Cammed lt1 actual torque numbers spiking while at idle?

So we have a cammed 2021 Camaro SS. BTR 225 cam. Car ran great, had an excellent idle. Chopped awesome. Customer brought it back saying it wasn't running right. Looks like the timing is negative at idle now. I scan it and I notice the actual torque numbers spike up to 400 while at idle. Overall it makes the average number in the scanner sit around 150-160. When I read it real time its 0-25 range and then spikes to 400+. Idle is being dragged down and is pulling negative timing. Any ideas what would make the torque numbers spike like that? The tune was spot on before and this wasn't an issue till recently. Maybe a defective TB or something?

Any ideas

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This is why I keep saying that these learn and just because they may be good when you're done, after dialing in VE or whatever, doesn't mean they're right. Guarantee even though I haven't looked at your log that commanded axle torque is shooting up causing the "idle blip" you're experiencing. Torque model will need shaping and min air set higher than actual. It's just the way it learned out. Alcohol may be playing into things too if you didn't tune the E torque model.

Man I swear these Gen V's have gremlins. I'm working on a cammed ZL1 that was previously cammed and ran fine. New cam, made some changes. Idle's perfect. But then out of nowhere the idle starts to ocellate a bit and timing gets out of whack and it starts to crackle out of the exhaust at idle. Then, it corrects itself and will idle just fine until the end of time. I just reworked the VVE table and so far is hasn't done it again.


Anyhow, I really came to agree with where Greg advised to look. I'll check the log later tonight when I'm on my tuning setup.

The idle isn't surging really. It's just getting pulled down by negative timing. The torque numbers look okay until that spike which you can't see in the scan. During a live scan it reads low and spikes every couple of seconds. On the scan it seems to be averaging it out and the number looks really high overall. If these things are learning (in a bad way) on the fly then we're in trouble lol. This thing idled like a champ when it left and sounds awful now. The scarier thing is, if these cars go negative timing and someone leaves it to idle for a long period of time, they can set on fire. I've seen negative timing make the headers glow red and it'll burn down a harness or anything close.

I just went over the ve fueling and it's solid just like the maf side. All fueling is 5% or lower on the fuel trims.

I have my customers put a couple of hundred miles on them for this very reason. Doesn't happen often at all for me anymore since I dial in a lot of the torque controlling factors - density table is a big one due to changing fuel trims, but I would see them have 10 degrees idle timing, which preferably it's better to have them in the teens and then drive and return with logs showing in the negatives and touchy throttles because of it. With dialing in the torque models it put an end to a lot of it. My problem is I'm still finding out things that the models control even to this day. Such as lowering the map model will cause the throttle plate to open - didn't know that, but has to be done to match the airmass model and other tables have to agree with it. Airmass directly controls reported torque even if failed. The models control fueling or the defined lambda of 1 somehow - I've actually used this to increase mpg's. AND so on and so on... Shaping the torque models to work through the cat and evap test will usually put them close to where they need to be in general. You know what I mean if you've ever had to do this.

Problem is the map side of the model. It learns along with the airmass side as far as that goes toward the other to balance themselves out or to line each other up with the other. I went as far as having someone create a tool for me to do this. Even with that it's a 50 50 shot as to whether or not it's good with "everything"...

Now what I find really interesting is the fact that the newer OS's add timing for dips instead of taking it away to control the rpm. Fixes a lot of these blips just with that.... Almost like they found one of the controlling switches were wrong and "flipped" it. Really wish we could see the coding in a newer one.

Is there any chance that a vacuum leak has popped up? I've had a customer leave the drain open on their catch can before and it caused idle timing to drop considerably and fuel trims to shoot up.

You should add these PID's to your config:

-TPS Hi Res (not SAE)
-Zero Pedal Torque

Also, I noticed fuel rail pressure is way high for idle. You need to adjust the rail pressure down since it's idling at a higher airmass now.

Quote:

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Originally Posted by TriPinTaZ

Is there any chance that a vacuum leak has popped up? I've had a customer leave the drain open on their catch can before and it caused idle timing to drop considerably and fuel trims to shoot up.

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This is what I was thinking off the top of my head. I too had someone leave their catch can open once and it threw everything out of wack.

I'll check the catch can. Was was going to vacuum test it anyway just in case but I'm not to confident that is the problem. Usually the fuel trims are off on cars with vacuum leaks. Maybe it's just a minor leak causing my spike I'm seeing? I'll give it all a look.
Huggins, when you say the new operating systems what are you referring too. The Global B stuff?

E90's and newer. E90's OS's will add timing instead of pulling it to aid in rpm dips. Which removing timing on a higher compression engine usually increases that firing cycles torque output but when cams lower compression adding timing seems to work better like the older gens did. Just something I noticed with E90's and their operating characteristics... I haven't personally messed with any of the Global B stuff.

Other things that will cause what you're seeing with the torque spike is your adaptives being too aggressive with your reserve being too tight, so once your timing is back right you "might" want to dial them back a touch or at least check them. I seem to deal with a lot of problem child's and see a lot of this BS now... Think I'm getting grayer by the day.