Anybody tweak your truck with HPtuners?

**Firebirdjones** · 09-05-2011, 11:47 AM

Originally Posted by Sweet Chops

I just did a full street tune w/ WB on my buddys 07 classic HO 5.3 Z71 and the IAT is also part of the Maf. I failed it that way it it worked fine. What year PCM are you using?

Well that's good to hear. My PCM is from an 05 Yukon.

So you were able to tune the VE tables using the wideband AFR % error and it worked fine??

**Sweet Chops** · 09-05-2011, 12:27 PM

Yep worked great. After tune it is only off +/- 1-2%. I know in 08 they started using a diffrent PCM more pin-outs or something. My 08 Saab has it and I haven't tuned it yet except for putting E-Fans in it. But I plan to once the Warranty is up. I hope Failing the Maf the way I have always done it works, I guess I will cross that bridge once I get there.

**Sweet Chops** · 09-05-2011, 03:15 PM

Originally Posted by Firebirdjones

Just today I also threw in a simple gas mileage tuning trick that I run in my wifes 4th gen.

Basically tricking the 02 switch points in the low rpm (low load) part throttle cruise areas to lean the AFR slightly.

On my wifes car it was worth a solid 3-4 mpg increase in gas mileage without any drivability issues. So I tossed it in the blazer today. I won't know any changes until next fillup later this week. But if my wifes car is any indication, I should see well over 20 mpg highway over my best of 19 before the change.

We talked about this once before and I'm just not seeing that much of an increase. Would you mind if I looked at your tunes so I can see what I should change. Or maybe you can just walk me though it. Im stuck at 18.6-19mpg. My goal a 20mpg average.

**Firebirdjones** · 09-05-2011, 03:40 PM

I'll try to explain since I seem to have trouble transfering the tune to a thumb drive off the laptop.

There are only 2 tables to work on. Your 02 sensor bank 1 and 2 vs. airflow mode, and closed loop mode vs. airflow. Both of these are found in engine/fuel control/ open @ closed loop.

On the 02 sensors I changed the switch points only under 6-8-10 airflow sections just as described in HP tuners. I left the switch points alone on either side of those airflow modes. they suggested to use 350 as a switching point to lean the mixture slightly, so I just used that.

Now the closed loop mode uses those numbers you just changed on your 02 sensor switch points, but to make that work right I had to log and see exactly what airflow sections I was running in while cruising. Depending the the gear your in, tire size, rearend ratio, it's different for every car.
So basically when looking at that airflow table, what ever number you put 6-8-10 under it will run leaner in those airflow modes. It gradually ramps up to 16 maximum, but all the other numbers will just run stoich (14.62) because you only changed the stoich value under 6-8-10 in the 02 sensor tables. Make sense??

You may not have seen an increase in mileage because you aren't hitting those airflow cells enough where you have 6-8-10. You will be in and out of it constantly while going through the gears, but logging while at a steady cruise should get you where you need to be.

I found that I had to change the tables a bit on my blazer as compared to my 4th gen. My blazer loafs along with 33's and 3.07 gears

I just filled up though, so I won't know any changes on that one until later this week.

**Cutlass** · 09-05-2011, 06:05 PM

Originally Posted by Firebirdjones

If I had to guess, the late PE is probably there because GM knew these engines would be used in towing applications and they may have been trying to improve on the fuel economy while towing.
Since this lean AFR would invite detonation under moderate loads, it might also explain why the timing tables on these trucks are so low. And I mean very low, in some cells you are looking at negative numbers, with total timing only as high as 12 degrees in some areas. Pathetic to say the least, but it probably cuts down on warranty claims considering what these trucks might go through.

I don't know, just shooting in the dark here.

Here's the stock WOT timing advance I logged today. As you can see its negative/retarded when you 1st mash on it from a dead stop then finally starts to climb. Whats also weird is the -9.5 at 4400 rpm. No knock retard there. Must be something else pulling timing there...maybe torque management.

