Topic: Predator Performance Tune

[oHIobellboy]

ok, here's what i came up with.  I've loaded the performance tune into it. there's been nothing done to the engine. It's all stock. these #'s were pulled in real time diagnostics while making about a 5mile run up the highway in 3rd gear. small rolling hills so no big load or anything.

mph  = 58
rpm   = 2376 (or close depending on the hills)
load  = 15%
ect     = 194* (slowly climbed to 196*)
ltft      = 6.25% average
map   = 4.8 psi ( again depending on hill)
spark = 36* (dep. on hill)
IAT  = 75*

Don't know what it all means so maybe someone can help. BOB? BD? any ideas what I can do to help it run a little better/more economical?

[KY_BOB]

ok, here's what i came up with.  I've loaded the performance tune into it. there's been nothing done to the engine. It's all stock. these #'s were pulled in real time diagnostics while making about a 5mile run up the highway in 3rd gear. small rolling hills so no big load or anything.

mph  = 58
rpm   = 2376 (or close depending on the hills)
load  = 15%
ect     = 194* (slowly climbed to 196*)
ltft      = 6.25% average
map   = 4.8 psi ( again depending on hill)
spark = 36* (dep. on hill)
IAT  = 75*

Don't know what it all means so maybe someone can help. BOB? BD? any ideas what I can do to help it run a little better/more economical?

To be honest, the only one of those numbers that really means anything is the LTFT.  It means that the computer is adding 6.25% to your tune to get the desired A/F ratio.  That's not too bad and well within what GM says is OK but tuners usually shoot to keep the fuel trims from 0 to -4.

[oHIobellboy]

should I try to adjust this? I've got my pred. book and can look up the "how to" or find it on their site.

[MightyMouse]

OBB,
I also answerd you on the nat'l site, but I'll answer here, too. Is it the high octane tune? Stupid question, but you're running high octane fuel, if so, right?
The Diablosport guys say to get the best results, you want your LTFT between 0 & -2, so to do that, subtract 7% from your current injector slope setting, and Power Enrichment (AFR) on all rpm ranges. This tells the truck that the injector is smaller and to spray more fuel, while the negative PE adjustment leans out the mixture to keep it from getting too rich. You'll want to give the new tune 20-30 mies before logging again.

Bob, does that sound about right???

My '07 runs a little too rich at WOT - 12:1, so I adjusted my inj. slope to spray less fuel, but left the PE alone, so that should lean it out.

On the next log, read these parameters only:
RPM
AFR
LTFT
Knock
commanded throttle position
You don't really need any more data.

***Update*** I just read on the Diablosport site that adjusting your PE isn't necessarily gonna help once your injector slope adjustments get you to 0>LTFT>-2, so I'd try that only to start. Just adjust your inj. slope to -7 from where it is right now & see what you get.

[oHIobellboy]

I'll give it a shot next time I wanna play with it, Prolly thursday. Thanks MM

[MightyMouse]

    

[KY_BOB]

OBB, if you were dealing with HPTuners, I could help you more.  It sounds like MM is a lot more familure with the Predator than I am.

[Main One]

It's just my opinion, but since it's a free country, I'll let you know what it is.

If you are going to be changing your injector info to target your ltfts, not to mention AFR, I'd be using a more powerful tool than the Predator.

At any time in my 03, my PCM has 44 different LTFTs, 22 per each side of the engine.  I'm not 100% up on the Gen IV engines that I believe you should have in your 07s, but I think you are running 80 different LTFTs, split to each side of the engine, and split again by whether the Evaporative Emissions Solenoid is open or closed.

For myself, if playing to that level of detail in my tune, I'd be doing it based upon more conditions than just one.

In my Gen III, there are per bank 16 different Fuel Trim Cells for normal operating, 4 for idle, and 2 with the EVAP closed.  At any point in time, my engine is making use of 2 of these LTFT values, one for each side of the engine.  As conditions change, the engine will move into a different LTFT cell area, and when it does, it will recall the last LTFT for those cells (engine banks 1 & 2) and starting using that value.  For the conditions you described, I would normally be in either cell 3 or 7.  (3 is low MAP pressure, high rpm; 7 is still high rpm, but low-medium MAP pressure.  Stock breakpoints between the 16 standard cells are at 900, 1400 and 2200 rpm, and 4.8, 8.0, and 11.2 psi.

The amount of time that the injectors is held open is based upon the calculated air going into your engine, together with the characteristics of your injectors.  You are changing your trims, and AFR, by changing the stored parameters of the injectors.

However, for many tuners, Bob and myself included, the thing we mainly try to change is not the stored injector parameters, but the calibration of the MAF and VE tables.  We like this method because not only does the amount of calculated air affect the added fuel, it also drives other computer calculations, one of the most obvious being spark advance.  We like to adjust the primary source of error, because if we fix that, we fix the other problems caused by it, not just fixing fuel, or fixing it for a fairly limited range of operating conditions.  Your error source is hopefully more likely due to MAF readings, which is what I've tweaked most often in my tuning, than due to injectors.  Think about it.  Do you really think your average injector, in your truck is off 7% from all of the injectors GM buys?  If there is that much variation among your average to GM's average injector, just how much variation do you think you have among all 8 of your injectors, or did you spend the extra $s for the matched injector set? 

It's your truck.  But I would say, and I believe Bob would back me up on this, if you are getting into the weeds that much with your tune, then you need a better tool.

I've been sort of where you are, although I had a Hypertech, which is even less of a tool.  I sold mine on ebay for 1/2 of what I bought it for, and then shelled out the $500 for HPTuners.  It's been the most educational of all of the mods I have done, and it allows me to get the most out of all of the hardware mods that I have made.

[oHIobellboy]

Thanks MainOne, that's a lot of info to absorb and consider. Mine's an 04  so I think the engine is the same gen. as yours. I got the pred. to try to help it run a little better and a little more efficient. Don't have the desire to go the route that Bob and Yourself have done as I've got 4 teenagers at home and I have to have a daily driver. I don't have the down time to do the extensive mods like a cam or SC like that. I appreciate the help with the info on the LTFT's and I'll keep an eye on it trying to duplicate the original test conditions.

[KY_BOB]

For myself, if playing to that level of detail in my tune, I'd be doing it based upon more conditions than just one.

That was kind of my thought when I made the first post.  The posted data is like a snapshot compared to a log of the truck over varying conditions for 20 to 30 minutes.