Measurement & Control of Fuel Injector Deposits in Direct Injection Gasoline Vehicles

Measurement and Control of Fuel Injector Deposits in Direct Injection Gasoline Vehicles S. Scott Smith Afton Chemical Corporation William Imoehl Continental Automotive Systems

Published 10/14/2013. Copyright © SAE International. This product contains SAE International copyrighted intellectual property, which has been and is licensed with permission for use by Afton Chemical Limited, in this publication only. No further sharing, duplicating, or transmitting is permitted. doi: 10.4271/2013-01-2616

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ABSTRACT Vehicle manufacturers are significantly increasing the production of Gasoline Direct Injection (GDI) engines to help meet the requirements of governmental regulations and the demands of consumers.

While GDI powertrains offer multiple advantages over conventional gasoline engines they can be susceptible to fuel related deposit formation, specifically within the fuel injector nozzle. Fuel injector deposits have been linked to a number of negative effects that can impact the normal operation of the engine.

A GDI deposit test has been developed to evaluate Deposit Control Additives (DCA) and their effect on injector deposits.

Multiple metrics for evaluating fuel injector deposits were investigated to determine a suitable method for quantifying deposit formation. Interrogation of the vehicle On-Board Diagnostic (OBD) system was identified as the optimal method for quantifying deposit formation throughout the duration of the test.

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Accelerated GDI deposit testing was carried out on a wide variety of late model GDI vehicles on a chassis dynamometer for the purpose of evaluating and discriminating GDI DCA products and candidates. In addition, ongoing testing with a vehicle fleet is being conducted to determine if realworld injector deposits will form while using commercial fuels with DCAs. Testing has shown that DCAs can be developed to specifically prevent and control deposit formation within GDI injectors. Conversely, DCAs that are formulated to reduce Port Fuel Injector (PFI) deposits may not effectively control GDI injector deposits.

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INTRODUCTION In order to comply with impending mandates of vehicle fuel economy and emissions legislation, and to satisfy the demands of the consumer, Original Equipment Manufacturers (OEM) are looking towards GDI powertrains as a path to help meet these requirements.

GDI engines allow OEMs to downsize the vehicle powertrain while still maintaining power and performance. In addition, GDI powertrains can offer up to a 15% fuel economy improvement over conventional PFI engines [1] without sacrificing power or acceleration performance.

100

Gasoline PFI Hybrid

Gasoline Port Fuel Injection PFI

60

40

Gasoline Direct Injection DI

Gasoline DI Hybrid Diesel CR Hybrid

20 Diesel Common Rail

30

29

28

20

20

27

Gasoline PFI

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25

20

24

Gasoline DI

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23

Gasoline DI Hybrid

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22

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21

20

20

20

19

Diesel Hybrid

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16

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15

Diesel Common Rail

20

14

20

20

12

13

Monovalent Fuel

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11

20

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20

20

20

E-Vehicles, Fuel Cell

26

E-Vehicles, Fuel Cell

0

20

Market Share (%)

80

Gasoline PFI Hybrid

Source: Estimation based on EUCAR 2002, SV, VDA, OEM feedback, IHS 1/2012, own estimations. ADAC Motorwell 10/2011

Figure 1. Worldwide powertrain mix for 2010-2030.

Courtesy of Continental Automotive Systems.

The market share for vehicles with GDI powertrains is rapidly increasing and is projected to reach 20% of new vehicles sold globally by 2020 [2]. North American production of light-duty vehicles with GDI engines has increased from essentially zero in 2007 to over 20% in 2012 [3]. The forecasted powertrain mix between 2010 and 2030 for new vehicles sold globally, shown in Figure 1, illustrates that the GDI powertrain is expected to outpace all other types of engine technologies in the near future [4].

problematic fuel deposit formation. Despite the seemingly new introduction of GDI technology to the public there is well over a decade of research investigating fuel deposit formation in GDI vehicles [5,6,7].

The increasing production of GDI vehicles and the lack of a recognized standard test highlights that a universally accepted method to demonstrate that fuels are fit for use in GDI vehicles is needed.

An appropriate test method should discriminate between fuels on the basis of deposit formation tendencies as well as differentiate the effectiveness of DCAs. Industry gasoline fuel injector test procedures such as ASTM D5598 [8], ASTM D6421 [9] and the GM Fuel Injector Fouling Test [10] are solely designed for PFI engines. These procedures have been extrapolated by some researchers in an attempt to quantify injector deposit formation in GDI vehicles [11], while others have developed novel tests specifically for GDI deposit formation [12,13]. This prior work has underscored the need for a GDI deposit test.

