Article: "Average daily ignition cycles in SDM equipped, GM vehicles," Little, D.

FX3 from Visual Statement is a state of the art reconstruction solution that allows you to perform accurate reconstructions ranging from simple sketches to detailed 3D Environments. FX3 was designed specifically for reconstructionists who benefit from a

software package that contains all the tools required for crash and crime reconstructions. Wether you do a linear momentum analysis, SMAC Simulation or create captivating 3D Animations; You never leave one application - FX3

;GDB I=: H8:C: Dc i]Z hXZcZ " LZ XVc ]Zae Ndj Use our B";M Pocket PC data collector with any total station – see your points recorded in 3D. Use 6XXZaZgZM on the same Pocket PC to measure deceleration ( drag factor ).

Use our EdX`Zi 8gVh]BVi] – to do preliminary calculations of impact speeds etc.

Use =Vl`:nZ our photogrammetry program to take accurate measurements with your camera.

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ID NDJG 9:H@IDE Dc ndjg E8 Ä LZ XVc ]Zae Ndj Use ;M( Reconstruction software to download your measurements points and auto plot your scene diagram.

Use ;M( to generate a powerful 3D scene complete with textured surfaces and any models you need.

Collision: The International Compendium for Crash Research

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Use our 8gVh] ;M momentum tool right on the diagram to generate impact speeds.

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ID I=: 8DJGI GDDB >c i]Z 8djgi Gddb " LZ XVc ]Zae Ndj Use our ;M( GZVaBdi^dc (9 to instantly animate your reconstruction results on your 3D scene.

Use our HB68 ;M to simulate or predict collision results.

Present powerful time distance reports and persuasive graphical output.

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                                                                                                          

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

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 

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

       

  

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&OR SERIOUS 2ECONSTRUCTIONISTS SEE HOW &8 CAN BE RIGHT FOR YOU

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Volume 2, Issue 2 - FALL 2007

Use our 8gVh]BVi] application with 720+ reconstruction formulae to get all the answers.

ollision C The International Compendium for Crash Research

Volume 2 Issue 2

Night-Time Pedestrian

Collision Reconstruction Factors

Average Ignition Cycles For GM Vehicles

Comparison Test:

Vehicle Speed vs Speed Recorded by an SDM

Validating Speed Analysis Calculations with Crash Test Data

e DVD c n e r e f n o c h s a r C www.CollisionPublishing.com PLUS: 2007 ARC-CSI

If you found this article useful, look into a subscription to Collision Magazine at www.CollisionMagazine.com

Find out more about the next EDR User’s Summit at EDRSummit.com

Contents Fall 07

4 8 10 12 15

18

of interest

Letter from the Editor Industy Partners Calendar of Events Organization News Errata Sheets

features

On the cover: Taken at the 2007 Annual Conference of the South Carolina Association of Accident Reconstruction Specialists, the photo shows the developing crash between a Chevy Suburban and Dodge Intrepid.

This test was one of several the Collision Safety Institute coordinated for SCARS Conference held in Charleston, SC. Photo by Jon Northrup.

On The Cover

General Motors Data Recording: A Visual Approach to the Logic Functions

32

Detailed Comparison of Vehicle Speed and the Speed Recorded by an SDM

42

Average Daily Ignition Cycles in SDM Equipped, GM Vehicles

46

Application of Drag Coefficients to ABS related Sideslip

52

Use of the Combined Velocity Equation In Cases Involving Post-Collision Movement

98

Vehicle Crush Measuring: Helpful For Extracting Key Details Of Crash Scenes

104

Implications of Symmetric Sine-Based Collision Pulse Models on Force-Deflection Characteristics: (Part 1)

114

Using GPS based Data Acquisition in Forensic Accident Reconstruction

120

Quantifying the Aerodynamic Forces Acting on a Vehicle and Projectile

124

Reconstruction and Analysis of Steering-Induced, On-Road, Untripped SUV Rollover Tests (Part 2)

66

32 120

70

2007 ARC-CSI conference Effects of Sample Rates on Accelerometer Based Skid Testing and Unit Comparison

70

Validating Speed Analysis Calculations with Crash Test Data

74

Snowmobile Data

82

Night-Time Pedestrian Collision Reconstruction Factors

92

European Accident Reconstruction by the Visual Comparison with Crash Tests

6

2007 ARC-CSI Crash Test Summary

case study

58

Case Study Problem

150

Case Study Solution

82 Collision

3

bstract Since 2000, the Vetronix CDR system has allowed public access to collision data stored in motor vehicle airbag control modules. Currently General Motors (GM) and Ford vehicles are accessible. Neither manufacturer provides a time clock, but GM Sensing and Diagnostic Modules (SDMs) do report the number of times the ignition has been turned on (the ignition cycles), which can be used to approximate the time between the event that was recorded, and the date of the investigation. The average daily ignition cycles can also be used to determine if there is likely to be any data in a non-deployment event file (or if it may have been erased), given the time delay between the event and the start of an investigation.

