E67 Stalling after blip in gear--follower tuning?

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Just finished the Gen IV Tuning epic post from BigMike42. Really helped me to solve a problem I had with the engine stalling when dropping from P to R/D.

So one big issue left to solve. When I'm in gear and need to do a quick input to the accelerator (moving the car in a long red-light line, creeping over a speed bump or curb, wheel caught in a hole on a grass field, etc.) the engine takes the accelerator input just fine, but the engine will undershoot idle speed and die about 90% of the time (on that last 10%, it will finally catch it at very low rpm and shoot back with power to spare--need to keep a firm foot on the brake!). I've been fiddling with the Base Minimum Airflow table plus the Airflow Overspeed and Underspeed tables with no luck. I'm hesitant to play with anything else as I'm just getting my bearings with HPT.

For reference, I posted the tune and a log here showing two such stalls--the first one happens at 4:13 in the log. The engine is an LS3 crate motor with the ASA cam (note the low idle vacuum) and an Edelbrock blower. The trans is a 4L80e with a 2600 stall converter (advertised) controlled with a TCI TCU. There is no VSS input into this ECU so it thinks speed is always 0.

Would appreciate any suggestions. Is this an area where the Throttle Follower settings might come into play? I haven't been able to find enough info on those yet to really understand how each setting works--any pointers on that or links to pages or posts would be appreciated.



Many Thanks!

[hjtrbo]

Can't open your log at the moment but, try setting your follower torque (air flow tab) at idle to the value reported in the scanner and also you can soften (lower) the increment decrement steps (rpm tab) in the first 3 cells to see if that helps. Try cutting them in half first to see effect.

[Jeff7577]

Try this. I made a few changes to idle airflow and spark. I may have lowered the airflow too much for your 900 rpm idle target so if it won't maintain 900 raise 250-800 until it does.

idle.hpt

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Thanks (again!) hjtrbo--great info, there! We just got 6" of snow (I'd gladly switch placed with you now...) so I'll need to wait until Friday when it's supposed to be warmer to try this out. The salt hit the roads today so it will be the driveway dyno to test your recommendations.

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Jeff7577--thanks for taking the time to look this over and to recommend some changes! I'll take a look at this tonight. Hope to try it out Friday or Saturday.

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Jeff7577,

Finally got a chance to look at your suggested changes. Interesting that you cut back on the spark retard/advance in the Adaptive Overspeed/Underspeed tables. And the values are zero for the extreme errors--are you expecting the ECU to catch the idle excursion more quickly so that those high error values won't come in to play, or are you trying to avoid excessive timing changes with high rpm errors? I also saw the changes you made in the Idle Base Spark tables to lower advance between 1200 - 2000 rpm at low cyl airmass values (extending up to 3400 rpm at higher airmass values). Did you think these were aggressive or are you doing this to give the Idle Adaptive Spark Control more authority to change actual advance value? Just looking to learn the thought process, here. THANKS

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OK--finally made some time to do more testing for this stalling issue when blipping the throttle in gear.

I tried Jeff7577's suggested changes in the file he supplied (THANKS!) and things got much worse. Lots of idle hunting and wouldn't maintain idle going into gear.

Put my cal back in and tried HJTRBO's suggestions:
A) Wasn't sure what PID to log to set in the Throttle Follower Torque as recommended. If this is Engine Torque, then the values in this Follower table are miles off the actual. What value should I record in the Scanner to put into the Follower Torque table?
B) I cut back the first three cells in the Idle Steps Increment/Decrement tables.

No real change in behavior. RPM response when transitioning from P to R (or D) is better which I'll bet is those Steps changes. However, still stalling in gear when blipping the throttle to move the car. A log file with two stall events along with the cal file are pasted, below.

Any help with the above or additional suggestions are appreciated!

12062020 gear blip stall rev 8 with stall.hpl
1967 Impala Ls3 idle tuning changes take 8 12062020.hpt

[hjtrbo]

transitioning from P to R (or D)

Manual PCM with an auto attached?

Have you got something hooked into the PCM to let it know it is in gear?

