C5 Z06 stalling on clutch in

[ryanbooth]

Hey guys,
I am about at my wits end with this car. Car was tuned by a reputable tuner, and everything seems to be fine besides it frequently stalling on clutch in.

I have played with the throttle follower, TF Decay, and Throttle cracker but have not been able to make any significant changes in the stalling issue.

I tried raising the base airflow at that seemed to help for a bit, but it seems that the car learned that back down and it began stalling again after some time.

Truthfully, I am having a hard time understanding what is doing what on this car. From what I have read, TC is only active on some C5s with clutch in. From what I have gathered in the logs, mine is doing nothing at all. Enable speed seems to be the same as my OE calibration. Rolling airflow also seems to be disabled? Car idles well once adaptive idle kicks in, but coming to a stop is nearly impossible. It hunts for idle maybe 30% of the time.

STITs seem okay, LTIT never moves from -.40. Another possible issue?

Set up is SBE LS6, BTR4 cam (233/248 .630"/.615" 111.5LSA) Fast 102 intake with NW102, ported heads, aluminum flywheel.

Tl;dr, I am looking for some direction on how to approach this issue.

Tune and most recent log attached

[Hondaeater]

Hey guys,
I am about at my wits end with this car. Car was tuned by a reputable tuner, and everything seems to be fine besides it frequently stalling on clutch in.

If it was a reputable tuner then he should fix it.
When I get a break I can look at your files posted but really if it's stalling with clutch in it's unsafe and the tuner should fix it that started on it.

[ryanbooth]

If it was a reputable tuner then he should fix it.
When I get a break I can look at your files posted but really if it's stalling with clutch in it's unsafe and the tuner should fix it that started on it.

Yeah I fully agree with you.

Unfortunately they are not a local tuner, so it is a full day to get the car there and back. No one local was willing to take on an older LS with big cam and TB.

We did do some remote work, but it never seemed to make any change. Which makes me think there is some kind of mechanical issue that I can't find....


If you get a chance to look at it, please let me know what you find

[Hondaeater]

Not enough info in channels list really. Scan for DTCs. Clear them. any Uxxx DTCs?

So you do have the DBWire 102mm right?
Use these channels and post log. I'll see what it may tell us.
If you would, Key on wait 2-3 seconds. Start car and if needed use pedal until it can idle by itself. If it won't do it by itslef, get it up to 170deg using pedal idling and keep trying to allow it to idle, catch it with pedal and let off the gas SLLOOWWLLYY not lift foot and see if it holds. Bring it up 1200-1500rpm and very slowly lift foot and see if you can get it to idle. If it can be driven, probably after the DTC tune file posted here is used, drive and keep pedal as steady as you can at times, for about 10-15 seconds of steady airflow. Air needs to be steady flowing into engine for any good data. This is a simple snapshot not a tuning log, we need to see how well it is dialed in at 2500rpm, at 3500rpm and idle. t the end of a drive let it idle for about 60-90seconds just resting and this is very important data. So is the key on engine off at start. It provides a lot of useful data. If you have a WB add the channel between the Commanded AFR and EQ channels.
Is this an automatic? It is set for manual but was originally an auto calibration.
You have the trunion upgrade and parts to support the 7000rpm redline right?


The DTC is set incorrectly. Here is that updated. Get a log before anything else is done.

[ryanbooth]

Not enough info in channels list really. Scan for DTCs. Clear them. any Uxxx DTCs?

