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Discussion Starter · #1 · (Edited)
I’m hoping to figure out the linkage between TC~Stabilitrak operation and the imposed “performance limiter” that I encounter. The complaint is that if I forget to shut down or change Stabilitrak , and then attempt a little impromptu hooning.... something quite unexpected occurs near but before redline. ——just before redline it seems that the fuel is momentarily shut off for one half second of more, which is to say that the car falls abruptly on its face— and whatever “pony/bee/snake” I was was showing the true way, suddenly takes the opportunity to jump right ahead in that split-second. The car doesn’t immediately recover from this, there’s a bit of hesitation (talking milliseconds, here) and then it’s back. If I turn off TC it acts about the same. If I double-click the TC button and get “Stabilitrak Competition mode” then the car drives as expected, full power to redline, bang a shift, carry on. If I long press the TC button to get Stabilitrak off, it drives as I would expect, pulls to redline etc.
I’m certain that it’s doing what it’s designed to do but I was wondering if y’all could shed some light on the mechanism. It seems that STABILITRAK has an unpublished nanny mode, not just a stability assist.

When I hit redline and the limiter in Competition mode, the effect is very different; fuel (or timing) is reduced- throttled, moderated, not shut off.

Note that I’m on MT DRs, on clean dry concrete and am convinced that it is NOT spinning at the top of the gear.

The limiter/safety/ nanny whatever it may be is kicking in before the shift, before the clutch.

The tires are all 27” diameter.

Switching to “Competition Mode” completely eliminates this intervention.

Curious if any of you know the story on this.
 

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Interesting that you bring this up... this past weekend while at the track, my engine unexpectedly died rolling out of the burnout box after the burnout. Engine RPM was at redline during a 2/3 shift burnout. It acted like the fuel just shut off. I stopped the car, put it in park, and I had to restart it, which it did absolutely normally and ran just fine. I only had TC shut off when this happened. It did not do that last year at all. I have installed 2" headers, 3" exhaust, new IC system only this past winter. I'm also running 28" rear DR's but did last year too and no issues. Curious to hear about this matter as I was unaware there were different Stabilitrak modes.
 

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So the easiest way to describe TC vs stabilitrak is this. TC uses wheel speed sensors and vss to recognize wheel slip and only cuts engine power... Very basic, and the engine power cut is obviously drastic.

Stabilitrak on the other hand uses these same sensors, along with the g sensor, steering angle, and probably another 1 or 2 I'd have to check the schematic... Anyways this system is obviously more advanced, STILL cuts engine power (more finesse here) and in addition can apply brake pressure on whatever wheel to change the trajectory of the car. (Think steering wheel turned opposite of the way the g sensor is being stimulated).

I actually find this nannie system to be pretty good. Much better than my c5 where you just get a dead peddle the moment you break traction.
 

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Discussion Starter · #4 ·
Curious to hear about this matter as I was unaware there were different Stabilitrak modes.
My limited understanding is that the options are:
On start-up, no button clicks: (default) TC ON; Stabilitrak ON (full Nanny)
One Click: Traction Control OFF; Stabilitrak ON (full Nanny)
Two clicks: Traction Control OFF; Stabilitrak Competition Mode
Long press: Traction Control OFF; Stabilitrak OFF
I could be wrong, straighten me out.

So the easiest way to describe TC vs stabilitrak is this. TC uses wheel speed sensors and vss to recognize wheel slip and only cuts engine power... Very basic, and the engine power cut is obviously drastic. <snip>
Drastic is the word... but I think it's not exclusively a TC application.

Stabilitrak <snip> STILL cuts engine power (more finesse here) and in addition can apply brake pressure on whatever wheel to change the trajectory of the car.
<snip>
I'm not convinced that it is NOT applying brake in the described event.


I actually find this nannie system to be pretty good. Much better than my c5 where you just get a dead pedal the moment you break traction.
I don't disagree that it works to make the ride somewhat safer, especially for inexperienced drivers (such as those famously leaving car shows on youtube) and helps prevent or reign in surprise fishtailing and severe yawing. I appreciate the oversight of stabilitrak in some cases. What has me hung up, here, is that this action is DRASTIC and occurs whilst the car is purely accelerating in a straight line. In the (presumed) absence of tire slippage, TC should have no input; in the absence of yaw or lateral Gs, Stabilitrak should have no input. The surprise fro me it that it seems that Stabilitrak or TC has some sort of rev limiter or 'speed in first gear" limiter or something weird. It could be that mine is broken.
Really, this is simply academic discussion ~pure curiosity~ as the issue goes fully away if I remember to push the right button. I would just like to understand it a little better. I'd also like to understand the value of ST 'competition mode' vs 'OFF'.
 

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Could you be hitting the rev limit and the tach is slightly inaccurate?

You can modify the Rev limit,, fuel or timing cut, as well as ECM - controlled TC in the tune. I had some wierd engine cut issues as well when getting into it on the highway, but that was straight up wheel spin at 80+ and resulted in totally dead car (engine off, etc) and I had to take the key fob out of the car to reset the ECM power - totally different than spinning wheels at low speed.

