Random timing dip causes bucking

[burnrbr]

My car bucks a little when driving mostly steady state. It correlates to when the log shows a sharp dip in timing. The timing dip does not happen when I'm WOT. The timing dip is not associated to any particular change in throttle and no knock is recorded. My car is a 2009 CTS V with 592whp.

Here is the mod list:

• ID 1000cc Injectors
• 2.4 Pulley
• Cat Delete
• LS7 throttle body
• Track Attach HX
• Varimax Intercooler Pump
• Norcal intercooler tank
• Dual NGK AFX widebands
• Airaid Intake
• Dual SMC catch cans
• Relatively new cooler spark plugs

I realize that most of those mods don't directly affect the directly engine, but I want to share the non-factory stuff just in case.


Timing_Dip.png

Timing Dips.hpl
CTS V Tune - HP Tuner Help.hpt


Thanks in advance for your help.

[burnrbr]

The timing dips are located at:

• 1:02
• 1:22
• 1:41
• 2:22
• 2:49
• 3:10
• 3:40
• 4:22
• 5:06
• 5:54
• 6:15

[Russ K]

Zero your A/C Torque Reduction table if the timing dips occur when the A/C is on.

Russ Kemp

[Michael_D]

Does that car have a manual? If so, disabling spark smoothing cured that in my car.

[burnrbr]

My car is a manual. I'll try both suggestions this weekend. Thanks

[openwheel25]

How did the suggestions work? I have the same problem. What I have found is that it is torque management advance. That is what comes up on the scanner when it does it. I have disabled all of the torque management but it didn't help.

[MikeOD]

It actually looks like at 1:22 it's switching from the high octane table to the low octane table, then switching right back...but the other instances don't appear to be doing that.

There are a LOT of spark retard PID's you can log that may help identify it.

I don't advocate leaving the tune this way, but have you tried copying the high octane table to the low octane table to see if it changes the problem?

[Nick@Newtech]

def ditch spark smoothing, I freaking Hate it.

[Nick@Newtech]

also, burst KR will cause massive unexplainable timing dips.

[burnrbr]

The car does it when the AC is off and spark smoothing is disabled in the tune. I'll try logging some knock PIDs, but the log doesn't show any knock correction.

[C5 2000]

Return to stock Injector Flow Rate Modifier vs IAT and Tip-In Limiting ETC Limit. Also Fast Torque Exit back to stock.

[burnrbr]

I've set low octane timing to the high octane timing. I tried disabling the ignition control on the traction control settings. None of the those settings has helped. I logged knock burst and it's not happening.

Return to stock Injector Flow Rate Modifier vs IAT and Tip-In Limiting ETC Limit. Also Fast Torque Exit back to stock.

I'll try this next.

[openwheel25]

Your scan looks just like what is happening to me. Next time also try to log Torque management advance. I know the timing is retarded, But when the timing is being pulled on my car the only thing that the scanner shows is torque management advance. It can't hurt to log it too.

[burnrbr]

Your scan looks just like what is happening to me. Next time also try to log Torque management advance. I know the timing is retarded, But when the timing is being pulled on my car the only thing that the scanner shows is torque management advance. It can't hurt to log it too.

I logged the Torque management advance and it showed up when the timing dip occurred, but only at the point bottom of the dip and on the way back up to normal timing. It seems that the ECU used it to smooth the transition back after the large drop.

I decided to use the process of elimination to debug the situation. I took my stock tune and only moved over the most required settings like MAF, high octane ignition timing and injector settings. The timing dip was gone. I slowly added settings back until the timing dip returned. The culprit was that the Supercharger Torque settings of Spark, Fuel Cut and ETC were disabled. I didn't test them individually, but having them all enabled like the stock tune cured my issue.

Thanks everyone for your help.

[openwheel25]

Thank you very much for keeping all of us informed. I have a question. Do you have supercharger fitted in your tune? I am not sure how I have my supercharger torque settings set but, I am sure I have it set as supercharger not fitted. I would think if it was set as not fitted any setting for it would be ignored. But, I can't wait to check how it is in my tune and try it. Thanks again for your feed back.

[seven ends]

That was my question in post #58 of below thread 3 weeks ago. Would be nice to know more about this tab in general for vehicles not originally fitted with S/C.

http://www.hptuners.com/forum/showth...U-really/page3

[burnrbr]

Thank you very much for keeping all of us informed. I have a question. Do you have supercharger fitted in your tune? I am not sure how I have my supercharger torque settings set but, I am sure I have it set as supercharger not fitted. I would think if it was set as not fitted any setting for it would be ignored. But, I can't wait to check how it is in my tune and try it. Thanks again for your feed back.

Yes, my tune has the supercharger set as fitted from the factory. CTS-V generation 2 and the upcoming 3 are supercharged from the factory.

[Nate007]

My camaro is having the same issue, and am wondering if you've found the issue? Seems to be steady state driving, almost always when cresting a hill or on flat roads. Any chance it could be something to do with DFCO spark?
I have a Cammed (comp 277Llr) and KB 2.8 s/c.