Tuning DOD, still disengaging early

[Overkill]

Hi everyone.

I'm doing some tuning on my buddy's 2006 Impala SS, LS4 5.3.

I'm having a perplexing time trying to tune the DOD to engage earlier and remain engaged longer.

I have adjusted the Enable Vac down to 35kpa from mid50s stock, upped the TPS MAX % to as high as 18% from 6% stock, and the RPM disables are set to 3000rpm from factory.

I watch the scanner and cannot determine what parameter is causing the DOD to disengage; the slightlest move on the throttle disengages DOD and it doesn't enable unless you're super light on the pedal. There are no airflow parameters in HPT, neither dynamic cylinder air or MAF g/sec, but I'm wondering if they are present and not yet mapped.

Here's a screenshot of my settings, any suggestions?

[01Formula]

have you looked at the under MAX V4 TIME at the VAC DELTA POS and VAC DELTA NEG, i believe these will kick you out in a change in vac poistive or negative

[SilverG]

I have a couple of things different. First I allow up to 20% TPS Max and I set the TPS Max Hyst = 3 (.5 stock). Secondly, I lowered the Disable Vac tables by the same amount as the Enable Vac table. In my case I lowered them by -4kPa in my cruise RPM for 4th gear.

[Texsrt4]

also, timing is key in 4cyl mode. its not just throttle but engine load/vacuum as well. add timing and it will smooth out quite a bit.

go to the repository and do a search for a 2007 GMC Sierra with the 5.3. you will see that I posed up a file that i dialed in the DoD. look at the specs.

[waynehartwig]

also, timing is key in 4cyl mode. its not just throttle but engine load/vacuum as well. add timing and it will smooth out quite a bit.

go to the repository and do a search for a 2007 GMC Sierra with the 5.3. you will see that I posed up a file that i dialed in the DoD. look at the specs.

Can you elaborate more? I downloaded it and tried comparing to a stock file, but I'm not sure what I'm looking at, or what you changed vs stock.

Also, I know this is a newbie question, but how do you see when it's enabled/disabled with VCM scanner? I don't see DOD in the PID list?

[SilverG]

also, timing is key in 4cyl mode.

I had forgotten about the timing.

Yes, there is a PID in the scanner under Display/Status Bits. You can monitor the DOD (on/off) but you cannot filter on it in the Histograms, yet. That makes tuning the timing a PITA. I bumped my DOD timing by 3-4.

To help see differences between files open them both and use Compare/View Comparison Log (CTRL-5). Then double click on one of the differences and use the 3 views (CTRL-2, CTRL-3, CTRL-4). Sorry if that is not what you were asking.

[waynehartwig]

I had forgotten about the timing.

Yes, there is a PID in the scanner under Display/Status Bits. You can monitor the DOD (on/off) but you cannot filter on it in the Histograms, yet. That makes tuning the timing a PITA. I bumped my DOD timing by 3-4.

To help see differences between files open them both and use Compare/View Comparison Log (CTRL-5). Then double click on one of the differences and use the 3 views (CTRL-2, CTRL-3, CTRL-4). Sorry if that is not what you were asking.

I don't see the PID under Display/Status Bits? I right click and everythign is greyed out. Maybe I need to be hooked up, so I'll try that later.

Thanks for the CTRL shortcuts! Didn't know about those!!!!

[Texsrt4]

i have a drivers information system on my gauges that tell me if in in 4 or 8 mode.

DoD is factored by throttle position and load. both have to be in spec for it to work in 4cyl mode. higher timing advance means more power with less load/throttle position. this allows for you to maintain within teh spec and still manage to keep the vehicle at speed. compare my modified spec to your factory spec using "compare" feature. you will see that setting the throttle and load settings are important, but not teh end-all-be-all.

[waynehartwig]

I've got other things to do on this, but I'll check on the PID thing and see what I've got going. If I need more help, I'lll just post my tune and you guys can then help me

BTW This motor/trans is now in an 04 Jeep Wrangler, and not a 08 Sierra anymore So I've still got gauges, emissions and lockers that I need to hook up and finalize. I leave on a 3k mile trip pulling a camp trailer. I'll be able to see more once I get it on the highway.

[MgpEagle]

I shut mine off so I didn't have to deal with it.

-Mike

[Nick 2K2 SS]

From the scan logs that I have ran on this over the weekend, I have found that manifold vacuum is pretty much the determining factor in turning DOD on and off. There is a status bit called "DOD Requested". Have that inserted into your status bit table while scanning. Then make sure to load the Manifold Vacuum & ETC Pedal Pos % PID's into your main scanning table and set the vacuum PID to metric for the units. Then drive your car and scan it. The reason I say to insert the manifold vacuum PID is because the DOD tables reference vacuum instead of absolute pressure. They are actually just inverses of each other but for whatever reason, GM uses vacuum as the reference in the DOD enable/disable tables. Then when you view the scan log, use the chart view to scroll through the frames. If you have your chart sized so you can still see your status bit window, you will be able to see your status bit change to Yes when you are at frame in your chart where DOD was active. Then I have found that it helps to at least check out what was going on in the PCM a few frames before the DOD actually turned on because there is a factory delay of 0.2 sec once the parameters have been met until DOD actually turns on. I hope this helps. If I am misunderstanding something, I hope someone will correct me so I can learn more too!!

[LazMan]

Here is the last tune I ran on my 2007 MonteCarlo SS 5.3L A4 before I traded it in for the 2009 Pontiac G8 GXP 6.2L M6. I tuned its DOD differently - made it come on less in first, 2nd and 3rd gears, and much much more in 4th. The timing curves are completely different than stock as well.

The car was, except for a de-screened and re-tuned MAF sensor, bone stock. This should show you what these kinds of changes can do.