I'm not sure I have ever actually solve the problem Tho. I suspect TC is handled through the body control modul and the ECM just distributes the commands much like the FPCM.

Sent from my SM-G991U1 using Tapatalk
 

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Discussion Starter · #6 ·
Could you be hitting the rev limit and the tach is slightly inaccurate?
Of course, it's possible the tach is inaccurate but seems oh, so unlikely as the engine speed sensed from the crank reluctor is so critical to the system that if it didn't match precisely the whole system would freak. the display mechanism I guess could be lagging(?) I could test this with HPT's rpm readout... but then, how lag-free is that?
You can modify the Rev limit, fuel or timing cut, as well as ECM - controlled TC in the tune. I had some weird engine cut issues as well when getting into it on the highway, but that was straight up wheel spin at 80+ and resulted in totally dead car (engine off, etc) and I had to take the key fob out of the car to reset the ECM .
]
Now THAT's weird... and I'm expecting that what you experienced wasn't some Nanny intervention, but a failure somewhere.
I suspect TC is handled through the body control module and the ECM just distributes the commands much like the FPCM
I would agree.
 

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Of course, it's possible the tach is inaccurate but seems oh, so unlikely as the engine speed sensed from the crank reluctor is so critical to the system that if it didn't match precisely the whole system would freak. the display mechanism I guess could be lagging(?) I could test this with HPT's rpm readout... but then, how lag-free is that?
HP Tuners reads the CANbus directly, which is the source signal that pushes Tach movement; so it's as accurate as you can get. I doubt it's a huge issue, but I'd certainly start comparing data logs to see what RPM this happens at and how consistent it is.

Now THAT's weird... and I'm expecting that what you experienced wasn't some Nanny intervention, but a failure somewhere.
If by failure, you mean "an electrical glitch that resets as soon as the ECM loses power and restarts" - then absolutely. But it happened ~3 times over a few months, and in every scenario it involved me inducing significant wheelspin at highway speeds, resulting in the same process / recovery.

My theory is that I so overwhelm the TC system, that the ECM divides by zero or shits itself or something and requires a reboot (ie key off, exit the car), as it pulls crazy amounts of timing to try to limit wheelspin (~25 degrees or so!). The fun part is that this happens in Competitive mode; which I always engage when I start the car. I've tried disabling various options in the ECM and haven't quite been able to convince myself the problem has been solved.
 

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I've had some issues with tc kicking on with a larger cam, had issues recovering after pulling the timing.

As far as mrsurly goes, I'd start by live data stream on all the wheel speed sensors to rule out a bad one.
 

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Discussion Starter · #9 · (Edited)
If by failure, you mean "an electrical glitch that resets as soon as the ECM loses power and restarts" - then absolutely. But it happened ~3 times over a few months, and in every scenario it involved me inducing significant wheelspin at highway speeds, resulting in the same process / recovery.
To clarify, I mean an electrical glitch that occurs incidental to the event, not an intervention driven by a misguided oversight system that is intentionally shutting it down. I cannot think of any system monitoring metric where the response programmed into the system would be "shut down the engine", not even Theft Deterrent or zero oil pressure have that tool in their bag. Prevent start up, maybe... but kill a running/moving car? As a designed-in action? No way. maybe OnStar thinks you ran off the road? GM had that big ignitions switch lawsuit fiasco. I wonder....

My theory is that I so overwhelm the TC system, that the ECM divides by zero or shits itself or something and requires a reboot (ie key off, exit the car), as it pulls crazy amounts of timing to try to limit wheelspin (~25 degrees or so!). The fun part is that this happens in Competitive mode
TC would necessarily be OFF while Stabilitrak Competitive mode is engaged, right?
 

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Discussion Starter · #10 ·
I would venture that your shutdown issue is possibly related to the event scenario by way of vibration(?)
Maybe the FPCM or the ECM is a failure point, or possibly a wiring issue. Likely something really difficult to find, but TC seems a stretch.
 

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To clarify, I mean an electrical glitch that occurs incidental to the event, not an intervention driven by a misguided oversight system that is intentionally shutting it down. I cannot think of any system monitoring metric where the response programmed into the system would be "shut down the engine", not even Theft Deterrent or zero oil pressure have that tool in their bag. Prevent start up, maybe... but kill a running/moving car? As a designed-in action? No way. maybe OnStar thinks you ran off the road? GM had that big ignitions switch lawsuit fiasco. I wonder....

TC would necessarily be OFF while Stabilitrak Competitive mode is engaged, right?
Right, TC should be off, but yet I have seen it pull timing anyway. It's kind of a black magic thing here but I'm not sure traction control is ever really off - It's just muted based on the modes your in (I don't care what the manual says!).
 