So you do have the DBWire 102mm right?
Use these channels and post log. I'll see what it may tell us.
If you would, Key on wait 2-3 seconds. Start car and if needed use pedal until it can idle by itself. If it won't do it by itslef, get it up to 170deg using pedal idling and keep trying to allow it to idle, catch it with pedal and let off the gas SLLOOWWLLYY not lift foot and see if it holds. Bring it up 1200-1500rpm and very slowly lift foot and see if you can get it to idle. If it can be driven, probably after the DTC tune file posted here is used, drive and keep pedal as steady as you can at times, for about 10-15 seconds of steady airflow. Air needs to be steady flowing into engine for any good data. This is a simple snapshot not a tuning log, we need to see how well it is dialed in at 2500rpm, at 3500rpm and idle. t the end of a drive let it idle for about 60-90seconds just resting and this is very important data. So is the key on engine off at start. It provides a lot of useful data. If you have a WB add the channel between the Commanded AFR and EQ channels.
Is this an automatic? It is set for manual but was originally an auto calibration.
You have the trunion upgrade and parts to support the 7000rpm redline right?


The DTC is set incorrectly. Here is that updated. Get a log before anything else is done.

Thanks, I'll give that a try tomorrow.

The car is stick with a DBW throttle body and the car is a z06 so stick was the only option. I have no explanation on the calibration being auto originally.

it did have a U1016 History code, but that is the only code UXXX code. Others were some TCS stuff that the car has had since I bought it.

And yes valve train has been beefed up. Trunion kit, morels. etc. Car made good power (459/430) and drives decently, just can't use the clutch when stopping reliably.

[Hondaeater]

I look forward to seeing it. the Cracker airflow is not registering, like the table is zeroed out? Any ideas because that table is populated in the tune I adjusted DTCs for. the Follower air is there but the cracker air is not.

[Alvin]

The light clutch/flywheel is going to be the challenge.

I do things like this all the time.. Airflow is not going to be the answer provided the STIT's and LTIT's aren't positive at a normal stabilized idle. In situations like this I'll target them to be taking out say 0.5 g/s just to make sure airflow is never short.

A big part of getting this correct is understanding airflow is a very slow idle correction. Airflow can't save a dip. Also while airflow adders like cracker, and follower are active.. any airflow learning is suspended.


What you need to do is set this thing up with something I refer to as "reserve torque." What I mean by that is that while your idling... if your timing (spark) is advanced to where the engine runs the best... there is nothing left over to save it in case of a idle dip. Your base spark tables are something like 27 degrees. The engine will idle strong there.. but there is literally nothing left to give it to save it.. Does that make sense?

I would set the idle up with a more reasonable amount of timing to leave some torque in reserve.. A number like 16-18 would be a good start spot. If the idle goes low set the idle base spark table to give it more timing (up to about 31 works). If the idle is high set the idle base spark timing to something low (10-12d). When you make this change the engine will be technically less efficient at an idle so it will take a little bump in base running airflow to be back at baseline.

I hope this makes sense.

******************************************


Lastly.. a lot of the time.. Fueling is actually responsible for a poor return to idle. If it is a bit rich while the engine is in decel than the idle will struggle. Your cam is a bit larger than what I would try to run in closed loop. There gets to be a point with overlap that the stock NB's will drive the engine a bit richer than it should be precisely in situations like this. So while fuel trims are decent, fueling checked with a wideband will show rich.


So IMHO..

Your first issue is no reserve torque, second is possibly rich return to idle. Impossible to tell without a wideband.

[Hondaeater]

Totally agree the idle timing is too high. That light aluminium flywheel is an issue too.
Cracker is 0 the whole log and is an issue in DBW TB. I Disagree that airflow can't save a dip. The Follower is needed to provide the air when you blip throttle and release, it must have air not a minimum open TB like desired idle. I would not rely on over/underspeed to calm the rising rpm from blip and be the only catch of the falling rpm into idle, it needs some air adder, same with speed vs rpm axis cracker table. You do not want "cruise control effect" air added but need some as you slow down.

Your ETC scalar could be ok but the starting point for that 102mm would be 0.0142, the 0.0186 that you have now is the setting of a 90mm TB. Whatever works is what it is, but you are having idle issues....

