2012 SRT8 Challenger Procharged with Cam Idle tuning and CEL's Issues

[jmb justin]

I am stuck fixing a tune that another shop did for one of my customers, and I'm not much of a tuner on this application, just trying to get this last couple issues lined out. Id idle hunts terribly in park or any gear, AC on or off. Adaptives look great once we made some slight changes, I have basically fixed the timing to a solid pretty solid 15*'s from 0-1800 rpm, and I changed his tune to "sensed map", also unplugged the blow off valve so it wouldn't be opening and closing as the idle hunted, and none it made a difference. Has a P2173 and a P0730 that keep coming back (Changed to sensed map to hopefully fix the P2173 issue)
Mods list
hellcat shortblock
stock heads
large cam/valvetrain
F1A procharger
Built auto with 4000 stall protorque
~16psi
E85
80# injectors
full dual pump fuel system

Original tune file attached, and the logs from that file (vaughn1) and the file (vaughn6) once all the changes were made (with little to no effect)

Any help would be greatly appreciated, it drives around great, starts right up, makes great power, but just has these few little issues. Will gladly pay for someones time if needed as well.
Thanks
Justin

[06300CSRT8]

You are very close to having it smooth out. Try these tweaks:

ENGINE>IDLE>AIRFLOW>IDLE TORQUE SPARK> Enable Rpm Error set to 350 (stops the timing from being used to correct the idle bumping around until its within 350rpms of your set point, gives it a little more room to move around before the ECU starts going nuts)

ENGINE>IDLE>AIRFLOW>IDLE TORQUE SPARK> Allow Negative VSS set to 128mph (basically disabling the ECU's ability to ADD timing above your PT Base spark table, its opposite of what you think , negative idle spark correction is actually adding timing, by disabling this you will keep the timing capped to your PT Base table and it can only pull timing when you over idle but never add more than your base spark table when rpms are too low. By setting it this way you eliminate half of the overshoot, helps a lot).

Your VE table is OK, but even though it is smooth you still have some big jumps and steps between pressure ratios at the idle area. I would suggest redoing it with two or three more pressure ratio rows added to where you idle and remove a few rows in the higher pressure ratios (remove 1.10 and 1.2, for example, you are never going to stay in that pressure ratio for more than a split second once the bypass closes).

[06300CSRT8]

I rechecked your logs, to me it looks like you need a little more timing than what you are giving it, try adding another 2* and see how it behaves. You have basically what I typically use for pump gas 93 timing, e85 usually needs a bit more. Your fueling is still actually off a bit. I also suggest adding 50rpms to all your idle set points, 775 is ok on a really well tuned engine, start with 825 until its dialed in and then lower it afterwards. trust me, this surge thing with a cam is a knife edge, very very little is needed to get it to stop. the identical tune with a 825 set point may never surge, then drop it 50rpms and itll run like a bag of ass. Try it, see what happens.

[06300CSRT8]

If you still have trouble, ignore your fuel trims and try adding 4-5% fuel to the idle area. Cams like to run rich on these cars forgetting what the trims tell you. Your surge is being caused by low timing but also your fuel trims are pulling fuel, causing rpms to drop, then in stall mode the ECU is cracking open the throttle body, then car goes lean, dumps fuel, pulls timing (and over shoots) and rpms fall again). Adding that fuel amount will stop that initial fuel trim pulling that starts the cycle.

The best way to figure out if it is spark or fuel causing your issue is to force the car into open loop and see how it acts. If she idles smooth then you know its fuel related. You can force open loop by changing ENGINE>FUEL>OXYGEN SENSORS>CLOSED LOOP ENABLE>COOLANT TEMP to 376*. Just note running this way for a few drive cycles might pop a DTC code for never reaching coolant temp for open loop but is no harm.

[jmb justin]

You are very close to having it smooth out. Try these tweaks:

ENGINE>IDLE>AIRFLOW>IDLE TORQUE SPARK> Enable Rpm Error set to 350 (stops the timing from being used to correct the idle bumping around until its within 350rpms of your set point, gives it a little more room to move around before the ECU starts going nuts)

ENGINE>IDLE>AIRFLOW>IDLE TORQUE SPARK> Allow Negative VSS set to 128mph (basically disabling the ECU's ability to ADD timing above your PT Base spark table, its opposite of what you think , negative idle spark correction is actually adding timing, by disabling this you will keep the timing capped to your PT Base table and it can only pull timing when you over idle but never add more than your base spark table when rpms are too low. By setting it this way you eliminate half of the overshoot, helps a lot).

