Saturn experts? DFCO parameters?

[cfg83]

Blacktree -

Originally Posted by Blacktree

I have a ScanGauge II in my '01 Saturn. And I can tell you that invoking DFCO takes some work. I don't know the exact parameters. But it takes more than 1500 RPM to trigger it. Plus there is a time delay, several seconds long. Like I said, I don't know the specifics. But I've only seen "9999" on the instant mpg display a few times, all of which were on long down-dill coasts.

When I see DFCO I don't think I see 9999 MPG on my Scangauge I, but I will watch more closely in the future.

The next time you do the test, be in 3rd gear or higher and above 2500 RPM.

CarloSW2

[YukonCornelius]

You can get DFCO on your own with a kill switch.

[cfg83]

Hello -

This video has some glare but it gets the point across. Basically, watch the red LED digital Air/Fuel Ratio (AFR) indicator. When is says "L" it means Lean, which means the oxygen sensor is indirectly detecting DFCO. This only occurs above 2500 RPM in thrid gear. At 2500 RPM or below, closed loop is king :

http://www.youtube.com/watch?v=avMAIPeKLto

CarloSW2

[arcosine]

I never drive above 2500 rpm, so Ive never seen DFCO in my Saturn.

[davelobi]

Originally Posted by arcosine

I never drive above 2500 rpm, so Ive never seen DFCO in my Saturn.

I don't think my saturn has ever seen 2500 rpm since I've owned it either and I'm in dfco very often.

Read my first post. I constantly get it to kick in at about 2000 rpm and coast (dfco) using zero fuel (just like eoc without having to kill engine) down to around 1500 rpm until I feel the fuel injectors kick back into action.

[Blacktree]

I also rarely rev the Saturn past 2500 RPM. But if I downshift into 4th gear at 50MPH+, I can get the ScanGauge2 to display the magical "9999" mpg reading. And if I let it coast down, it'll hold until around 1300-1400 RPM. If I touch the gas pedal, take the transmission out of gear (it's a manual 5-speed), or let the RPMs drop below that threshold, the "9999" will go away. This seems to suggest that the "9999" reading is caused by DFCO.

But since I live in a relatively flat area, and am not in the habit of downshifting at 50MPH+, I rarely get to see the "9999" reading.

The only other time I see "9999" on the SG2 is when the engine computer is in open-loop mode.

[cfg83]

arcosine -

Originally Posted by arcosine

I never drive above 2500 rpm, so Ive never seen DFCO in my Saturn.

That's why it has little use for me except for steep downhills + engine braking.

CarloSW2