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6 Search Results for ""volumetric efficiency""

  • Firing on All Cylinders? Firing on All Cylinders?

    • From: KathiKankis
    • Description:

      Firing on All Cylinders?

      Running Compression Test is a Great Tool for Diagnosing Density Misfires

       

      The ALLDATA Community Automotive Diagnostic Team

       

      A running compression test or dynamic compression test is an often overlooked engine diagnostic tool. Why is this test significant? It can pinpoint the cause of a misfire when the usual tests are normal.

      When you perform a static compression or cylinder leak-down test, you’re checking the sealing capability of individual cylinders. A running compression test however, indicates how efficiently each cylinder pulls air in, retains it for the correct time then releases it into the exhaust. Not performing these functions properly will result in a loss of volumetric efficiency or a density misfire.

      How to Perform the Test

      1. Create a chart (see samples) to record your test readings.

      2. Begin with a normal ("static") compression test on a warm engine to eliminate problems such as worn rings, burnt or bent valves or holes in pistons. If you have a DTC, you may know which cylinder is misfiring, but test the compression of all cylinders in that bank for a comparison. Record the readings.

      3. Install all of the spark plugs except the one for the suspected cylinder.

      WARNING: Ground that plug wire to prevent module damage, or when equipped with a coil-on-plug ignition, simply disconnect the coil harness plug.

      4. Disconnect the injector for that cylinder on a port fuel injection system.

      5. Install your compression gauge in the suspected cylinder. You can remove the Schrader valve, but most techs recommend leaving it in the gauge and "burping" the gauge every 5-6 "puffs".

      6. Start the engine and record the results of an “Idle” reading (1200 rpm).

      7. From idle, snap the throttle to 2500 rpm. Release quickly. Record the results.

      NOTE: Don't use the gas pedal for this snap acceleration. Manually open then close throttle as fast as possible, forcing the engine to take a "gulp" of air.

      Sample Test Readings

      Compare measurements between cylinders. Running compression at idle should be 50-75 PSI (about half cranking compression). Snap throttle compression should be about 80% of cranking compression.

      EXAMPLE 1

      CYL

      STATIC

      IDLE

      SNAP

      1

      150

      75

      85

      2

      175

      80

      130

      3

      160

      75

      120

      4

      160

      80

      120

      Example 1 – A low snap test in cylinder #1 is much less than 80% cranking compression. Look for air intake problems: severe carbon deposits on intake valves, worn cam lobes, valve guides and springs, rockers or push rod problems, or "shutter valve" incorrectly positioned in a variable runner intake system.

       

       

       

       

       

      EXAMPLE 2

      CYL

      STATIC

      IDLE

      SNAP

      1

      150

      75

      130

      2

      175

      40

      90

      3

      160

      75

      120

      4

      160

      80

      175

      Example 2 – A low Idle and snap test in cylinder #2 indicates that the cylinder is not holding compression efficiently. Look for slightly bent or burned valves, excessive carbon build-up on valves or seats, worn valve guides and springs, scored cylinder wall, or a leaking head gasket.

       

      NOTE: A significantly higher snap measurement (over 80% of cranking compression), means the air is not leaving the cylinder efficiently. Check the exhaust side of that cylinder for a worn cam lobe, bent push rod or collapsed lifter. If the snap readings are all high, look for a clogged catalytic converter or muffler.

       

      As you can see, a running compression test is a great test to add to your diagnostic arsenal. Try it on the next vehicle with an unexplainable misfire.

       

      Written by the ALLDATA® Communitysm Automotive Diagnostic Team, a select group of automotive experts dedicated to helping technicians fix hard-to-repair vehicles more efficiently. Meet the team by visitinghttp://support.alldata.com/alldata-community.

      © 2014 ALLDATA LLC. All rights reserved. All technical information, images and specifications are from the ALLDATA Product. ALLDATA is a registered trademark of ALLDATA LLC. All other marks are the property of their respective holders.