Your VE table is OK, but even though it is smooth you still have some big jumps and steps between pressure ratios at the idle area. I would suggest redoing it with two or three more pressure ratio rows added to where you idle and remove a few rows in the higher pressure ratios (remove 1.10 and 1.2, for example, you are never going to stay in that pressure ratio for more than a split second once the bypass closes).

Working with Torrie @ Unleashed Tuning, we have the idle very stable now by messing with the Idle torque throttle integral and proportional, but it still wants to die after you rev or apply a load. I will try your suggestions next, thank you!

[GeForce1986]

If you still have trouble, ignore your fuel trims and try adding 4-5% fuel to the idle area. Cams like to run rich on these cars forgetting what the trims tell you. Your surge is being caused by low timing but also your fuel trims are pulling fuel, causing rpms to drop, then in stall mode the ECU is cracking open the throttle body, then car goes lean, dumps fuel, pulls timing (and over shoots) and rpms fall again). Adding that fuel amount will stop that initial fuel trim pulling that starts the cycle.

The best way to figure out if it is spark or fuel causing your issue is to force the car into open loop and see how it acts. If she idles smooth then you know its fuel related. You can force open loop by changing ENGINE>FUEL>OXYGEN SENSORS>CLOSED LOOP ENABLE>COOLANT TEMP to 376*. Just note running this way for a few drive cycles might pop a DTC code for never reaching coolant temp for open loop but is no harm.

that was helpful for me 2 thanks .. my car die at idle when am on drive or r and its read lean there so from where i can add some % to the idle on d ?
thanks again ^^

[Nigel Pitsch]

I had a look at your tune 2 obsevations
1 Cam timing as you have the NN disabled the cam timing map is current and active , normally the NN does it all for you but now its hard so , you have 134 deg at idle and min airflow but at any higher airflow it jumps to 92 or so I would think that you could try changing a few more rows to the 134 deg , to give it no change in the idle areas,, if you have mapped the cam position at your idle perhaps it will show any instability in this area
2 Your VE shows quite big changes around the idle area I'm thinking 035 to 0,40 at 700 ish rpm ? if after you have treid the cam map you might look a little more closely at where it is at idle and reduce any large changes somewhat
3 15 deg at idle sounds high to me
I have a 6.4 srt8 not hellcat with the F1A on it noisy thing it is and that's what I have found , it may not be relevant to you tho as they are quite different
if it is of any help .

[jmb justin]

Ok tried post 2 and 3, and put the Idle torque throttle integral down 50% with Torries help. The hunt is pretty much gone now, but anytime a load is applied (ac on, putting car in gear, etc.) it drops very low in rpm or dies still. The recovery is quicker and not as dramatic on the above idle overshoot. Tune attached and logs of the exact same drive cycle with ac off and on attached. I'm open to the cam timing map, I honestly don't even know where that is located in the tune though. IMO (for whatever thats worth), it is not a fuel or timing issue, it is a airflow based on load issue (or if cam timing is making big jumps that could certainly do it as well). Thanks again for the help.

[06300CSRT8]

set your in gear idle rpm and ac on idle rpm 25 rpms higher than your in park idle rpm settings. If it wants to go up when you put it in park or neutral, you need more idle rpms in gear or with AC on.

[jmb justin]

Thanks for the help, it needed more fuel at idle, that fixed a bunch of the issues instantly. We changed the stoich (thanks Torrie) and it was a different car at idle. It is much better but still has an occasional RPM drop. At this point I think its done considering the size of the cam, etc.

[06300CSRT8]

Awesome, what stoich did you end up using? I usually use 14.3

[mxatunerjg]

I have to question the stoich part. Setting Stoich does not change closed loop fueling from what I've seen. It does not seem to be a targeting value, but a value that says it is the base for adders for PE fueling. What I have not tested is changing this value and setting up and running open loop only. So my question is, are you seeing a difference with the stoich values adjusted for closed loop operation? If so what stoich values are you changing?

[JoshCP527]

I have to question the stoich part. Setting Stoich does not change closed loop fueling from what I've seen. It does not seem to be a targeting value, but a value that says it is the base for adders for PE fueling. What I have not tested is changing this value and setting up and running open loop only. So my question is, are you seeing a difference with the stoich values adjusted for closed loop operation? If so what stoich values are you changing?

Stoich does not change the fact that the narrow band oxygen sensors switch at lambda 1. Stoich is used for fuel mass calculations and in the fa pe lambda calculations.Fuel Air Ratio Calc.xlsx Here is a calculator to simplify this. Set stoich close to what fuel you are using that way you scale the injectors right when you dial all the trims in.

