[ASKED] How to decipher eLSD display?
07-26-2017, 09:18 AM
#1
Drifting
Thread Starter
[ASKED] How to decipher eLSD display?
Tadge,
Can you tell us what the information in the eLSD display screen means and how one might make use of it or understand what its trying to tell us.
Can you tell us what the information in the eLSD display screen means and how one might make use of it or understand what its trying to tell us.
07-26-2017, 11:58 AM
#2
Melting Slicks
I guess if someone isn't mechanically inclined might have issues interpreting the displayed information. Sure you could fine lot of YouTube videos that would explain the safe operating ranges. The C7 also will display additional warnings when not operating in the safe areas.
Last edited by BlueDevilZ51; 07-26-2017 at 12:05 PM.
07-26-2017, 12:06 PM
#3
Drifting
Thread Starter
If its so darn obvious, then would you kindly explain what the numbers displayed on the eLSD page mean? Its not in the owners manual and I did not ask about rpm, oil pressure or any of the other items you mentioned. Only eLSD page. I was very specific in my question.
That page is NOT self explanatory and the question has come up in various forums several times with no clear answer that I could find. And instrumentation engineering is my field.
That page is NOT self explanatory and the question has come up in various forums several times with no clear answer that I could find. And instrumentation engineering is my field.
07-26-2017, 12:14 PM
#4
Melting Slicks
If its so darn obvious, then would you kindly explain what the numbers displayed on the eLSD page mean? Its not in the owners manual and I did not ask about rpm, oil pressure or any of the other items you mentioned. Only eLSD page. I was very specific in my question.
That page is NOT self explanatory and the question has come up in various forums several times with no clear answer that I could find. And instrumentation engineering is my field.
That page is NOT self explanatory and the question has come up in various forums several times with no clear answer that I could find. And instrumentation engineering is my field.
07-26-2017, 12:35 PM
#5
Drifting
Thread Starter
Under light throttle (absolutely zero wheel slip) the display increases with acceleration and or speed and then decreases again as you approach cruise velocity but does not go back to zero. It actually looks more like it displays 0 to 100% of actuator force applied to the eLSD clutch but that has never been validated and is only a guess. Then there are the bar graph display at the bottom that is labeled wheel slip but again shows data when there is no slip. Then there is also the color coding of the display, what do the color changes indicate?
I actually thought this was a good question to pose to Tadge so he could give us the more complete description that would never make it to an owners manual. He has been very helpful on some technical aspects of the car in other areas. Helpful in giving the owner community a greater understanding of how this amazing machine works.
Last edited by jcthorne; 07-26-2017 at 12:38 PM.
07-27-2017, 09:20 AM
#6
I agree good question. There have been some claims and speculation as to what the data it is displaying actually is but it would be good to get a firm response from someone in the know like Tadge.
08-07-2017, 03:07 PM
#7
Melting Slicks
Yes this is a very good question and I suggest it be expanded to include a variety of points that I will outline below. The reason I dug into these details is because I have been having intermittent problems with the eLSD not locking for about 3,500 miles. My car is a 2018 Z06 M7 with 4,000 miles. I hope some of this could be passed on to Tadge.
First, basically what is/was occurring with my car was intermittently experiencing lost communication between several modules resulting in "service parking brake light", "service rear axle" warning, and "rear axle system off" warning. Over time what I started to observe using the eLSD screen is prior to the warnings occurring, the eLSD clutch stayed at 0% no matter how I was driving or the amount of wheel slip.
Additional points to clarify:
1. Please clear up once and for all if the eLSD screen is providing useful information. It has been reported that there are GM engineers and/or technical support telling owners and dealer service technicians that the screen is of no use, the screen is garbage, and the screen shouldn't have been included with the C7. I disagree for several reasons. For one thing, when my eLSD stops working as noted above it has occurred before any warnings are displayed. What I started to observe is excessive spinning of the inside wheel when accelerating at the exit of corners. Sometimes the differential would not lock at all and other times it would lock after the car went straight for some distance. Without the eLSD screen I would have no way of evaluating what I feel the car doing. After I started to realize what was occurring I monitored the eLSD screen, and found it was very accurately showing me what I was feeling.
2. Please explain how the eLSD is commanded to adjust including what systems are involved and where all the control logic resides? The reason behind this question is when communication is lost it appears the differential becomes an open differential and significantly affects performance driving. My dealer per instruction from GM thinks turning all systems off will make the differential work like a standard unit (spring applied clutches). It would be helpful if this was cleared up for technical staff trying to troubleshoot eLSD issues. Furthermore, GM's latest direction to my dealer for fixing my problem is a recommendation for me to use PTM modes. While PTM modes do affect amount of wheel spin they will not fix lack of differential clutch lock.