       

       

       

       

    • Blog post
    • 2 months ago
    • Views: 686
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  • Delphi Presents New Developmen Delphi Presents New Developments In Injection Technology

    • From: Peter
    • Description:

      AACHEN, Germany – Delphi Automotive presents new developments in fuel injection and

      engine control systems that reduce carbon dioxide and nitrogen oxide emissions, helping

      automakers meet demanding new regulations.

      Delphi is presenting the new technologies during the Oct. 4-6 Aachen Colloquium, where

      the company is also showing how developing cost-effective system architecture translates into

      cutting edge products for all powertrain alternatives, whether gasoline, diesel or hybrid.

      Some of the new developments are already being used in state-of-the-art powertrains, such

      as in the 2010 World Car of the Year, the Volkswagen Polo BlueMotion.

      “The future of powertrain technology remains the subject of lively debate,” said Mary

      Gustanski, director of Engineering, Customer Satisfaction, Program Management and Operations

      for Delphi Powertrain Systems. “We can see some convergence in diesel and gasoline strategies

      as both now use direct injection, turbocharging, downsizing and even 3-cylinder engines. Heavily

      boosted, downsized engines provide high power density with low CO2 emissions, but the higher

      combustion temperatures and pressures involved make the reduction of NOx emissions more

      challenging. Delphi’s mission is to deliver undiminished vehicle performance while satisfying fuel

      economy needs and emissions regulations.”

       

      Delphi diesel technology helps achieve ultra low CO2 emissions

      Delphi’s Multec® common rail system, which is a robust, cost-effective modular diesel fuel

      injection system, helps the Volkswagen Polo BlueMotion achieve emissions of 87g/km CO2. The

      world’s most economical five-seater car, the 1.2-litre three-cylinder diesel Polo is capable of fuel

      economy of 3,3l/100km (71mpg). Delphi helped achieve this exceptional performance by applying

      the latest evolution of its common rail system, which includes the state-of-the-art solenoid type

      diesel common rail injector technology DFI1.5 and the next generation DFP6 fuel pump.

      Delphi will open the afternoon session of the Colloquium on Oct. 5 with a technical paper

      that will provide a comprehensive review and explanation of this latest Multec system as well as its

      capabilities, with specific focus on these two components.

      The technology uses balanced-valve fast servo-solenoid injectors that offer equivalent

      performance to servo-piezo systems but at a greatly reduced cost. The combination of DFI1.5

      injectors and the DFP6 common rail pump provides improved fuel delivery control, extended

      multiple injection capability, enhanced spray atomization and superior air mixing. Up to six

      injections per cycle are possible, providing a smoother combustion event with exceptional

      refinement.

      Vehicle stop-start functionality is supported by the DFI1.5’s ability to restart injection from

      rail pressures below 100bar, generating faster restart without the need to hold high rail pressure

      when at a standstill. Development is underway to make 80bar minimum pressure operation

      possible.

      “The Multec® system, with its unique, battery voltage driven, fast servo-solenoid injectors,

      enables a low-cost, structured approach at system level to support EU6 and beyond,” explained

      Dr. Hans-Josef Schiffgens, technical director of Delphi Diesel Systems. “The DFP6 pump sets new

      standards for mechanical and volumetric efficiency while eliminating any chance of high pressure

      leakage, offering development extension to robust operation above 2,000bar.”

      Delphi’s Multec common rail latest evolutions’ improve robustness to world market fuel quality and

      compatibility to alternative fuels.

      In addition to the Multec diesel common rail, Delphi offers a direct acting piezoelectric

      injector common rail system for larger and higher performance engines.

      Delphi’s unique Direct Acting Diesel Common Rail System has proven its ability to help

      high performance four-cylinder engines offer the power of a larger six-cylinder engine with

      excellent refinement and substantially improved emissions and fuel economy. Indeed, the

      innovative award-winning injector, whereby the piezo actuator directly drives the needle position,

      delivers unprecedented control of the rate and shape of injection events, independent of rail

      pressure. This allows substantially reduced smoke emissions and therefore the use of increased

      EGR for affordable NOx reduction, while the elimination of fuel backflow allows significant system

      simplification and reduction in CO2.