Code:

RPM	400	600	800	1000	1200	1400	1600	1800	2000	2200	2400	2800	3200	3600	4000	4400	4800	5200	5600	
Timing		       -4.50	-1.50	-1.00	6.50	12.50	14.50	18.00	19.50	20.50	22.00	24.00	25.00	25.50	-9.50	24.00	24.00	24.50

BTW, using the "code" text box was the only way I could keep the numbers aligned up with each other. So just ignore the "code" label

**Firebirdjones** · 09-05-2011, 06:55 PM

That's interesting Cutlass.

Those negative numbers don't surprise me, since that is what used to be in my stock timing tables. I noticed that -9.5 number you mentioned happens at 4400 which is right about where peak torque occurs. Then it comes back to 24 again.
Usually through the peak torque areas you might drop your total timing about 2 degrees, then bring it back up, but what you have going on there is pretty extreme.
What also surprises me are those total timing numbers of 24 and 25 degrees. Have you bumped those up?? Because I don't believe my stock timing tables were even close to that.

**Cutlass** · 09-05-2011, 08:22 PM

nope. Not modified at all, but with all the add/subtract tables for spark, I'm not too surprised its way different then the Main Spark Advance table. It actually kinda follows the Max Torque Timing table in the upper RPMs pretty closely. Not sure if its actually using that table or not.

Oh and BTW I ran the log again and that -9.5 must have been an one time thing. the actual average was for that point was actually around 22 degrees

**Sweet Chops** · 09-06-2011, 06:38 AM

I can not find the closed loop mode vs. airflow. This is a pic of Fuel Control OL & CL Page. I looked at my 99 Camaro Z28 and I couldn't find it in there also.

**Firebirdjones** · 09-06-2011, 12:09 PM

I'm not seeing it on your screen shot. It's under "general" and then "mode vs airflow" on both 4th gens (00, 02) and this 6.0 using an 05 computer.

That's probably why you haven't seen the mileage changes since just changing the 02 switch points probably won't do it if those cells aren't used much in the airflow tables.
I would think it has to be in there somewhere, those 02 switch points work off that table.

**Firebirdjones** · 09-06-2011, 12:23 PM

Originally Posted by Cutlass

nope. Not modified at all, but with all the add/subtract tables for spark, I'm not too surprised its way different then the Main Spark Advance table. It actually kinda follows the Max Torque Timing table in the upper RPMs pretty closely. Not sure if its actually using that table or not.

Oh and BTW I ran the log again and that -9.5 must have been an one time thing. the actual average was for that point was actually around 22 degrees

My main spark table wasn't anywhere close to the numbers you are getting. One thing I like to do is dummy down all the add/subtract timing tables so you get a more consistent spark curve all the time every time.
The only thing I keep is the knock retard, and I even tame that down a bit. I see no need to have that thing pulling 10-12 degrees of timing. If I have the main spark tables that far off then I shouldn't be messing with it,,,lol.
I like to have the knock retard pulling maybe 5-6 degrees at the most, because I'll tweak the tune along with the grade of gas I run to see no knock retard when I'm finished anyway. Even seeing 1 or 2 degrees isn't that big of a deal. If you are seeing it pull 5 or 6 then the main spark tables need more work or the AFR is too lean, especially around peak torque areas.
Another retard table to tame down is the amount of timing it keeps pulling after it senses knock. This table "for me" needs to be almost nil. In stock form, once it senses knock, it will keep pulling timing for several cells, even if knock isn't there. Makes it hard to determine which cells actually need the timing pulled and which ones don't. So you can't decide where the main spark needs work if this is happening.

Basically all I care to keep working is a little knock retard as a safety precaution, and idealy it's only pulling in the cells that are necessary and not carrying over to more than one or two other cells, but if it's tuned properly you shouldn't be seeing it.

**Firebirdjones** · 09-06-2011, 03:24 PM

Another timing table you don't need is the one that pulls timing for quick throttle changes. If you move the gas pedal quickly it pulls timing whether it pings or not. Ridiculous. Just because I move the throttle quickly? That just kills throttle response, gas mileage and performance. I zero that one out completely. It's not necessary. If you dig around enough you'll find all kinds of table multipliers for the main spark table. Some might be a good idea but I find the majority of it just isn't needed for me. Just a timing retard feature that pulls 4-6 degrees is really all that's needed for a safety cushion in case of a bad batch of gas. The rest just costs HP.
But this is just my opinion which is based from tuning, restoring, driving, and racing classic cars for the last 30 years that never had this stuff. I've never needed all that timing retard junk then, and never destroyed an engine from detonation, so I see no need for it now.