[ryanbooth]

I look forward to seeing it. the Cracker airflow is not registering, like the table is zeroed out? Any ideas because that table is populated in the tune I adjusted DTCs for. the Follower air is there but the cracker air is not.

Log is attached. Naturally it didn't stall on this run but I think I captured the rest of the data you asked for.

The cracker thing confuses me as well. From what I have read, some say it isn't used on C5s, some say it does work. Seems to be a lot of conflicting information based on what the cable throttle cars did.

Does anyone know what the parameters are to activate the cracker? Is it just vehicle speed? Clutch switches involved in someway?

[ryanbooth]

The light clutch/flywheel is going to be the challenge.

I do things like this all the time.. Airflow is not going to be the answer provided the STIT's and LTIT's aren't positive at a normal stabilized idle. In situations like this I'll target them to be taking out say 0.5 g/s just to make sure airflow is never short.

A big part of getting this correct is understanding airflow is a very slow idle correction. Airflow can't save a dip. Also while airflow adders like cracker, and follower are active.. any airflow learning is suspended.


What you need to do is set this thing up with something I refer to as "reserve torque." What I mean by that is that while your idling... if your timing (spark) is advanced to where the engine runs the best... there is nothing left over to save it in case of a idle dip. Your base spark tables are something like 27 degrees. The engine will idle strong there.. but there is literally nothing left to give it to save it.. Does that make sense?

I would set the idle up with a more reasonable amount of timing to leave some torque in reserve.. A number like 16-18 would be a good start spot. If the idle goes low set the idle base spark table to give it more timing (up to about 31 works). If the idle is high set the idle base spark timing to something low (10-12d). When you make this change the engine will be technically less efficient at an idle so it will take a little bump in base running airflow to be back at baseline.

I hope this makes sense.

******************************************


Lastly.. a lot of the time.. Fueling is actually responsible for a poor return to idle. If it is a bit rich while the engine is in decel than the idle will struggle. Your cam is a bit larger than what I would try to run in closed loop. There gets to be a point with overlap that the stock NB's will drive the engine a bit richer than it should be precisely in situations like this. So while fuel trims are decent, fueling checked with a wideband will show rich.


So IMHO..

Your first issue is no reserve torque, second is possibly rich return to idle. Impossible to tell without a wideband.

Where is the ideal place for a wideband on these cars? I can add one in the next week or so if that will help get this fixed. Car is headers into Xpipe with a very small merge. Ideally you want to measure both sides?

I'll give the timing thing a try. The car definitely idles very strong but I think I understand what you're saying.

One thing that may be worth mentioning (and is what sent me down the airflow road) is that the car is much more likely to return to idle when it is cold and still running in OL. Assumed it was richer in that case but didn't consider the overlap in the cam throwing off the NB fuel trims.

[Hondaeater]

Speed vs rpm.
Cracker air is while driving.
Follower air is when P/N, clutch in same thing. When you start driving you'll see the follower error come in because of throttle position soon as you get off the throttle that follower airflow decays away. This is when the cracker airflow which is speed versus RPM based values in the table. Do you have the original file on this car? I'm not at my computer to verify but the enable and disable speed may not be set up correctly.

[Alvin]

Where is the ideal place for a wideband on these cars? I can add one in the next week or so if that will help get this fixed. Car is headers into Xpipe with a very small merge. Ideally you want to measure both sides?

I'll give the timing thing a try. The car definitely idles very strong but I think I understand what you're saying.

One thing that may be worth mentioning (and is what sent me down the airflow road) is that the car is much more likely to return to idle when it is cold and still running in OL. Assumed it was richer in that case but didn't consider the overlap in the cam throwing off the NB fuel trims.

Ideally where the narrow bands are.. But other than that it will still work futher back. Just avoid collectors or any joint that might leak immediately before/after the wideband. If possible.

It's typical that a car with a lot over overlap will drive itself too rich with the narrow bands. Airflow adders like cracker and follower doesn't change OL to CL.. Fueling does.

