Porsche training p21 fuel ignition diag + repair

Electrically or electro-pneumatically actuated flaps, forexample, are used for switching the variable intakesystems Tuning Flap and Double-flow Distribution Pipe 1 - Flange to electronic

AfterSales Training

Fuel/Ignition Diagnosis & Repair

P21

Student Name:

Training Center Location:

Instructor Name:

Date: _

Important Notice: Some of the contents of this AfterSales Training brochure was originally written by Porsche AG for its

rest-of-world English speaking market The electronic text and graphic files were then imported by Porsche Cars N.A, Inc and edited for content Some equipment and technical data listed in this publication may not be applicable for our market Specifications are subject to change without notice.

We have attempted to render the text within this publication to American English as best as we could We reserve the right to make changes without notice

© 2012 Porsche Cars North America, Inc All Rights Reserved Reproduction or translation in whole or in part is not permitted without written authorization from publisher AfterSales Training Publications

Dr Ing h.c F Porsche AG is the owner of numerous trademarks, both registered and unregistered, including without limitation the Porsche Crest®, Porsche®, Boxster®, Carrera®, Cayenne®, Cayman™, Panamera®, Tiptronic®, VarioCam®, PCM®, 911®, 4S®, FOUR, UNCOMPROMISED SM and the model numbers and distinctive shapes of Porsche's automobiles such as, the federally registered 911 and Boxster automobiles The third party trademarks contained herein are the properties of their respective owners Specifications, performance standards, options, and other elements shown are subject to change without notice Some vehicles may be shown with non-U.S equipment Porsche recommends seat belt usage and observance of traffic laws at all times Printed in the USA

Electrical Troubleshooting Logic

1 -Do you understand how the electrical consumer is expected to operate?

2 -Do you have the correct wiring diagram?

3 -If the circuit contains a fuse, is the fuse okay & of the correct amperage?

4 -Is there power provided to the circuit? Is the power source the correct voltage?

5 -Is the ground(s) for the circuit connected? Is the connection tight & free of resistance?

6 -Is the circuit being correctly activated by a switch, relay, sensor, microswitch, etc.?

7 -Are all electrical plugs connected securely with no tension, corrosion, or loose wires?

Chapter Description Section

Introduction i

System Type Designations 1

Engine Mechanical 2

Intake Systems 3

Ignition System 4

Fuel Supply Systems 5

Exhaust Systems 6

Mixture Formation 7

On-Board Diagnostics (OBD II) 8

Additional DME Functions & Special Control Systems 9

Conversion Charts 10

Over the past several years, the engine management and related systems of Porsche vehicles have had

to respond to ever-lower emissions standards and increasingly complex legislative requirements While each new engine design produced more torque and horsepower and lower fuel consumption, engine management systems become increasingly efficient and complex This has increased the amount of information that the technician must have command of and the complexity of the systems the technican must understand, exponentially This training book attempts to organize the information and system theory of Porsche engine management in an understandable and organized manner We hope this will make your study of Porsche engine management a successful undertaking that will improve your ability

to repair and diagnose Porsche engine management systems.

Viel Spass!

AfterSales Training Department

Model Model Year System Designation

911 1984-89 DME 35 Pin Control Unit

911 (964) 1989-94 DME 55 Pin Control Unit

911 (997) 2nd Gen DFI .2009-11 EMS SDI 3.1 (Siemens)

911 (991) .2012-on EMS SDI 9 (Continental)

