strange rev delay off idle

[8aHemi]

I have a 09 G8 (l76) that ive been through several tuners with and noone can seem to get it right, so i decided to get myself HPTuners and try and learn the ropes. Thus far the only thing ive tinkered with was the MAF curve, as my fuel trims tend to go negative, still trying to get it dialed in. I only really have 2 issues with the tune, WOT is great, higher RPMs are great, but if I give it a rev from neutral or clutch in ect, from idle the rev will seem to hit a wall in the 1300-1500rpm range, drop a little, then bounce up a tiny bit more back to 1500ish RPM. Id have to assume its something to do with either A: my blowoff valve opening and messing things up (procharged) or b: something with timing, but I could be completely wrong, as i really am not that confident with what im doing just yet. the second issue is breaking up also around 1500-2100rpm that only seems to happen when your at very low TPS input that seems to go away when i reflash the tune for whatever reason, Id assume its some learned parameter messing things up, and my fuel trims were out of wack, -15-25% at times setting the CEL. Like i said im slowly working on getting those dialed in yet. Car is MAF only from my understanding of looking at the file, as dynamid airflow enable/disable values are 300-200RPM. I read somewhere that the car will still referance the VVE table still though, which that table looks ROUGH, peaks, vallies, ect. The biggest valley is where im assuming someone took a lot out of it when the BOV opens up, as its at a very low Kpa and around 1800-3200rpm. If anyone is able to point me in the right direction, id appriciate it, Like i said im about a week into having HPTuners, and ive been doing nothing but watching videos and reading forums on how to-s. because at the end of the day, im the only one who can log it consistantly and dial it in, and hopefully not blow it up in the learning process lol. In the log file, you can see at 05:42:33 i give it a wack to around 90%TPS and instantly back off of it, and it has some strange RPM behavior, maybe im crazy but id expect more than 1400RPM out of that.

[Alex14SS]

When you mention the rev hitting a wall around that 1300-1500 rpm range, two main things come to mind. First, with your car being Procharged, your Blowoff Valve (BOV) might be opening a bit too early. If it's releasing pressure prematurely, that could be causing the air/fuel mixture to get out of balance and leading to that rpm drop you're experiencing. Secondly, there might be something happening with the engine timing. Maybe there's a specific timing retard happening in that rpm range? It could be the ECU detecting knock or some pre-configured timing table kicking in.

The breaking up you're observing around 1500-2100 rpm is interesting. Your fuel trims are showing that the car is running pretty rich. The ECU is pulling a significant amount of fuel. This richness could be the root cause of the breaking up. Refining the MAF curve is definitely the right direction to correct this. But the fact that it goes away after a reflash suggests there might be a learned parameter or an adaptive value that's causing problems.

Regarding the MAF vs. Dynamic Airflow, if your values are showing 300-200 RPM, the ECU is mainly leaning on the MAF. However, it can still reference the VVE (Virtual Volumetric Efficiency) table in some situations. If that table has peaks and valleys as you described, it could be contributing to the erratic behavior. It's important to have that VVE table smoothed out, especially if it doesn't match the current setup of the car.

When you were logging, particularly around that 05:42:33 mark, I'd advise looking into parameters like Spark Advance, Knock Retard, and Air/Fuel Ratio. It'll provide a clearer picture of what's happening during those odd rpm behaviors.

Keep working on that MAF curve to get the fuel trims closer to zero. Check the timing around that 1300-1500 rpm range, and perhaps experiment with a different BOV setting or even try another BOV. And, of course, given the state of the VVE table, I'd recommend focusing on it, especially around the areas causing problems.

[edcmat-l1]

Need the full list of mods. What blower, what injectors? Be specific don't just reply "80 lbers". What intake, t-body, headers? Cats? Stock or aftermarket cam?

Looking through the file, it looks like the idle airflow is way too high. That's most of your idle hang problem. I'd go back to stock and if it has a problem idling or returning to idle increase it slowly. I think you'll find it doesn't need to be nearly as high as it is.

