Displacement on Demand - Highway Use

[Spartus]

I'd like any pointers you guys may have on how to get DOD/AFM to function properly when on the highway. I live in a hilly area, and currently get better gas mileage with it disabled, than with it enabled. That must be due to how often it switches on and off, which is similar to a yoyo about 5 to 10 times per minute. BTW, my Instant economy drops to 13 mpg every time it switches back to V8 mode. With DOD enabled, I get about 16-16.5 mpg highway.. With it Disabled I get 17-17.5 on the highway. Currently, I have my tune set to shut off DOD after 1850 rpm, that way it still works around town.

Below is my tune, which has MANY MANY MANY changes to it.

[WarWagon]

This is the big engine vs. the small engine problem. Hilly areas are the best example an engine that does not have to work as hard gets better fuel economy. Thus a big engine gets better fuel economy in a hilly area. (Unless you floor it.)

What you want to do is post a log of DOD going on and off x times a min.

Sounds like you have a loop going on. This is where DOD is enabled and a parameter like MAP, TPS, Knock, etc changes enough, because of DOD being enabled, to call for DOD to exit.

Do you have any mods to the vehicle? (And what kind of vehicle?) If you flash a stock tune does it still jump in and out of DOD that often?

[Spartus]

This is a stock 2007 1500 crew cab 4x4 with the 5.3L. All I have done is installed a K&N filter, which was good for 1/2 mpg.

With the stock tune, DOD would engage disengage more often than it does now. And yes, it does seem like a loop to me too, since most of the time it only stays engaged for 2-3 seconds then drops out. In the city though, DOd will stay engaged for longer periods of time. The only log I currently have for highway cruising is from several weeks ago towing a empty snowmobile trailer and getting 13 mpg, so it never dropped into DOD on that trip.

Mileage results to date:

Stock = 14.5-15.5 highway
K&N + tune = 16-16.5
Disable DOD = 17-17.5

[TiredGXP]

I notice that your DOD disable RPM is set quite low. Did a quick comparison to my LS4 settings. The only major difference is as follows:

Attachment 10004

I'm wondering if raising your disable RPM will eliminate some of the cycling you describe.

Hills really do matter - any incline on the highway usually throws me out of DOD (at least when I had it enabled).

[Russ K]

Spartus,

Copy the DoD enable & disable vacuum threshold tables from this tune & paste into your tune.
This will allow the V4 mode to stay enabled under more load.

Russ Kemp

[Spartus]

TiredGXP: As noted in my first post, I currently have DOD set to disable (1850 rpm) when on the highway so I don't have to live with YOYO enable/disable performance. I'll take a look at your file too and see what I can find.

Russ: Will do, thanks.

I did try -10 kpa for Enable but it seemed to turn on very very early, and it wasn't happy with my TCC enable/disable settings of 100% / 90%. The truck sure jerks hard when DOD turned on/off. I'll compare the setting from Russ and see what type of a difference it makes.

[Spartus]

Hi guys, a little update for you. I copied over the table entries that Russ supplied, and now the DOD engages a lot more often, and seems to stay enabled for a little bit more too. I have a nice log file if anyone wants to see it. THANKS RUSS!

I have one problem though. The truck surges each time DOD enables when on the highway. Is this because I have the TCC DISABLE up to 90??

I did four 10 mile tests. 2 with DOD on, and 2 with DOD off, on the same stretch of highway, here are my results:

Northbound:
18.8 mpg DOD engaged, traveling @ 67 mph.
17.7 mpg DOD disengaged, traveling @ 70 mph.
Southbound:
18.5 mpg DOD engaged, traveling @ 67mph.
16.5 mpg DOD disengaged, traveling @ 70mph.

The reason for the 3 mph difference is because I had the program set to disable DOD at 2000 rpm for these tests, and 67 mph was the earliest I could get DOD to still engage.

-TJ

[TiredGXP]

Well, looks like DOD is making a reasonable difference.

I noticed on my logs that the PCM blips the throttle when engaging DOD. If your TCC is locked, that may be what you are feeling.

Looking back at one of your posts, I see that you noticed the jerkiness with the 90% - 100% TCC duty cycles, I found that a milder setting eliminates that. (double the stock Min duty cycle, maybe 10% added to stock Max - it may not be optimal, but DOD is more or less transparant).

[BBA]

Man...I wish DOD lifters were good for high RPM's in an LS2..I would consider adding it to my TBSS then. 2600-3000 RPM on the highway in OD sucks gas like hell with a 6.0L.

[LazMan]

They need to start putting 6-speeds into "light duty" trucks and stuff like the TBSS.