911 Turbo (997) DFI .2010-12 EMS SDI 3.1 (Siemens)

924S 1986-88 DME 35 Pin Control Unit

928 S 1984-86 LH-Jetronic - EZF

928 S4 1987-89 LH-Jetronic - EZK

928 S4/GT 1990-95 LH-Jetronic - EZK

944 1984-89 DME 35 Pin Control Unit

944 S 1987-89 DME 55 Pin Control Unit

944 S2 1990-91 DME 55 Pin Control Unit

944 Turbo 1986-90 DME 35 Pin Control Unit with KLR

968 1992-95 DME 2.10.1

Boxster/S (986) 1997-99 DME 5.2.2

Boxster/S (986) 2000-02 DME 7.2

Boxster/S (986) 2003-04 DME 7.8

Boxster/S (987) 1st Gen .2005-08 DME 7.8_40

Cayman/S (987) 1st Gen .2006-08 DME 7.8_40

Boxster (987) 2nd Gen (2.9 liter) 2009-12 DME 7.8.2

Cayman (987) 2nd Gen (2.9 liter) 2009-on DME 7.8.2

Boxster S (987) 2nd Gen (3.4 liter) DFI .2009-12 EMS SDI 3.1 (Siemens)

Cayman S (987) 2nd Gen (3.4 liter) DFI 2009-on EMS SDI 3.1 (Siemens)

Boxster/S (981) DFI 2012-on EMS SDI 9.1 (Continental)

Cayenne (V6) 1st Gen .2004-06 DME 7.1

Cayenne S 1st Gen .2003-06 DME 7.1

Cayenne Turbo 1st Gen .2003 06 DME 7.1

Cayenne (V6) 2nd Gen (E1) DFI .2008-10 MED 9.1 (Bosch)

Cayenne S 2nd Gen (E1) DFI 2008-10 EMS SDI 4.1 (Siemens)

Cayenne Turbo 2nd Gen (E1) DFI .2008-10 EMS SDI 4.1 (Siemens)

Cayenne (V6) (E2) DFI .2011-on MED 17.1.6 (Bosch)

Cayenne S Hybrid (V6) (E2) DFI .2011-on MED 17.1.6 (Bosch) (Hybrid Manager)

Cayenne S (E2) DFI .2011-on EMS SDI 8.1 (Siemens)

Cayenne Turbo (E2) DFI 2011-on EMS SDI 8.1 (Siemens)

Model Year – Porsche System Designations

Fuel/Ignition Diagnosis & Repair

Model Model Year System Designation

Panamera (V6) DFI 2011-on EMS SDI 7.1 (Siemens)

Panamera S Hybrid (V6) DFI .2012-on MED 17.1.6 (Bosch) (Hybrid Manager) Panamera S DFI 2010-on EMS SDI 6.1 (Siemens)

Panamera Turbo DFI 2010-on EMS SDI 6.1 (Siemens)

Carrera GT 2004-06 DME 7.1 x 2 (Master/Slave)

Subject Page

Engine Mechanical System 2

The Four Strokes Of The “Otto” Cycle 2

By dividing the engine management system into its basic

systems, and subsystems, we can gain a better

under-standing of engine management as a whole, and the

rela-tionships between these systems The engine mechanical

system compresses the air and fuel mixture provided by

the fuel system and the ignition system ignites the air and

fuel mixture to produce torque and horsepower at the

crankshaft

A solid knowledge of engine management is essential for

understanding of the complex computer controlled

systems utilized by Porsche today As well as being

essential for the diagnosis of system faults

Engine Mechanical System

The engine mechanical system consists of the intake

system, the engine mechanical (motor-block, pistons,

valves, etc.) and the exhaust system The operational

principal of this system is the “Otto” cycle

The Four Strokes of the “Otto” (combustion) Cycle

The operation of an internal combustion engine can beunderstood by looking at the operation of one cylinder ofthe engine through an entire combustion cycle Thecombustion cycle consists of two crankshaft revolutions During each of these revolutions the piston will travel fromthe top of the cylinder to the bottom of the cylinder, andthen from the bottom of the cylinder to the top Thesemovements are called strokes and there are four strokes

in a combustion cycle (down, up, down, up) The valvetrain of the engine operates the valves in synchronizationwith these strokes: opening the intake valve during onestroke and the exhaust valve during another stroke

Intake (1)

