idle coming to a stop

Hey guys. I have a 2012 Camaro SS l99 auto with a GPI SS3 vvt cam, fast lsxr 102mm intake, nick williams 103 mmm throttle body, 1 7/8 long tubes, and a 3600 circle d single disc. So I have a little annoying problem, when I come to a complete stop it seems like you can feel every downshift dropping the rpm really low. It drops real low I want to say like 2-300 rpm lower than it's set to in the idle parameters and then catches itself and raises back up to where I have it set to. Is this normal? I've tried playing around with the integral and proportional airflow in the normal and coastdown setting by raises them up 20% but it still does the same thing? Can someone point me in the right direction please. I really would like the rpm to stay stable when coming to a stop. Thanks

Joseph

updated sorry forgot the details

c'mon man, you've been around long enough now to know a tune and decent log of it happening are mandatory...

ok so the rpm doesn't drop as much as I thought. It only dips down like a 100 rpm lower than my desired idle rpm but it still is annoying.

Sorry that data log doesn't show it but this one does. Sorry for the confusion.

Attachment 126643

So I just did a new data log. It shows I'm dropping about 75 rpm lower then where I want it to be on stops. It doesn't seem like much but it just doesn't feel right.

Attachment 126644

i think you are just showing off how good your car runs which by the way sir you have a race car. i dont see the problem but im not a senior tuner

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Originally Posted by biholliday

i think you are just showing off how good your car runs which by the way sir you have a race car. i dont see the problem but im not a senior tuner

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Well thank you I guess. But coming to a stop and your car feeling like it wants to die on you in an intersection isn't really fun. Other than that it does run really well.

This is really a downshift timing issue.. The 0% TPS column in downshifts is where you will make the most difference. You want it to make the downshift to the next lower gear before going lower than idle speed.

It would also be helpful to turn off CT downshift torque management too if you haven't already.

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Originally Posted by Alvin

This is really a downshift timing issue.. The 0% TPS column in downshifts is where you will make the most difference. You want it to make the downshift to the next lower gear before going lower than idle speed.

It would also be helpful to turn off CT downshift torque management too if you haven't already.

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Thank you sir for your advice. I will try and disable the ct downshift first since that is the easiest thing to try. lol

Well Alvin you are good. I disabled the ct downshift in the torque management in the transmission setting and it worked. No more rpm drop in between shifts on a stop. So thank you my friend.

Awesome! Good for you.

Does your rev matching on manual downshift still work after disabling CT TM?

Picking you lost your rev matching.

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Originally Posted by hjtrbo

Picking you lost your rev matching.

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I believe that I did. Don't know exactly what rev matching consist of but know that when down shifting the rpm's don't lower at anymore. But it feels so much more responsive now. And I'm not sure about manual downshifts I'll have to check it out and report back.

Ok guys I need your help. I recently had Greg help me with getting my VVE dialed in, which he did and it runs awesome except one little hi cup. When I'm coming to a stop the car wants to die on me. Or if I rev the engine just a little bit while in gear from a stop and let off the throttle it wants to die. Or when I'm going up a hill and let off the throttle it wants to die. I noticed that while the rpm's drop the timing goes up. I'm sure that has something to do with it but I've played around with all the idle spark advance, idle adapts, and the braf settings with no luck. If someone could tell me on what to change in the timing to not have it go so high at idle (keep advance to around 10*-12*) or offer anymore opinions I would greatly appreciate it. If your wondering why I don't keep bugging Greg on this it's cause we went through several tunes that didn't help and I didn't want to keep pestering him to death with this problem. Thanks guys.

Attachment 131856
Attachment 131857

if u look on the engine side i think its the ''fast torque exit'' that u have maxed out relates to the rev matching for the downshifts, try that back as stock values if u want it working, and i think it was the CT downshift torque reduction needed to be enabled for it to work too, not sure if that will help your current issue also tho

The log doesn't seem to show the issue.. no idle dip.

You want the timing to go high on a idle dip. I'd say you could go much higher than you are set with the adaptives.

I'd come up to 18 degrees on the base timing too. 11 is a bit low for a gen4 engine. Just my opinion

The VE when zoomed into the idle area has some boundary issues.. it has sharp jumps in it. This could cause a issue but i'd look at the timing first.

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Originally Posted by Alvin

The log doesn't seem to show the issue.. no idle dip.

You want the timing to go high on a idle dip. I'd say you could go much higher than you are set with the adaptives.

