PCM programming discussion/questions

[zippy]

trying to give it a shot to give you guys a place to ask questions about programming and discuss it without a ton of daily posts on the same thing. no advertising, but those (you know who you are) who do it as a business are ok to discuss and offer help unless other noted. ANY QUESTIONS ABOUT PRICING OR DIRECTLY ASKING TO HAVE WORK DONE WILL BE DELETED!!! use pm's for that please guys. this will be frequently moderated.

[deezel]

VE tables - anybody tuning them yet? I suspect the FI guys are, but any N/A guys changing your VE tables?

 

Here's what I have found:

1) The VE table for the 345hp 6.0L LQ9 is the same as the VE table for the 300hp 6.0L LQ4. This seems wrong. They have different pistons (higher compression ratio), so the two engines should have different VE tables. But, the only significant changes I see in the programming are in the timing tables.

2) Looking at tons of logged data from EFILive, I have begun putting together a calculated VE table for my truck (basically stock - the CAI and efans shouldn't change the VE much if any). This calculated table is quite different from the stock one - almost 10% off in the worst spots.

3) I made a "blended" VE table by averaging my calculated values with the stock table. After installing this tune the truck runs great!!! The best way to describe it is much improved throttle repsonse at all RPM ranges. This fixed almost all of the "dead spots" in the throttle. I'm quite surprised and pleased!

 

So, my advice to you guys with stock programming is this: The hesitation/dead spots you feel at part throttle are likely tuning related. A good tuner or LS1Edit+logging+calculating should be able to fix this.

 

**Edited to correct the info on the differences between the engines. Thanks for correcting me BigTex.**

[Farmtruc]

This was very nice of you zippy! I'm sure this topic will be full of questions.

 

For those who are interested in editing your own PCM, here are the tools you need:

 

LS1Edit: Carputing

Diagnostic/Scanning software: Autotap or Ease

A Bench Harness: Speartech or make your own by getting yourself a harness from the salvage yard and wiring in some power and a toggle switch. I did, and it cost about $30.

Laptop :

 

LS1Edit is the only software out (that I know of) that enables us GenIII guys to edit our engines. It's not the most user friendly application nor does it come with support, other than the forums and mailing lists. Speaking of mailing lists, go to LS1edit to sign up and learn about programming your truck.

Tuner Cat will be releasing thier own software that allows OBDII editing soon, expected release is in about two months. I can't wait for this one.

 

Hand held devices , like HPP3, Predator, Superchips are nice and most ppl actually feel some performance increase. However, keep in mind these are one size fits all. They have to do this just like the stock tuning from GM , becuase there are so many variables they must consider. A custom tune is far better than any hand held like the others said. There's no comparison.

 

Also, as much as programmers/tuners try to extract from a truck, every truck will react differently. Some trucks love the tune and others don't really wake up much , but one thing is for sure, you'll gain more Power from a custom tune. Most programmers prove their tune on dynos and try to extract every last ounce of power. There's also a flip side to this. Having all that power is great, however driveability is just as important imo. Shift points, firmness, downshifting, and throttle response are just as important, that's what makes the truck so fun to drive.

 

Hope this helps answer some questions and concerns.

 

good luck,

 

allen

[Farmtruc]

Wide band 02 tuning:

 

This is the best way to get your a/f ratio in line. It uses a wide band 02 sensor that is able to accurately read the engines a/f ratio. Our stock O2's are only useful to the PCM. It's very hard or impossible to get an exact reading from the stock O2's. However, if you're able to get a steady reading from the O2's at wot with say Autotap, you can get it pretty darn close. Having Atap and a wide-band hooked up at the same time will give you an idea on how far Atap is off. Knowing that, you can safely tune a truck with Atap if a wide band is not an option.

I use and like Innovate's wide band setup. It works great and I haven't had any problems with it.

Just keep it away from moisture, the connectors aren't sealed and any type of water or condensation will skew your reading.

A wideband will usually read 10:1 all the way up to 18:1 accurately.

For NA engines, at wot you should be around 12.5-12.8:1. On boosted engines, I like to see a point lower.

Also, generally speaking, a leaner condition will result in more HP, a richer condition will give more Torque. You have to find a happy medium. Remember lean is mean, however it can also cause problems if you go too lean.

 

hope this bit of info helps,

 

allen

[BigTex]

Deezel - The heads are the exact same between our trucks and the denali. The compression difference is in the pistons. I'm interested in seeing what your spreadsheet and what you have done with VE. I've seen a few of your posts around various tuning forums, and actually read a VE post that you had replied to this week on the ls1tuning.com forum.

 

I have made a few minor changes with my VE, but basically just to work on idle issues.

[deezel]

BigTex, thanks for the correct engine info. Been thinking of doing a mild P/P on my TB myself. I'm still working up the confidence for a cam swap...

Ok, tuning... I'm not an expert, but being an engineer-type I pick up pretty quickly on the programming logic being used in the PCM. Anyway, I'm happy to discuss tuning with like-minded auto enthusiasts.

So, I have attempted a few test tunes by lowering IAC numbers, throttle follower, and running air flow. This has helped some, but it still starts at 2500 and has the cruise effect. Its worse when cold, but still does it when hot. What table directly effects the initial cranking airflow? I have not touched the throttle cracker tables, because I don't know what the values mean.

