LS3 Big Cam Idle Hunting

[Nick912]

I had tune dialed, but recently swapped the 6 speed to a manual valvebody 4l80e with a custom 4000 stall converter from Jake's Performance. I was expecting the converter to not affect idle much due to its relatively high stall speed, but it is surprisingly nice and tight down low. The only issue I am having now is getting a solid idle. Because this trans has no electronics, I am continuing to use the manual trans tune, and am unable to access airflow adder tables for P/N and when in gear. I went back to the drawing board and followed Big Mike's idle tuning guide to a T. I found optimal base running airflow in park. This trans has line pressure set at 185psi at all times, so it really likes to slam into reverse and in gear. I could help decrease this issue if i could get it to idle at a lower rpm. Also, it needs significantly more airflow to keep it running in gear. I have already added nearly 30% base running airflow, yet it still hunts for idle badly in gear. Idle is VERY stable right after startup though. In the current tune I am running, the idle is very floaty in P/N, yet doesn't seem like it has enough running airflow in gear. I feel lost and like I am chasing my tail, if anyone can look over my tune and log and give suggestions on what direction to head or what tables i should focus on, it would be greatly appreciated. Also, if anyone is familiar with any threads discussing how to get a solid idle in P/N and in gear with a manual trans file, please send it my way.

Vehicle: 2011 Camaro SS

Cam Specs at .050":

235/248 .649/.615 111 LSA 109.5 ICL

Advertised Duration (.006"):

292/301

4l80e VVE only 4 more spark less agressive idle spark.hpl4l80e VVE only 4 more spark less agressive idle spark.hpt

Side question: I no longer have a VSS, but the wheel speed sensors pick up vehicle speed for my speedo. Does anyone know if all of the tables in the tune based on VSS are affected? I do know that cruise control no longer functions unfortunately...

[smokeshow]

Not sure who Big Mike is or where he got his procedure from, but disabling all closed loop controls and increasing air, spark and RPM until idle stops oscillating is just a way to use engine friction to dampen out oscillations. That's what the control system is for, so you should use it accordingly. For reference, the final idle airflow minimum should be the minimum airflow required to produce enough torque to maintain idle at a desired RPM as well as a spark advance that yields some desired torque reserve for idle load disturbance rejection. How much torque reserve you need is another topic entirely, but essentially...you want to be able to account for anything that might unexpectedly consume torque from the crankshaft. In your case, this includes garage shifts. So you will need more airflow than someone with a full function electronic transmission. Not RPM...airflow. RPM makes the gear slam, but the airflow is what prevents you from stalling. Your target RPM will be a function of brake effort in gear, fuel economy, drivability and other things. In this case, pick what feels best. I'd say 900 or so.

Some general tips to keep this brief:

Re-enable proportional airflow....set rpm deadband to stock, around 50rpm. This will help prevent the driven oscillation on return to idle.
Increase the throttle follower everywhere to start...10lbft to start. You'll need more with the cam. This will be a tweakable thing later on.
Decrease throttle follower steps by half, both up and down steps.
Set dynamic air enable settings back to stock. Reference my procedure for simultaneous calibration of both air models.
If all the above is helpful, you can try decreasing minimum airflow. You won't want too much as it will dampen the return to idle, which can get pretty sloppy.

[Nick912]

Smokeshow, I followed the tips you so generously provided and was finally able to get my car idling properly, return to idle properly, and go into gear without throwing a fit. I am still running MAF only at the moment due to its simplicity, but I have come across your simultaneous calibration guide for MAF and VVE before, and will take those steps in the near future. The only issue I still need to address is startup. No matter how much I massage the startup airflow table, I can not get the car to start without using the throttle. Is the startup airflow table the only table that needs to be addressed, or are their other areas that need attention? Also, how can I determine what startup airflow values are needed?

[cadillactech]

Smokeshow, I followed the tips you so generously provided and was finally able to get my car idling properly, return to idle properly, and go into gear without throwing a fit. I am still running MAF only at the moment due to its simplicity, but I have come across your simultaneous calibration guide for MAF and VVE before, and will take those steps in the near future. The only issue I still need to address is startup. No matter how much I massage the startup airflow table, I can not get the car to start without using the throttle. Is the startup airflow table the only table that needs to be addressed, or are their other areas that need attention? Also, how can I determine what startup airflow values are needed?

Looks like someone added some extra spark to the cranking spark table, you could add a few degrees and see if that helps.

I think the start up airflow table has had quite a lot added, not sure if any more will help.

[Nick912]

I have tried adding a lot more startup airflow with no luck... same goes with cranking spark table. After it begins cranking over and it initially tries starting, it very aggressively sparks to life for what only seems like a couple engine rotations then dies right back down unless I catch it with the throttle. Even adding another 50% to the startup airflow table didn’t solve this issue. I’m not sure what to try next...

