COT and DFCO??

[Sunburst_SS]

So, I gathered when tuning my VE and MAF I need to be in open loop, and the disable COT and DFCO. How would I go about disabling the COT and DFCO?? Also, when done tuning my VE and MAF do I enable closed loop again? How about COT and DFCO, do I re-enable those as well?? Thanks

[SuperSlow07]

To disable my cot (I dont have a cat) I put the on temps to max (7000 something) and set the minimum and max inrich values to 0.0.


What does dfco stand for?

[Julex]

Closed loop enable would be best unless you don't have any winter, but if you choose not to enable it couldcause rough start ups. COT and DFCO being enabled are your choice, although COT will effect PE fueling so if your tuning for performance leave disabled, and DFCO doesn't mess with anything performance wise just need to disable during MAF and VE tuning.

DFCO and COT tables are in the fueling tabs. Jes set DFCO to max, and set COT fueling to 0.

[Julex]

Decel fuel cut off, it runs the engine leaner when you let off the gas, helps save gas and cuts the ricer exhaust pop (which is unburned fuel in the exhaust) unless you have a backflow muffler then the popping is just airflow pressure.

[Sunburst_SS]

ok, so when I'm done tuning my VE and MAF.....leave the COT disabled when I'm done tuning. After I'm done tuning re-enable the Closed loop and DFCO. Should I just reset those to the previous settings before I disabled them?


then to disable the DFCO just set the enable temp. to the max setting of 493 degrees? And to disable the COT would I change the COT temp. threshold to the maximun setting?

[Sunburst_SS]

also, to disable closed loop....could I just change the ECT vs. Startup ECT to the max value of 306 degrees? Then when done tuning, just change it back to the factory settings?

[an0malous]

Decel fuel cut off, it runs the engine leaner when you let off the gas, helps save gas and cuts the ricer exhaust pop (which is unburned fuel in the exhaust) unless you have a backflow muffler then the popping is just airflow pressure.

DFCO doesnt just run lean. it doesnt give it any fuel at all.
hence the name

and its one reason i always laugh at people who say they are saving fuel by neutral coasting

[Julex]

Well.... it doesn't cut them completely lol or else your engine would stall, your still pumping a little fuel, hence why I said lean, but close enough lol.

Sunburst, you answered all your own questions lol. Tuning is much easier then it seems you think, you already knew the answers. And yes that is all you do to all 3. Simple. And yes put them back to stock, then if you want to modify them do it after back to stock, aka maybe you want dfco only on at a certain point.

[Sunburst_SS]

haha, I was just trying to make sure.....thank for the help

[an0malous]

Well.... it doesn't cut them completely lol or else your engine would stall, your still pumping a little fuel, hence why I said lean, but close enough lol.

Why would it stall?
During decelleration the fuel is not whats keeping the engine turning over, the inertia of the car is forcing the wheels to turn, and hence the engine.

a good way to see this first hand is to just watch your A/F gauge when you decel down from highway speed.
it will enter DFCO, and WHAM so lean your gauge cant read it.


here ya go heres a little snippit on it.

DECELERATION FUEL CUTOFF:
During closed throttle deceleration periods, from moderate to high engine speeds,
fuel delivery is not necessary or desirable. To prevent excessive decel emissions,
and improve fuel econemy, the ECM will not open the injectors under certain decel conditions.
The ECM will resume fuel injection at a calculated RPM.

[Julex]

Look at the Injector pulse width, they still open, I understand your saying it's acting as a air pump, but I've never seen either of my cars in dfco cut fuel 100%, I wouldn't want that since cutting fuel off completely could do more bad than good after a good run, since there would be alot of heat in the cylinders and no fuel to cool it down, you'd be relying on just oil.

[an0malous]

still lots of air flowing through
and there is no longer any burning happening, so the heat would disspate very quickly
remember its the pressure and heat of burning fuel that is making the heat.
thats no longer there now
IMO running a tiny amount of fuel and burning it at very lean conditions in a hot cylinder would be more dangerous than running none at all