The purpose of this paper is to suggest a method to measure, monitor and control fuel injector deposit formation in GDI engines.

Given that GDI powertrains now represent nearly one quarter of all new vehicles sold in North America, reports have surfaced alleging that GDI engines can experience

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GDI DEPOSIT MEASUREMENT METHODS Several methods have been developed to determine the presence of GDI injector deposits. The three most common techniques are: 1. Removing and visually rating the injector tip 2. Removing and measuring fuel flow through the injector 3. Interrogating the vehicle OBD system The advantages and disadvantages of each of these methods are discussed below.

Visual Rating of Injector Deposits A common method for determining the presence of injector deposits is to visually rate the face deposit of the fuel injector tip.

Typically the injectors are removed from the vehicle, photographed and visually rated. This is similar to how Intake Valve Deposits (IVD) are visually evaluated [14].

Figure 2 is an example of a fuel injector with a significant amount of deposit formation on the injector tip.

Other researchers have shown that the amount of deposit on the injector tip may not correlate with the performance of the injector, largely due to subjective nature of the analysis. Therefore, this type of rating alone does not reliably predict or quantify the loss of injector performance [15].

Figure 2. A GDI fuel injector with heavy deposit formation.

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Measuring fuel flow loss through an injector is another method to determine if injector performance has been compromised by deposits. Typically the injector is removed and flowed on an external test rig for a given amount of time using a reference fluid, such as Stoddard solvent. Injector flow loss is based on volumetric or gravimetric difference between the Start of Test (SOT) measurement and the End of Test (EOT) measurements.

This technique is similar to methods used for determining fouling in PFI injectors, but unlike PFI fueling systems that operate at approximately 50 PSI, GDI fueling systems operate at pressures approaching 3,000 PSI. Furthermore, PFI injectors reside in the intake ports, while GDI fuel injector tips are located in the vehicle combustion chamber. Removal of the GDI injector to conduct the flow loss measurement can disturb the deposit, leading to a loss in testing discrimination.

Interrogation of the Vehicle OBD System The third deposit measurement technique is interrogation of the vehicle OBD system. The purpose of the OBD system is to monitor, detect, store and diagnostically interpret errors and faults within various vehicle systems [16].

The vehicle diagnostic system can be accessed through the OBD port, usually located in the cabin of the vehicle, using a vehicle scan-tool or computer. This method monitors specific adaptive fueling parameters that directly correspond to the amount of fuel flow through an injector for a given period of time.

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Figure 3 shows injector deposit formation quantified by injector pulse-width and the OBD fueling parameter. As the fuel injector orifices are restricted by deposits, the injector pulsewidth, the amount of time that the injector remains open for a given cycle, must increase to deliver the proper volume of fuel necessary to maintain a stoichiometric Air Fuel Ratio (AFR) [15].

Additionally, the vehicle OBD adaptive fueling parameter and pulse-width of the fuel injector are shown to trend in the same direction as injector deposit formation occurs. The adaptive fueling parameters are discussed later in detail.

Injector Pulse-Width

OBD Fueling Parameter

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Change in Injector Deposit Measurement, %

Injector Flow Loss

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500

1000

1500

2000

2500

3000

3500

Kilometers

Figure 3. Monitoring injector pulse-width and interrogating the on-board diagnostic system to quantify injector deposit formation during a DU test.

Comparison of Measurement Techniques A side-by-side comparison of three different GDI injector deposit measuring techniques was conducted to determine if one method is superior for injector deposit testing discrimination. Each Dirty-Up (DU) test was run with the same set of injectors in the same 2008 2.0L GDI vehicle.

Results for each measurement method were taken at SOT and EOT and the difference in these results is presented in Figure 4. Tests A and B produced heavy deposits on fuel injectors during the DU

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test, while tests C and D generated a more modest amount of injector deposit formation. Injector pulsewidth and the adaptive fueling parameter from the vehicle OBD system consistently trend directionally over all tests that were conducted. Injector flow loss, performed in accordance with ASTM D6421, confirms a trend with the other measurement methods in tests A and B showing a flow loss as injector deposit formation occurs.

