2008 Vortec Max

[J-Rod]

I have a 2008 CCSB VMax 4x4

Just wondering if anyone has done much tuning with Max Package trucks.

I have removed the 4 second PE delay which seemed to wake the truck up a bunch.

I removed the speed limiter and have set it to use the tune calibration instead of from GMLAN.

I have not changed the Torque mgmt yet. Any recommandations based on the 4L70E which is reported to be in the trucks?


I've been mostly focused lately with working on the mileage. I've move the TPS max to 20% to allow you to actually give the car some throttle but keep DoD active. But the vacuum seems to be most critical for AFM.

I think the biggest area that needs work is the Dod enable/disable Vac tables. Mine have been modified, but I have not had time to fine tune them. Has anyone had time to log them and see what seems to be optimal? The truck is holding DoD mode longer, but I think with some more tune time it will hold much better and off course mileage will go up. And these days every gallon counts. So I wanted to see if anyone else had done any logging or had any data. I have heard of some tuned 4x4 truck running 22mpg, and 2wd running 24.

I have not leaned the truck out or jacked up the timing since I am pretty much going to run 87 octane exclusively. I know these trucks can benefit from some timing. So, has anyone found what the trucks seem to be happy with?

I can log all the data, and play with the tune myself, I jsut figured it never hurts to ask. If no one posts up, I will post results as I have time to mess with it.

[Texsrt4]

find my 07 5.3 DoD tune in the repository. the real trick to keeping DoD active is 4 cyl timing.

[EC_Tune]

What kind of mileage are you getting with your VMAX truck? A buddy in FL is getting crap for in-town mileage.

[Texsrt4]

I have the 5.3 but I get around 25 mpg while driving on the freeway if I am really making a conscious effort to get good mileage

[J-Rod]

I can get 22-24 mpg if I can keep it in AFM, but right now it is dropping out of 4 cylinder mode too easily, and I am working on logging road data to see how far out I am on vaccum enable disable.

I will look at your tune srt4, thx...

[J-Rod]

older thread on the VMax tuning....

http://www.hptuners.com/forum/showthread.php?t=14720

[EC_Tune]

Wow that's significantly more MPG than my buddies 4x4 truck. He was getting ~9 MPG around town and *maybe* 17 on the highway before we did anything to it. He's run 93 in it as well and only picked up about 1/2 MPG. I think his truck has a serious problem somewhere. We've tried all the tricks I know about increasing MPG as well and it does little to nothing. And I've been tuning since 1989...

[Texsrt4]

Wow that's significantly more MPG than my buddies 4x4 truck. He was getting ~9 MPG around town and *maybe* 17 on the highway before we did anything to it. He's run 93 in it as well and only picked up about 1/2 MPG. I think his truck has a serious problem somewhere. We've tried all the tricks I know about increasing MPG as well and it does little to nothing. And I've been tuning since 1989...

sounds like your boy has a serious problem. what kind of truck? year/make/model

[EC_Tune]

Same as yours but it's an 07 Chevy VMAX CC 4x4 truck. He even got the latest updates from Chevy but that was just for an A/C issue. No biggie there. We're still working on it but he has a buddy with the same truck except 2wd and he gets 14-15 around town and 20 highway. I can see the 4x4 costing him a MPG or two max but this is rediculous!

He just swapped to TR55 plugs because he had some intermittant idle issues. First it was a plug wire that slipped loose but not off the coil pack. Then the idle issue came back again but no loose wire. Waiting to hear back from him on the plugs.

[J-Rod]

Yup, the only time I see mileage like that is when I pour the coals to it. Here is a question. Obviously there are some of the 5.3L tunes which have really picked those trucks up ~25MPG on 2wd trucks. The issue is the AFM tables vary since the 6.0 is obviously not a 5.3.

I tried logging data by selecting manifold vaccum as that is the table in question for enable/disable of AFM. On my captures I get no data in chart mode. I also logged MAP, but of course that is not manifold vac, it is, but the values don't match the table. I am sure its a simply mistake in terms of what I am logging. I guess I can sit down and figure up wha tthe delta from vac to MAP is and extrapolate my data, I jsut wanted to figure out what I had done wrong.

Also, has anyone given any thought to other mileage improvements like DFCO enable, etc... Obviously you can do thinks like tune to run in O/L only but that is not exactly what I want to do on the DD.

http://www.hptuners.com/forum/showthread.php?t=18278

And post #9 and post #37, in this thread.

http://www.hptuners.com/forum/showthread.php?t=15606

[J-Rod]

Never mind, I found this thread which has a .cfg file I am going to test to see if it helps out with logging the DoD.

http://www.hptuners.com/forum/showthread.php?t=15624

Some good suggestions on AFM there including Texsrt4's comments about raising timing. I am of the opinion that I would like to optimize the combination with tuning both.