[mxatunerjg]

Stoich does not change the fact that the narrow band oxygen sensors switch at lambda 1. Stoich is used for fuel mass calculations and in the fa pe lambda calculations.Fuel Air Ratio Calc.xlsx Here is a calculator to simplify this. Set stoich close to what fuel you are using that way you scale the injectors right when you dial all the trims in.

So Lambda is not changed for fuel type and stoich values are calculations off of Lamda. Dialing in injector scale should not be affected by stoich setting. If fuel trims are off by 10% the type of fuel does not matter, it is still 10%. The only part that would be affected by the stoich setting is the for PE fueling final value after the PE adder is applied (the PE target). The numbers would look wrong on the PE tables if the stoich value is wrong for the fuel, but the injector scaling would not change due to a stoich value change. Now injector scaling would change if you go from say, gasoline to ethanol, but you could do that and change or not change the stoich value, injector scaling would still only change for the fuel quantity needed.

[B00STJUNKY]

So Lambda is not changed for fuel type and stoich values are calculations off of Lamda. Dialing in injector scale should not be affected by stoich setting. If fuel trims are off by 10% the type of fuel does not matter, it is still 10%. The only part that would be affected by the stoich setting is the for PE fueling final value after the PE adder is applied (the PE target). The numbers would look wrong on the PE tables if the stoich value is wrong for the fuel, but the injector scaling would not change due to a stoich value change. Now injector scaling would change if you go from say, gasoline to ethanol, but you could do that and change or not change the stoich value, injector scaling would still only change for the fuel quantity needed.

Your thinking is off.

The stoich FA value is a fueling target for surface fueling (base fueling calculation), and closed loop trims reel in the fueling to achieve the Lambda switching point in reaction to inadequacies in the ability to account for various running condition changes.

A simple example of this is seen during throttle tip-in. There are known quantities that aid in throttle tip-in tuning, but there are also unknown quantities during transitional conditions like this that necessitate closed loop feedback to correct for momentary miscalculations.

The airflow modeling and various algorithms in the PCM do their best to calculate required fuel flow for a given set of conditions, and the FA Stoich value has a direct impact on that calculation.

Say you had your tune dialed so well that your LTFT was at 0%, but then you made a +10% change to the Stoich value. After doing so, your LTFT values would end up settling in at (or very near) -10% to compensate due to the closed loop STFT system always having to pull 10%.

After the LTFT populated and settled at -10%, the STFT corrections would then perform similarly to the same pattern they performed before the Stoich value was changed.

Changing the stoich value doesn't change what the o2 sensors target for a switching point. The o2 sensors are engineered to always switch around 1.0 Lambda, regardless of fuel type, and regardless of incorrect stoich values set in the open loop base calculation.

[mxatunerjg]

Your thinking is off.

The stoich FA value is a fueling target for surface fueling (base fueling calculation), and closed loop trims reel in the fueling to achieve the Lambda switching point in reaction to inadequacies in the ability to account for various running condition changes.

A simple example of this is seen during throttle tip-in. There are known quantities that aid in throttle tip-in tuning, but there are also unknown quantities during transitional conditions like this that necessitate closed loop feedback to correct for momentary miscalculations.

The airflow modeling and various algorithms in the PCM do their best to calculate required fuel flow for a given set of conditions, and the FA Stoich value has a direct impact on that calculation.

Say you had your tune dialed so well that your LTFT was at 0%, but then you made a +10% change to the Stoich value. After doing so, your LTFT values would end up settling in at (or very near) -10% to compensate due to the closed loop STFT system always having to pull 10%.

After the LTFT populated and settled at -10%, the STFT corrections would then perform similarly to the same pattern they performed before the Stoich value was changed.

Changing the stoich value doesn't change what the o2 sensors target for a switching point. The o2 sensors are engineered to always switch around 1.0 Lambda, regardless of fuel type, and regardless of incorrect stoich values set in the open loop base calculation.

I've tested this in the past, but thinking about this now I don't think I was testing things in the way you are talking about. I believe what I was trying to do was find a way to get a target fueling at idle of say 13.9-14.1 AFR for engines with a cam that had a lot of valve overlap. It has been probably 2 years since trying all of that, and I'm betting that at the time I was probably thinking about what my widebands were reading, not so much what the computer was doing at the time. I remember setting stoich to something in the range of .075 FA, primarily because at the time Diablo had told me that I could do what I was attempting by changing the stoich value. I do remember noticing that no matter what the stoich value was, the trims still targeted a Lambda value of 1 or approx 14.7.

