2016 Silverado 5.3 Idle below commanded right after start up

Hey guys, I, like many others am still trying to get my head wrapped around the in and outs of tuning these Gen V engines. The current one I'm working on is a 2016 Silverado with the L83 engine. I've installed a GPI STG1 cam, Speed Engineering long tube headers, and an L86 intake manifold and throttle body. I'm working on tuning the MAF curve right now. The issue I'm having is that as soon as I start it up it does its initial flare and then seems to 'chug' for about a minute or so before jumping back up to commanded RPM. By chug I mean undershoot desired idle by 100-200 rpm. It sometime does this "chugging" when rolling up to a stop. I'm almost sure its a torque table issue due to the timing being retarded during the event but I do not have enough experience tuning these engines to spot the issue. I'm also getting also getting an engine power reduced message but the truck other than the intermittent chugging seems to have every bit of its power. I also want to mention that I have messed with the transmission settings, mostly TCC and inertia settings. I have posted the tune file and a couple of logs of this situation happening. If anyone cares to take a peak and point me in the right direction, I'd happily pay for it. I'm not looking for a freebie, only to learn. Thanks guys.

Edit- I believe the reduced engine power message is from me maxing out the speed limiter.

The speed limiter shouldn't be maxed. You don't want to go above 115 with a stock driveshaft anyway. You need to lower the tm in your idle area and then keep things smooth. Make sure to modify every table fuel and cam related - there's lots...

Yep, decrease tq

I have the same GPI STG 1 cam in a '16 Suburban and absolutely love it. With a Whipple, NW103 throttle body, LT4 injectors and long-tube headers I have it idling rock-steady at 720 RPM.

I can't give you the exact numbers, but here's a general overview and a few links to read:
1) MAF curve spot-on (combo of wideband and fuel trims)
2) VVE dialed in (combo of wideband and fuel trims)
3) VT lowered in idle region & smoothed out everywhere
4) Idle Torque External Load lowered to match Zero Pedal Torque PID

I can't stress enough how critical it is to have the airflow model correct for all this to work. That's your foundation.

https://forum.hptuners.com/showthrea...ers-idle-surge

https://forum.hptuners.com/showthrea...nal-load-table

https://forum.hptuners.com/showthrea...ation-for-gen4

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Originally Posted by pisces_0

I have the same GPI STG 1 cam in a '16 Suburban and absolutely love it. With a Whipple, NW103 throttle body, LT4 injectors and long-tube headers I have it idling rock-steady at 720 RPM.

I can't give you the exact numbers, but here's a general overview and a few links to read:
1) MAF curve spot-on (combo of wideband and fuel trims)
2) VVE dialed in (combo of wideband and fuel trims)
3) VT lowered in idle region & smoothed out everywhere
4) Idle Torque External Load lowered to match Zero Pedal Torque PID

I can't stress enough how critical it is to have the airflow model correct for all this to work. That's your foundation.

https://forum.hptuners.com/showthrea...ers-idle-surge

https://forum.hptuners.com/showthrea...nal-load-table

https://forum.hptuners.com/showthrea...ation-for-gen4

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Thanks so much for the links! Great information! I don't expect to be spoon fed the number either, just wanted a little shove in the right direction. I've bought and read the Tuning School Gen V book (It was okay but certainly not $500 okay) and bought and watched all of Greg Banish's media on the GEN V stuff. I'm still trying to find a formula that I can follow for tuning these so I can produce good results for my customers consistently. Thanks again!

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Originally Posted by GHuggins

The speed limiter shouldn't be maxed. You don't want to go above 115 with a stock driveshaft anyway. You need to lower the tm in your idle area and then keep things smooth. Make sure to modify every table fuel and cam related - there's lots...

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After a bunch of digging I ended up finding a post Bill had pinned concerning the reduced engine power message when maxing that table out. I knew better and maxed it out anyways. I have since backed it up and fixed that issue. I know larger cams are less efficient at idle. I guess what confused me was that after about 30 seconds the idle would jump back up and follow commanded as it should. Thanks for taking the time to help a guy out!

Will do sir! Thank you!

At least your cam is minor, so shouldn't have to do a lot. You want to target something around 16 to 17ish degrees of idle timing and something probably around 0 to 7 torque. Make sure you do the same mods to ALL of the cam positions and fuels being used. Don't go below 0 (0 pedal torque) as that will make things super stable, but also cause downshift clunks unless you have the ability to disable tcc in your lower gears and raise the disengagement settings slightly in the higher gears. If you don't have access to the trans - cam tuning on these gets super complicated ;)

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Originally Posted by GHuggins

At least your cam is minor, so shouldn't have to do a lot. You want to target something around 16 to 17ish degrees of idle timing and something probably around 0 to 7 torque. Make sure you do the same mods to ALL of the cam positions and fuels being used. Don't go below 0 (0 pedal torque) as that will make things super stable, but also cause downshift clunks unless you have the ability to disable tcc in your lower gears and raise the disengagement settings slightly in the higher gears. If you don't have access to the trans - cam tuning on these gets super complicated ;)

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Yes, fortunately for me the customer is really cool and understands that I'm learning on this one, in combination with having a smaller camshaft. I have removed all TCC lockup in 1st-4th and moved the lockup/unlock in 5th and 6th to higher speeds. Man that seemed to make a major difference in driveability! Forgive my ignorance but which tables are you referring to when you say 0 to 7 torque? I don't have my laptop with me right now and I'm trying to picture what table(s) you're speaking of. I assuming TM spark table(s)? Not looking for any hand holding, just making sure I'm understanding the nomenclature correctly. Once again, thank you for taking the time :worship:

Yes, it's the torque model spark tables. The "target" will be found through experimenting and not so "cut and dry"...

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Originally Posted by GHuggins

Yes, it's the torque model spark tables. The "target" will be found through experimenting and not so "cut and dry"...

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Thanks again! You're the man! :cheers:

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Originally Posted by SpeedMonger

Thanks again! You're the man! :cheers:

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Yup
When you get Greg and Ben chiming in on a thread, you're getting some of the best available!!!!

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Originally Posted by dhoagland

Yup
When you get Greg and Ben chiming in on a thread, you're getting some of the best available!!!!

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I know that's right! I take their words as gospel for this stuff!

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Originally Posted by SpeedMonger

I know that's right! I take their words as gospel for this stuff!

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would be cool if there were updates to help others