Chasing Misfire / Fuel Cut at High Boost 22.5 psi

[Crewz]

Hey Gang,

Been chasing my tail trying to figure out why, what seems like a fuel cut, at high boost.

First, here is the platform and the hardware mods relevant to tuning.
2012 Cruze Ecotec 1.8 (Came NA)
Reground Stage 2 cams by Crower
SuperTech Beehive springs / retainers
10.2:1 CR
1050x ID injectors
Radium pulse damper / and fuel pressure regulator
DW300c fuel pump
Pump E85
VIM delete with custom aluminum intake manifold / LSJ throttle body
GT3582r turbo with billet wheel
3.5" intake with bellmouth w/ MAF
3" Turbo back exhaust
14 lb spring in waste gate
AEM TruBoost X controller
3 bar GM sensor
N2MB WotBox

RPM fuel cut is set to 8,192 (have done a write entire)


Have both MAF and VE tables pretty dialed in, both in closed and open loop. PE is set to .8 Lambda.

Things I have tried to eliminate the issue:
BKR7E gapped from .015-.020
4554 8's gapped from .015-.020
LS D585 coil upgrade


Tuning side of things I've tried:
Accel Thresh
Raising boost cut on fuel system to 30 psi
Adjusting max high flow psi to 88 psi
Played with timing, even pulling it down to 1-2? advance.


I'm stumped here. I've logged many runs and tried many tweaks. Attached is my current tune, and the OE tune pulled before any mods. I've also attached a run where I pull in 1st, 2nd and 3rd. As soon as boost hits 22.5 it just falls on it's face. Ideally I'd like it to hold that boost throughout until the rev limiter I've set of 8,200 rpm.

Any help or thoughts is greatly appreciated.


-Matt

[Dutch]

Can you give this a try? I increased the torque limits around where I see boost ramping in.
If this helps, rescale the X axis to match your intended RPM range, and try to keep the numbers close to the values for Engine Torque in the logs.

Id also recommend disabling VVT entirely (Set camshafts to None instead of zeroing the table) - im seeing reported cam error and we dont want the ecm trying to correct it.
Please return the minimum spark to its stock values. Because of the way the ECM operates, not allowing the ECM control authority to pull a bunch of timing could make the engine rev out unexpectedly in certain failure modes, like if you develop a crack the intake manifold.
Mod289-tmtest01.hpt

Have you considered switching to a standalone like AEM Infinity?

Whats happening is the following:
The ECM believes in its mind that its controlling a completely stock 2012 Cruze.
It knows how much torque the engine should be making at a particular rpm, airmass, etc.
When you floor the accelerator, you are telling the ECM "Hi I want to make 100% torque now"
Unlike the E38 ECMs, 100% pedal does not mean "I'm gonna hold the throttle 100% open regardless of what the engine is doing".
100% pedal instead means something like, "Ok you want approximately 138lb/ft of torque. According to my model, in order to achieve that the throttle should be wide open."
The engine behaves normally because so far the predicted torque is more or less matching what its model expects it to see...
until your AEM TruBoost X controller spools up that GT3582R.

The ECM sees the 550g/s of airflow, does the math, and then soils itself because it calculated 318lb/ft when its expecting 138 lb/ft.
It then freaks out, first tries to control the situation by pulling timing, but because you capped the lower limit to 2 degrees, it didnt help.
So in a last ditch effort to try and wrestle control back, it pulls fuel.

Thats what I see in the logs.

Torque based systems are not enthusiast friendly. HPTuners gives you access to the model and better ways of visualizing it but its not pretty. Unless you only made minor changes to the underlying engine system (changed a cam or added a cold air intake), it takes way more time and effort than its worth to correct the model to match the actual engine configuration.
There are no master disables for this system in these ECMs. You will have to play with torque limits and its torque models until the engine does what you want it to do.

If playing around with those settings still makes the ECM panic, you may have reached the limits of what can be done with the factory ECM.
I think you'll get better, quicker results by switching to a standalone like AEM Infinity or megasquirt.

Remember the factory controls are designed to meet emissions requirements and keep the engine from blowing up in its warranty period no matter what.
GM clearly did their homework in that regard - it managed to wrestle control back despite having its spark control authority essentially disabled, and having no idea a GT3582R was bolted to it.

[RoninDusette]

May I suggest some things? I've been tuning the Cruze for like 4 or 5 years now consistently. I may be able to shed some light or ateast my experience.