During the intake stroke the piston ismoving down and the intake valve isopen As the piston moves down, theair and fuel mixture enters the cylinder

to occupy the space vacated by thepiston as it moves down At the end ofthe intake stroke the piston is at thebottom of the cylinder and the intakevalve closes

Compression (2)

During the compression stroke thepiston is moving up and the valves areclosed The piston movement com-presses the air/fuel mixture thatentered the cylinder during the intakestroke At the top of this stroke theair/fuel mixture that filled the entirecylinder at the bottom of the intakestroke has been compressed into thecombustion chamber Compressingthe mixture by the ratio of the totalcylinder volume to the combustionchamber volume

Power (3)

During the power stroke the valves

are closed and the air/fuel mixture

has been ignited by the ignition

system The pressure that is

generated by the burning of the

air/fuel mixture pushes the piston

down This stroke creates rotational

force (torque), which is transmitted to

the crankshaft via the connecting rod

Exhaust (4)

During the exhaust stroke, the exhaust

valve is opened and the piston begins

moving up and forces the by products

of the combustion process out past

the exhaust valve and into the exhaust

system

This cycle is repeated continuously as long as the engine

is supplied with air/fuel mixture and ignition spark Thevalve train that controls the intake and exhaust valvesoperates at half crankshaft (piston) speed So, for tworevolutions of the crankshaft, the camshaft will only rotateone time and open the valves it controls (intake andexhaust) once per cycle during the appropriate stroke,intake valve(s) on the intake stroke and exhaust valve(s) onthe exhaust stroke In the other two strokes the compres-sion and the power strokes, no valves are open

A one-cylinder engine will only have one power pulse everyother crankshaft rotation, as cylinders are added, powerpulses are also added A four-cylinder engine will have twopulses per revolution and a six-cylinder engine will havethree As the number of pulses per revolution increasesthe smoothness and power of the engine also increases

The engine mechanical system(s) need to always be ingood working order to ensure consistent complete com-bustion They must always be considered when examiningthe over health of our complex system(s) and performingdiagnostics

Notes:

Subject Page

General Information 2

Air Flow Through The Engine 2

Porsche Intake Systems 2

Variable Intake Manifold Geometry 3

911 Carrera (996/997/S) 4

Boxster/S (981) 6

911 Carrera/S (991) 8

V8 DFI Naturally Aspirated Engine 11

V8 Turbo Engine 11

V6 Cayenne DFI 12

Expansion Intake Systems 13

Hot-film Mass Air Flow Sensor 14

Pipe Hot-film Mass Air Flow Sensor 15

Pressure Sensor for Load Detection 17

Electronic Throttle Valve 18

Basic Principal of E-Throttle 19

Throttle Valve Control Unit 20

Throttle Valve Adaptation 21

Accelerator Pedal Sensor 21

Sport Button 23

Fuel/Ignition Diagnosis & Repair

General Information

Air Flow Through Engine

When the vehicle is at idle, the throttle plate will close off

the intake air flow path and the engine will be held to a low

RPM This will cause the pressure in the intake system (7)

