LS1/LS2/LS3/LS4/LS7 etc. - LOGGING, ADJUSTING INJECTOR SLOPE

Predator support for GM gas vehicles

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DaveAN55

Post by DaveAN55 »

Hello All, I'm a noob as well and it's April in the D and temps are around 42F. Am I reading Monte right that the averages should be on the positive side during colder weather? I'm averaging -1 ltft right now. Is that too lean for these temps? If I leave them can I just re-log in a month or two to check where they're at?

I bet if I went thru all 29 pages I might be able to answer this on my own! (':oops:')

Thanks for any input!
Last edited by DaveAN55 on Thu Apr 12, 2012 9:07 am, edited 1 time in total.
DaveAN55

Post by DaveAN55 »

Ooops, My bad...I guess that would be rich not lean! I adjusted the injector slope and now my ltft's are 1.56 (both banks). If the temps start to rise, according to the posts, I should be in pretty good shape IF I'm following things correctly! I'll double check them when it starts to warm up. Now on to some WOT testing! (':D')

BTW, the temps were in the low 50's on my last cruise here in Michigan.
Last edited by DaveAN55 on Thu Apr 12, 2012 9:07 am, edited 1 time in total.
DaveAN55

Injector slopes?

Post by DaveAN55 »

Well, it doesn't seem like these threads get reviewed much, so.....I'll continue to ramble on until someone stops me! ;)

Since I'm new (and obviously excited about tuning my car) I have a few questions and PLEASE don't take what I'm about to ask the wrong way. I have tried to read thru all of the 29 pages in this thread and I want to respectfully ask (Monte I guess) where the 0 to (-)2 target range comes from for the injector slopes? I saw in the awesome opening an explanation on HOW to do all of the logging, data viewing and adjusting. But what I was also looking for was WHY? Why does the slope targets need to be between 0 and -2? I am an automotive test engineer (bla, bla, bla I know) ;) and I test other parts of the vehicle, not the engine itself. I test to specific test specifications and I'm just wondering what the slope ranges are based on. Is it because a totally stock engine with no mods typically runs between 0 and -2 and when mods/tunes are added we need to get the fuel adjusted back to that setting to make sure we don't cause engine damage? Or is it based on some other test data or specs from the OEM?

Again, I'm not trying to be a douch, I'm just looking for some knowledge here cuz I'm a test guy. This is probably talked about somewhere on this forum and if so, can someone post a link? I would love to check it out! :mrgreen:
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xSpiraledx
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RE: Injector slopes?

Post by xSpiraledx »

I'm new to this but have dug through these pages and spent an unhealthy amount of time with my Predator recently so I can tell you what I've concluded with the info I could gather and the admins can correct me later lol.
The leaner (+) the LTFT's, the more knock and pissed off your engine will be as it's getting choked out. Choke it out enough and you'll start to throw codes assoc. with throttle performance and oil pressure switches.
The richer (-) you run, the more gas gets wasted after the ignition in the cylinder and thrown out your exhaust, most likely angering your O2 sensors.
So.. definitely don't want to choke our beasts out when we need to put a Mustang GT in it's place, but don't want to be throwing $4 a gallon out the tailpipe when we're cruising on the highway to work either. Denying the engine from gas when the throttle says it needs it is where I think the damage comes into play (knock and whatnot), and is the more evil of the 2. LTFT's at 0% is ideal because your at the best fuel efficiency. If you're off from 0%, it's better to be in the negative and spew that little extra gas than starve your baby. So thats where the -2>0% originates.
Now we have to factor air temps because we live in sporadic weather. Cold air is denser and the denser the gases are the more explosive, so less gasoline is needed in the cylinder to achieve compression. So we want to log in hot weather. The hotter the intake air, the more gasoline is needed for the same compression, making us run richer. Once we dial in to -2>0% in that weather, the colder night air will bring us up into leaner LTFT's, but the cold air is making up for the gasoline. At that point we can start in on WOT adjustment, which will hone in the fueling even more among 3 rpm ranges. One guy asked if doing all of this damages the engine and it was answered that it if anything increases longevity because its running with proper fueling slope and max. potential. The obvious caution when jumpin up HP over stock is overworking the transmission, but you have far less to worry about than Grand Prix owners. 65E's are temperamental vaginas. G8's are a lot of fun, it'll be mean as F@#$ when you get it fine-tuned.
You should swapcheck and see how much your var. intake affects air temps. If it has a considerable impact, you may want to ask about what it'll do to dslogredux recommendations. Other people in here have needed custom tunes to change the MAF tables and whatnot when they add cold intakes. Lew knows best.
2006 Pontiac GP GXP LS4 Predator U7191 93 No damn dubdubDod
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06MonteSS
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Post by 06MonteSS »

DaveAN55 wrote:Hello All, I'm a noob as well and it's April in the D and temps are around 42F. Am I reading Monte right that the averages should be on the positive side during colder weather? I'm averaging -1 ltft right now. Is that too lean for these temps? If I leave them can I just re-log in a month or two to check where they're at?