Id also recommend disabling VVT entirely

No. Don't do that at all. So it's not VVT it's variable cam timing I guess you can call it variable valentiming but it's not like vtech. It's very cool cam timing as in it changes the advance and retard or rather how much retarded how advanced your intake and exhaust cams are from top Dead center respectively. It's a fundamental function and it's part of how this engine or these engines work. You don't want to disable it because you're disabling a fundamental aspect and actually a really cool feature that if you learn how to use it right you can actually make more power and certain areas where you otherwise weren't able to even without getting another cam. You can adjust your overlap have more or less and place that overlap where you want it or don't want it be on the cases where you want less overlap to get your turmer to smoke quicker faster acceleration higher cylinder pressures etc. Like it's not something to be afraid of but it's something that you know takes some work I am kind of screwing around with until you get it right I still play with my cam timing not all the time but like every couple months I go back and kind of just revisit it and you know move a couple of degrees here and there and I've had it to where my car makes mad power at the bottom and actually still carries power all the way through 6,000 RPM. I just don't have a built head so I tend not to take it up there all the time although I still bring it up there quite frequently and I really need to stop doing that. LOL

As far as you hitting a boost cut what's your running into at least what I think anyway is you're running into either the end of the resolution or the maximum resolution of your mass air flow sensor. Mine does the same exact thing. If I hit a certain psially right about where you're saying it falls on its face it just like hits this hard cut like everything shuts down. So to be honest I got tired of dealing with it. The mass air flow sensor is nice don't get me wrong it helps with a nice buttery smooth idle at least in my opinion it does it just things tend to run a little bit nicer when I have the mass air flow sensor enabled but during the course of tuning I realize that when my car isn't speed density the vehicle runs more reliably and more consistently without the mass air flow sensor in the way. The mass air flow sensors are very temperamental sensor and while useful you run into issues where the mass air flow sensor at like 14,000 Hertz or whatever it's maximum resolution is isn't enough to account for all the air and I think that's why it's falling on its face because I've tried everything from changing the airflow correlation tables to I mean you name it I've changed every single table that I can think of and maybe I'm missing something but I gave up on trying to keep the mass air flow sensor enabled at all. I don't get me wrong you don't want to just unplug it either it has the temperature sensor in there it's still plays a fundamental role but I just failed the math and just run in speed density with closed loop or speed density closed loop whatever you want to call it. I failed the math and I just dial in my ve tables just keep dialing in the vde tables like very very well if you're having issues where you're running super rich or lean then you need to start going over to your temperature modifiers your adders and multipliers blend tables if you're running E85 those need a bunch of attention. And if you're wondering what I mean by the temperature tables I mean injector valve temp so your ivt tables those more have to do with cylinder temperature but those help out a lot and then you have some intake air temperature modifiers as well that you know kind of play around with the base air fuel mixture that's going to go into it when you're running in closed loop. You have your open loop tables and those are relatively straightforward. You can just leave those unless you're really really heavily modified or you're running E85 but even then does ecuse if I'm not mistaken I still have alcohol tables so if they have alcohol tables modify the alcohol tables and the IBT table is based on your blend so if you're running 80% ethanol there's a 60 and a 60% and an 80%, you're not going to be in the 80% range you're going to be too you're going to be tuning everything in the 60% alcohol range because you're probably not going to be pure 80 all the time I know out here I'm lucky if I get. I get about 79.99% and that percentage means that I'm in that I'm in the road right below it far right above it. So it'll be in the 60% range tune to 60% range and then don't worry about the 80% I mean scale it a little bit you know above what that is but just in the 60% everywhere around there. If you're not running flex-fuel you don't have to worry about it but if you do that and you set your blend tables correctly you will get proper fueling it just takes time to dial it in.