to drop below atmospheric pressure (6) since the engine

is attempting to pull air past the closed throttle plate As

the throttle plate is opened, the pressure will rise towards

atmospheric pressure, at wide-open throttle the pressure

will be close to atmospheric pressure

The exhaust system directs the combustion by-products

from the engine (9) to the rear of the vehicle The pressure

in the exhaust system (10) pulses positive/negative, due

to the gas inertia of the exhaust flow The exhaust gas

continues to move after the exhaust valve has closed,

forming a low pressure in the exhaust runner below the

closed valve

Porsche Intake Systems

The main components of the intake system are the air

cleaner, the load detection components, the throttle valve

(electronic throttle), the intake manifold and the valves

The achievable engine torque is almost proportional to the

amount of fresh air in the cylinder charge The maximum

torque can therefore be increased within certain limits by

compressing the air before it enters the cylinder

The gas cycle processes are not only influenced by valve

timing, but also by the intake and exhaust systems In

response to the suction work performed by the pistons,

the opening intake valve triggers a returning pressure

wave At the open end of the intake manifold, the pressure

wave hits static ambient air, and is reflected back to the

intake valve The resultant fluctuations in pressure at the

intake valve can be used to increase the fresh gas charge,

thereby achieving the highest possible torque

This supercharging effect is therefore based on utilizingthe dynamics of the air that is drawn in The dynamiceffects in the intake manifold depend not only on thegeometric conditions in the intake manifold, but also onthe engine speed

Ram-effect Supercharging

With ram-effect supercharging, each cylinder has anindividual ram tube of a specific length which is generallyconnected to a collecting tank The pressure waves canspread out independently of each other in these ramtubes

The supercharging effect depends on the intake manifoldgeometry and the engine speed The length and diameter

of the individual ram tubes are therefore matched to thevalve timing so that a pressure wave reflected at the end

of the ram tube runs through to the next cylinder’s openintake valve in the desired rev range, thus allowingimproved cylinder charging Long thin ram tubes have ahigh supercharging effect at low revs for a high torque,while short, wide ram tubes have a favorable effect onpower output at high revs

Resonance Induction

At a certain engine speed, the gas vibrations in the intakemanifold, triggered by the periodic piston movement,produce resonance This results in an additional increase

in pressure and an additional supercharging effect Withresonance intake manifold systems, groups of cylinderswith the same firing intervals are connected via shortintake pipes to one resonance tank The rev range forwhich the supercharging effect from the resultantresonance is required determines the length of theresonance intake pipes and the size of the resonancetank Separation of the cylinders into two cylinder groupswith two resonance intake pipes prevents overlap of theflow processes from two adjacent cylinders in the firingorder

To understand how resonance tuning systems work, we

need to return to the Otto cycle When the intake stroke is

occurring, the intake valve is open, the piston is

descending, and the air fuel charge is rushing down the

intake runner As the piston approaches the bottom of the

stroke, the intake valve closes However, the air fuel

charge that is in the intake tract cannot immediately stop

moving, it has mass and inertia, so it continues to move

down the intake runner

With the intake valve closed, the intake tract becomes a

sealed chamber, so the air fuel charge is compressed on

top of the intake valve When the inertia bleeds off, this

compressed air fuel charge expands back up into the

intake tract as a pressure wave It is this pressure wave

that resonant intake tuning utilizes to move air into the

motor

The design of the intake manifold causes the pressure

wave to arrive at a companion cylinder while its intake

valve is open and force additional air fuel mixture into that

cylinder The tuning flap changes the intake geometry so

that this pressure wave effect is operational for a wider

RPM band

Variable Intake Manifold Geometry

The additional charge as a result of dynamic charging depends on the engine’s operating point The twosystems mentioned above increase the maximum chargethat can be achieved, particularly in the low rev range

super-An almost ideal torque curve is achieved with variableintake manifold geometry (variable intake systems) inwhich various adjustments are possible using flaps, forexample, depending on the engine operating point:

• Adjustment of the ram intake pipe length

• Switching between various ram intake pipe lengths ordifferent ram intake pipe diameters

• Switching to a different accumulator volume

Electrically or electro-pneumatically actuated flaps, forexample, are used for switching the variable intakesystems