3. On the eLSD screen do we see what is command or is there a sensor telling us what the clutch lock actually is? If it is not the command then how does the system sense clutch lock. Is it based on hydraulic pressure or a position sensor? In other words, is there anyway for the control system to know the differential is not locking when it should be?
4. The lower sweeping bar occasionally shows wheel slip when slip is impossible. Such as slowly starting, coming to a stop and moving at 1st gear idle speed. Under these conditions it will turn red and bounce to 30%. Is it correct to assume this is due to sensors not being accurate at low speeds, and this inaccuracy is ignored by the eLSD control logic?
4. Please provide a better explanation of what wheel slip is. One reason I ask this is the lower bar occasionally shows a small amount of wheel slip when moving in a straight line at highway speeds and when accelerating in a straight line. Is it correct to assume this is due to highway cross slope and there is actually a difference in slip/speed between the two rear wheels?
5. Why is the wheel slip range limited from 0% to a max of 30%?
6. Occasionally when moving at a slow speed such as idling in 1st gear, the eLSD will show clutch locking to 100%. It appears to be cycling the system to do a "self check" or limit switch check. Please explain why this 100% clutch lock occurs?
7. There is another reason behind question #6. My cars eLSD has occasionally malfunctioned and stopped locking when accelerating in left hand turns rather than completely not locking. This is very problematic because when I attempt to slide the car in a left hand turn once the G forces return to a straight line the differential quickly locks offsetting the balance of the car. On the other hand, if I attempt to slide in a right hand turn worse things happen because once the car straightens and the G forces are equivalent to a left hand turn the differential unlocks causing the car to become excessively unbalanced. Is it possible that trying to spin the tires prior to the "self check" occurring causes the differential to malfunction?
8. Is there another way besides the eLSD screen to monitor how much the differential is locking? The reason I ask this is because my issue is intermittent, making it difficult for the dealer service personnel to resolve the issue. It would be helpful if there was a way to collect data that could pinpoint sources of problems with the eLSD.
In conclusion, a better understanding of the eLSD, related components, and system operating protocols would be helpful for owners and service centers. Some owners have had unexplained handling dynamics resulting in lost control. Is it possible the eLSD was malfunctioning and had they been given an explanation of the eLSD they may have identified their problem.
By the way, my lost communications issue may be due to one particular 40 pin connector that is used for CEBUS communication, but this hasn't been confirmed because the issue is so intermittent I am not trusting it wont return. I should add, my car has been to the dealer a half dozen times to diagnose this problem, but because the lost communication codes are stored in history, and not active when the car is at the dealer it has been impossible for them to pinpoint the problem.
First, basically what is/was occurring with my car was intermittently experiencing lost communication between several modules resulting in "service parking brake light", "service rear axle" warning, and "rear axle system off" warning. Over time what I started to observe using the eLSD screen is prior to the warnings occurring, the eLSD clutch stayed at 0% no matter how I was driving or the amount of wheel slip.
Additional points to clarify:
1. Please clear up once and for all if the eLSD screen is providing useful information. It has been reported that there are GM engineers and/or technical support telling owners and dealer service technicians that the screen is of no use, the screen is garbage, and the screen shouldn't have been included with the C7. I disagree for several reasons. For one thing, when my eLSD stops working as noted above it has occurred before any warnings are displayed. What I started to observe is excessive spinning of the inside wheel when accelerating at the exit of corners. Sometimes the differential would not lock at all and other times it would lock after the car went straight for some distance. Without the eLSD screen I would have no way of evaluating what I feel the car doing. After I started to realize what was occurring I monitored the eLSD screen, and found it was very accurately showing me what I was feeling.
2. Please explain how the eLSD is commanded to adjust including what systems are involved and where all the control logic resides? The reason behind this question is when communication is lost it appears the differential becomes an open differential and significantly affects performance driving. My dealer per instruction from GM thinks turning all systems off will make the differential work like a standard unit (spring applied clutches). It would be helpful if this was cleared up for technical staff trying to troubleshoot eLSD issues. Furthermore, GM's latest direction to my dealer for fixing my problem is a recommendation for me to use PTM modes. While PTM modes do affect amount of wheel spin they will not fix lack of differential clutch lock.