I don't believe that it's the ECM thinking that it's doing anything different than it is and torque based systems are very enthusiast friendly. They're only unfriendly to those that don't understand how they work and I mean that with all due respect. Torque is air if you just think about torque is just another word for air in GM language it makes a little bit more sense. Spark and fuel we can control to a very precise degree inside the engine. Air not so much even if we can precisely push in a certain amount of error keep that air in there and push it out fast we're still at the whim of humidity air temperature and barometric pressure which all plant factor and how much air is going to get in and out and or combusted or not combusted so on and so forth. Torque management is freaking awesome if you learn to play with it and work with it I mean you don't have to do much to get these things to really give you some juice which is nice and it also leaves a bunch of safety factors in place. That being said with the maf and that cut you're hitting in my opinion just from what I've seen it's not anything else except for your mass air flow sensor running out of room to read and that it's just falling on its face. Now I can't look at your large right now I don't have my laptop setup but that's what I'm guessing the issue is but again I stopped looking into looking into it a long time ago and just went pure speed density as you'll find most people that run high boost applications do not run a Mass Air Flow Sensor. Especially if they're full race I mean you'll see dudes that tune naf only but that's a really really like I'm not old but I guess like antiquated mindset because those sensors suck. Like sure they're easy to tune and take out a lot of the variables to make it simpler but simpler is not always better you know some of these things in their complex for a reason and they put a lot of checks and balances in place but they also give you a lot of granularity when it comes to tuning. And no don't switch to a standalone like a.m. infinity or megasquirt unless you run out of things that HP tuners and a OEM GM ECU can't do for you. Most people buying to be honest you could run a gmecu in damn near anything or not damn near anything but you can run a gmecu as a standalone ECU with all the stuff that HP tuners adds to it I mean dude like my car isn't supercharged and they're supercharged tables in there if I wanted to go supercharge on my card there's the tables right there it's got to set up for twin turbo systems with dual throttle bodies or at least do a maf ensors, a plethora of like adders and multipliers and one tables for your spark different ways of controlling spark depending on how you want to you know run the vehicle I mean the possibilities aren't endless but my e78 ECU that's in my cruise gives me a lot of flexibility it's one of my favorite ECU so far to work with and not because I'm most accustomed to it but because every other car that I tune and I tune a lot of cars lately I'd actually do this for a living now and iTunes anywhere from 2:00 to 5:00 or 6:00 different cars different people every week so 2 to 6:00 different GM vehicles are even just different vehicles in general but they're mostly GM and by and large the Gen 5 ecos give you all sorts of lovely good stuff and disabling those things like variable cam timing and your torque management I don't really see the point of it when they're put there as a good thing not just to get in your way they're very enthusiast friendly it just depends on how enthusiastic you are about learning.

The ECM sees the 550g/s of airflow, does the math, and then soils itself because it calculated 318lb/ft when its expecting 138 lb/ft.

That's not the case at all what it'll do is it'll close the throttle body and not necessarily relatively quick as it starts approaching that peak number if it thinks it's going to go over it'll start gradually closing the throttle body in anticipation of having you know it overshoot that peak or maybe having an overboost event happen so it starts slowing down the turbo speed it starts slowing things down so it's easier to play ketchup or even just mitigate disaster if it does happen to hit that peak and keep going it doesn't usually just fall right on his face though there are some tables that will do that but the tables that do make the thing kind of just black where it just gives you the finger like your your maf MAP correlation tables that throw a p0068 or reduced engine power motor what have you. Those tables are to make sure that the correlation or the Delta well the correlation between those two sensors is in line if the delta or the difference between the two becomes bigger than a certain amount then it starts throwing that because it means something's either out of control or one of the sensors is not reading properly for the for the resolution or for the type of air that's running through it it's they're there to help everything else out but at the end of the day your mass air flow sensor though it reads all of that air coming in everything in there is based off of your virtual volumetric efficiency tables. Even your virtual torque tables are heavily dependent on how good your vve is. So one thing you can look at in the dynamic airflow table you'll see air mass filter or air mass filtration I think it's called. It doesn't take all of the input from the mass air flow sensor and use that as what it wants to use it for it doesn't just take that like that's what it is and just ignore the ve table it's the vbe table and then it takes a percentage of blend of whatever it suggesting is fine-tuning and kind of feathers that in with its own results and then uses that output or use that to output to the other actuators and then takes input for no centers but when it comes to speed density and your vve tables the math always play second fiddle it's more there for like fine-tuning than anything that's one of the reasons you see that it sets so high like that is like 6,900 or 7,000 it's set unreasonably High because you're not really going to get in there and use it even though you're not hitting that that threshold you're still getting input from it but like a percentage of it but I said just kind of very lightly dusted on top of what the VTE table says it needs. That helps when you have different temperatures or wildly swinging temperatures humidity it can only account for so much with the table sometimes it needs some real time input that's what the mass air flow sensor is for to help provide that real time right now type input to help everything else kind of adjust to what the vde table or the coefficients and all that stuff has to say the air model for your engine is all the vbe table everything else included the math all base everything off of that if your bve isn't right your virtual torque tables are going to be way way off and so you shouldn't even touch them. If you move your cams one degree in like the 3,000 to 3200 RPM range wide open throttle your vde has now changed you need to tune that part of it and then everything else will follow suit. So have you learned to tune your vve and torque management properly there's no need to disable them and you'll find it a lot easier to tune working within those limits and then when it comes time to break the rules or do things that you want to do that don't concern those you can disable them their ways to disable them but learn to play within the confines of it first and you'll find it once you start doing it you'll have a safer better running engine and just a happier time all around that they're really really neat ideas that are in these things that make them way easier than tuning like I don't know like an old p01 or p06 or I don't know any old Silverado ECU for my 2003 you know what I mean? I'm using Google speech to text so if some of this didn't come out very clear I apologize but I think you guys get the gist of it and if I'm wrong on any of those factors by all means feel free to you know correct me