I bet if I went thru all 29 pages I might be able to answer this on my own! (':oops:')

Thanks for any input!
no, that's not too lean.. that's too rich...

at 42*, you want your average ltft's to be around +3.xxx
06MonteSS / DiabLew Tune
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DaveAN55

RE: Injector slopes?

Post by DaveAN55 »

Awesome! Thanks very much for that info. My last log was with temps around 42F and I'm averaging in the positive ~1.5. It sounds like if temps warm up the slopes will adjust into the proper range. Is that what I'm hearing? And I agree with you, when the temps are hot I'll be checking them again. Until the temps warm up should I not be doing WOT's? ITS soooo much fun though....=)

I'm really impressed with how the predator has brought the car to life. After I installed the Vararam intake and logged my first run my LTFT's were (+)9.5! I was starving the beast apparently, well the Vararam was! The car pulls really really hard now. I noticed on my cruise yesterday that my intake air temp was identical to the ambient air temp! They were both at 16C with no difference between the two. I don't have my original intake any longer so doing an A to B will not be possible. I have had a home made CAI for the last couple years and finally broke down and bought a proper one. My original is long gone.

I have one more question that I hope someone can point me in the right direction. Where can I get a list of changes from v9r28 to v9r29 for the u7194? I'm just looking for what changed between the two revs. What improvements were made etc.?

Thanks again xSpiraledx
DaveAN55

RE: Injector slopes?

Post by DaveAN55 »

Monte, since im at +1.5 and temps are on the rise should I bother adjusting the LTFTs?

Thanks!
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06MonteSS
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RE: Injector slopes?

Post by 06MonteSS »

if you're at 1.5 and it's only about 42* out, I would lean it out a little to get your average up to around 3.xx... because once it warms up and gets in the normal 80 and 90 degree weather, the ltft's are gonna drop, and in those normal higher temps is when you want the average to be about -2.xx ...

so if you're at only 1.5 now and it warms up, thats gonna plummet down and you'll probably be around -4.xxx or so...
06MonteSS / DiabLew Tune
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2014 Camaro SS - 2SS, RS pkg., short-throw shifter, NPP perf. exhaust, BMR strut-tower brace, Cold Air Inductions cold air intake
www.diablewtune.com -- www.diablocustomtune.com -- www.diablocustomtunegm.com -- www.diablocustomtuning.net
DaveAN55

Post by DaveAN55 »

Thanks Monte...sounds good!

I'm curious....why doesn't the ECM or ECU or computer adjust the slopes automatically (where they're supposed to be) with the atmosphere/temp changes or do they? You mentioned that they will "plummet" Is that the ECU "auto-adjusting"? Would seem to me that should be the ECU's job to keep that optimal. I'm sure I'm missing something.
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xSpiraledx
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Post by xSpiraledx »

Please correct me if I'm wrong...
Pretty sure the goal of the ECM is to keep AFR balanced through it's sensors. LTFT's are the emission results of the AFR, and the fuel amount is ever changing with the density/temp of the air brought through intake (which is the MAF doing it's job). When we adjust + or - in the tuner, I'm pretty sure we're tricking the PCM/ECM into believing there is a different size/pressure of injector (usually smaller so it sprays more), which will be fed differently. So you may be pushing the same amount of fuel to meet your AFR, but the injector size will determine how much to spurt in at a cycle, or more importantly when revving up a larger injector is capable of passing more fuel through it when needed, hence when ppl slap on a turbo or S/C and are dealing with all of that forced air they usually have to install aftermarket injectors to keep up with the revolutions. Remember, +/-%'s on slope represents size of injector, and +/-%'s in LTFT's is presence of fuel in the exhaust.
Using the slope tuner is basically custom fitting an injector to the computer using the ones already existing.
So when the LTFT's plummet like he's saying, your ECM is auto-adjusting the AFR, and the resulting LTFT will be a richer -2% because the air is thin and hot so more fuel is needed in the ratio. And vice versa, when that air is cold, dense, and explosive, the ECM will back off the fueling to let the O2 do the work, and LTFT's will be in the +3 range we're dealing with now.
Last edited by xSpiraledx on Sun Apr 15, 2012 9:39 pm, edited 1 time in total.
2006 Pontiac GP GXP LS4 Predator U7191 93 No damn dubdubDod
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xSpiraledx
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Post by xSpiraledx »

The hottest it gets around here is usually 87-91F, and that is at peak. My guesstimate for avg. summer temp is 78-81F with high humidity. My intake (stock) usually runs 20ish degrees warmer than ambient when I'm up to running temp.