       

      Delphi GDI systems reduce gasoline engine CO2 emissions by up to 22 percent

      In a technical paper entitled “Three-Cylinder Turbocharged Gasoline Direct Injection: A

      High Value Solution for Low CO2 and NOx Emissions,” Delphi recently illustrated the impressive

      CO2 reductions possible with directly injected gasoline engines, using a three-cylinder

      turbocharged unit. Compared to the baseline four-cylinder port-injected engine, the analysis

      showed that homogeneous direct injection (DI) operation reduced CO2 output by 15 to 18 percent

      while stratified operation achieved up to 22 percent saving.

      GDI improves downsized turbocharged engines because it cools the charge, allowing

      higher boost levels without reducing the compression ratio, essential for efficient part-load running.

      Delphi offers a family of GDI injectors that support the evolution from homogeneous to spraystratified

      operation without requiring modification of the engine controller architecture. They use the

      same approach as Delphi’s cost-effective diesel common rail technology by employing solenoid

      instead of servo piezo technology.

      In addition to showcasing its homogeneous injector, Delphi also will focus on its spray

      stratified GDi injector Multec 20. Both injectors use a patented design to give extremely low noise

      with precise fuel control by eliminating pintle bounce. The injectors have a broad dynamic range

      and are compatible with all widely-available biofuel blends.

      “Delphi’s systems have the flexibility to accommodate different customer requirements for

      fuel flow, spray pattern, injector length, electrical connections, and other essential parameters,”

      explained Jim Zizelman, engineering director, Gasoline Engine Management Systems and

      Powertrain Products. “We provide that flexibility by application engineering delivered through our

      global network of technical and manufacturing resources.”

      In addition to injectors, Delphi’s product portfolio also includes high-pressure fuel pumps,

      fuel rails, electronic control modules, multi-spark ignition systems and wide-range oxygen sensors.

       

      Delphi supervisory controller ideal for hybrids

      Delphi has developed a supervisory controller that coordinates the individual propulsion

      sources and energy storage devices in a hybrid electric vehicle. Such vehicles rely on complex

      high-speed interactions between different sub-systems in order to make best use of the energy

      available and minimize CO2 emissions.

      The controller, which is on display at Delphi’s booth during the colloquium, makes

      decisions based on input from the driver, such as throttle or brake demand, and communicates

      with the engine and transmission electronics, electric motor or motor/generator and energy storage

      devices. It provides a gateway, for example between a CAN bus and Flexray bus and can also

      support safety monitoring. A total of four CAN bus interfaces; one Flexray and two LIN are

      provided. The software architecture is based on Autosar standards for communication between

      software and hardware modules to enable software module development by the OEM or a thirdparty.

      Suitable for micro, mild or medium hybrids, full and plug-in hybrids, the controller can be

      mounted within the cabin or in the engine compartment and is scheduled for production in 2012.

      Giving an overall view on Delphi’s diverse powertrain product range, Gustanski said,

      "Delphi's mission is to deliver undiminished vehicle performance while satisfying fuel economy

      needs and fuel emissions regulations."

      Along with the hybrid/ electric vehicle products and advanced gasoline and diesel engine

      management systems, Delphi is showcasing fuel handling systems and powertrain cooling

      solutions.


    • Blog post
    • 4 years ago
    • Views: 1161
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  • Using The Volumetric Efficienc Using The Volumetric Efficiency Calculator

    • From: Peter
    • Description:

      All technicians know that an engine has to have good compression in order to run well.  But an engine also has to "breathe" well, or be able to move the air in and out with minimal restriction.  Restricted catalytic converters, improper cam timing, even clogged air filters, can impact the ability of the engine to do this with various driveability concerns as a result.

