Tuning DFCO
08-10-2008 | 12:18 PM
#11
I see what you mean, i think i can work that out in HPT but i get a little more experience before i give it a try.
In DFCO, i just dont really understand how to make the most of it. ex. when i let off the gas going down a hill in drive it takes like 10 seconds for DFCO to kick in but if i manually downshift it seems to kick in almost right away, how do i change that? also, is DFCO cutting ALL fuel, or just some and is there a way to change that as well?
i think i'll do a little more searching to see if i can actually make the lean cruise work. i just cant see GM taking the time to hardwire the inability to use lean cruise into our PCMs. it seems more fitting that they just disabled it and there is some complicated way to re-enable it. maybe i will try and get a hold of a stock Holden tune and see what that looks like. Anybody have one?
In DFCO, i just dont really understand how to make the most of it. ex. when i let off the gas going down a hill in drive it takes like 10 seconds for DFCO to kick in but if i manually downshift it seems to kick in almost right away, how do i change that? also, is DFCO cutting ALL fuel, or just some and is there a way to change that as well?
i think i'll do a little more searching to see if i can actually make the lean cruise work. i just cant see GM taking the time to hardwire the inability to use lean cruise into our PCMs. it seems more fitting that they just disabled it and there is some complicated way to re-enable it. maybe i will try and get a hold of a stock Holden tune and see what that looks like. Anybody have one?
Look at the MAP pressure enable parameters and RPM for DFCO, you should be able to get rid of as much delay as you want at various speeds. There is a hysteresis function that has an additional delay if DFCO has enabled then disabled and the parameters are met to enable again. You won't hurt anything experimenting with the parameters. I think DFCO cuts fuel off 100%.
08-10-2008 | 12:23 PM
#12
I dont think it goes 100 percent, just some deemed safe level.
Read the first page in this thread. http://forum.efilive.com/showthread.php?t=4785
Im not sure about swapping pcm and such. Let me find that dam thread.
Read the first page in this thread. http://forum.efilive.com/showthread.php?t=4785
Im not sure about swapping pcm and such. Let me find that dam thread.
08-10-2008 | 12:30 PM
#13
You can get a stock holden tune from the repository on the HPT site. I have looked at several of them. Pretty sure it wont do you any good though as I'm pretty sure it is hard coded in the pcm not to allow those settings to work. It probably wasn't much trouble for GM to do it that way and it was probably mandated from the government not to allow it in US vehicles.
As far as DFCO goes. I start by increasing the Entry Spark blending table. I doubled mine which cuts spark much faster and allows full fuel cut-off twice as fast. I have also made some changes to my enable map vs. baro tables, but most of that is due to my cam and those changes have to be figured based on your logs. One other thing that help me enter DFCO faster was a big reduction in my throttle cracker table.
On my first go-round I had the DFCO enabling way to easy, almost immediatly anytime I let off the throttle. I believe that is what led me to also decrease the Enable TPS by about 30%.
As far as DFCO goes. I start by increasing the Entry Spark blending table. I doubled mine which cuts spark much faster and allows full fuel cut-off twice as fast. I have also made some changes to my enable map vs. baro tables, but most of that is due to my cam and those changes have to be figured based on your logs. One other thing that help me enter DFCO faster was a big reduction in my throttle cracker table.
On my first go-round I had the DFCO enabling way to easy, almost immediatly anytime I let off the throttle. I believe that is what led me to also decrease the Enable TPS by about 30%.
08-10-2008 | 12:49 PM
#14
As far as DFCO goes. I start by increasing the Entry Spark blending table. I doubled mine which cuts spark much faster and allows full fuel cut-off twice as fast. I have also made some changes to my enable map vs. baro tables, but most of that is due to my cam and those changes have to be figured based on your logs. One other thing that help me enter DFCO faster was a big reduction in my throttle cracker table.
08-10-2008 | 02:08 PM
#15
As far as DFCO goes. I start by increasing the Entry Spark blending table. I doubled mine which cuts spark much faster and allows full fuel cut-off twice as fast. I have also made some changes to my enable map vs. baro tables, but most of that is due to my cam and those changes have to be figured based on your logs. One other thing that help me enter DFCO faster was a big reduction in my throttle cracker table.
thanks.I understand why lean cruise it would be disabled in the states but it seems weird that we are able to tune out everything related with our catalytic converters but we cant use lean cruise.
08-10-2008 | 02:48 PM
#16
As stated above, I think the fact that lean cruise was disabled here was due to government mandated emissions deals. When you enable lean cruise, it burns less fuel, but one of the "greenhouse gas" levels goes up. I can't remember which one it is, but it goes way up. Also, when you go to lean cruise your EGT's will go up, so if you're running cats still it's not a good idea to use it because they can burn up.
08-10-2008 | 02:56 PM
#18
Yeah the emissions aspect of lean cruise sucks.
what are the clutch transitions in DFCO all about? something to do with the tranny so it can handle engine braking?
what are the clutch transitions in DFCO all about? something to do with the tranny so it can handle engine braking?
Last edited by sprayed8; 08-10-2008 at 04:17 PM.
08-10-2008 | 10:03 PM
#19
There are many values that have to be met for dfco to enable/disable,when you figure out where to put them dfco works great
I have done alot of things with my tahoe and others that is giving them an additional 3.5-4MPG increases.it works very very well
Avgerage they were doin about 14.5-15MPG,now they are getting 18.5-19MPG and this is with hardly any highway driving
There are a lot of things you can do for much better mileage,you just have to mess with it
I have done alot of things with my tahoe and others that is giving them an additional 3.5-4MPG increases.it works very very well
Avgerage they were doin about 14.5-15MPG,now they are getting 18.5-19MPG and this is with hardly any highway driving
There are a lot of things you can do for much better mileage,you just have to mess with it
06-24-2009 | 01:46 AM
#20
TECH Apprentice
Joined: Dec 2002
Posts: 308
Likes: 0
From: Socal
Sorry to dig this thread, but I'm clueless here.... I've been searching the forum and am still entirely confused about DFCO. Anyone willing to post their parameters for a DFCO-enabled, relatively stock truck?
My TP% never goes below 6-10. (04 Sierra 5.3, it's electronic) The DFCO throttle enable table (stock) requires less than that until you get above about 4500 RPM. do I want to raise these values to enable it, and if so by how much? Or am I looking at the wrong PID? (Max TP% is 99.6-ish).
The minimum MAP enable values also seem very close to what I'm seeing under _initial_ deceleration...take it this is desired.
Additionally, the minimum activate/deactive RPM values are *below* the enable/disable values. I assume this means that RPM is not used to activate it?
Any help would be appreciated!
My TP% never goes below 6-10. (04 Sierra 5.3, it's electronic) The DFCO throttle enable table (stock) requires less than that until you get above about 4500 RPM. do I want to raise these values to enable it, and if so by how much? Or am I looking at the wrong PID? (Max TP% is 99.6-ish).
The minimum MAP enable values also seem very close to what I'm seeing under _initial_ deceleration...take it this is desired.
Additionally, the minimum activate/deactive RPM values are *below* the enable/disable values. I assume this means that RPM is not used to activate it?
Any help would be appreciated!