DFCO tuning

[LETZRIDE]

Just a few questions on tuning DFCO for a 2002 LS1 Camaro. My car is bolt ons currently with a 3600 stall, it appears as if I just do not hit DFCO conditions at all as the car always wants to command 14.7 while coasting, foot off the gas on the highway.

so I am trying to get a more aggressive fuel efficient tune on here for the street.

Looking at the DFCO tables, I have some questions/clarification that I need.

Starting under the cutoff, DFCO tab

1) what does hysteresis mean?
2) Enable RPM vs Gear > Entry - is set at 1500 for all gears it says the engine RPM must exceed this value? meaning what- that in order for DFCO to occur, my rpm must be above 1500 rpm while below my throttle threshold?
The exit table is set to 900 and also says it must exceed that value...am I understanding correctly in that the exit number is once that RPM is below that number, you drop out of DFCO?

So in other words, your entry and exit values are your range in which DFCO operates? Hp tuners words this weird in my opinion...

3) my entry Baro is 18 exit is 28 kpa...again is my operating range only in between those values? That seems like a very small window?

4) Can someone better explain the DFCO entry spark threshold? This is the degree spark advance that must be reached to turn the fuel off...what does this mean?

5) we have two spark advance tables- A and B... one is set at 100% tps the other is at 99%...do we not use these tables then?

6) What is the "Stall" mine is set to 800 rpm...


sorry if some of these are dumb questions... my problem is if I don't understand the explanation of each function, I can't strategize or figure out how to best set the car up. I wish Hp tuners had a better glossary/explanation of terms

[mowton]

Just a few questions on tuning DFCO for a 2002 LS1 Camaro. My car is bolt ons currently with a 3600 stall, it appears as if I just do not hit DFCO conditions at all as the car always wants to command 14.7 while coasting, foot off the gas on the highway.

so I am trying to get a more aggressive fuel efficient tune on here for the street.

Looking at the DFCO tables, I have some questions/clarification that I need.

Starting under the cutoff, DFCO tab

1) what does hysteresis mean? To prevent from oscillating in and out of a selected value (turn off at a value of 1.00) a window is setup for enable and disable control. Hysteresis is that window. In this example, when a value his 1.00 it would turn off something, without hysteresis, when the value went to .99 it would turn on again. This would cause the enable/disable to oscillate on and off under normal conditions. If you assigned a hysteresis value of say .1, the signal could vary between 1.0 and .9 after satisfying the turn-off criteria of 1.00 and stay off until the signal hit .9. Allowing normal signal variances from causing on/off oscillations.

2) Enable RPM vs Gear > Entry - is set at 1500 for all gears it says the engine RPM must exceed this value? meaning what- that in order for DFCO to occur, my rpm must be above 1500 rpm while below my throttle threshold? Yes
The exit table is set to 900 and also says it must exceed that value...am I understanding correctly in that the exit number is once that RPM is below that number, you drop out of DFCO? Yes, based on the hysteresis as explained above

So in other words, your entry and exit values are your range in which DFCO operates? Hp tuners words this weird in my opinion...

3) my entry Baro is 18 exit is 28 kpa...again is my operating range only in between those values? That seems like a very small window? ​DFCO says you have come off the throttle and your Throttle body blade is closed and there is actually negative torque being demanding so there is no load on the engine. This will result in very high vacuum (low Map) and that is what is used to in part to trigger DFCO. reapplying the pedal will disengage DFCO and your map will then increase and in a stock setup with stock cam those are reasonable values. If you have a cam or a vacum leak, you may not be able to hit the 18 kPa trigger. To that you either fix the leak or increase the value to match the cam influences.

4) Can someone better explain the DFCO entry spark threshold? This is the degree spark advance that must be reached to turn the fuel off...what does this mean? My understanding of this value is as the spark is reduced in DFCO, it must be reduced to this level to enable fuel cutoff. Just another of the many triggers that must be satisfied to enable fuel cut in decel.

5) we have two spark advance tables- A and B... one is set at 100% tps the other is at 99%...do we not use these tables then? I The spark values are the set poins per rpm when in decel. I have to say I don't know what the TPS at 100% and 99% distinguishes other than maybe WOT vs Non-WOT...Hopefully someone else can help. Looks like a description deficiency perhaps :-)

6) What is the "Stall" mine is set to 800 rpm... Again under my understanding, under no circumstance can the fuel remain shut off at an rpm lower than 800 rpm, again a stock value where idle is like 550 rpm....a fail safe.


sorry if some of these are dumb questions... my problem is if I don't understand the explanation of each function, I can't strategize or figure out how to best set the car up. I wish Hp tuners had a better glossary/explanation of terms

[LETZRIDE]

Thanks- I got it working now, but I have a few questions still.

First for the Enable MAP vs Baro both the entry and exit values must be below the number specified in the table...this has me confused? how do both the entry and exit numbers need to be lower?