If I dial in to 0% LTFT on an upcoming 72-74F day, is that enough allowance for peak temp days to max at -2%?
If so, would it be ok at that point to start working on WOT in dsredux because its within parameter range, or should I still wait for the hottest weather?
2006 Pontiac GP GXP LS4 Predator U7191 93 No damn dubdubDod
DaveAN55

Post by DaveAN55 »

Nice write up xSpiraledx! Koodos for that explanation (if the admins dont disagree! ;) Alright then, I think I'm going to have to read that a few more times for that to all sink in!

Your next question is a good one too. I was going to make a small adjustment like Monte suggested but I was wondering if I could go and do some WOTs at the temps that are out there NOW. From the sounds of it I'll have to redo them anyway when the warmer weather hits. From what I can surmise from all the info, doing WOTs at the same temps that I've done the cruising should be OK.

Is that logic sound?
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xSpiraledx
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Post by xSpiraledx »

Thing is Dslogredux doesn't want you to, nor will make recommendations for WOT unless the logs read -2>0% LTFT, we're kinda stuck until we can get those logs in warmer weather, so that makes WOT logs kinda pointless. It would suck to assume slope and do all the WOT's only to have to readjust because of LTFT's and do it all over. I'm sure it's pretty safe to flash repeatedly and replacing a PCM wouldn't be the end of the world, but I still don't want to treat mine like an Etch-a-Sketch. You dont have to be logging to have fun with WOT lol. Plus I think it makes more sense to just be patient and dial both of those at the same time in the same warmer temp., right now we're just estimating because of colder weather. 93 is $4.29 right now where I live so the hour long trips just to highway log can wait, I think I'm dialed in close enough until those sunny days. In the meantime I just do practice runs wrestling stupid torque steer with the pedal to the floor through the tunnels in the early am.
Once we can get to 0% redux will be good to go on recommendations, we just need to find out whats an acceptable temp for 0% without ending up to lean/rich on those days in the 90's.

I'm curious if your CAI should have you expecting excessive recommendations in redux because of the higher LTFTs than a stock intake. Running identical ambient/intake air with a hot 6.0 sounds pretty damn good and may require some allowances in the App. or maybe even a custom tune.
2006 Pontiac GP GXP LS4 Predator U7191 93 No damn dubdubDod
DaveAN55

Post by DaveAN55 »

I hear you. I don't want to treat my baby that way either. I hold my breath every time I flash that ECM.

Well this whole WOT thing has me a bit concerned. If we cant calibrate the WOTs till it warms up, do we run the risk of damaging something if we DO WOT right now? I dont have torque steer to deal with just rear end drift! I really like RWD!

Yeah, my CAI is the Vararam OTR style and they claim that the intake temps will be much cooler than a traditional CAI where the filter is located inside the engine compartment. I was a bit skeptical at first but the data isn't lying. I have seen people attach files, maybe someone that has more experience looking at those can take a look at mine and see if I need to adjust something else or if I need a custom tune?
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xSpiraledx
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Post by xSpiraledx »

When you try to move onto WOT in dslogredux without the app reading -2>0% in the analyzed log, 3 or so popups appear with lots of exclamation marks in them warning you not to proceed until injector slope is dialed in correctly, so I would say that's a bad idea.
I much prefer RWD but I only had 12k to spend so no G8 or CTS spec, I don't like Fords, I wanted 300+hp under 60k mi, and I'm 6'2" 295lbs. which rules out almost all coupes and midsized sedans. That didn't leave a long list. I was drawn to the quirkyness that is the GXP and even though every time you work on it it results in yelling, "Why the F@#% would they engineer that like that!??!!!" I love that car more every time I drive it. I like the contour of the body, it's super light (4d and only 3600lbs.), 0-60 in 6, and tons of options like tapshift/HUD/H. leather/18" wheels/r. start/6 disc/and black on black, so FWD was just the unfortunate compromise, but back on topic...
As for your CAI, you'll just have to find out from Lew if dsredux is cool with it or if it needs further examination. Just remember to show some love in the tire/alignment dept. too if needed, so that HP you're buildin up shines through. Worn or cheap rubber can throw a second or possibly more onto your times easy, and you want that grip for your 'stang-eater.
2006 Pontiac GP GXP LS4 Predator U7191 93 No damn dubdubDod
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