      In addition, many of today's cars use Mass Airflow sensors to tell the ECM how much air is being drawn in.  If this information is incorrect, the ECM will not supply the correct fuel charge for optimum performance and may also result in the Check Engine light illuminating.  There is an easy way to tell if the engine's ability to "breathe" or an inaccurate MAF sensor are the cause of the driveability complaint you are diagnosing. 

      It's called Volumetric Efficiency and is a measurement in percentage of the actual ability of the engine to move air versus what it could move in a perfect world.  To use this test, you need a scan tool capable of recording data and a VE Calculator like this one you can get for free here:

      http://autoservicetech.com/vecalculator1.html

      The calculator requires the engine size in cubic inch displacement, airflow in grams/second, engine rpm and intake air temperaure when tested.  Set your scan tool to record these PIDs (Parameter Identifications) and take the car out for a test drive.  If you want to test the accuracy of the MAF sensor, record the fuel trim PIDs (STFT and LTFT) as well. 

      From a rolling start in first or second gear, perform a wide open throttle run while recording the data.  Make 3 or 4 passes in order to compare results.  Back at the shop, find the point in your recording where airflow reported by the MAF and engine rpm are at their highest.  Enter these values into the calculator.  The result is a percentage to "ideal".  Ideal would be 100% of the engine's displacement.  However, "ideal" is not real world and normal efficiency is generally 80% or more.  Turbocharged and supercharged engines will run higher than 100%, naturally, so bear that in mind if testing an engine so equipped.

      If VE is low, and fuel trims are correcting positive (for a lean condition), then suspect an inaccurate reading from the MAF sensor.  If VE is low, and fuel trims are normal, then look for restrictions to air flow.  A "running" compression test can help isolate whether the restriction is on the intake side of the combustion chamber or the exhaust side.

      The VE calculator is another diagnostic tool that can provide quick direction in diagnosing various driveability complaints.  But just is as the case with other diagnositic tools, it should be followed by more pinpoint tests to verify the results...and the failure.

       

    • Blog post
    • 4 years ago
    • Views: 6214
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  • All Choked Up All Choked Up

    • From: Peter
    • Description:

      Using a Volumetric Efficiency Calculator

      All technicians know that an engine has to have good compression in order to run well.  But an engine also has to "breathe" well, or be able to move the air in and out with minimal restriction.  Restricted catalytic converters, improper cam timing, even clogged air filters, can impact the ability of the engine to do this with various driveability concerns as a result.

      In addition, many of today's cars use Mass Airflow sensors to tell the ECM how much air is being drawn in.  If this information is incorrect, the ECM will not supply the correct fuel charge for optimum performance and may also result in the Check Engine light illuminating.  There is an easy way to tell if the engine's ability to "breathe" or an inaccurate MAF sensor are the cause of the driveability complaint you are diagnosing. 

      It's called Volumetric Efficiency and is a measurement in percentage of the actual ability of the engine to move air versus what it could move in a perfect world.  The scan tool PID "Calculated Load" is a rough representation of VE.  To use this test and check VE for yourself, you need a scan tool capable of recording data and a VE Calculator.  The calculator requires the engine size in cubic inch displacement, airflow in grams/second, engine rpm and intake air temperaure when tested.  Set your scan tool to record these PIDs (Parameter Identifications) and take the car out for a test drive.  If you want to test the accuracy of the MAF sensor, record the fuel trim PIDs (STFT and LTFT) as well. 

      From a rolling start in first or second gear, perform a wide open throttle run while recording the data.  Make 3 or 4 passes in order to compare results.  Back at the shop, find the point in your recording where airflow reported by the MAF and engine rpm are at their highest.  Enter these values into the calculator.  The result is a percentage to "ideal".  Ideal would be 100% of the engine's displacement.  However, "ideal" is not real world and normal efficiency is generally 80% or more.  Turbocharged and supercharged engines will run higher than 100%, naturally, so bear that in mind if testing an engine so equipped.

