2016 Mustang GT with Whipple - Need some help tuning return to idle

My car is a 2016 GT with a modified Whipple tune, E85, id1050x, and a T56 swap. I've got most everything running well except for a hanging idle and very slow return to idle, especially when hot.

I'm not really sure what to look at. I've researched a lot of threads about tuning torque based decel, but it seems like every thread ends in disabling it and going back to dashpot. I don't think I have that option in a 2016.

I'm attaching a log in case anyone can shed some light. In this log, I sat at a hot idle and did various slow revs and blips and most of them result in a slow decay back to idle. Sometimes driving on the street, it will get stuck around 1500rpm and take a very long time to get back to 800rpm. The car does have better manners when the engine is still cold. I also was running a purchased tune from a tuner and the car did not have this problem, so I know it's not a mechanical problem. I switched back to my own tune for various reasons, but I'm not sure how to tackle this problem.

I assume it is something torque based that I need to adjust. Mapped point 0 torque model? Does driver demand play a factor here? Any help would be greatly appreciated.

Attachment 120451

I would suggest increasing your feedback correction to max and min of 75. See if that lets your ETC torque get brought down closer to 0 or near where the engine brake torque is. This will tell you if you are at the limit of the feedback loop or something else is going on.

From there it would be easiest to raise/ lower that higher MAF period, lower airmass part of the MAF transfer. Your fuel trims may be thrown off some, but its the quickest easiest way to modify engine brake torque directly.

Theres usually not a whole lot that needs to be done for idle from stock. It works of a feedback correction. Even whipples/ Roush tunes don't change much about the feedback loop or even anything at those target loads and RPMs in the DD or torque model. Sometimes the MBT spark value throws off the actual spark value to the point of the throttle not closing enough to achieve the right torque. Some times its the SD, delta above baro can throw things off at the low RPMs, its ok to leave that 0 below 1500-2000RPM where you shouldn't being going into boost any way. Let the calculated load be accurate for good idle control.

Thanks murfie. I tried changing the feedback correction, but I haven't been able to get a log under the same conditions. I actually got some snow here over the weekend, and just took a short drive today, but I didn't get the hot temps that duplicated the problem previously. One thing I did notice is that ETC torque always seems to be almost exactly 40 lb ft under scheduled torque. Is that delta what increasing the feedback correction is supposed to change? I don't understand the torque system very well, so I'm struggling to follow what you wrote.

You mentioned delta above baro for SD... one thing that has always bothered me about my Whipple tune is they have the baro sensor shown as equipped in the tune, but my OEM Ford tune had it disabled. I don't understand why Whipple would do this when there is no physical sensor. I know they use it for GT350's and install a sensor. I was thinking about trying to disable it, but I don't know how the tune works without a sensor. I assume there is some background calculation going on to infer baro. I logged the sensor PID and so far it is always stuck at 17.8psi.

Before I started making tune changes, I always had a slow return to idle with the default Whipple tune. I even sent them a video of it a long time ago and they said it was normal "anti-stall" and not to worry about it. It wasn't until I tried another tuner's tune that I discovered how nice the return to idle can be if I can just figure out how to tune it correctly.

Here's a log of return to idle with the feedback correction change to +/-75. Like I said, it wasn't as hot for this one, but it did return a little sluggishly once or twice. We should have some hot weather at the end of the week and I'll try some more experiments.

Attachment 120605

If your whipple calibration has Barometric pressure sensor equipped - enabled, then what characteristics does it have populated?

I would disable it if your car doesn't have one. Set the learned min/max to 29.92 and see how it goes.
Things would probably work better than the false reading of 36 you are getting now.

Here's the Whipple settings:

Attachment 120609

This is what my OEM Ford tune had:

Attachment 120610

I should also mention that I live at about 6000ft above sea level.

Disabling the baro sensor did not go so well. Car was hard to start and while driving, I was getting a ton of IPC errors. I also think something was closing the throttle when I tried some heavier acceleration. Needless to say, throttle response was poor. Logging the baro sensor produces 0psi, and I don't see a way to log what the internal baro calculation is producing.

murfie, do you know how the internal logic works? With the baro sensor set as equipped, it defaults to 36 in hg, and the baro sensor voltage is about 5V, so it must be looking for a sensor on the harness. However, that is above the max learning, so is the logic just using the max for its calculations? I'm curious if I can adjust the calculated values by playing with the min/max learning. I might also see if Whipple will sell me the sensor that they use for the GT350 and see how it affects things.