Edit: After looking at my VVE table, the shapes produced by the zones I have set up actually led to the 400 column to have slightly higher numbers than the 1000 column when I was dialing in the VVE for idle. Tomorrow, I'm going to go ahead and reduce the cranking VE table and see if that solves my problem (there was a very strong fuel smell when cranking, so I believe this to be the culprit).

[07GTS]

look in the steady state maf start up airflow table should help if it's too low, also get the throttle follower torque table right can help alot too as a big cam throws out the map readings and corresponding VT value

[smokeshow]

I have tried adding a lot more startup airflow with no luck... same goes with cranking spark table. After it begins cranking over and it initially tries starting, it very aggressively sparks to life for what only seems like a couple engine rotations then dies right back down unless I catch it with the throttle. Even adding another 50% to the startup airflow table didn’t solve this issue. I’m not sure what to try next...

Edit: After looking at my VVE table, the shapes produced by the zones I have set up actually led to the 400 column to have slightly higher numbers than the 1000 column when I was dialing in the VVE for idle. Tomorrow, I'm going to go ahead and reduce the cranking VE table and see if that solves my problem (there was a very strong fuel smell when cranking, so I believe this to be the culprit).

Startup airflow is a bit of a misnomer. It might be more accurately called 'afterstart airflow', as you actually cannot control airflow with the throttle during cranking and very low running RPM. The flow is too small for a closed throttle to generate any meaningful pressure drop. I could detail this more, but as I do not think that's your problem, I'll refrain. Looks to me that the issue is open loop EQ IVT gain. You'll notice that table has a sharp drop-off as MAP decreases, which is typical of a stock calibration. Your cam being as large as it is will have a much more difficult time producing torque when ECT/IVT is cold and the mixture leans out, which is what that drop in EQ ratio causes on the engine run-up. As a quick test, you can try shifting the table up, enriching OL fuel to lower MAP values. Try copying all rows from 40-180kpa into the 20-160kpa rows. This will fatten up the mix when cold as MAP decreases on the run-up. I won't comment on the 1.06 multiplier to that table lol...assuming you have a reason for that. The cal has other issues too, but one thing at a time.

[Nick912]

Startup airflow is a bit of a misnomer. It might be more accurately called 'afterstart airflow', as you actually cannot control airflow with the throttle during cranking and very low running RPM. The flow is too small for a closed throttle to generate any meaningful pressure drop. I could detail this more, but as I do not think that's your problem, I'll refrain. Looks to me that the issue is open loop EQ IVT gain. You'll notice that table has a sharp drop-off as MAP decreases, which is typical of a stock calibration. Your cam being as large as it is will have a much more difficult time producing torque when ECT/IVT is cold and the mixture leans out, which is what that drop in EQ ratio causes on the engine run-up. As a quick test, you can try shifting the table up, enriching OL fuel to lower MAP values. Try copying all rows from 40-180kpa into the 20-160kpa rows. This will fatten up the mix when cold as MAP decreases on the run-up. I won't comment on the 1.06 multiplier to that table lol...assuming you have a reason for that. The cal has other issues too, but one thing at a time.

As for the 1.06 multiplier... when I was still a 6spd, no matter how spot on my airflow tuning was or how high or low of spark advance I would run, I would have some slight, but very aggravating surge at cruise in all gears besides 6th... running at ~13.5afr smoothed the motor out enough for me to call it a day. Still now, it feels more stable at cruise and responsive at tip in commanding a ~13.85 afr. Motor just doesn’t run happy at lambda. As for my startup woes, I noticed it was commanding the 10deg spark while cranking, but immediately dropped to 2deg once reaching ~500rpm due to my high oct table only having 2deg in it at low rpm high load. Once I raised those values to 10, it never commanded under 10deg and got the motor started up nice quick and clean. Also had to dampen startup flare table a bit. I have yet to let it get cool enough for a cold start, but I will definitely make your suggested changes to the ivt gains table if it gives me any further issues. Fueling across the board all from idle to WOT is also sorted enough to make me happy, and the car feels drivable enough for me to call the tune “complete” for now. But before I do that, what other issues did you notice? I’m sure there are plenty lol... I’ve just been itching to finish this project up as the stall converter I ordered took 10 weeks instead of 4 to ship and killed the ocd mindset I usually have and really tested my patience... but if there are any blatant issues in the tune as of now I have no reason not to address them, so any more info from you would be a blessing! I’m always willing to learn more, and appreciate you taking the time to write up very detailed replies that go above and beyond to answer my simple questions