Too many people get hung up on idle airflow controls when in reality it is the slowest way to catch or fix an idle and is just a bandaid if the engine is rich or not timing isn't correct.

[ryanbooth]

Speed vs rpm.
Cracker air is while driving.
Follower air is when P/N, clutch in same thing. When you start driving you'll see the follower error come in because of throttle position soon as you get off the throttle that follower airflow decays away. This is when the cracker airflow which is speed versus RPM based values in the table. Do you have the original file on this car? I'm not at my computer to verify but the enable and disable speed may not be set up correctly.

I just checked the original file and the cracker enable/disabled speeds are set to the same as the new file.

I attached it just in case you were curious

[ryanbooth]

Ideally where the narrow bands are.. But other than that it will still work futher back. Just avoid collectors or any joint that might leak immediately before/after the wideband. If possible.

It's typical that a car with a lot over overlap will drive itself too rich with the narrow bands. Airflow adders like cracker and follower doesn't change OL to CL.. Fueling does.

Too many people get hung up on idle airflow controls when in reality it is the slowest way to catch or fix an idle and is just a bandaid if the engine is rich or not timing isn't correct.

May be a dumb question, but one sensor would suffice?

The Base Running Airflow vs coolant temp is what made me think the airflow changed with ECT.


I did dial the timing back to 18* and the car runs fine, idles about the same just hunts for idle a bit at start up, but still having issues with clutch in stalling. Do I need to adjust the High/Low octane tables to match as well? From the log I can see it's idling around 18* but I'm assuming it jumps to whatever is in that range in the timing table once it exits the idle state. Should Idle over/underspeed tables also be adjusted to compensate since there is more reserve torque available now?

[ryanbooth]

So I went ahead and adjusted the timing down as mentioned in an earlier comment and dropped the ETC Scalar down to match the actual TB size. Car runs noticeably worse but I think it may be a gets worse before it gets better type scenario.

STITs are down to 0 or a little positive so I will add some airflow on the next revision. I am leaning towards the mixture being rich as it returns to idle.

[Hondaeater]

Which tune file used for this log in post 15? Is it the 03Z06 421 Base DTC?

[Hondaeater]

Which injectors are you using? I added some to the details into the edit tab so it is easier to keep up with your build.
Adjusting the Normal boundary before having the fuel right is not best practice. Do that after you have a known good calibration.
Base air is already too high in the log, it is taking out 4g/s so adding air to BRA is not the answer.
You mentioned: STITs are down to 0 or a little positive so I will add some airflow on the next revision. I am leaning towards the mixture being rich as it returns to idle. Your Dynamic and idle desired is off so your injector and or TB Scalar was off in this log. I do not see a log after you adjusted the Scalar, but in this one it is too large.
Adaptive only works after Follower air is diminished and that table is set to 2x the lower rpm. Too much air is bogging and rpm dips as shown. This is at the end of log and last throttle blip.

Weak startup commanding very lean AFR from cranking fuel at 187 deg. temp. bounces after restart 22:58 time stamp. Cranking spark is low at warmer temps but not clutch idle related so lets keep the focus.
When you lift throttle/clutched in, the Follower air goes away but the cracker air is NOT there and dips rpm to 250ish but spark is 30 plus deg so that won't catch a starving engine. MAP is very high even though you should be at vacuum when slowing, you have no torque and stall. You have some speed so the adaptive spark is not there, looks like you clutch out maybe??? and back in but again no cracker air so falls and MAP rises and stalls.

Can you follow that?

WHY the cracker air is not showing up I hope someone can help sort that out because the table has it but no adder populates the channel?
The idle routine kicks off at 1.5% in your tune so that real light throttle can be tricky with this cam.

Remember the cracker air is speed referenced so 0 speed should be 0 adder in table, the enable/disable speeds should override that anyway but to be consistent, set the 0 speed to 0 adder no conflict. There should be some decay rate (0.6 is good start) not 0 in table too.
The right amount of air, the decay and delay are something that you have to work on, there is no copy and paste someone else's tune here, whatever the engine wants it needs to get.