Quote:

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Originally Posted by Ruiner46

Disabling the baro sensor did not go so well. Car was hard to start and while driving, I was getting a ton of IPC errors. I also think something was closing the throttle when I tried some heavier acceleration. Needless to say, throttle response was poor. Logging the baro sensor produces 0psi, and I don't see a way to log what the internal baro calculation is producing.

murfie, do you know how the internal logic works? With the baro sensor set as equipped, it defaults to 36 in hg, and the baro sensor voltage is about 5V, so it must be looking for a sensor on the harness. However, that is above the max learning, so is the logic just using the max for its calculations? I'm curious if I can adjust the calculated values by playing with the min/max learning. I might also see if Whipple will sell me the sensor that they use for the GT350 and see how it affects things.

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Try these out see if it helps.
Make default baro 29.875
cylair wot multiplier make 1.99
Cylair max multiplier make 1.99

Disabling baro is easy:

Attachment 120640

Quote:

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Originally Posted by mstang_man

Try these out see if it helps.
Make default baro 29.875
cylair wot multiplier make 1.99
Cylair max multiplier make 1.99

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I had default baro at 27 and I left the cylair multipliers at the Whipple settings. The car ran terribly. Actual barometric pressure where I live should be around 12 psi, so I would think closer to 24 in hg would be more appropriate. However, I'm wondering if Whipple is doing something odd with their OS since they leave baro enabled without a sensor.

If I recall correctly, it's enabled and slope is like 7. What is you change that to 5. Does the baro reading in the scanner get closer to what you would expect?

Quote:

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Originally Posted by murfie

If I recall correctly, it's enabled and slope is like 7. What is you change that to 5. Does the baro reading in the scanner get closer to what you would expect?

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Yes, great idea. I went through the slope/offset math with the voltage I log in the scanner and targeting pressure for altitude at 5000ft. I came up with a slope of 4.993... good guess, did you already do the math? :)

Loaded the tune up and baro is sitting at a constant 12.2 psi in the scanner. Car started up just fine. I'll run with this for a few days and see how it turns out.

That's weird. I don't know what voltage they are using to determine baro, it can't be an actual sensor if you didn't install one. I'm not sure what all else it will change in their tune. Can't hurt to make it accurate tho.

I'm not sure how Whipple hooks up the baro sensor on GT350 kits, but I'll bet it's similar to the IAT2 sensor where they use the IMRC harness. A really simple circuit is a 5V supply, a ground, and a signal wire that has a known resistor value connected to 5V. Then the sensor will have a variable resistance based on pressure and acts as a resistor between signal and ground. This creates a voltage divider.

When the sensor is not present, the signal wire gets pulled up to 5V because there is no connection to ground through the missing sensor. This is why the baro voltage in the log is a constant voltage very close to 5V (4.98V in my logs). So we just scaled the slope so that 4.98V is equal to the pressure we want.

Right, I figured an IMRC connector but why tie baro to something thats not a baro sensor and with such strange slope and offset that makes 36inHg at 5 volts.. Unless they have it tied to the small relay that kicks on the IC pump. which drops the voltage to something more like 4 volts making the reading come out near a standard 29.92. Then if some one hooks it into the wrong IMRC plug the car runs bad and hints to the IC pump not operating. Like if someone connected the position sensor and not the solenoid control.

IDK just a guess and weird to me. I'll stick to my stock calibration and modify from that.
Then if they have logic like that, why did they tell you its normal, ignore it?

Quote:

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Originally Posted by murfie

Right, I figured an IMRC connector but why tie baro to something thats not a baro sensor and with such strange slope and offset that makes 36inHg at 5 volts.. Unless they have it tied to the small relay that kicks on the IC pump. which drops the voltage to something more like 4 volts making the reading come out near a standard 29.92. Then if some one hooks it into the wrong IMRC plug the car runs bad and hints to the IC pump not operating. Like if someone connected the position sensor and not the solenoid control.

IDK just a guess and weird to me. I'll stick to my stock calibration and modify from that.
Then if they have logic like that, why did they tell you its normal, ignore it?

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According to Whipple, only the GT350 is sensitive enough to need a baro sensor. So they include an actual sensor in the GT350 kit and that slope/offset must represent the transfer function of that sensor. They stated that it is disabled in the normal GT tunes, but it was not disabled in mine. They say " The GT's are dialed in for all ambient/elevation conditions and not reliant on the baro sensor for fueling control".

I'm not sure if it was supposed to be turned off in my calibration and someone made a mistake, or if they think the cal is flexible enough to use the sensor input railed at 36 in hg.

Unexpected issue after changing the baro to 12.2 psi... car will not start when IAT is hot. I had to flash a tune while stuck at a gas station pump, lol.

I swapped back to the original tune that just has idle feedback set to +/-75, but I still have a sluggish return to idle. At least the car starts now...