Tuning Flap and Double-flow Distribution Pipe

1 - Flange to electronic throttle

2 - Partition wall of double-flow distribution pipe

3 - Distribution pipe flap

4 - Tuning flap

5 - Air distributor for left bank

6 - Air distributor for right bank

The resonance intake systems in the Boxster and Boxster

S (987 as of MY 2005) also have a double-flow distributionpipe With this system, the distribution pipe flap (3) in theintermediate pipe connecting the two intake air distri-butors is closed in the low rev range The distribution pipefeatures a partition wall running along its length (betweenthe electronic throttle and the distribution pipe flap in the

intermediate pipe) This means that the 6-cylinder engine

behaves like two 3-cylinder engines running in parallel in

the low rev range (with the distribution pipe flap closed),

resulting in an improved torque characteristic in the low

rpm range

There is a switchable tuning flap (4) in the perpendicular

resonance pipe between the air distributors The air

oscil-lations in the intake system can therefore be adjusted to

the respective engine speeds so as to ensure high torques

even at low revs, an even torque curve and high maximum

output The tuning flap is closed in the low rev range The

tuning flap is opened at full throttle between 5,000 and

7,200 rpm

Switching Points of the Distribution Pipe Flap on the

Boxster (987)

The distribution pipe flap on the Boxster is opened in the 2

rev ranges from 3,100 to 5,000 rpm and from 5,600 to

2 - Tuning flap (red)

3 - Distributor pipe flap (yellow)

911 Carrera (996/997/S)

911 Carrera (996/997/S) engines have a switched tuningflap between the intake-air distributors, which improves theengine charge The tuning flap is open in the low revrange, is closed by an electro-pneumatic valve that appliesvacuum to the vacuum unit at medium revs and is openedagain at high revs

Picture below: On the 997 the tuning flap is closedbetween 2,600 and 5,100 rpm

1 - Plastic intake manifold incl intake pipe supports

2 - Resonance chambers integrated into the intake distributor

3 - Tuning flap

4 - Throttle housing (electronic throttle)

Fuel/Ignition Diagnosis & Repair

911 Carrera MY 2009 3.6/3.8-liter DFI Engines

The resonance intake system of the 3.8-liter engine is

distinguished from the intake system of the 3.6-liter engine

by virtue of an additional, actively switchable tuning flap in

the resonance distributor between the intake distributors

This resonance intake system, which can be activated in

two stages, influences and utilizes air oscillations in the

intake system at different engine speeds, thereby

producing high torque values at low engine speeds, a

uniform torque curve in the medium rev range and high

maximum power at high speeds by way of the improved

engine charging values generated in this manner The

pictures show the intake system of the 3.8-liter engine and

the resonance tube with tuning flap

The tuning flap (1) is actuated by a vacuum-controlled

diaphragm cell (2) Activation is map-controlled by an

electro-pneumatic switching valve installed on theresonance tube Under load, the tuning flap is closedbetween approx 3,000 and 5,500 rpm and opened atlower and higher engine speeds

Tuning Flaps in the Intake Distributors

The intake systems of both engine versions are enhanced

by sound volumes in the intake distributors They uate disturbing resonance sounds in the higher rpm range(5,000 - 6,000 rpm) and make an important contribution

atten-to the harmonic, powerful sound profile at full throttle

The design principle for the resonance chambers wasadopted from the 3.8-liter engine used in the previousmodels The additional chambers are integrated into thelateral intake distributors and are connected to them via aperforated partition with numerous small openings whichalso act as Helmholtz resonators (acoustic tuners)

Notes:

Fuel/Ignition Diagnosis & Repair

Boxster/S (981) MY 2013 2.7/3.4-liter Engines

Air Routing

Due to the new routing of the intake air, the intake section

has been derestricted and the volumetric efficiency of the

engine at full throttle has been improved

The intake air travels from the twin branches of the air

intakes (1) on the left and right side sections via the air

cleaner housing (2) with the air filter elements (3) to the

throttle unit (5) for the electronic throttle The intake sound

is optimised by the Helmholtz resonators on the left and

right (4)

Note !