3. On the eLSD screen do we see what is command or is there a sensor telling us what the clutch lock actually is? If it is not the command then how does the system sense clutch lock. Is it based on hydraulic pressure or a position sensor? In other words, is there anyway for the control system to know the differential is not locking when it should be?
4. The lower sweeping bar occasionally shows wheel slip when slip is impossible. Such as slowly starting, coming to a stop and moving at 1st gear idle speed. Under these conditions it will turn red and bounce to 30%. Is it correct to assume this is due to sensors not being accurate at low speeds, and this inaccuracy is ignored by the eLSD control logic?
4. Please provide a better explanation of what wheel slip is. One reason I ask this is the lower bar occasionally shows a small amount of wheel slip when moving in a straight line at highway speeds and when accelerating in a straight line. Is it correct to assume this is due to highway cross slope and there is actually a difference in slip/speed between the two rear wheels?
5. Why is the wheel slip range limited from 0% to a max of 30%?
6. Occasionally when moving at a slow speed such as idling in 1st gear, the eLSD will show clutch locking to 100%. It appears to be cycling the system to do a "self check" or limit switch check. Please explain why this 100% clutch lock occurs?
7. There is another reason behind question #6. My cars eLSD has occasionally malfunctioned and stopped locking when accelerating in left hand turns rather than completely not locking. This is very problematic because when I attempt to slide the car in a left hand turn once the G forces return to a straight line the differential quickly locks offsetting the balance of the car. On the other hand, if I attempt to slide in a right hand turn worse things happen because once the car straightens and the G forces are equivalent to a left hand turn the differential unlocks causing the car to become excessively unbalanced. Is it possible that trying to spin the tires prior to the "self check" occurring causes the differential to malfunction?
8. Is there another way besides the eLSD screen to monitor how much the differential is locking? The reason I ask this is because my issue is intermittent, making it difficult for the dealer service personnel to resolve the issue. It would be helpful if there was a way to collect data that could pinpoint sources of problems with the eLSD.
In conclusion, a better understanding of the eLSD, related components, and system operating protocols would be helpful for owners and service centers. Some owners have had unexplained handling dynamics resulting in lost control. Is it possible the eLSD was malfunctioning and had they been given an explanation of the eLSD they may have identified their problem.
By the way, my lost communications issue may be due to one particular 40 pin connector that is used for CEBUS communication, but this hasn't been confirmed because the issue is so intermittent I am not trusting it wont return. I should add, my car has been to the dealer a half dozen times to diagnose this problem, but because the lost communication codes are stored in history, and not active when the car is at the dealer it has been impossible for them to pinpoint the problem.
Last edited by djnice; 08-08-2017 at 11:26 AM.
08-10-2017, 09:34 AM
#8
Pro
Going straight line at freeway speed doing 70mph, it typically shows a 13% slip!!! What's stranger is when going around a freeway bend at the same constant speed, slip "decreases" to 9%!!! Very confusing information.
Last edited by Kamran; 08-10-2017 at 09:34 AM.
08-10-2017, 11:25 AM
#9
Melting Slicks
That number is not slip. That is the amount of clutch lock. If you go to WOT straight or in a corner the clutch lock will increase. Unless your car is malfunctioning like mine does intermittently. For track driving at corner entry under deceleration the lock will reduce to near 0% to give you an open diff for stability going into the corner.
08-10-2017, 03:19 PM
#10
Pro
^ I understand that. But that's not what the instrument cluster "says". Like you and others (well except for one) on this thread, I'd like to hear it from the horse's mouth!
My apologies for trying to reinforce the need for a clarification on display!
My apologies for trying to reinforce the need for a clarification on display!
Last edited by Kamran; 08-10-2017 at 03:24 PM.
08-10-2017, 06:57 PM
#11
Melting Slicks
Oh I wasn't trying to say you don't need an explanation from GM. I would like to hear their explanation and 8 or so other things related to the eLSD.
My understanding based on the photo below is the display is showing eLSD 11%. That is what it says. I don't know why people say that is not what it says? It doesn't say wheel slip is 11%. The screen shows two things. At the top is eLSD % and bottom is wheel slip. Wheel slip in the screen below is showing there is none. When it does show wheel slip it is a green bar rather than a number.
My understanding based on the photo below is the display is showing eLSD 11%. That is what it says. I don't know why people say that is not what it says? It doesn't say wheel slip is 11%. The screen shows two things. At the top is eLSD % and bottom is wheel slip. Wheel slip in the screen below is showing there is none. When it does show wheel slip it is a green bar rather than a number.