DFCO questions

[Jay2TheRescue]

Originally Posted by theholycow

Oops, I don't know why I thought yours was a '99, that would be the new body style...

ScanGauge isn't good at detecting DFCO nor can it measure fuel rate. It reports fuel rate by guessing and calculating. Set one of its readings to show Open/Closed Loop; if you see Open Loop while off the gas pedal you're almost certainly in DFCO.

In my 2002 5.3, it takes 6 to 10 seconds of engine braking above 1500 rpm before it will DFCO. For demonstration purposes, take it up to 70mph and drop to 3rd; that should put you in the 2500-3000 rpm range and should last long enough to assure DFCO even if you're not going downhill.

I will have to put open/closed loop on there again. I took it off the other day for CPM. I wonder then, if going downhill on I-95 if its DFCO'ing in OverDrive? We do have some really long hills on the highways around here. DFCO would be nice to do on the highway.

-Jay

[theholycow]

It could DFCO downhill in OD...you'll find out.

[Jay2TheRescue]

Originally Posted by theholycow

It could DFCO downhill in OD...you'll find out.

I'll look for it now... Before I didn't think it was even a possibility. Now I just have to figure out how to get it into DFCO and keep it there. Maybe I can push my mileage up with this. If I can confirm DFCO then I won't be scared to engine brake either. My guess was that it overreved the engine so more fuel is sent to the injectors. As you mentioned earlier too, I wonder what's involved in reprogramming the computer to go into DFCO earlier...

[GasSavers_BEEF]

the way I noticed it on my wife's honda was the fact that the MPG meter hit 9999 so I figured that is what it was. I thought it was just on hondas like the VX or something super fuel efficient and sold that way.

obviously I was wrong

[R.I.D.E.]

I think it is on most cars, at least it was first noticed by me on early Nissan Z cars with fuel injection, beginning in 1975.

When you take your foot off the gas pedal, before FI you had to add air to the exhaust to burn off the hydrocarbons. With FI you can simply kill all fuel to the injectors.

Put the car in any gear and let off the gas at bout 2500 RPM, see if it kicks back in (fuel delivery) at a lower speed. On my VX with AC it comes back on at BOUT 1300 rpm, and will actually keep the car going at a significant speed.

regards
gary

[Jay2TheRescue]

Originally Posted by R.I.D.E.

I think it is on most cars, at least it was first noticed by me on early Nissan Z cars with fuel injection, beginning in 1975.

When you take your foot off the gas pedal, before FI you had to add air to the exhaust to burn off the hydrocarbons. With FI you can simply kill all fuel to the injectors.

Put the car in any gear and let off the gas at bout 2500 RPM, see if it kicks back in (fuel delivery) at a lower speed. On my VX with AC it comes back on at BOUT 1300 rpm, and will actually keep the car going at a significant speed.

regards
gary

So, any bets on a 76 Eldorado with a an EFI 500 ci V-8?

I know, I'm pushing it...

That would be something to DFCO in a 76 Eldorado though...

[R.I.D.E.]

If it doesn't have an air pump from the factory, it probably has FI and DFCO. at least since 1968-69.

My 76 Z had no air pump, no EGR, and no Catalyst. Federal version. California was different.

regards
gary

[Jay2TheRescue]

Originally Posted by R.I.D.E.

If it doesn't have an air pump from the factory, it probably has FI and DFCO. at least since 1968-69.

My 76 Z had no air pump, no EGR, and no Catalyst. Federal version. California was different.

regards
gary

The 76 Eldorado was a really high tech car for the time, despite the fact that it was a land barge. They came with FWD, EFI, and a 500 cubic inch V8.

-Jay

[theholycow]

Originally Posted by Jay2TheRescue

My guess was that it overreved the engine so more fuel is sent to the injectors.

Therein lies the rub. If it's not in DFCO, it's using MORE gas than at idle speed...the air/fuel ratio has to stay the same and at higher RPM it moves more air. SG's fuel rate readout ought to give you an idea of just how much you're looking at there.

As you mentioned earlier too, I wonder what's involved in reprogramming the computer to go into DFCO earlier...

http://www.efilive.com -- but it's expensive. BlackBear Performance can probably do it, I think they're using a shop-licensed EFILive. I'll probably go with them eventually.

[Jay2TheRescue]

Originally Posted by theholycow

Therein lies the rub. If it's not in DFCO, it's using MORE gas than at idle speed...the air/fuel ratio has to stay the same and at higher RPM it moves more air. SG's fuel rate readout ought to give you an idea of just how much you're looking at there.



http://www.efilive.com -- but it's expensive. BlackBear Performance can probably do it, I think they're using a shop-licensed EFILive. I'll probably go with them eventually.

I tried to DFCO on my way home tonight. The big problem is that the max speed limit between work and home is 45MPH, and I'm only on that road for 1 block. The rest of the way is 35 and 25. I tried to DFCO on the 35 mph stretch... I don't think it happened. On the 25 mph roads there is a relatively steep hill a few hunderd yards long. I tried to keep it in the sweet spot. Whenever it fell to 1600 RPM I'd downshift. Still SG did not report open loop. I guess I can't hit DFCO in my normal driving. I will try to DFCO next time I'm on the highway. If there's a way to make this thing DFCO I will find it. I was going to go to visit my parents tomorrow, but I was planning on taking the Buick as she hasn't been driven in a while and she needs a good highway run. I need to drive it more anyway... I haven't put gas in it since I've joined here... She needs some gaslog data.

-Jay