Conversely, tests C and D show an increase in injector flow at EOT. The conflicting results from the injector flow loss measurement are attributed to a lack of resolution when the PFI injector testing method is used to quantify deposit formation with a GDI injector.

Because of the ease of monitoring the adaptive fueling parameter from the OBD system, and because this parameter produces the largest signal, which enhances testing resolution, the adaptive fueling parameter was selected to monitor the formation of injector deposits in GDI vehicles.

20 Injector Flow Loss

Injector Pulse-Width

OBD Fueling Parameter

Change in Injector Deposit Measurement, %

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In closed loop operation, the primary purpose of the fuel delivery control strategy is to maintain an ideal AFR for optimal catalytic conversion of engine-out exhaust emissions [17].

The Powertrain Control Module (PCM) accomplishes this by precise monitoring and control of parameters and inputs such as Oxygen sensors, the Mass Air Flow (MAF) sensor, Intake Air Temperature (IAT), battery voltage, Long-Term Fuel Trim (LTFT) and Short-Term Fuel Trim (STFT). The PCM ensures that the proper amount of fuel, calculated from calibrated tables, models and inputs, is delivered to obtain a stoichiometric AFR. Equation 1 is an example of how the quantity of fuel delivered can be calculated [18].

Fuel Mass =

Air Mass · STFT · LTFT Equivalence Ratio · 14.64 (1)

Where,

Equivalence Air Fuel Ratio Ratio = Air Fuel Ratio Stoichiometric (2)

10

5

0

-5 A

B

C

D

Tests

Figure 4. Comparison of different techniques to quantify fuel injector deposit formation.

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ADAPTIVE FUELING STRATEGY

The fuel delivery control strategy is designed to adapt to multiple parameter variations such as the ethanol content of the fuel, rapid changes in engine speed and load, changes in intake air temperature, changes in barometric pressure, component wear, component failure(s) or fuel injector deposit formation and still maintain an AFR close to stoichiometric.

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STFT is the dynamic adaptive fueling parameter responding to the feedback of the oxygen sensor on a cycle-to-cycle basis [16]. STFT quickly responds to the transient fueling demands of the engine and the variations in the environment by increasing or decreasing injector pulsewidth to maintain the proper AFR. STFT is a proportional multiplier that adjusts the base injector pulse-width calibration to ensure optimum catalytic conversion of engine-out exhaust emissions. Once the STFT reaches a prescribed limit and can no longer influence injector pulsewidth to achieve a stoichiometric AFR, a longterm fueling bias is introduced to the fuel delivery control strategy.

Increases in LTFT indicate that the fuel delivery control strategy is compensating for a fuel lean shift from the original base calibration, thereby increasing the injector pulsewidth.

Figure 5 shows an increase in LTFT, which is due to fuel injector deposit formation. Because the fouled fuel injector is not delivering the proper amount of fuel prescribed by the base calibration the fuel delivery control strategy increases LTFT to correct for the loss of injector performance.

Injector Plugging by LTFT, %

STFT and LTFT are two adaptive fueling parameters used for maintaining a stoichiometric AFR.

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5

0 0

1000

2000

3000

Kilometers

Figure 5. Fuel injector plugging shown by LTFT.

LTFT is an adaptive fueling parameter that biases the fuel delivery control strategy, either fuel lean or fuel rich, which allows STFT to return to its operational bounds to maintain a stoichiometric AFR. LTFT is slowly adjusted over time for longterm adaptive fueling corrections and is stored in the memory of the PCM.

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OBD Limits of LTFT Injector Plugging by LTFT, %

The primary purpose of the fuel delivery control strategy is to maintain an ideal AFR. This is accomplished by monitoring several parameters, including the adaptive fueling parameters. The adaptive fueling parameters compensate for changes in the vehicle, environment, and the heating value of the fuel to maintain a stoichiometric AFR, but only up to a certain limit.

OBD limit for LTFT LTFT

Check Engine Light

20 See Figure 7

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10

5

0 0

4000

8000

12000

16000

Kilometers

Figure 6. DU test without a DCA resulting in a check engine light at 14,000 kilometers due to a high LTFT.

Once STFT and LTFT have reached the designed limits of each parameter, the system can no longer function properly and the OBD system detects a fault in the system. The OBD system illuminates a Malfunction Indicator Lamp (MIL), commonly called the check engine light, on the dashboard of the vehicle. Figure 6 shows a 16,000 kilometer DU test in a 2012 2.4L GDI vehicle that produced a large amount of fuel injector deposits.