Secondly after getting DFCO to work, I unplugged my hp tuners and plugged my aeroforce gauge back in the Camaro which has a function for instant mpg. I took the car for a spin, let off the throttle at highway speeds and before the car enters DFCO I read an instant of about 50-53mpg (still decel just at stoich) then DFCO kicks in and my instant mpg drops to 47-49mpg which is not what I was expecting given I am now cutting fuel and going from 14.7afr to 17's

So that made me look at spark- during decel when dfco is active I am getting an advance of only 2.5-3* of spark whereas I was coming from about 40*...that is a drastic drop is that normal? What should I have my spark be at when in DFCO?

[mowton]

Thanks- I got it working now, but I have a few questions still.

First for the Enable MAP vs Baro both the entry and exit values must be below the number specified in the table...this has me confused? how do both the entry and exit numbers need to be lower? I assume that to be in error in the description and read it as enable and disable...

Secondly after getting DFCO to work, I unplugged my hp tuners and plugged my aeroforce gauge back in the Camaro which has a function for instant mpg. I took the car for a spin, let off the throttle at highway speeds and before the car enters DFCO I read an instant of about 50-53mpg (still decel just at stoich) then DFCO kicks in and my instant mpg drops to 47-49mpg which is not what I was expecting given I am now cutting fuel and going from 14.7afr to 17's Are the mph,rpm, airflow values the same for each mpg reading. Perhaps a difference in how the it calculates MPG....

So that made me look at spark- during decel when dfco is active I am getting an advance of only 2.5-3* of spark whereas I was coming from about 40*...that is a drastic drop is that normal? What should I have my spark be at when in DFCO?

​With no fuel you don't need timing...moves it very close to TDC.

[6speedblazer]

Thanks- I got it working now, but I have a few questions still.

First for the Enable MAP vs Baro both the entry and exit values must be below the number specified in the table...this has me confused? how do both the entry and exit numbers need to be lower?

Secondly after getting DFCO to work, I unplugged my hp tuners and plugged my aeroforce gauge back in the Camaro which has a function for instant mpg. I took the car for a spin, let off the throttle at highway speeds and before the car enters DFCO I read an instant of about 50-53mpg (still decel just at stoich) then DFCO kicks in and my instant mpg drops to 47-49mpg which is not what I was expecting given I am now cutting fuel and going from 14.7afr to 17's

So that made me look at spark- during decel when dfco is active I am getting an advance of only 2.5-3* of spark whereas I was coming from about 40*...that is a drastic drop is that normal? What should I have my spark be at when in DFCO?

the aeroforce gauge freaks out a bit when DFCO comes in. at least in my experiences. On an aeroforce gauge instant MPG goes DOWN when dfco kicks in. I can do the same thing with a scan gaugeII and it shows 9999 for MPG.

i never got my aeroforce gauge to rear correctly in DFCO and aeroforce was no help.

[LETZRIDE]

​With no fuel you don't need timing...moves it very close to TDC.

even if it is enable and disable it still doesn't make sense to me. I mean I have it working right now, but I need a better explanation on enable MAP vs Baro for entry and exit so I can fine tune it a little more...entry I believe I understand, exit im baffled.

Are the mph,rpm, airflow values the same for each mpg reading. Perhaps a difference in how the it calculates MPG....

good point, not sure on the calculations as this uses a predetermined PID in the gauge and not an hp tuners one I can edit.

the aeroforce gauge freaks out a bit when DFCO comes in. at least in my experiences. On an aeroforce gauge instant MPG goes DOWN when dfco kicks in. I can do the same thing with a scan gaugeII and it shows 9999 for MPG.

i never got my aeroforce gauge to rear correctly in DFCO and aeroforce was no help.

I remember being on a hill doing 80mph or so and I popped the car into neutral and went from 50mpg to like 100mpg before I had dfco...now I pop the car into neutral and it reads the same as the DFCO engaged reading does...which can't make sense...im cutting fuel, therefore I must be getting better mileage.

I figured that thing would be pretty accurate determining fuel mileage as it reads injector pulse, gas in the tank, airflow and all that fun stuff right from the OBD port...

[LETZRIDE]

​With no fuel you don't need timing...moves it very close to TDC.

What do you mean moves it very close to TDC?

[6speedblazer]

even if it is enable and disable it still doesn't make sense to me. I mean I have it working right now, but I need a better explanation on enable MAP vs Baro for entry and exit so I can fine tune it a little more...entry I believe I understand, exit im baffled.



good point, not sure on the calculations as this uses a predetermined PID in the gauge and not an hp tuners one I can edit.



I remember being on a hill doing 80mph or so and I popped the car into neutral and went from 50mpg to like 100mpg before I had dfco...now I pop the car into neutral and it reads the same as the DFCO engaged reading does...which can't make sense...im cutting fuel, therefore I must be getting better mileage.

I figured that thing would be pretty accurate determining fuel mileage as it reads injector pulse, gas in the tank, airflow and all that fun stuff right from the OBD port...

Aeroforce never would tell me their formula for calculating instant econ, but it cant be using injector pulsewidth because of how it reacts.

[6speedblazer]

What do you mean moves it very close to TDC?

timing goes from say 20* advanced when driving to almost 0* advanced when in DFCO. Ignition advance is referenced from TDC or top dead center.