Here's how I understand these tables:

IAC Park, Idle Air and Throttle Cracker are all tables of commanded airflow (gms/cyl) at 0% throttle (when your foot is off the pedal). IAC and Idle air are airflow vs coolant temp. Throttle cracker is airflow vs rpm and speed.

Throttle Follower decay is how fast the PCM allows the throttle blade to close (airflow reduction in gms/cyl per 12.5ms PCM time cycle) when the throttle pedal is released. I'm not clear on the delay in neutral table.

It seems to me that you would want to increase the values in the throttle follower decay tables to cause the throttle to release faster. I've been considering upping these a little to get throttle response more like a mechanical TB. For your situation I would suggest try raising these 2 tables by maybe 40-50% from stock. I'll report if I try this anytime soon.

As far as the commanded airflow tables are concerned, I guess there are two possibilities. 1) The PCM uses an internal calculation to get gms/cyl from MAF and RPM. 2) The PCM has a preset table for throttle blade position when in "idle" or "decel" states. My impression is that #1 is true most of the time, except when cranking the engine. Porting your TB should only cause problems when #2 is true (likely during cranking). I'd say that the PCM uses only VE during cranking and probably has a preset throttle blade position for cranking that stays until the MAF/RPM data can be used (probably a few seconds after the engine is running). This would explain your surge at starting. Unfortunately, I am not aware of a table that controls cranking throttle blade position directly. Perhaps this is linked to the crank VE table... I would say that lowering these airflow tables is one possible way of getting the PCM to do what you want (telling it to command less air to get the throttle closed more).

Hope this helps. I'll send you an email about my VE modifications...

Best regards,

Darren

[Farmtruc]

I'll give the 02 / wide band thing a whirl. I use mine all the time so that's why I haven't done it, that and not enough time,lol.

 

I think you and deezel are on the right track, running airflow and throttle cracker is where I'd start.

It's funny, a bunch of buttons in edit are pretty much useless, I've zeroed/max a bunch of them out before (one at a time) and most had no affect on driveability, lol.

 

TESTING IN THE TRUCK WITH EDIT, haha, I just tried again the other day while at the dyno and NO WAY , hahah, it still doesn't work. I have the "J" version.

Make sure you have a flasher available, you're gonna need it.

 

thanks,

 

allen

[m396 #00-011]

I'll give the 02 / wide band thing a whirl. I use mine all the time so that's why I haven't done it, that and not enough time,lol.

 

I think you and deezel are on the right track, running airflow and throttle cracker is where I'd start.

It's funny, a bunch of buttons in edit are pretty much useless, I've zeroed/max a bunch of them out before (one at a time) and most had no affect on driveability, lol.

 

TESTING IN THE TRUCK WITH EDIT, haha, I just tried again the other day while at the dyno and NO WAY , hahah, it still doesn't work. I have the "J" version.

Make sure you have a flasher available, you're gonna need it.

 

thanks,

 

allen

I'm testing the Safe programmer that doesn't write to the PCM. So when it fails, it doesn't mess things up. I did it 4x last night, and it faild twice. I cleared a miscomm error w/ Live, and all was well.

[BSER]

I had a couple issues with my tuning prior to going to Dallas. The first was a severe rich condition; you could see it on the exhaust with only a short run. And second was a hesitaition at start up, I use very little throttle and it seemed like I lost all power momentarily, after the engine warmed up it went away.

 

Both of these issues are now resolved and I think I even picked up a little on the gas milage. The custom tune didn't seem to be all that noticeable at first (maybe because of all the other mods)but the last few days I can really tell the diffrence. Is this normal? I've read heard that it can take some time for the computer to adjust to the chagnes.

[detjoe]

has anyone adjusted the COT? Turned it off? Or do other tuning things change the groan at 80? Just wondering?

[Farmtruc]

has anyone adjusted the COT? Turned it off? Or do other tuning things change the groan at 80? Just wondering?

COT is catalytic overtemp protection, for those who were wondering.

 

This table will dump additional fuel if the pcm thinks the cats will be overheated , for whatever reason, aggressive driving, hard driving, hot ass weather, this cools the cats and prolongs the life of the cats. That's the most reasonable explanation i can come up with.

If you are tuning and you're using a wide band, you can see the a/f ratio drop about a point once COT is enabled. If you don't take care of this , you'll be chasing your tail trying to correct for a/f ratio.

If you don't have cats, you can disable this protection.

 

thanks,

 

allen

[deezel]

Good explanation of COT, Allen.

Well... I do have my COT turned off currently for a little A/F tuning. But, I'm not sure if it would help a groaning at 80?? I haven't noticed anything when cruising at 80mph.

I posted once before that I wondered if COT caused an unusual underhood noise - but this occurred at WOT around 100mph and was not a constant or recurring noise.

Can you describe the noise in a bit more detail, including engine operating conditions?

[PCMFORLESS]

Also, all of the diagnostics will still work even after being programmed as we are all just modifying GM's original code and not replacing it. Thus if you take it into the dealer they can still diagnose the truck as normal and honestly have no way of knowing the code has even been modified All the GM techs can do is load in factory stock GM programs.

Later,

Bryan

[zippy]

for those looking to learn a bit about wide band 02's, there is a pretty good article in the febuary 04' car craft on the subject.

[zippy]

this is pretty new to me, anyone know much about this? tuner