At approximately 14,000 kilometers into the DU test the MIL illuminated due to a fuel lean condition that was outside the normal operational envelope of this vehicle model, which occurred at LTFT ≥25%.

A picture of the fuel injector at EOT can be seen in Figure 7. Operating a vehicle outside stoichiometric AFR can lead to an increase in fuel consumption [19,20], engine power loss [15,19,21], an increase in engine-out emissions [15,16], damage to the threeway catalytic converter, and possible damage or accelerated wear to vehicle hardware components.

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Figure 7. GDI injector tip with a LTFT of 25%.

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TEST DESCRIPTION

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Test Fuels and Lubricants Two different test fuels were used during the vehicle testing to evaluate the effectiveness of DCAs for both preventing and cleaning-up fuel injector deposits. One test fuel was formulated to mimic a U.S. EPA 65th percentile gasoline. Properties for this test fuel were are described by DuMont et al. [22]. The second test fuel was a commercially available, nonoxygenated, Regular Unleaded (RUL) gasoline fuel without DCAs. Proprietary compounds were added to the fuel to accelerate injector deposit formation to shorten the duration of the GDI injector deposit test.

All vehicles were tested with fresh commercially available viscosity grade SAE 5W-30 engine oil and new oil filters.

Test Cycle The GDI deposit test cycle used in this work has been shown previously to accelerate injector deposit formation in a wide variety of vehicles [22]. The test cycle, shown in Figure 8, consists of mild speed and load transitions between stages and has an average speed of 70 km/h.

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80 70

Speed, Km/h

All vehicle testing described in this section was conducted on a chassis dynamometer and LTFT data was continuously logged through the entire test to monitor fuel injector deposit formation.

A new set of fuel injectors was installed at the beginning of every test to ensure that no residual injector deposits carried over from the previous test.

60 50 40 30 20 10 0 0

20

40

60

80

100

Time, Minutes

Figure 8. GDI deposit test cycle.

Vehicle Test Fleet Several GDI vehicles were examined in order to gain a better understanding of how DCAs would respond across a variety of GDI vehicles currently available in the market. Vehicles from model years 2008 to 2013 of various makes and models were tested. Both turbo-charged and naturallyaspirated GDI vehicles were included in the testing fleet.

DISCUSSION OF RESULTS A series of tests were run to evaluate the impact that various DCAs have on GDI fuel injector deposits. All tests were run with a consistent base fuel during the Dirty-up (DU), Clean-up (CU) and/or Keep Clean (KC) phases of the respective test. Several DCAs were tested to evaluate the fuel additive’s ability to reduce injector deposits in GDI vehicles.

Visual Inspection of Injector Flow Holes GDI deposit tests were conducted for the purpose of visually inspecting the deposits inside the injector flow orifice at EOT. The tests were conducted with a 2008 2.0L GDI vehicle and a consistent base fuel was used throughout the tests. The duration of each test was 3,200 kilometers. Tests were conducted both with and without

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a DCA present in the base fuel. At EOT, fuel injectors were carefully removed and sectioned to expose the backside of the injector orifice plate and then photographed by a Scanning Electron Microscope (SEM). Figure 9 shows the backside of an injector nozzle hole after a GDI injector DU test, without a DCA, that resulted in a 28.1% shift in LTFT. Figure 10 shows a fuel injector flow orifice from a KC test with a LTFT of 3.9% shift at EOT. Visually comparing the fuel injector holes highlights the fact that DCAs can play an important role in minimizing GDI injector deposit formation.

Keep-Clean Testing A KC demonstration of a DCA at a concentration typically found in commercial gasoline is shown in Figure 11. The test was conducted with a 2008 2.0L GDI vehicle and a consistent base fuel was used throughout the test. The duration of the KC phase was 3,200 kilometers after which the DCA was removed during the DU phase for an additional 3,200 kilometers of testing. In the KC phase it can be seen that the DCA prevented deposits from being formed in the fuel injector. Once the DCA was removed, the LTFT increases from −5% to 7% to compensate for the formation of the injector deposits.

Injector Plugging by LTFT, %

8 6 4 2

Keep Clean Phase (DCA Present)

0

Dirty-Up Phase (DCA Removed)

-2 -4 -6 0

1000

2000

3000

4000

5000

6000

6500

Kilometers

Figure 9. Fuel injector nozzle orifice from a DU test without a DCA with a 28.1% shift in LTFT.