[BBA]

No doubt...I was thinking if I could find one with a 4WD transfer case flange, it would be the perfect swap trans. I would have to figure out a pedal arrangement, maybe a second adjuster on the clutch pedal, wired into the brake pedal position adjuster motor connector.

Would make a huge difference. WTH is GM's problem? They afraid we would burn clutches or something with all the weight?

[Penguin]

Hi guys, a little update for you. I copied over the table entries that Russ supplied, and now the DOD engages a lot more often, and seems to stay enabled for a little bit more too. I have a nice log file if anyone wants to see it. THANKS RUSS!

I have one problem though. The truck surges each time DOD enables when on the highway. Is this because I have the TCC DISABLE up to 90??

Just wondering how all this turned out? Did you get the surge to go away? Never heard any more so assuming all is well??

[Spartus]

Yes, I had to lower the TCC DISABLE back down to stock settings. I did stock settings X 15% and am happy with that.

My last two highway trips though have been rather disapointing with only 14-15 mpg. This winter stuff is killing my mileage, as I am now getting about 12 mpg around town.

I have considered disabling DOD altogether though, and bumping the TCC DISABLE back to 90% and compare my mileage with that. Around town according to my DIC, my instant fuel economy is only 1mpg higher when in V4 mode, so maybe the TCC disable can make the difference, I don't know for sure.

[Texsrt4]

i must have a fluke of a truck. i get upwards of 20 regularly with my crewcab. i adjusted the engagement/disengagement, but still wasnt happy. once i played around a bit with my DoD timing, thats what made the difference

[Spartus]

Yeah, a guy I work with claims to get 16-17 around town and 19-21 on the highway with his crew cab 4x4 too.. I don't think you guys got fluke trucks, you just got what you paid for. Mine is a hunk of junk. Yesterday I noticed my rear main seal is leaking, and with only 11,485 miles on the clock.

[LazMan]

I'm playing around with a 2007 Monte Carlo SS 5.3L. DOD is incredibly pain-in-the-ass to tune.

[TiredGXP]

I'm playing around with a 2007 Monte Carlo SS 5.3L. DOD is incredibly pain-in-the-ass to tune.

Yeah, I turned it off to do VE and MAF tuning. Radically different airflow when DOD is active, the cam lobes for cylinders that stay active have different lift (not sure about duration) than the cylinders that deactivate. If you leave DOD enabled in SD OL, you end up with a weird secondary peak in the VE table.

I only activate DOD in a CL tune, and let the fuel trims take care of the differences.


2007 has the E67 without a VE table doesn't it?

[SilverG]

i must have a fluke of a truck. i get upwards of 20 regularly with my crewcab. i adjusted the engagement/disengagement, but still wasnt happy. once i played around a bit with my DoD timing, thats what made the difference

Could you elaborate on how much you changed your timing? A little or a lot? Did you monitor KR to know when to stop or did you not make that much of a change?

I too am playing with my DOD right now and finally have it making a smooth transition from V8 to V4 and back, at least as far as MPG. Stock V4 used to only go down to 23 then it jumped to V8 at 19 then back to V4 at 23. I moved the TPS max up a little and now V4 goes down to 20 and stays engaged longer at a higher mpg, before V8 kicks in. I did see an overall 1.5 mpg change on this tank of gas.

Yes, my '07 does not have a VE table. Luckily for me the LTFT and STFT are not too bad.

[06black]

Question guys.

I just recently snagged a 08 silverado with the 5.3, 4X4, ext-cab to use a DD truck / winter ride so the big turbo cobalt can go away when the snow flys!

the DOD is a huge thing for me, one of my main selling points in fact.

i was looking at the TPS, load, ect tables for the DOD and have no fear or issues with adjusting them so it'll stay in V4 mode on the highway at ~70-80, HOWEVER i was looking at some of the tables for the limits and modifiers for the DOD mode and a few have me worried.

oil aeration, max time in V4 mode, ect.....has any one seen any adverse effects (mechanicly wise) from running the engine for prolonged times (say 20-30min) in DOD mode?

the timeing tables are sure going to get bumped and i'm going to lean out the stoic afr a bit as well (tricks for MPG from the LSJ world)

I just know this truck will end up with more tuning then i want to do to it rite now.....

[Texsrt4]

Man...I wish DOD lifters were good for high RPM's in an LS2..I would consider adding it to my TBSS then. 2600-3000 RPM on the highway in OD sucks gas like hell with a 6.0L.

my truck, under wot, sees 5500rpm at its shift factory. are we sure that the new lifters arnt capable?