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Yeah I agree that the issues where the car shut down and you had to reboot things sounds more like an electrical issue than a computer/software related issue. Battery and ground issues do really weird things and can manifest at odd times.
I had a loose ground in my trunk by the battery for the first 2 years I had the car and it gave me such weird random issues. One where it was completely dead for 15 mins after flashing a new tune with HPtuners and just randomly came back to life like nothing happened and then was fine for months. Then months later it would intermittently have weird random errors with the security system or the doors wouldnt unlock etc etc.
Once I found tightened the ground it has been perfect, no gremlins.

My Porsche was even weirder with a slightly failing battery it acted like it was possessed with random honks and lights flashing and as soon as I put a new battery in it there have been no issues. I put the "old" battery in my older BMW and it has been perfectly fine for over a year lol.
 

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Discussion Starter · #13 ·
So the easiest way to describe TC vs stabilitrak is this. TC uses wheel speed sensors and vss to recognize wheel slip and only cuts engine power... Very basic, and the engine power cut is obviously drastic
A minor point: TC will apply braking to slow a faster-spinning wheel to force more torque to go to the slower wheel. We don't see a lot of that as we are blessed with pretty darned good limited slip diffs, but TC-braking can happen. It (ABS pump) may even be audible.
 

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I don't think TC by itself has anything to do with brakes for gm, at least not v2 but I could be wrong... I haven't been lucky enough to dive that deep into one yet
 

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Discussion Starter · #15 · (Edited)
I don't think TC by itself has anything to do with brakes for gm, at least not v2 but I could be wrong... I haven't been lucky enough to dive that deep into one yet
Actually you've got it somewhat turned around. Modern Traction Control systems originally were an offshoot of the ABS braking systems. Because A.B.S. by design provides the capability of applying individual brake positions even independently of operator input, instead relying on individual wheel sensors and a computer to compare and then control them separately, it is a natural extension of this technology to use that ability to "replace" a limited slip's function by using controlled brake application. A lot of AWD systems are also developed around this same ability (with various less-than-awesome results). The 90's brought universal ABS, TC immediately followed. Some early TC systems were brake only, no engine management, just herky-jerky shuddering if you stayed in it. TC is PRIMARILY active brake application but less obvious with a limited slip. Stabilitrak was another extended use of the ABS hardware. It added a further dimension by going after yaw using (again) the ABS hardware to do the work. When Stabilitrak was first offered on Chevy & GMC trucks in 2003, you couldn't get a LSD if you got it. times have changed. (Stabilitrak was offered on Escalades and Corvettes prior).
 

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I actually find this nannie system to be pretty good. Much better than my c5 where you just get a dead peddle the moment you break traction.
I fixed this on my 02 Z06 after I supercharged it. I changed to 18" wheels up front, and when I did, I tweaked the tire stagger so that the rears where proportionally bigger relative to the fronts by about 2.5% (which was as far as I was willing to push it for fear of having general TC issues). The results were great. I could get a little wheel spin before the system cut in, and if I feathered the pedal just right I could actually keep them spinning for a bit. I'm betting the same trick will work for the V's TC system.
 

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It sure sounds like you’re hitting the rev limiter. The rev limiter is violent and I would described hitting it exactly as you have described your problem. If you’re a cunt hair away from touching redline it will shut your hooning ass down. I’m not sure how close an eye you can keep on the tach when giving it the sauce, but I’ve looked and thought I was grabbing the next gear before redline, only to have my car fall on its face.

Test the rev limiter theory. Run it up in second and let it touch redline to see if that is the same thing you’re experiencing. Mine will fall on its face when hitting redline regardless of TC / ST settings.
 

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Yeah I agree that the issues where the car shut down and you had to reboot things sounds more like an electrical issue than a computer/software related issue. Battery and ground issues do really weird things and can manifest at odd times.
I had a loose ground in my trunk by the battery for the first 2 years I had the car and it gave me such weird random issues. One where it was completely dead for 15 mins after flashing a new tune with HPtuners and just randomly came back to life like nothing happened and then was fine for months. Then months later it would intermittently have weird random errors with the security system or the doors wouldnt unlock etc etc.
Once I found tightened the ground it has been perfect, no gremlins.

My Porsche was even weirder with a slightly failing battery it acted like it was possessed with random honks and lights flashing and as soon as I put a new battery in it there have been no issues. I put the "old" battery in my older BMW and it has been perfectly fine for over a year lol.
I should clarify that the car didn't lose electric- just REP, Christmas Tree dash mode and then the motor stumbles and dies.

Sent from my SM-G991U1 using Tapatalk
 

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I dont know if our situations are similar but here's what I experienced with my V2 a few times. I had the pilot sport 3's or something like that on. I had a few races on a closed highway in Mexico. At about 75mph my car would hit a violent stutter and cause me to lose boost and pretty much start over. I thought it was a glitch in my tune since my car isn't stock. One time it did it though and I happened to see the traction control light come on. I was breaking loose in third gear just enough for the traction control to cut fuel or whatever it does. I switched to the toyo r888's last week and during a few spirited pulls, this has happened again.

May not be the same issue, but I posted just in case it is. Good luck., Jay
 
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