been stranded yet however.
Last note (sorry this post is so long),
I now can easily feel when my fuel injectors kick back on if I have been in dfco.
I can not feel when dfco kicks in because it is usually exactly when my foot comes off the accelerator so car is slowing down anyway. Interestingly, while listening to my injectors, they kick back in (start clicking) a second or two before I "feel" the difference in the car.
I hope this helps someone.