Civic DFCO Conditions - Fuel Economy, Hypermiling, EcoModding News and Forum

ben98gs · 04-30-2010, 08:39 AM

I remember reading this at one point, but just spent what seemed like forever searching as many different terms as I could to try and find it, to no avail.

Anyone have a link to the conditions that need to be met in a Civic for DFCO? If it matters, my car is a '95 DX.

dcb · 04-30-2010, 09:06 AM

if you have a convenient kill switch (mine is a small microswitch on the gear shifter) you can tell when you are NOT in dfco, as the sound will change when you hit the button and you may notice a faster deceleration.

if you have a mpguino, your instant gph should go to zero and your instant mpg should go to 999999 when in dfco

FYI, I don't think an OBD II open loop indicator necessarily means dfco, could mean any change from closed loop. In fact now that I think about it, the metro would show open loop any time I decelerated in gear, but later monitoring of the injector revealed more specific conditions.

iirc, my metro would not go into dfco unless I was going above 40mph and would drop out of dfco (start burning fuel again) at about 25mph, in top gear.

This might be a good wiki candidate too to "publish" different dfco conditions for different cars
http://ecomodder.com/wiki/index.php/Main_Page

PaleMelanesian · 04-30-2010, 09:59 AM

On my 1996, it has to be in gear, foot off the pedal, and above 1200 rpm. If you try a few coast-downs, you can feel a "surge" when the fuel flow comes back on. Our cars are different generations, sort of, but both have D-series engines.

With a DX, I'm assuming you also, like me, have no tachometer. Note the speed and which gear you're in for the coast-down, and you can calculate the rpm. Example: Max speed in 2nd gear is 62 mph. DFCO shuts down (surges) at 11 mph. Max rpm is 6900. 6900*(11/62) = 1224 rpm.

ben98gs · 04-30-2010, 12:42 PM

Quote:

Originally Posted by PaleMelanesian

On my 1996, it has to be in gear, foot off the pedal, and above 1200 rpm. If you try a few coast-downs, you can feel a "surge" when the fuel flow comes back on.

I can feel it in the lower gears, but not in the higher... One of the main things that I was wondering about was if it was linked to the brake switch as well. That is part of the reason I was looking for the post, because whatever post I remember reading I almost want to say that it says the DFCO kicks off (or in other words the injectors start again) when the brake is pressed. I did some DFCO last tank but did brake while decelerating in gear (normally I just shift to neutral while braking) and MPG went down... So I was trying to prove (to myself at least) that this was because I was failing to DFCO because I was braking.

Quote:

Originally Posted by PaleMelanesian

With a DX, I'm assuming you also, like me, have no tachometer. Note the speed and which gear you're in for the coast-down, and you can calculate the rpm. Example: Max speed in 2nd gear is 62 mph. DFCO shuts down (surges) at 11 mph. Max rpm is 6900. 6900*(11/62) = 1224 rpm.

Does not apply... I swapped in a tach a while back, but you are correct, it did not have one originally.

Quote:

Originally Posted by dcb

if you have a mpguino, your instant gph should go to zero and your instant mpg should go to 999999 when in dfco

Maybe I should just wait and not try to DFCO until I have my MPGuino hooked up (currently started assembling the parts last night I had acquired to build my own "kit").

Just wish I could find the information that I remember reading. I do not remember if it was on here or somewhere else... And hell, for that matter it could have even been for another car (not the Civic) and I just made it up in my mind that it was for the Civic... lol Would not be the first time I remembered something incorrectly.

If I do find it though, I might try and figure out how to add it to the wiki and start a DFCO condition list.

comptiger5000 · 04-30-2010, 02:38 PM

Also, be aware of this: Even if it stays in DFCO down to 1200, it may not enter DFCO unless you're above 1500 or so.

PaleMelanesian · 04-30-2010, 02:53 PM

Not true on mine. Engine braking above 1200 rpm, triggers an Open Loop status on the ECU, which indicates DFCO.

I try to avoid dfco. It's more efficient to start an EOC glide earlier, than to burn a little more gas and then bleed it off through any kind of braking. DFCO is braking.

ben98gs · 04-30-2010, 04:34 PM

Yeah, but most of the hills that I go down have stop lights at the bottom of them that during my daily commute I would say I get stopped at them 80% of the time. I actually saw a decrease in MPG when I would EOC on my daily commute. If I can DFCO down the hill, it would be great, because more than likely I will have to brake anyway.

But again, that is why I want to know the conditions, because if using the brake causes it to kick out of DFCO, that would be good to know so I could just neutral coast rather than trying to DFCO when it wont.