If not, it makes setting the min air / follower a bit hard to set as there are different air flows / torques when the car is P or D.

I think the tune below will help with your blips in gear at the expense of a hanging throttle when in P. If you have got something hooked up then put your min air flow values for park and neutral back as you had them as they are close.

1967 Impala Ls3 idle tuning changes take 9 12062020.hpt

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HJTRBO,

Thanks, again, for the edits to the cal file. I need to find some time this week to test it out. Going to have to wait about 5 months before I can get it back on the road and see how these calibration changes might impact driveability. Shouldn't, but....

As for letting the PCM know it's in gear; no, I haven't found a way to do that. GM provides very little in the way of info beyond the minimum wiring they provide with the PCM and harness kit. Any suggestions on how to provide such a signal?

Again, thanks for your ongoing help!

[hjtrbo]

Would be good to see what others have done in your case. It will be hard to have a dialled in min air flow table if the pcm doesn't know where the trans is. There is also some feed forward air flow for the park to drive transition as well. All of these things help.

My adjustments are probs going to cause a hanging idle when in park. You will have to find a balance. Trim down 0.5g at a time till you get a halfway point of acceptability.

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Thanks, HJTRBO. Yes, I looked over your changes and can see that it will be aggressive in Park. Will take some playing with it. I'm eager to see how the big change in Follower Torque is going to change things--I was too afraid to make that kind of change on my own! I hope to get some time on Thursday or Friday to fiddle with this.

As for getting the E67 a signal for gear selection: I did some searching last night and it looks like this was done over the CAN (or serial?) bus between the E67 and a TCU. Not sure yet if the aftermarket TCUs put this message on the CAN bus or not. As you state, I may just have to find an optimization point to balance between P/N and R/D for now.

Again, thanks for your continued help with this!

[hjtrbo]

Not sure dude. Worthy of a new thread perhaps??? If you're not using air con, maybe that pin could be used.

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Might start a thread. Not sure how putting a High/Low signal into the A/C pin could be used to tell the car it's going into gear? Unless you're saying to use the A/C table provide the extra airflow when dropping into gear? THANKS

[hjtrbo]

Yeah man, extra airflow when in gear will help your idle tuning out heaps.

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HJTRBO,

A bit of progress today. Tried your mods and it ran pretty well. Idle hung a bit high, but that's OK. The transition from P/N into gear was good. However, it still had a hard stall when blipping the throttle in gear. I put everything back to the previous tune except for the Throttle Follower Torque and the changes you made to the Proportional RPM error and the Follower Idle Decrement Steps. Still good transition from P/N into gear and the engine recovered from a blip in gear two out of 4 times. Granted, RPM dropped very low and there was a strong flare on the return, but it didn't die. I added more Follower Torque at 800 rpm and lower and increased the Follower Airflow Max with the theory that the follower was being capped at a value than steady idle airflow. This cal file and two logs are attached. This cal allowed the engine to recover from a throttle blip (although not particularly heavy) but also stalled twice with heavier blips. I think my next move is to increase the max spark advance in the Idle Adaptive Spark Control Underspeed tables as it's currently capped at 23 degrees when the engine idles around 18-20 degrees. As always, any additional thoughts will be appreciated!

THANKS

G

[hjtrbo]

At work so cant check your logs. But you could try upping the proportional airflow in the cells say 150rpm and above. If you are aggressive, it will add considerable amounts of air if the rpms drop to low. With your idea of increasing the max spark should i think after mbt you won't get any additional benefit. I do not know if 23deg additional timing will be mbt???? That said, perhaps in the cells 150rpm and above, make your spark correction more aggressively try and catch the dip earlier.

Did you find any information out in forum world to get the ECU to know it is in gear vs park?

[hjtrbo]

Had a look at your changes. Make the 0 to 800rpm values the same as the 1000rpm column in your min air flow.

Add in heaps of proportional air. Grab the +/- 128 and above cells and double or triple the values.

Effective area section, increase the max and max brake to 4%. This will allow the throttle to open more.

These changes should give it a good kick up the ass.

This process would be a lot easier of you could buy an auto PCM...