DFCO settings on a 93 lt1 corvette w/ $DA2

dizwiz24 · Post by **dizwiz24** » Mon Nov 12, 2012 3:32 pm

I wanted to ask about where my DFCO (deceleration fuel cut off) settings should be at for best performance (smoothness and fuel economy).

I have a bunch of scalars and tables for this on my $DA2 definition file.

I have:
DFCO enable RPM
DFCO disable RPM
DFCO enable MAP
DFCO disable MAP
DFCO diasble RPM decrease threshold
DFCO enable coolant temp threshold
DFCO enable TPS threshold hysteresis

For the tables I have:

DFCO enable TPS threshold vs. RPM
(currently set around .78 to 1.2% threshold from 0 rpm to 3600 rpm)

Any help on optimizing thse settings is appreciated.

The car is a 93 supercharged corvette lt1 with zf6spd transmission, 60 lb/hr fuel injectors, headers, cam, heads, ostrich, etc.

Post by **Mangus** » Wed Nov 14, 2012 4:06 pm

Are you having DFCO-related issues that you're trying to tune out? Generally, DFCO should be set up to engage when you're completely off the throttle under pretty much all conditions above a certain RPM threshold (e.g. 1200 RPM), with a bit of hysterisis between engage and disengage. Most likely the stock settings are correct, unless you've changed out your load-sensor setup (MAF/MAP), in which case you may need to change the load-based enable/disable settings.

But basically, enable above 1200, and remain (disable RPM in your list) until 1000. Set the load settings only as light as is needed for off-the-throttle enablement of DFCO.

dizwiz24 · Post by **dizwiz24** » Sat Nov 17, 2012 4:18 am

Ok this is good info as my dfco is set to engage below 1200 rpm, which you advise against.

I can zero that out.

People on other forums say I should just zero the whole dfco out to eliminate it entirely

Post by **robertisaar** » Sat Nov 17, 2012 6:50 pm

i don't use DFCO so much for fuel economy gains (though there is some to be found if you drive in the right situations often enough), but i use it more for engine braking to save on the actual brakes.

decipha · Post by **decipha** » Sat May 04, 2013 3:34 pm

Also worth noting, dfco can cause the wheels to lockup if you have a locker rear end at high speeds

Had it happen once coming through the traps, back wheels locked up and the car went sideways at 145+ mph, thank god the driver survived with minimal injuries

In any case I always put a 3 second delay at CT before allowing dfco