Concentrate on the RPM columns up to 1200.

The VVE is not correct that's for sure. Need to fail the maf and dial it in.

[8aHemi]

When you mention the rev hitting a wall around that 1300-1500 rpm range, two main things come to mind. First, with your car being Procharged, your Blowoff Valve (BOV) might be opening a bit too early. If it's releasing pressure prematurely, that could be causing the air/fuel mixture to get out of balance and leading to that rpm drop you're experiencing. Secondly, there might be something happening with the engine timing. Maybe there's a specific timing retard happening in that rpm range? It could be the ECU detecting knock or some pre-configured timing table kicking in.

The breaking up you're observing around 1500-2100 rpm is interesting. Your fuel trims are showing that the car is running pretty rich. The ECU is pulling a significant amount of fuel. This richness could be the root cause of the breaking up. Refining the MAF curve is definitely the right direction to correct this. But the fact that it goes away after a reflash suggests there might be a learned parameter or an adaptive value that's causing problems.

Regarding the MAF vs. Dynamic Airflow, if your values are showing 300-200 RPM, the ECU is mainly leaning on the MAF. However, it can still reference the VVE (Virtual Volumetric Efficiency) table in some situations. If that table has peaks and valleys as you described, it could be contributing to the erratic behavior. It's important to have that VVE table smoothed out, especially if it doesn't match the current setup of the car.

When you were logging, particularly around that 05:42:33 mark, I'd advise looking into parameters like Spark Advance, Knock Retard, and Air/Fuel Ratio. It'll provide a clearer picture of what's happening during those odd rpm behaviors.

Keep working on that MAF curve to get the fuel trims closer to zero. Check the timing around that 1300-1500 rpm range, and perhaps experiment with a different BOV setting or even try another BOV. And, of course, given the state of the VVE table, I'd recommend focusing on it, especially around the areas causing problems.

Gotcha good to know I'm atleast headed in the right direction, would I have to worry about changing my WOT afr on accident via getting the fuel trims to 0? I?ve just been messing with 6000hz and lower on the maf, because as of now WOT is awesome and AFRs on point.

[8aHemi]

It has some sort of cam in it, I'm unsure of which as the previous owner put it in. Full exhaust, its actually a torque storm blower, which makes 8.9psi through my intercooler. (Not procharger I know but its more well known same concept) it has siemens deka 80lb injectors, I'm not sure of the maf and map sensors but they are the appropriate ones that are needed for boost. Everything else is original on it for the most part, but they come with ls3 heads and intake ontop of a 6L. Car is also manual swapped to a tr6060 from a 6l80e if that matters

Another thing I noticed on the tune was that the Low octane spark table timing is set higher than the high octane table, and its my understanding that if it starts to knock it will switch to the "low" table. I ended up copying my high table to the low table and subtracted 5 degrees across the board. In my mind that seems much safer

[Alvin]

Typically when the VVE isn't tuned at all you'll a issue exactly like that.. Looking at yours. it looks pretty obvious no one did it. You have a dip in VVE exactly where you describe the problem. The car will reference VVE on fast throttle movements and such.

The rest of the tune is a bit sketchy too.. The PE especially.

[8aHemi]

Typically when the VVE isn't tuned at all you'll a issue exactly like that.. Looking at yours. it looks pretty obvious no one did it. You have a dip in VVE exactly where you describe the problem. The car will reference VVE on fast throttle movements and such.

The rest of the tune is a bit sketchy too.. The PE especially.

Yeah I figured as much, I just don?t know what to look for, does PE matter so long as AFR is right at wot? It?s always around 10.9-11.5 wide open up to 6700. It?s my understanding that PE is used to richen it up when wide open? I?m assuming he just played with the maf curve to richen it up instead

[GHuggins]

Almost looks like someone using a software that doesn't allow them to see the virtual VE tuned it and just multiplied the coefficients. Only way I can make sense of what was done to the VVE table. Timing also has some weird dips off idle.