A

Thus, a retrospective study was conducted to determine the average daily ignition cycles for GM vehicles over the life of the vehicle.

The study of 135 vehicles revealed that the average ignition cycles for vehicles that were not used commercially were between 6 and 7 per day. Commercial vehicles, such as taxis, had considerably more ignition cycles, in the range of 20 to 30 per day. iterature Review

L

The author is aware of only two previous studies of average ignition cycles. These were both conducted through the CDRtool group – a web based group of police officers, engineers and investigators who share experiences with, and knowledge about event data recorders. The CDRtool studies involved a relatively small sample size and occurred over one month.

The current study involved a larger sample size and extended 42 Collision

across the life of the vehicle, from assembly to the collision under investigation. ethod The database that was utilized encompassed GM airbag control modules previously downloaded by engineers at Baker Materials Engineering Ltd. in the course of other collision investigations. This encompassed collisions throughout the province of British Columbia, Canada from 2000 to 2006.

M

In order to calculate the average ignition cycles over the life of the vehicle, start and end times were required. The end time was readily established from the collision date, but the start time was not so apparent. The vehicle was not being driven by the consumer from the moment the vehicle was first made. During the early stages of its life, the vehicle would have spent some time sitting idle on a dealer’s lot.

Thus, any calculation of daily ignition cycles had to account for this early time when the vehicle was not being driven by the consumer.

Two start dates were located on the vehicle and two start dates were obtained from the General Motors Vehicle Inquiry System (VIS), for a total of four start dates for each vehicle.

The following dates were obtained from examination of the vehicles:  

Date of vehicle manufacture (located on the driver’s door or B-pillar) Date of manufacture of the module (located on the top of the module)

The manufacture date of the SDM was obtained from the “AS” code www.collisionpublishing.com

on the top of the module. A typical code is shown below:

 

Warranty start date (when the vehicle was purchased by the consumer) SDM scan date (when the SDM was installed in the vehicle, which is also when the vehicle was built)1

The number of ignition cycles at the time of the collision and the investigation were obtained for the study from the SDM download, using the Vetronix CDR kit.

In this example, the build year is shown by the 9th digit – a 9, signifying 1999, and the 10th to 12th digits indicate it was built on the 334th day of that year. Thus, this SDM was built on 29 November 1999.

Three different exceptions to this rule were noted: 1 - 2006 Chevrolet Trailblazer: There was no shift code recorded after the plant location (K). The year is the 8th digit (6, for 2006) and the day is shown in the 9th through 11th digits (048, for 16 February).

2 - 2006 Malibu Maxx (all SDM-Epsilon modules): This module was made in Mexico and had completely different coding. The coding sequence is currently unknown to the author.

3 – GM Replacement SDM. These modules can be identified because the Part number and the Service number are the same.

This indicates that the SDM was replaced at a GM dealership as a result of a prior airbag deployment. The date on this module will not correspond with the date of manufacture of the vehicle. The ignition cycles will start from zero after the repair.

The GM VIS was then accessed to determine the following:

It was expected that the first three start dates noted above would underestimate the actual daily ignition cycles because those dates included time before the vehicle was purchased by the consumer.

The last start date was expected to overestimate the cycle count because it did not consider any time when the vehicle was driven between the date of manufacture and the date of sale to the consumer. esults A. Earlier CDRtool Surveys: Two online surveys were conducted: one in April 2003 and one in March 2005.

Participants were asked to track their ignition cycles daily for one month. There were 28 participants in the first study and 40 participants in the second study. Some respondents participated in both surveys, so the two surveys are not entirely independent. The results have not been previously published. They were as follows:

R

Daily Average Standard Deviation Median Maximum Minimum N

First Study

Second Study

4.9 1.9 4.7 10.1 1.7 28

4.0 1.3 3.9 7.3 0.9 40

There were certain limitations noted with these studies, including the following:  The results were dependant on the participants remembering to record each ignition cycle. As a participant in the first study, the author noted it was possible to forget to record each ignition cycle.  The participants were a select group of people, and were not necessarily representative of the general motoring public.  Each study covered only one month of driving habits.

B. Current Retrospective Study: The database was obtained from all SDMs downloaded by Baker Materials Engineering between 2000 and 2006. It included vehicles built from 1995 to 2006 that were involved in collisions in the province of British Columbia, Canada. In all, 135 SDMequipped GM vehicles were examined. Complete data on each vehicle were not always obtained, for various reasons.

The average daily ignition cycles were calculated based on the four different start times:

1

If the SDM was not accessed on the vehicle, the SDM date of manufacture was obtained from the GM VIS.

Collision

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   

When the SDM was manufactured When the SDM was scanned during installation into the vehicle (a.k.a. vehicle build date) = Day of vehicle manufacture When the vehicle was manufactured, per the date on the door = Month of vehicle manufacture When the vehicle was purchased by the consumer

consumer. Note that there were a few vehicles that took much longer to sell than the median.

