07-11-2020, 04:07 PM | #15 | |
Drives: 2016 1SS NFG A8 Join Date: Aug 2017
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2016 NFG 1SS A8
Options-2SS Leather/NPP Perf. mods-Whipple 2.9/Fuel System/Flex Fuel/103mm TB/Rotofab Big Gulp/Cat Deletes/Corsa NPP Per. times- 10.5 @ 137 w/ 1.8 60ft Full weight on 20's 1200DA |
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07-11-2020, 05:53 PM | #16 | |
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07-11-2020, 07:31 PM | #17 | |
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It is, however, what you touched on is much more important, repeatability in a consistent matrix of comparison. What were your induction points before the mods? Remember also atmospheric density is a factor in actual MAF calculations. Simply looking at someone else’s MAF readings is a bit of a misnomer. A person on a dry winter night at sea level is going to have drastically different reading than a hot humid day in Denver Colorado. The other side of efficiency is valve curtain, or more over duration/lift/lobe acceleration as well as opening closing event points, in relaton to TDC/BDC, & given engine dynamics. The main thing to realize is VE is also a function, to a point, of spacial displacement over time, or more over not piston velocity but piston acceleration. In other words the faster the piston creates cylinder vacuum the faster the that negative pressure is transferred to the incoming air molecules. Someone even mentioned a compression test, I even say a leak down would be in order, in truly diagnosing a possible issue. That being said, you, personally, could have an issue with cam timng, which I alluded to before, & that you acknowledged, that could be causing you a detriment in VE. Last edited by gtfoxy; 07-11-2020 at 07:43 PM. |
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07-11-2020, 10:22 PM | #18 | |
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Also can you explain more about what you are saying about spacial displacement over time? I don't see what piston acceleration has to do with anything, and to me I see VE more so as a "dynamic" or "effective" displacement, which is time dependent. I see "tuning" an engine (bigger cams, longer/shorter intake runners, headers, etc.) as just doing everything at the right time, or matching its "resonant frequency", just like when you push someone on a swing you want to push them at the right time, the time being when you push in the same direction of their current velocity. This is most "efficient" because you want to do you work/energy input into the system at the right time. Last edited by cmitchell17; 07-11-2020 at 10:43 PM. |
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07-12-2020, 06:45 AM | #19 | |
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What I was trying to get at is, as it relates to VE as well as energy conversion, it’s all cyclical. Well, you touched on something with your swing analogy that is exactly right, albeit it’s way more complicated than that due to piston acceleration rates (looking at it from a static RPM perspective for comparative purposes) & is also a function of Rod/stroke ratio, as it pertains to energy conversion, ie. BSFC. That is pumping losses. Ask yourself a questions; Why is WOT ignition timing always BTDC? With that question in mind, apply it to your swing analogy as it relates to pumping losses. |
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07-12-2020, 07:25 AM | #20 |
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Let us know how that lt376 cal works for you.
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‘22 2SS 1LE M6 Summit White - RF, Flexfuel, LT2 intake, 95mm tb, ATI udp, VT ramair, full 28” dragpack - 11.68@122
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07-12-2020, 10:44 AM | #21 |
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Yeah haha, I know its just more confusing mess that we see in stock tunes that has zero explanation.