Figure 11. KC and DU test with a DCA at a commercial gasoline concentration.

Clean-Up Testing

Figure 10. Fuel injector nozzle orifice from a KC test using a DCA with a 3.9% shift in LTFT.

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GDI deposit tests were conducted to demonstrate the removal of deposit that had been formed in the fuel injector.

Several CU tests were run with a variety of DCAs ranging from a highly concentrated commercial product, a commercial product at a concentration typically found in commercial gasoline, and a nextgeneration DCA. The same base fuel was used in the DU and CU phase of the respective test. The DU and CU phases were conducted without DCA and with DCA, respectively.

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Highly Concentrated DCA

Next-Generation DCA

Figure 12 shows a CU test using a commercially available DCA in a 2012 2.4L naturally-aspirated GDI vehicle. The DU test was run for approximately 4,300 kilometers after which a DCA was introduced during the CU phase. The highly concentrated DCA demonstrated a rapid CU of 97% in approximately 2,200 kilometers.

Figure 14 shows the performance of a next-generation GDI DCA chemistry in a 2008 2.0L turbo-charged GDI vehicle. The DU phase produced a LTFT of 6.7% in approximately 3,200 kilometers and then the next generation DCA was introduced during the CU phase which resulted in a 96% CU with a one fuel tank fill-up, less than 640 kilometers.

Dirty-Up Phase (No DCA)

Clean-Up Phase (DCA Present)

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0 0

1000

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7000

Injector Plugging by LTFT, %

Injector Plugging by LTFT, %

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Dirty-Up Phase (No DCA)

Clean-Up Phase (DCA Present)

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-1

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-5

Kilometers

0

1000

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7000

Kilometers

Figure 12. DU and CU test with a high concentration of DCA with a 97% CU in 2,200 kilometers.

Figure 14. DU and CU test with a next-generation DCA with a 96% CU in less than 640 kilometers.

Commercial Gasoline DCA

VEHICLE FLEET STUDY

Figure 13 shows a CU test run in a 2008 2.0L turbo-charged GDI vehicle with a DCA in the CU phase at a concentration typically found in commercial fuels. The DU phase showed an increase in LTFT of 12% in approximately 3,700 kilometers.

Subsequently DCA was introduced, which resulted in a CU of 63% in 3,000 kilometers.

A fleet of twelve 2012 2.0L turbo-charged GDI vehicles are currently being monitored for shifts in LTFT. The purpose of this fleet program is to better understand fuel injector deposit formation and to evaluate the ability of DCAs to prevent and CU real-world injector deposits. The vehicles are fueled at random gasoline stations with commercial gasoline containing at least the Lowest Additive Concentration (LAC) mandated in North America and with a 10% minimum level of oxygenates (E10). The testing location, situated in the Southwestern United States, can experience extreme ambient temperature fluctuations between 4°C and 40°C and the vehicle fleet, which is being used in a taxis fleet, is subjected to a demanding drive cycle.

Injector Plugging by LTFT, %

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0

-4

Dirty-Up Phase (No DCA)

Clean-Up Phase (DCA Present)

-8 0

1000

2000

3000

4000

5000

6000

7000

Kilometers

Figure 13. DU and CU test with a DCA at a commercial gasoline concentration with a 63% CU in 3,200 kilometers.

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Figure 15 shows a fuel lean shift in LTFT from one vehicle in the described test fleet.

Over the course of 32,000 kilometers, LTFT continuously increased, reaching 18.0% at last report.

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6

3

Used Injectors

New Injectors

Figure 16. LTFT before and after the original fuel injector set was replaced.

Figure 17 is a histogram of the vehicle fleet categorized by the LTFT. Currently two thirds of the vehicle fleet has shown a LTFT of greater than 10% and a quarter of the vehicle fleet has a LTFT of greater than 15%.

10 6 5

0 75000

85000

95000

105000

Kilometers

Figure 15. Example of a real-world shift in LTFT fueled with commercial gasoline using conventional DCAs.

In order to ensure that shifts in LTFT are primarily driven by fuel injector deposits a test was conducted where LTFT was continuously monitored before and after the set of fuel injectors were replaced.