I think if you continue dialing things in it will get a lot better. Might even want to start with some of the tables put back to stock.

[8aHemi]

Update, I got my MAF dialed and im happy with the result there, -3% everywhere up to 6000Hz, I then failed the MAF and started working on the VVE, to which i eventually gave up and started with a stock ctsv v2 VVE file. I only got it up to 3000rpm while playing with VVE, as i plan on setting my dynamic airflow lower than that, and didnt want to take it WOT with the maf failed. Anyway with the MAF still failed I noticed the area i was having my problem seems to be much smoother, however if it drops below idle (its manual and thats just how i drive) for even a split second its VIOLANT breaking up surging, and its also hard to start up with the MAF failed, itll crank for a while, then eventually fire then die. If i give it throttle assistance while its starting i can get it to hold idle, and then its fine for the remainder of the trip. Id have to guess my VVE is way off below idle RPM, but how would you get good data in those areas? I did get some cell hits when taking off from stop signs intentionally letting it drop and freak out, but they come back to -4-6% so im kinda lost. When i was happy with the numbers I then re enabled the MAF and turned DFCO back on, and it still has the same issue below idle. But all else is well so far. I believe i have the dynamic set at 2900rpm if i remember correctly. anything i could do to hopefully get this ironed out? Also im worried about going WOT after drastically changing the VVE. From what I understand it pretty much exclusively uses the MAF at higher rpm/load, so I should be fine?? attached is both the tune, and the log on this tune. The VVE graph looks alot smoother, but still isnt perfect by any means. I just cant get data in some areas, and as I said, its only been tampered with up to 3000rpm

[GHuggins]

You still have some pretty bad dips and jumps in the VE. Look at it in 1 bar format to see them. Hand edit the areas outside of where you're getting data for to keep transitioning zones the same. Cringer's new Ve tool allows you to do this fairly easily. Just make sure to watch his version 1.5 video on youtube for clarification on how to use it.

Also since you have a manual. gears and engine loads are your friend especially when combined with the scanner's output controls. Use the scanner to lower the rpm down and then ease out the clutch to change the load for that rpm then either do it starting onto a hill or ease the brakes on some.

Finally - VE still plays into wot fueling no matter how the dynamic settings are set, just not as much so don't be surprised if it's off just a little from what it was. It shouldn't be bad enough to keep from going wot as long as it was close to begin with.

After all of that you can start tweaking the min air and idle controls to get things even better.

[edcmat-l1]

Update, I got my MAF dialed and im happy with the result there, -3% everywhere up to 6000Hz, I then failed the MAF and started working on the VVE, to which i eventually gave up and started with a stock ctsv v2 VVE file. I only got it up to 3000rpm while playing with VVE, as i plan on setting my dynamic airflow lower than that, and didnt want to take it WOT with the maf failed. Anyway with the MAF still failed I noticed the area i was having my problem seems to be much smoother, however if it drops below idle (its manual and thats just how i drive) for even a split second its VIOLANT breaking up surging, and its also hard to start up with the MAF failed, itll crank for a while, then eventually fire then die. If i give it throttle assistance while its starting i can get it to hold idle, and then its fine for the remainder of the trip. Id have to guess my VVE is way off below idle RPM, but how would you get good data in those areas? I did get some cell hits when taking off from stop signs intentionally letting it drop and freak out, but they come back to -4-6% so im kinda lost. When i was happy with the numbers I then re enabled the MAF and turned DFCO back on, and it still has the same issue below idle. But all else is well so far. I believe i have the dynamic set at 2900rpm if i remember correctly. anything i could do to hopefully get this ironed out? Also im worried about going WOT after drastically changing the VVE. From what I understand it pretty much exclusively uses the MAF at higher rpm/load, so I should be fine?? attached is both the tune, and the log on this tune. The VVE graph looks alot smoother, but still isnt perfect by any means. I just cant get data in some areas, and as I said, its only been tampered with up to 3000rpm

Your VVE doesn't look at all like a gen2 V. Even if you consider <105 Kpa and >3000 rpm it doesn't even look close.