I am not here to argue and these others may have way more time to help you.

Stay tuned,
Hondaeater.

[ryanbooth]

Which injectors are you using? I added some to the details into the edit tab so it is easier to keep up with your build.
Adjusting the Normal boundary before having the fuel right is not best practice. Do that after you have a known good calibration.
Base air is already too high in the log, it is taking out 4g/s so adding air to BRA is not the answer.
You mentioned: STITs are down to 0 or a little positive so I will add some airflow on the next revision. I am leaning towards the mixture being rich as it returns to idle. Your Dynamic and idle desired is off so your injector and or TB Scalar was off in this log. I do not see a log after you adjusted the Scalar, but in this one it is too large.
Adaptive only works after Follower air is diminished and that table is set to 2x the lower rpm. Too much air is bogging and rpm dips as shown. This is at the end of log and last throttle blip.

Weak startup commanding very lean AFR from cranking fuel at 187 deg. temp. bounces after restart 22:58 time stamp. Cranking spark is low at warmer temps but not clutch idle related so lets keep the focus.
When you lift throttle/clutched in, the Follower air goes away but the cracker air is NOT there and dips rpm to 250ish but spark is 30 plus deg so that won't catch a starving engine. MAP is very high even though you should be at vacuum when slowing, you have no torque and stall. You have some speed so the adaptive spark is not there, looks like you clutch out maybe??? and back in but again no cracker air so falls and MAP rises and stalls.

Can you follow that?

WHY the cracker air is not showing up I hope someone can help sort that out because the table has it but no adder populates the channel?
The idle routine kicks off at 1.5% in your tune so that real light throttle can be tricky with this cam.

Remember the cracker air is speed referenced so 0 speed should be 0 adder in table, the enable/disable speeds should override that anyway but to be consistent, set the 0 speed to 0 adder no conflict. There should be some decay rate (0.6 is good start) not 0 in table too.
The right amount of air, the decay and delay are something that you have to work on, there is no copy and paste someone else's tune here, whatever the engine wants it needs to get.

I am not here to argue and these others may have way more time to help you.

Stay tuned,
Hondaeater.

Tune file used was the file you provided with the updated DTC and corrected scalar.

They are OEM LS2 Injectors.

This 525 log did have the adjusted scalar.

I think I follow what you are saying, there is something definitely going on with the cracker.


I will update the file with your suggestions and test it out.

I do appreciate all of your input. I apoligize if I came off argumentative, for the most part I am just confused and thinking out loud.

[Alvin]

May be a dumb question, but one sensor would suffice?

The Base Running Airflow vs coolant temp is what made me think the airflow changed with ECT.


I did dial the timing back to 18* and the car runs fine, idles about the same just hunts for idle a bit at start up, but still having issues with clutch in stalling. Do I need to adjust the High/Low octane tables to match as well? From the log I can see it's idling around 18* but I'm assuming it jumps to whatever is in that range in the timing table once it exits the idle state. Should Idle over/underspeed tables also be adjusted to compensate since there is more reserve torque available now?

Use the base idle timing tables to dump timing in when the RPM is low and you can pull timing from it when the timing is high. There are also idle spark corrections that should be looked at.

Hopefully that is a good hint in the right direction.

[JoeB1978]

So here is a question totally unrelated to tune. I had a similar issue on my 04 C5Z. Is this happening when you are coming to a stop? Mine had the same symptoms and it was a leaking master cylinder booster that would lean the engine every time I came to stop, at first it would high idle like you say and then as the leak got worse it would stall when I pushed in the clutch with my foot on the brake. If this is your problem you need to replace the master cylinder and booster at the same time. If you listen closely to the booster when someone presses the brake pedal you can hear the leak.