E38 Computer ~ EFI Live Speedometer Calibration?

[1project2many]

BTW, I based all of my answers under the assumption that this screenshot was taken while trying to calculate the speedometer for the drivetrain transplant that Dave is assisting with currently.

You're saying it's something like a snapshot taken between no changes and job complete? Interesting. Dave??

[pmkls1]

You're saying it's something like a snapshot taken between no changes and job complete? Interesting. Dave??

No, I meant that I was assuming that this question was regarding the drivetrain swap he was working on and that the technical info I gave would pertain to the particular vehicle that the drivetrain was out of (2012 Chevy 1500 4x4). Since the E38 ecm is used in several applications some of my statements might not be correct for a different type of vehicle. That was why I stated that my reply was based on an assumption so as to avoid confusion. I did, however, originally think that the wheel pulses per rev value of 32 in the screenshot might have been where he had begun to make changes to correct the speedo because I had confused myself while making my first reply as stated above.

[dave w]

The screen shot is from the stock .ctz file (2012 project I'm involved with). My question for parameters (H0152) & (H0153) was to understand if (H0152) & (H0153) needed to be changed for a larger tire. I was hoping to learn and understand the conversions for (H0152) & (H0153). The other parameters in the screen shot I have a good understanding on how those parameters are calculated. I was thinking, maybe someone would share their experience calibrating a similar vehicle (stock) with larger tires. Seems logical to me, someone owning a 2012 vehicle would change tire sizes and require speedometer calibration.

I don't have the 2012 vehicle, which limits the available information I would like. It seems logical to me that (H0152) & (H0153) are from the wheel speed sensors. It seems logical to me the ECM and BCM would have some communication back and forth about the wheel speed sensors. The E38 is about 1.7 Meg in size, which might have programming not fully understood, except for a few GM engineers. I might be years from now, if ever, that all the programming in the E38 is fully understood. I would have liked better comments from EFI Live about (H0152) & (H0153)! As an EFI Live customer, I feel EFI Live has ample room for improvement with the E38!

dave w

[pmkls1]

I can explain to you with confidence how the vehicle is configured which will answer most of your questions as I have intimate knowledge of those vehicles. I have no knowledge of EFI Live, but can make a logical assumption based on my knowledge of the vehicle and interpretation of the screenshot. I got a little too carried away in my original reply and overcomplicated the answer as well as making it wrong. The simple answer is yes H0152 and H0153 should be from the wheel speed sensors based on the screenshot you provided. But, no those values should not be effected by tire size as 1 revolution is still 1 revolution regardless of the tire circumference.

I'll delve further into the technical workings of these systems as I know that you like to know how things operate. Those two values are simple and based on the tooth count of the reluctor and I don't see any purpose for needing to change them unless you have a situation where the wheel speed sensors and reluctors are not OE. An example would be if you were utilizing the drivetrain and EBCM from the donor and utilizing the new vehicle's existing wheel speed sensors. I don't know exactly how the ecm behaves in a transplant situation like yours where you are not using an EBCM. But the way modules on the high speed lan network are designed to communicate is that if a module is not detected then the remaining modules would operate properly unless they were not receiving critical data which wheel speed sensors would not be considered critical data for the ecm. On the donor vehicle the front wheel speed sensors and reluctors are contained within the front hub assembly. The rear wheel speed sensors mount on the axle tubes and the reluctor is on the axle shaft a couple inches behind the wheel bearing. As I stated in my last reply the wheel speed sensors are wired to the EBCM for ABS and Stability Control functions (if equipped with stability control). The VSS, or what is labeled in the screenshot as the TOS, should be wired to the ECM. The EBCM and ECM communicate directly on the high speed lan network and work closely together to control traction (and stability if equipped with stability control) and possibly other functions. The speedometer calibration should not be effected by these two values.

I hope that I made some sense of this for you,
Phil

[1project2many]

The simple answer is yes H0152 and H0153 should be from the wheel speed sensors based on the screenshot you provided. But, no those values should not be effected by tire size as 1 revolution is still 1 revolution regardless of the tire circumference.

Exactly. Values that represent pulses per revolution are tied to the configuration of the sensors and do not change with tire size or gear ratio. Values that contain or reflect distance will change with tire size or gear ratio.