[J-Rod]

I was playing with a 5.3L tune, to see what they did with enable and disable values. I just ended up copying back in my tables for enable and disable. I dropped 4th gear for both enable and disable values. I will be spending some time logging to see how much more I can lower those values.

I set the TPS hystresis to 1.5%

I add 1 degree of timing across the board to the DoD high octane table, but I need to verify that the truck is actually using the high octane table. The truck seems to be staying in DoD longer.

I believe that it is a compromise between adding a bit more power by way of the A/F and the timing along with lowering the values in the vaccum tables. I think both go hand in hand.

[J-Rod]

Ok, I've had some time to play with the tune, and here is what I have found thus far.

I took the hi-octane tables and copied it into low octane. I have been monitoring for KR but saw none. I went ahead and copied the same tables into the DoD timing. I saw no KR there either. I bumped the timing up just a bit (2º) and saw about 2 degrees of KR in certain cells. So, I basically put the table back to the base hi-octane table and KR has run 0 degrees on 87 octane.

Right now I have the TPS max at 20%. I have set the enable down -4 from stock values from 1100 to 2500 in 4th gear only. This allows me to put it into V4 mode by a quick lift off the throttle.

I have set the disable down -4 from stock values in 4th gear from 700 to 1300. From 1400 to 2500 I have it set to zero.

I know there has been discussion about the vibration in the 5.3L. The VMax has enough power that you get no vibration, bucking or surging in 4 cylinder mode. The one issue that you do see is that with it set this way you can actually go up overpasses, climb small hills. The issue is that the truck does not have enough power in V4 mode to maintain its speed. On flat ground, the truck will maintain a constant speed in V4 mode with no real drama at all. If the truck is going 70, and you go up an overpass. The truck will drop back to about 65 by the time to crest the top of the overpass. You can maintain the throttle and accelrate slightly down the backside of the overpass and be to 75 at the bottom. So, if you have mutiple overpasses, you maintain close to a relative speed.

With DoD and AFM at 70MPH thus far I am seeing about the same mileage in V8 or V4 mode. The big difference is when the truck has to go uphill. as I pointed out in V4 mode it looses some speed. But, the fuel economy stays right at 17MPG. In V8 mode it runs about 17 on flat ground. Going up overpasses, etc... it drops back to 9MPG.

I can set the throttle position to get 22-24mpg in the truck. But, the issue is that its not enough power to maintain a constant speed. The truck begins to loose speed about 10mph over a mile or so. So, its a constant speed up slow down which is not really usable on the freeway. I know other people report getting tuned and getting 22-24mpg on Vmax trucks. I thus far have not been able to duplicate anyhting close to those results yet.

I believe one of the issue on the Vmax trucks is the heads. The L92 head makes good power up top, but it has a big port with a lot of volume. Its just not condusive to good cylinder filling at lower RPM. I believe the cathedral port head while not the same in peak power production probably would have better performance down low.

In back to back testing with AFM and DoD if you factor in overpasses speeding up and slowing down, etc... and an average speed of 70-75MPH V8 mode is about 14.5 MPG.

If you run in AFM and DoD mode and just let it stay in 4cyl mode, averge economy goes to about 17MPG. But, you can actually get that in V8 mode with a lighter touch on the pedal.

Where I have seen the most difference is over 70MPH. Average MPG on the truck goes down dramatically over about 72. Once you get to 80MPH, the truck will only run 14MPG in V8 mode. That sub-optimal for me as that is about the speed I like to run.

I still have some playing to do. I looked over the fuel economy thread where the forumla to calculate MPG was posted.

12096 * [SENS.20] / [PID.6210] / [SENS.112] / [SENS.70]

I am going to put that into a log histogram to see if I can identify cells that might require more "attention".

The transmission tune is still stock, per the threads I have read from RussK it seems like the best course of actiont here is to put in a Corvette Servo before doing anything with the tranny tune.

It was also suggested that I work on the air transient tables, and lean out WOT.

I have already set the delay RPM for PE to zeroand the enrichment rate to 2.0000.

Right now I need to raise PE slightly as it is set at 55kpa. I am going to raise it up to 85 to keep out of PE unless I really want it there.

[brantsz]

I agree with the above post in regards to enabling DOD at or above 70MPH on the V-max truck. I played with this for a few months with the same results. Anything other than a perfectly flat road at or around 70mph the truck would slowly loose speed forcing you to roll into the throttle more. If you have any sort of exhaust and are at highway speeds with DOD active be prepared to have your teeth vibrated out. I also noted at higher speed the transition to and from DOD was more abrupt, neither of these I cared for. I put the vac tables back really close to stock, and TPS to 18% and actually seen an improvement in AVG MPG. I also have dabbled with the timing quite a bit with the exact same results. With 1 to 2 deg of timing over the stock high octane table I detect knock with 87 octane I can push 3 deg but only with 93