I'd come up to 18 degrees on the base timing too. 11 is a bit low for a gen4 engine. Just my opinion

The VE when zoomed into the idle area has some boundary issues.. it has sharp jumps in it. This could cause a issue but i'd look at the timing first.

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Thanks Alvin I will bring the base timing up some and see if it helps. One of the dip in rpm is at 2.111 in the log. What I would like is the rpm not to drop more than 950 because that's where I have the minimum setpoint in the idle settings but for some reason it ignores that. It will actually stumble down to 600 rpm and then start to surge up and down a few times until it catches itself but usually just dies on me.

I honestly didn't know it was still having issues Joe. I changed the adaptives in this one to step the throttle down slower. You can try the other suggestions too if this doesn't help...

I changed his idle timing to 11 to give more headroom to his idle adaptives and to improve the idle sound as it did not like idling at 15+ degrees and I only changed and smoothed out portions of his original tune to correct issues that tuning in the VE revealed.

If you want to cap your idle timing to a specific set point then remove the difference from the adaptives - idle timing 11 / adaptive adding 20, but you want idle timing to max at 20 = -11 from the higher adaptive values then interpolate back down to the next lowest value in the table.

Then if I screwed up the lower rpm areas of the VE table it'll make it worse, but I'm pretty sure we dialed fueling in to the 600 range? You can watch transients on the wideband when it goes to dip to know for sure.

Thanks Greg I just didn't want to keep bugging you with this issue because we did several tunes with it but I figured I could figure it out on my own so I that I would through it out there and see what info I could get. I'll give that tune a shot and let you know.

When in park and I blip the throttle a little bit the rpm raises and holds there for a few seconds and then returns to a normal idle, what settings cause that?

idle torque follower ?

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Originally Posted by 07GTS

idle torque follower ?

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I'm not sure. I thought it had something to do with the idle rpm adapt. Like on 2198, 2199, 2196, 13540, and 2197 as for when the rpm raises in or out of gear. Because I was messing with 2198 / 2199 and it definitely has something to it because I set it to 0.03 seconds and it seems like it goes back to a normal idle after 0.03 seconds.

Maybe what I need to know is the ecm in idle adapt mode or not when you are just idling?

It should be. Usually slow drop is too high of min air or the rpm settings. If you're still using the throttle step settings that were in there with the high min air that might be part of it.

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Originally Posted by GHuggins

It should be. Usually slow drop is too high of min air or the rpm settings. If you're still using the throttle step settings that were in there with the high min air that might be part of it.

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Say when I put it in reverse and everything it idling perfectly and I start to roll backwards and I get over 1 mph, something kicks in and raises the idle momentarily and then goes back to normal as soon as I stop the car completely. Is that the idle rpm vss max / vss hyst 2196 / 2197 doing this?

That could be either or. Once the ecm see's motion - i.e moving car - it switches from park/neutral min air row to the "calculated gears" row that it thinks it's in and if that row is significantly higher - well that could be your problem. Once it gets above the speed you're referring to it will "prioritize" more to the torque and min air controls. Once below it, it uses torque and more of the rpm controls... The ecm will switch to adaptives anytime you're coasting or in "idle mode" with no pedal application - doesn't matter how fast you're going - it just prioritizes one area vs the other more.

What are you referring to as the torque controls?

This will piss one individual on here off even though the man that helped come up with it himself stated it's used for idle and given things in 4th gens just like it is in 5th gens, but the torque model needs to be close to matching throttle follower torque. Once they're close to one another the ecm can better implement it's idle controls and cams greatly throw off the idle area in particular of the torque model no matter how dialed in your airflow models are.

Lol who will it piss off? Is that what you think of people that disagree with you? Disagreement isn't being hostile.

Send him a updated file to correct his torque issue?

Attachment 132614 current tune

Got to have a log to go with it Joe, but looking at the torque model it should "theoretically" be close - granted the idle air didn't greatly change things. You can give this one a go... It's all about making the two more in line with one another. If they were already in alignment or close to it then you need to address it elsewhere. Just keep in mind if the torque model is too high or vice versa too low in the rpm area you're getting to then letting off it will cause the throttle to do funky things. The throttle after all is still electronically controlled.

It's one thing to disagree, but to put blinders on and only believe you're right is another ;) Also as I clearly stated. Having this right will make the rest of the idle tuning work more in line - it's not the cure all... The min air being at 22 then stepping down and back up will affect it as much as anything.

Thanks Greg I'll give that a try.