[blindsquirrel]

It then freaks out, first tries to control the situation by pulling timing, but because you capped the lower limit to 2 degrees, it didnt help.

Hell, pulling timing probably makes it worse (from the ECM's point of view, trying to reduce torque), not better. Lower timing = more heat to the turbine = more shaft speed = moar boost.

[Dutch]

just want to reiterate to future posts that OP is running a heavily modified 1.8L, not a 1.4L.

Hell, pulling timing probably makes it worse (from the ECM's point of view, trying to reduce torque), not better. Lower timing = more heat to the turbine = more shaft speed = moar boost.

OP runs an aftermarket boost controller - ECM does not know a turbocharger is there.

lots of good info in Ronin's post regarding torque management. hope he can edit it in the future to include info the OP already posted (zeroed out cam angle table, AEM boost controller, etc) and so it doesn't read like a giant run on sentence :P

[Crewz]

Thank you for all the feedback. Dutch is correct, it's a 1.8. Looks like I left out the fact I had custom forged pistons made by JE, installed h-beam rods, and I'm using SRT-4 ARP heads studs... not that it affects the current situation lol.

As for the timing, I pulled 1? per psi of boost to keep it on the safe side until I get the this fuel cut sorted out. Same for the Variable Camshaft(s) advance. Seeing as it had a VIM intake, I'm sure the current VC tables are optimized for the VIM, EGR, and economy. I plan to dial in the VCs torque / power curves in once I rent some dyno time, as well as trickle in some more timing advance as long as I keep seeing returns.

She'll run great up to 18-19 psi, but as soon as I add some more waste gate duty to the dome and I surpass 22.5 psi, it'll cut fuel. Ultimately I'd like to increase boost up to 3bar for track days.

I'm going to chew on all the information provided and will report back. Some of the torque tables such as TCS, virtual torque, etc, I've adjusted and it tends to result in two outcomes. Either I'll fire the engine up after the flash, and it'll just rev to the moon with no control, or it'll only allow the car to idle... I can press on the accl pedal and nothing.

Hopefully we can get this sorted. I have considered going the stand alone route (FT550), even though it will make managing the engine a breeze, the additional headache will be getting the factory ECU to play nice with the rest of the modules, from ABS, electronic power steering, etc. It's nice still having all the features and safety like the airbags atm. Although, the end result will ultimately be converting the car to a purpose built FWD drag car, but that'll come down the road. Atm I'd like to see what this platform will / can do with the current mods. For now I'd just like to keep the sleeper status going and have some fun with it. Goal is 10.9's in the 1/4 as is... just need to sort out this issue.

Thanks again for all the tips, tricks, and advice and I'll report back.

-Matt

[sbarisic]

She'll run great up to 18-19 psi, but as soon as I add some more waste gate duty to the dome and I surpass 22.5 psi, it'll cut fuel. Ultimately I'd like to increase boost up to 3bar for track days.

3 bar is not going to work with the GT3582R turbocharger you mentioned above. Look at the compressor map, you are going to be way above the max RPM and efficiency islands. You're just going to heat up air and risk damaging the engine and turbo. 2 bar is the most i would personally run on it, it also depends on the airflow you're going to get. 60 lbs/min (453 g/s) and above is going to heat up air like crazy and you're going to lose torque.

GT3582-Comp-Map-Kg-Sec-scaled.jpg

(Map from https://www.garrettmotion.com/racing...turbo/gt3582r/ )

[cobaltssoverbooster]

I ran one at 3 bar and 55-60 lb/min. Its within the 75% efficiency range and max rpm at 3 bar is way out at 68 lb/min which is like 670 hp equivalent according to the map. Most people aren't making more than 550 hp on these turbos or a stock transmission. That power figure is more in line with he 50-57 lb/min so they should be just fine, particularly with a decent charge air cooler.