The graph of the daily ignition cycles is shown below, versus the age of the vehicle, for all of the data collected.

Graph 1 – All Vehicles This database had a range for the average daily ignition cycles of 6.6 to 9.0 and a median value of 6.0 to 7.8, depending on which start dates were used. The values calculated based on the warranty start dates were at the high end of the ranges, and these values overestimated the actual daily averages and medians. The median values were calculated because it was noted that a few values were significantly different than the rest, which would skew the averages.

Several high values were also noted for a few older vehicles. A review of these outliers revealed that they were from vehicles used for commercial purposes. Because of this, a second graph was prepared with the commercial vehicles removed, as well as with all data points less than one year old removed.

Graph 2 – Non-commercial vehicles older than one year

Details are provided in Appendix A and a summary is shown in the following table:

6.7

4.6

6.3

4.0

3.9

6.0 30.2 0.5 49

7.8 49.0 1.4 120

6.0 29.5 0.4 107

6.2 30.3 0.5 113

Veh Build

6.6

SDM mfg

9.0

Warranty Start

Veh Build

SDM mfg

7.0

Daily Average Standard Deviation Median Maximum Minimum N

Door Date

Daily Average Standard Deviation Median Maximum Minimum N

Warranty Start

Door Date

This database had both a median and an average of approximately 6 to 7. Details are provided in the following table. Note that the standard deviation is approximately half the value reported for all the vehicles in the previous table.

6.1 2.2 5.9 13.9 0.5 39

7.2 2.3 6.9 15.7 1.4 84

6.5 2.4 6.2 13.6 0.5 76

6.4 2.3 6.1 13.7 0.5 82

The commercial vehicle database was small, however a trend was still evident in some types of these vehicles. The data from these vehicles are shown in Appendix B.

A large fluctuation of average daily ignition cycles was noted in the first year of a vehicle’s life, depending on how the value was calculated. Higher values were noted when the warranty start date was used in the calculation. This was more apparent if a vehicle did not sell for quite a while after being built, but then had a collision shortly after being purchased.

Taxis had the highest ignition cycles with an average and a median of 24 to 26 and a range of approximately 20 to 30.

Police vehicles had a range of 8 to 18 with an average of 10 to 13 Rental vehicles were found to have average daily ignition cycles typical of normally used vehicles, so were not included in the commercial vehicle category.

The following histogram shows the time frequency distribution between when a vehicle was built and when it was sold to the 44 Collision

www.collisionpublishing.com

iscussion The ignition cycles reported above are daily averages over the life of a vehicle and, as such, do not reflect the daily fluctuation in ignition cycles. The CDRtool surveys recorded individual days, which fluctuated in some cases by up to three times the daily average, while still having a monthly average within the reported values.

D

It was also noted from the data gathered, that GM vehicles were sold to the consumer, on average, just over three months after being built. The median lag time between when the vehicle was built and when it was purchased by the consumer, was two months.

However, in one case, the vehicle was 18 months old before it was purchased. Because of this lag time, the average daily ignition cycles calculated based on the warranty start date were higher than based on the vehicle’s build date. For vehicles that were quite new (less than approximately one year old) this had the potential to substantially skew the calculated average daily ignition cycles.

The date of manufacture posted on the door was noted to always be equal to the vehicle build date as reported by the GM VIS. Thus, the door date can be used reliably as the vehicle’s build date (provided the door was not replaced during a prior repair).

The date of manufacture of the SDM was within half a month of the vehicle build date approximately 80 percent of the time, so the SDM manufacture date can be used as a good approximation of the vehicle’s build date. However, it could be out by as much as 12 weeks, so caution should be exercised when using this date.

The maximum number of ignition cycles that can be stored in the SDM has been reported2 as 65,535 cycles or 16,777,215 cycles, depending on the module type. Based on an average daily ignition cycle of 6 to 7, the module with the smaller peak value would still require 25 to 30 years to reach its maximum value. Since the oldest vehicles that can be downloaded are 13 years (1994 model year), it is unlikely that any of these vehicles will be reaching their maximum retention value for another decade or more. However, commercial vehicles such as taxis would require 6 to 9 years to reach their maximum. Hence some of them may have already reached their maximum The author has yet to find any modules that have reached their maximum value. It is understood3 that the ignition cycle count stops at the maximum value as opposed to resetting to zero and starting to count again. Thus, if the value of 65,535 appears, it should be recognized that the actual ignition cycles were likely higher. onclusion Average daily ignition cycles in GM vehicles used for noncommercial purposes were 6 to 7.

C A possible.

2 3

cknowledgments The author would like to thank Kevin Conrad, of Dueck GM, Vancouver, for providing access to the GM VIS database, without which this paper would not have been

Per W. R. Rusty Haight, Collision Safety Institute ibid

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