So car is a cammed Z06. Idles great, drives great but the idle flairs a little when coming to a light or stop. What would you guys look at?
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So car is a cammed Z06. Idles great, drives great but the idle flairs a little when coming to a light or stop. What would you guys look at?
Adaptive idle, reserve and peak. A lot will be in adaptive for the throttle controls.
Is it flaring from throttle or spark? (predicted or immediate)
Just a quick look at the scan, when the clutch goes in the rpm pulls down and bogs a little. Spark goes negative for a bit and then it flares back up. The timing doesn't go negative during idle which is weird. Only when falling back to idle.
Looking at the log it looks like the predicted torque is spiking and the car is pulling timing. I'll see if I can get that number down with the VTT
Quote:
Originally Posted by JASON11WS6
I pulled some back in the VTT and it really didn't change much. 10% and another 20%. Still having the same issue
Yeah that VT change is no Bueno. It needs to be smooth and slope lower below idle speeds than the rest of the VT RPM range. I don't know if that is your problem, but it likely caused another one. Your VVE is not good either. The Adaptive Idle area needs some work. But depends how big the cam is. Think of Adaptive Idle section as acting like the IAC valve in the old LS days. However, you need to get your Virtual Torque and VVE in line or you will chase your tail in circles with the surging.
I've gone back to stock VVT tables and the same issue. Added subtracted and everything. I'm gonna check for a vacuum leak maybe. Maybe raise the idle while coasting as a bandaid. The car runs perfect otherwise and idles great
VVE tables play a roll in the idle quality regardless if you have the dynamic air set to MAF high speed mode at all times. If the cam is big enough, sometimes you have to play with the VE Coefficients.
Yeah, you could honestly probably put your vve table to a 17 cam position, copy and paste that into your 0 position and that would probably be closer to your actual to start with. I will say of the tunes I've seen where a lot of things weren't tuned in that they really cut the idle speed multiplier tables substantially to help with stuff like this. You can also change your base and long term idle timing tables to allow for more timing control and dfco speed settings to get out of dfco sooner. Torque model will help, but you REALLY have to work to find that perfect sweet spot - just first observation - your idle timing in general needs to be higher - this allows room for the timing control. If nothing else you can just play with the speed multiplier.
I would listen to Jason and get everything dialed in, but you can play with the above to help.
What do the stft's do when it dips?
Looks like the short terms are spiking lean before the idle drops. When it flares back up they go normal and then spike again as it drops.Quote:
Originally Posted by 32vape
I cleaned up the VVE and it didn't make a difference. I went back to the stock VTT and it nothing, I modded it in every direction. I wonder if it's something physical. We smoke tested it and it didn't leak. I wonder if its the bypass valve or something like that.
Also, the car has a 5" intake on it. The cam isn't huge (BTR stage 2), I've tuned this cam in a ton already and never had this issue.
I tuned a similar setup recently. But without seeing your tune I can't help you much. If its going lean when the idle is dropping, it may just need more fuel in the MAF curve below the idle area. The 5 inch intake needs a very large change in MAF values across the board. Additionally, maybe your Predicted Adaptive Idle control isn't allowing enough adjustment when the error is too large. The throttle body area size plays a roll in how this behaves too.
Most of the gen v stuff will add a large amount of fuel through the stft for a few seconds when fuel is re-enabled after dfco or cfco. It may be to test o2 sensor response or cat efficiency. With stock exhaust, it will pass the test and no longer dump the extra fuel. With long tubes it won't pass and continually run the test. You would see the stft's both go to a large positive amount at the exact same time. Like 27-30%. That can make the idle drop then flare with a cam.Quote:
Originally Posted by JASON11WS6
This was the fix in this case. I set the vtt all back to stock. Then I checked the Driver demand tables and it looks like whoever tuned it before me was messing with this table for some reason. When I tune I only really mess with the full throttle portion and some light mid throttle adjustments. Never idle. Car ran better right out of the gate, played with the vtt some and it got the idle right.