The original set of fuel injectors had approximately 117,000 kilometers of use and registered a LTFT of 12.5% at idle. The original injector set was replaced with a set of new factory OEM fuel injectors and driven for an adequate amount of time allowing the adaptive fuel delivery control strategy to produce a stable LTFT. The LTFT was then logged and was shown to be 6.25%. The results of this test, shown in Figure 16, suggest that a portion of the shift in LTFT could be attributed to deposits in the fuel injector. The test is being rerun to verifying that the shifts in LTFT are attributable to injector deposit formation.

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Number of Vehicles

Change in LTFT, %

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12

Change in LTFT, %

During the fleet test the vehicle OBD system is periodically interrogated at an idle condition and LTFT is logged. Vehicles experiencing large shifts in LTFT are continuously monitored with OBD data loggers for more vehicle information.

5 4 3 2 1 0 0-5

5-10

10-15

15-20

LTFT, %

Figure 17. Histogram of the vehicle fleet categorized by LTFT.

Future Vehicle Fleet Testing Results from the fleet study show that it is possible to demonstrate shifts in LTFT using an E10 commercial gasoline with DCAs. Further investigations into GDI fuel injector deposit formation will be pursued.

The next step forward will be to introduce a DCA into a control group within the vehicle fleet to determine if the deposits can be controlled.

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SUMMARY

CONCLUSIONS

The production of vehicles with GDI powertrains is rapidly increasing globally and is projected to eclipse the production of vehicle with PFI powertrains in the near future.

1. A GDI deposit test has been identified that can discriminate the performance of a DCA on fuel injector deposits.

While GDI powertrains offer multiple advantages over conventional gasoline engines they can be susceptible to fuel deposit formation, especially within the fuel injector nozzle. Fuel injector deposits have been linked to a number of effects that can negatively impact engine operation, resulting in increased fuel consumption, engine power loss and increased emissions.

2. Interrogation of the vehicle OBD system was found to be the best method for determining fuel injector deposit formation.

3. DCAs formulated for GDI vehicles have demonstrated the ability to prevent and clean-up GDI fuel injector deposits.

4. A real-world vehicle fleet suggests that DCAs formulated for PFI engines may not be sufficient to control GDI injector deposits.

A test method has been used to discriminate between fuels that may be prone to forming GDI injector deposits and to evaluate the performance of DCAs. Testing has shown that DCAs specifically formulated for GDI engines have the ability to keep fuel injectors clean from deposits and to clean-up existing injector deposits.

Finally, a fleet of twelve taxis with GDI powertrains are currently being monitored for fuel injector deposit formation under real-world conditions. Data from the vehicle fleet indicates that shifts in LTFT are occurring while being fueled with North American commercial gasoline.

Testing suggests that the shifts in LTFT experienced in the vehicle fleet may be attributed to fuel injector deposits. Further testing is being conducted to substantiate that the shifts in LTFT are actually attributed to injector deposit formation.

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REFERENCES 1. Achleitner, E., Bäcker, H., and Funaioli, A., “Direct Injection Systems for Otto Engines,” SAE Technical Paper 2007-01-1416, 2007, doi:10.4271/2007-01-1416.

2. Technology Cost and Adoption Analysis: Impact of Ultra-Low Sulfur Gasoline Standards - Final Report, API, April 2010.

3. Light-Duty Automotive Technology, Carbon Dioxide Emissions, and Fuel Economy Trends: 1975 through 2012, US Environmental Protection Agency, March 2013.

4. Imoehl, W., “Fuel Injection System Trends and Emissions Implications,” SAE, Detroit, MI, January 2013.

5. Aradi, A., Imoehl, B., Avery, N., Wells, P. et al., “The Effect of Fuel Composition and Engine Operating Parameters on Injector Deposits in a High-Pressure Direct Injection Gasoline (DIG) Research Engine,” SAE Technical Paper 199901-3690, 1999, doi:10.4271/1999-01-3690.

6. Aradi, A., Colucci, W., Scull, H., and Openshaw, M., “A Study of Fuel Additives for Direct Injection Gasoline (DIG) Injector Deposit Control,” SAE Technical Paper 2000-01-2020, 2000, doi:10.4271/2000-01-2020.

7. Aradi, A., Evans, J., Miller, K., and Hotchkiss, A., “Direct Injection Gasoline (DIG) Injector Deposit Control with Additives,” SAE Technical Paper 2003-01-2024, 2003, doi:10.4271/2003-01-2024.