I do understand the o2 sensors switching at 1.0 Lambda, that is normal. I also understand the PE being an adder to the stoich value for the target PE fueling. My guess would be when I saw the change in fuel trims I was focused on trying to change a fueling target for closed loop and it didn't work. Over time my memory of that testing probably got foggy and I changed my thinking to be that the stoich value was nothing more than a value used for the base adder for PE fueling.

So if all your saying is true, then I believe if an injector setup was dialed in on a vehicle running say 93 octane, and a switch to e85 was made, changing the stoich value should put the fueling very close to where it needs to be. Meaning, if the injector scaling and fuel tuning was correct on 93, that should all stay pretty consistent when making the switch if the stoich value was changed in the ecu. Example....A car is dialed in to a perfect 0% trim on 93 octane, and let's say the difference between 93 octane and e85 is exactly 30% fuel required, a 30% increase in the stoich value should net a 0% trim, and PE fueling should be very close as well?

[06300CSRT8]

I've tested this in the past, but thinking about this now I don't think I was testing things in the way you are talking about. I believe what I was trying to do was find a way to get a target fueling at idle of say 13.9-14.1 AFR for engines with a cam that had a lot of valve overlap. It has been probably 2 years since trying all of that, and I'm betting that at the time I was probably thinking about what my widebands were reading, not so much what the computer was doing at the time. I remember setting stoich to something in the range of .075 FA, primarily because at the time Diablo had told me that I could do what I was attempting by changing the stoich value. I do remember noticing that no matter what the stoich value was, the trims still targeted a Lambda value of 1 or approx 14.7.

I do understand the o2 sensors switching at 1.0 Lambda, that is normal. I also understand the PE being an adder to the stoich value for the target PE fueling. My guess would be when I saw the change in fuel trims I was focused on trying to change a fueling target for closed loop and it didn't work. Over time my memory of that testing probably got foggy and I changed my thinking to be that the stoich value was nothing more than a value used for the base adder for PE fueling.

So if all your saying is true, then I believe if an injector setup was dialed in on a vehicle running say 93 octane, and a switch to e85 was made, changing the stoich value should put the fueling very close to where it needs to be. Meaning, if the injector scaling and fuel tuning was correct on 93, that should all stay pretty consistent when making the switch if the stoich value was changed in the ecu. Example....A car is dialed in to a perfect 0% trim on 93 octane, and let's say the difference between 93 octane and e85 is exactly 30% fuel required, a 30% increase in the stoich value should net a 0% trim, and PE fueling should be very close as well?

Your thinking is right.

[B00STJUNKY]

I've tested this in the past, but thinking about this now I don't think I was testing things in the way you are talking about. I believe what I was trying to do was find a way to get a target fueling at idle of say 13.9-14.1 AFR for engines with a cam that had a lot of valve overlap. It has been probably 2 years since trying all of that, and I'm betting that at the time I was probably thinking about what my widebands were reading, not so much what the computer was doing at the time. I remember setting stoich to something in the range of .075 FA, primarily because at the time Diablo had told me that I could do what I was attempting by changing the stoich value. I do remember noticing that no matter what the stoich value was, the trims still targeted a Lambda value of 1 or approx 14.7.

I do understand the o2 sensors switching at 1.0 Lambda, that is normal. I also understand the PE being an adder to the stoich value for the target PE fueling. My guess would be when I saw the change in fuel trims I was focused on trying to change a fueling target for closed loop and it didn't work. Over time my memory of that testing probably got foggy and I changed my thinking to be that the stoich value was nothing more than a value used for the base adder for PE fueling.

So if all your saying is true, then I believe if an injector setup was dialed in on a vehicle running say 93 octane, and a switch to e85 was made, changing the stoich value should put the fueling very close to where it needs to be. Meaning, if the injector scaling and fuel tuning was correct on 93, that should all stay pretty consistent when making the switch if the stoich value was changed in the ecu. Example....A car is dialed in to a perfect 0% trim on 93 octane, and let's say the difference between 93 octane and e85 is exactly 30% fuel required, a 30% increase in the stoich value should net a 0% trim, and PE fueling should be very close as well?

You got it! That's my understanding of it.

[mxatunerjg]

You got it! That's my understanding of it.

Got my thinking twisted on it while thinking it through I guess. This makes a lot more sense to me than the way I thought it was working so I'm much happier using this mindset anyway.