But I think I notice less unburnt fuel smell now, it could be placebo but I let it run in my garage and I noticed less of the 2 stroke exhaust smell that sticks to your clothes and hair. I copied over the proportional constants and lean/rich switching voltages from the O2 feedback section and it appears like the O2 sensors are switching faster and have a more stable switching as well. I used most of the GMPP timing settings as well. I would hope that the very high low load timing in the GMPP map is just the result of the calibration engineers not at the mercy of keeping emission in check. I did notice the cranking timing doesn't work correctly, its way to high and makes the engine rev up too much on startup, I took my existing cranking timing table and blended it but I will probably switch back to my stock one since that seemed to work, except for the common hot start cammed engine issues that intermittently come up randomly on hot restarts. What's interesting is they use the same virtual torque tables as a stock LT1. This is exactly what I suspect as I feel for a proper tune VT shouldn't have to be touched unless you make fundamental changes to compression or significant changes that would reduce load or friction. I did not use the VVE yet, but I may try it. The slight off idle stumble/hesitation is still present, especially when cold, but I had the same issues on my previous tune. I just assume this is just something you have to deal with on a big cam. I also still have the low rpm stumble that happens when rolling in reverse or drive at a higher rolling idle then switching gears and it allows the idle speed to dip to low, which it doesn't kill the engine its just annoying. I copied all the other timing adder tables as well, expect for the alcohol adder table I used my existing one that came from a 5.3 flex fuel truck, at WOT I get about a flat 25-26 degrees of timing which I think looks pretty optimal with no KR. I am also using their transient coefficient tables which I saw were different than my stock ones, I would hope they tuned these to optimize them for a cam. I kind of want to see how it does MAF only since they have it set to disable dynamic airflow and use MAF above 400 rpms, although they still populated a VVE table for torque prediction I guess. Also its interesting that their driver demand tables, which is in engine torque and not trans torque (mine are in trans torque so I'm not sure I can copy those over) only requests a max torque of 455, which I think it makes over 455 ft-lbs? They do however raise the "max torque" table as well. |
07-12-2020, 11:32 AM | #22 |
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I wouldn’t change the o2 settings, been there done that got the t-shirt etc. Those are just run of the mill vette values and I could not get them make this car run better...total waste of time. If you compare the lt376 file against a vette File you will what was changed just for the H/C. For this tune they started with a vette base file so I was looking on what they modded. I see they didn’t touch the o2 values, I tweaked mine for headers but after seeing this tune I went back to OE myself
I’d stick with vve, dd tables, virtual torque, the pedal torque rate limit tables(keep the stationary one to disable), idle tables(including proportional), max torque, timing table Ok. For DD I think mine are the same because they are both M6 I wonder if u can lie the lt376 dd map on the ca6 ss m6 map to solve for percentage changes and then u can apply that to yours so units wouldn’t matter? Edit: The vve tables are turned off on this tune. Dynamic airflow is set to disable at 400rpm. If you try to set yours this way, I would not be convinced the vve table is completely ignored and believe it could still be referenced for lesser significant calculations. I would likely just stick you oe vve table back in there. Idk why you’d run maf only on a cammed car. Honestly.
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‘16 1SS M6 LT2 intake + boltons on DR 11.0@126+ (Sold) Last edited by 6spdhyperblue; 07-12-2020 at 06:42 PM. Reason: I got to read The rest of your post |
07-12-2020, 07:27 PM | #23 | |
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I really wonder who is programming the GMPP tunes? I wonder if its the same people who do the OEM tunes? Or if its someone not as experienced with OEM calibration and who doesn't communicate or talk with any one else that does? |
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07-12-2020, 07:43 PM | #24 | |
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07-12-2020, 09:02 PM | #25 |
Drives: 6th gen Join Date: Aug 2013
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Yeah I don’t get this tune. The injection timing is unchanged too. You think that would’ve been changed but it doesn’t look it
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‘22 2SS 1LE M6 Summit White - RF, Flexfuel, LT2 intake, 95mm tb, ATI udp, VT ramair, full 28” dragpack - 11.68@122
‘16 1SS M6 LT2 intake + boltons on DR 11.0@126+ (Sold) |
07-12-2020, 09:28 PM | #26 |
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Why do you think the injection timing would need that much changing? I think most of the reasoning behind why the stock injection timing is all over the place is probably emissions and trying to balance how much time is allowed for the fuel to mix with the air vs the heat transfer from the air charge into the fuel mixture. I think there is a trade off to optimize emissions and combustion quality since you can't just inject it as early as possible I think?
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07-12-2020, 10:42 PM | #27 | |
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07-12-2020, 10:51 PM | #28 | |
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It drives me insane to see all the inconsistency in the stock GM tables, I don't know if we could ever get to the bottom of why unless we could actually ask the calibration engineer who did it. I have a feeling they are not using a nice GUI interface like we have with HP Tuners and EFI Live and they may even have to handoff parameters they choose over to a software engineer who then complies the code and maybe stuff gets lost in translation? |
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