8. ASTM D5598-01, Standard Test Method for Evaluating Unleaded Automotive Spark-Ignition Engine Fuel for Electronic Port Fuel Injector Fouling.

9. ASTM D6421-99a, Standard Test Method for Evaluating Automotive Spark-Ignition Engine Fuel for Electronic Port Fuel Injector Fouling by Bench Procedure.

10. TOP TIER GASOLINE, Deposit Control Standards, April 2013. http://www.toptiergas. com/deposit_control.html 11. Arters, D. and Macduff, M., “The Effect on Vehicle Performance of Injector Deposits in a Direct Injection Gasoline Engine,” SAE Technical Paper 2000-01-2021, 2000, doi:10.4271/200001-2021.

13. Von Bacho, P., Sofianek, J., Galante-Fox, J., and McMahon, C., “Engine Test for Accelerated Fuel Deposit Formation on Injectors Used in Gasoline Direct Injection Engines,” SAE Technical Paper 2009-01-1495, 2009, doi:10.4271/2009-01-1495.

14. ASTM D6201, Standard Test Method for Dynamometer Evaluation of Unleaded SparkIgnition Engine Fuel for Intake Valve Deposit Formation.

15. Russell, M., Cummings, J., Cushing, T., and Studzinski, W., “Cellulosic Ethanol Fuel Quality Evaluation and its Effects on PFI Intake Valve Deposits and GDI Fuel Injector Plugging Performance,” SAE Technical Paper 2013-010885, 2013, doi:10.4271/2013-01-0885.

16. Robert Bosch GmbH, “Gasoline-Engine Management,” 3rd edition, 2006.

17. Heywood, J., “Internal Combustion Engine Fundamentals,” 1988.

18. Ford Motor Company, “2012 MY OBD System Operation Summary for Gasoline Engines,” July 2011.

19. Joedicke, A., Krueger-Venus, J., Bohr, P., Cracknell, R. et al., “Understanding the Effect of DISI Injector Deposits on Vehicle Performance,” SAE Technical Paper 2012-01-0391, 2012, doi:10.4271/2012-01-0391.

20. Imoehl, W., Gestri, L., Maragliulo, M., DelFrate, L. et al., “A DOE Approach to Engine Deposit Testing used to Optimize the Design of a Gasoline Direct Injector Seat and Orifice,” SAE Int. J. Fuels Lubr. 5(3):1078-1095, 2012, doi:10.4271/2012-01-1642.

21. Bennett, J., “Application and Testing of Fuel Detergents for Direct Injection Gasoline Engines,” TAE, Esslingen, Stuttgart, Germany, January 2011.

22. DuMont, R., Evans, J., Feist, D., Studzinski, W. et al., “Test and Control of Fuel Injector Deposits in Direct Injected Spark Ignition Vehicles,” SAE Technical Paper 2009-01-2641, 2009, doi:10.4271/2009-01-2641.

12. Smith, D., “Report on the Work of the CEC/ CRC/ OACIS TASK FORCE on the Development of a Test Method to Evaluate Fuel Quality with Respect to Injector Fouling in Direct Injection Gasoline Engines,” Final Report, April 3, 2007.

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ACRONYMS

CONTACT INFORMATION

AFR

scott.smith@aftonchemical.com

Air Fuel Ratio

CU Clean-Up DCA

Deposit Control Additive

GDI

Gasoline Direct Injection

DU Dirty-Up E10

10% Ethanol Gasoline

EOT

End of Test

IAT

Intake Air Temperature

IVD

Intake Valve Deposits

KC

Keep Clean

KM/H Kilometers per Hour LAC

Lowest Additive Concentration

LTFT

Long-Term Fuel Trim

MAF

Mass Air Flow

MIL

Malfunction Indicator Lamp

OBD

On-Board Diagnostics

OEM

Original Equipment Manufacturer

PCM

Powertrain Control Module

PFI

Port Fuel Injection

PSI

Pound per Square-Inch

RUL

Regular Unleaded

SEM

Scanning Electron Microscope

SOT

Start of Test

STFT

Short-Term Fuel Trim

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ACKNOWLEDGMENTS We would like to acknowledge Allen Aradi and Peter Hou for creating the foundation that made this work possible. Additionally, we would like to recognize Mike Bakken, Joel Evans, Gary Payne and Brandon Davis for their expertise and support during all of the vehicle testing.

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