**Cutlass** · 09-06-2011, 05:11 PM

Originally Posted by Sweet Chops

I can not find the closed loop mode vs. airflow. This is a pic of Fuel Control OL & CL Page. I looked at my 99 Camaro Z28 and I couldn't find it in there also.

Change your view to advanced. Go to Edit>View>Advanced. You'll see WAY more stuff.

**Sweet Chops** · 09-07-2011, 06:41 AM

I found the table CL mode vs airflow. Now what are you logging? Did you set up a histogram for this? I tried and im just not geeing the info I need to change that table. How do I know what mode I'm in when crusing?

**Firebirdjones** · 09-07-2011, 08:02 AM

Ah, I checked mine and thought it was g/sec I was looking at but it wasn't. I was looking at MAP in the VE tables. So I wasn't logging correctly.

Since you found that table you need to make this work, I would start with the graph that is provided on Hptuners site in the gas mileage saving thread. That gets you in the ball park to the point you should see an immediate change in mileage. It's easy to tweak from there. I think I just go lucky with my logging

I'm sure you could setup a histogram logging g/sec though. You only want to affect the low g/sec areas (say 30 and below) for light throttle cruising.

**Sweet Chops** · 09-07-2011, 08:09 AM

I was able to use a table I already had. I'm not sure if this fuel econ thing is going to help me. My truck is already running in the modes I leaned out. g/sec 4-40 were already running in modes 6-10.

**Firebirdjones** · 09-07-2011, 11:41 AM

Sounds like you had a handle on it already then.

I've driven the blazer about 100 miles since I filled up Monday after I threw in the changes. So far the gas gauge has only moved about 1/8 of a tank, which seems alot slower than usual. I'll fill up Friday and get exact numbers and see if there is really any change on mine.
It was huge on my wifes camaro. I couldn't believe picking up 3-4 mpg would have been possible AFTER I had already tuned it with a wideband.

I think it's going to be difficult to see that much difference in a 4,700 lbs. truck with 33's but I'm hopefull

**Sweet Chops** · 09-07-2011, 03:50 PM

I have a 400mile round trip comming up this weekend so I wanted to make sure I had it taken care of before then. I haven't decided if I'm going to pull my small 12' boat and trailer or not. We will have to see. I will post my MPG on Monday.
Thanks for the help Firebird and Cutlass.

**Firebirdjones** · 09-07-2011, 04:16 PM

I'd love to hear about it. I'll report back with mine later this week, I hope this is helping Cutlass and not ruining his thread

I don't know how it's going to affect mine, since I haven't done any fuel tuning on it yet, just timing changes. I might have to take it back out,,,,then tune the VE and the MAF,,,,drive it and check mileage,,,,then maybe put it back in again and see if there is a change.

I just haven't had time to do any extensive fuel tuning with it yet, and I'd like to wait for the weather to cool off a bit too.

Hey Cutlass, so how is it coming along? Change anything else?

**pajeff02** · 09-07-2011, 05:46 PM

Looking forward to you guys having this all figured out for when my warranty expires.

**Cutlass** · 09-07-2011, 05:49 PM

I'm learning a bunch from you guys. Feel free to talk about any tuning stuff you want to. I'm just absorbing it all up.
As for my tuning so far, I started over.
I changed some of the Power Enrichment settings as far as making it come on sooner. I'm hoping that with a little more power enrichment, I can bump up some ign timing.
I'm gonna try out O2 Rich/Lean switch voltage vs Airflow mode modification and see how that works out for me.
I cut the torque Management in half.
Disabled the EGR, zero'd its spark table, and set its codes to 3/no error report
Adjusted the trans Desired shift times
Adjusted the TCC duty cycle

I've just been tinkering with it a little bit here and there. I haven't flash it to the truck yet. Maybe I'll get out there later tonite.