Most of you injector data is still stock. That's going to bake a lot of incorrect data into your tune, both VVE and MAF tables. That will lead to incorrect idle airflow data, weird tip-in issues, etc. Biggest problem with using incorrect inj data is almost all of the incorrectness is going to be at idle and right off idle.

Need to find the appropriate data for your injectors, set them up correctly, then redo everything.

[8aHemi]

I guess I dont know what im doing wrong then, I started with a base CTSV VVE, first log showed -30% everywhere i could get data, so i just did the whole VVE x .8. Graphs still smooth as expected at this point, but in order to fine tune areas Id copy data against fuel trims paste special half % and after doing that a few times i ended up wiith the graph as shown. As for injector data, I couldnt really find much but came across someone on here that had his injector data hpt file, and when compared to mine they were identical. Its my understanding that this ECU wont accept 80lb injectors and you have to scale something up to get it where it needs to be. Also, apparently I lied, as the 1800-2000 stumble is still present, its annoying that it wont do it every time, for whatever reason

[edcmat-l1]

I guess I dont know what im doing wrong then, I started with a base CTSV VVE, first log showed -30% everywhere i could get data, so i just did the whole VVE x .8. Graphs still smooth as expected at this point, but in order to fine tune areas Id copy data against fuel trims paste special half % and after doing that a few times i ended up wiith the graph as shown. As for injector data, I couldnt really find much but came across someone on here that had his injector data hpt file, and when compared to mine they were identical. Its my understanding that this ECU wont accept 80lb injectors and you have to scale something up to get it where it needs to be. Also, apparently I lied, as the 1800-2000 stumble is still present, its annoying that it wont do it every time, for whatever reason

The injector flow rate is only one part of the equation. Your offset and small pulse widths tables are still setup for the stock injectors. If these are wrong, all of your trim data will be wrong. Which will lead to your airflow tables being wrong.

[8aHemi]

I ended up playing with fueling some more, on both the MAF and VVE side. As of now my 2000 stumble/breaking up has gone away, fuel trims are better than ever, For whatever reason it tends to drive rich when cold, I havent kept a tune in it long enough to see if it will continue or not. Anyway yeah its driving better for sure, however I am now trying to figure out a surging going on at 1500rpm in low gears, Its done it since it got manual swapped, so I kinda just checked it off as something with the clutch but that doesnt seem to make sense the more i think about it. Itll be smooth up to 1500, and smooth past 1700ish but somewhere in that range, also at VERY low TPS input (scanner will read 24% and idle it reads 22%) Feels exactly like your at too low of a rpm for the gear, just overall jerky in nature. I think im going to do as edcmat suggested and mess with some injector data to see what happens, I cant really find reliable data on the Deka 80s, however I found a few and the only thing they have in common is the Min pulse width, at 2.508 if i remember correctly. Mine was set at 4.000. I plan on changing that, what other tables should I be looking at? I know He stated offset and pulse width tables, if you could be more specific I would appriciate it, as it seems every ECU has slightly differant names for functions, that are also very close in wording lol. I ended up setting my dynamic airflow back to 200/300rpm as it was having problems starting and stalling when the clutch was let out with the MAF failed, I havent tried both active at the same time long enough to say if that issue is still present or not. I also ended up doing alot more manual smoothing to the VVE table. Just tinkering away testing things. Is there some table that makes the transition from idle to off idle? Also is the car considered idling to the ECU as long as your off the throttle?(even if your coasting down?) The idle I know is like 800RPM but after looking at things im curious. Honestly my biggest problem right now is parking lot / drive through scenarios where you gotta creep around that 1500 range that it hates so much. Thanks

[8aHemi]

step 8 halved prop CL.hpt1500Surge + slight spark fluctuation.hpl

log was trimmed way down focusing on the issue area, I noticed the spark is slightly fluctuating, even though that range is all set to a constant 30degree. I cant seem to figure out the why behind that. Id have to assume this issue is spark related??