      If VE is low, and fuel trims are correcting positive (for a lean condition), then suspect an inaccurate reading from the MAF sensor.  If VE is low, and fuel trims are normal, then look for restrictions to air flow.  A "running" compression test can help isolate whether the restriction is on the intake side of the combustion chamber or the exhaust side.

      The VE calculator is another diagnostic tool that can provide quick direction in diagnosing various driveability complaints.  But just is as the case with other diagnositic tools, it should be followed by more pinpoint tests to verify the results...and the failure.


       
       
    • Blog post
    • 5 years ago
    • Views: 1698
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  • The Misbehaving Beemer--Part 2 The Misbehaving Beemer--Part 2

    • From: Peter
    • Description:

      This is the continuing saga of the 2003 BMW 325i from my last post.  To recap, the customer was complaining of an intermittent stall while driving, and I had already installed a new fuel filter and pump.  The car behaved just fine afterward…for about 200 miles!  Now it is back with the same complaint.

      My boss test drove the car and shortly returned, pronouncing the fault as a bad Mass Airflow sensor.  He told me it drove fine under normal conditions, but when performing a WOT pass, the car would bog down.  I wasn’t convinced.  I had inspected the sensor for contamination and had found no evidence.  I had already monitored the MAF sensor signal, idling in the bay, to see if the signal dropped out or changed.  That test also passed.

      I, of course, drove it for myself. 

      Now I have limited capability when it comes to monitoring scan data on a Beemer.  That puts me in the same company as most of you…relying on aftermarket scan tool capabilities, and Global OBD2.  I connected the tool and set it up to record, hoping I could capture the information I needed if the symptoms reared their ugly head again.  I also wanted to gather information to plug into my Volumetric Efficiency calculator, in an attempt to determine the REAL health of the MAF sensor, and also to see if the engine had any breathing problems I didn’t know about.

      The engine was at full operating temperature when I started my test drive.  Idle fuel trims looked normal, as did those at cruise.  Nothing really stood out as being out of whack.  Next, a WOT throttle pass, rolling in first gear, to capture the data I needed for the calculator.  (You can download one for free at www.autoservicetech.com).  With that done, I headed out on my 12 mile test loop, scan tool still connected and standing by.

      10 miles into the drive the engine started stumbling and I hit the record button to save the data.  Letting off of the throttle restored some performance, and for the next few miles the car behaved.  Then the problem began again, worse this time.  I also recorded this with my scan tool.  Almost home, and the engine acted up yet a third time…got that capture too.  At no time did the engine actually stall, so something was better than before.

      Once home, I downloaded the events to my laptop so I could see the data captures easier.  The first one I looked at was the WOT pass.  Plugging the numbers into the VE calculator revealed no evidence of misinformation from the MAF, and no evidence of air flow restrictions.  (I thought perhaps a clogged cat was one possible problem).  Taking a closer look at the captured data did reveal a few question marks, though.  I have included them below for your information and comment.

       

      misbehaving bmw scan data 2misbehaving bmw scan data 1

      The two factors that stood out for me was:

      1.        Fuel trims

      Short Term Fuel Trims headed straight for full rich correction as the failure began and stayed there until I got back to the shop.  The question now is why?

      2.       MAF response compared to Throttle position

       

      In both captures, it seems that the MAF signal was not in synch with the throttle position.  I maintained, or tried to, a steady throttle while recording the failure.  Was this a result of the refresh rate of my scan tool, or the key to the problem? 

      Since my boss was dead set on a bad MAF, one was ordered.  I’ll let you know next time what the results were.  Do you agree with this diagnosis so far?  What would you do differently?  Why?

    • Blog post
    • 5 years ago
    • Views: 1070
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  • Misbehaving Beemer--Part 2 Misbehaving Beemer--Part 2

    • From: Peter
    • Description:

      This is the continuing saga of the 2003 BMW 325i from my last post.  To recap, the customer was complaining of an intermittent stall while driving, and I had already installed a new fuel filter and pump.  The car behaved just fine afterward…for about 200 miles!  No

    • 5 years ago
    • Views: 845
    • Forum: Automotive ...
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