The air filter elements on the left and right can be changedfrom the rear luggage compartment The maintenance interval for the air filter elements can be found in the main-tenance schedules in the PIWIS information system

Intake Manifold, Pressure Sensor

The intake manifold has been modified compared with the

987

Intake Manifold on the Boxster S (3.4 l) With Tuning

Flap

The 3.4-liter engine of the Boxster S has a tuning flap for

greater volumetric efficiency and a high engine torque at

low to medium rpm as well as an even torque curve The

tuning flap of the Boxster S is closed by the

electro-pneu-matic switching valve between 3,000 and 5,300 rpm by

applying a vacuum to the diaphragm cell

1 - Throttle housing (electronic throttle)

2 - Pressure sensor for detecting the engine load and intake air

temperature

3 - Resonance chamber in the intake distributor

4 - Diaphragm cell and tuning flap on the air distributor (Boxster

S only)

Intake Manifold on the Boxster (2.7 l)

1 - Throttle housing (electronic throttle)

2 - Pressure sensor for detecting the engine load and intake air temperature

3 - Resonance chamber in the intake distributor

Notes:

Fuel/Ignition Diagnosis & Repair

911 Carrera/S (991) MY 2012 3.4/3.8-liter

Engines

Air Guide

1 - Two-branch air guide from the air intake on the engine cover

to the air cleaner housing

2 - Sound openings at the bottom and top of the air cleaner

housing

3 - Silencer (resonator) in the air cleaner housing

4 - Diaphragm cell between the intake and silencer in the air

cleaner housing on both engines

5 - Flap in the air cleaner housing silencer

The dual-branch (1) air guide from the engine cover to the

air filter housing has optimized/derestricted this area of

the intake system

Sound Opening

The mesh on the sound openings (2) allows the intake

sound to travel into the engine compartment, but prevents

warm air from the engine compartment from being sucked

Air Filter Housing and Air Filter Element

The flow-optimized air cleaner housing and the two airfilter elements result in higher volumetric efficiency of theengine at full load

Sound Symposer

The 911 Carrera models (991) are equipped with the new

sound symposer as standard for the first time for a more

emotive driving experience This passive sound

transmis-sion system produces an even richer and sportier engine

sound in the passenger compartment and can be

activated and deactivated via the standard Sport button

1 - Sound symposer (acoustic simulator)

2 - Control flap (vacuum-controlled)

3 - Diaphragm (amplifies the vibrations)

4 - Passenger compartment inlet at the rear shelf

5 - Intake noise transmission into the passenger compartment

6 - Unfiltered air intake

7 Air filter

8 - Throttle valve (electronic throttle)

9 - Engine, intake system

The sound symposer is a passive system for transmitting

engine noise into the passenger compartment In other

words it does not generate an artificial engine sound, but

rather amplifies the unique sporty sound of the 911

Carrera flat engines and directs it into the passenger

compartment at the push of a button

The sound symposer is located within the intake tract of

the engine and is installed between the throttle valve and

air cleaner It is connected with the passenger

compart-ment out of the customer’s sight via a line in the area of

the rear shelf The engine’s load-dependent intake pulses

cause the diaphragm integrated in the sound symposer to

vibrate; the diaphragm amplifies these vibrations before

they are transmitted directly into the passenger

compart-ment as sound via the line

2 - Control flap (vacuum-controlled)

3 - Diaphragm (amplifies the vibrations)

4 - Passenger compartment inlet at the rear shelf

6 - Unfiltered air intake

10 - Switching valves for sound symposer and silencer tor in the air cleaner housing)

(resona-Sound Symposer Switching Strategy

The sound symposer can be electropneumaticallyactivated or deactivated via an controllable flap locatedupstream of it

With the standard exhaust system, the control flap isopened by pressing the Sport button With the Sportsexhaust system, the control flap is opened when theexhaust system button is pressed

Fuel/Ignition Diagnosis & Repair

Intake Manifold, Pressure Sensor

On the 991 vehicles, the engine load is detected

downstream of the electronic throttle by the pressure

sensor on the intake manifold

The derestriction of the intake system means that the

intake manifold pressure at full load (throttle valve fully

open, dependent on the engine speed) is approximately in

the -20 mbar range relative to the ambient pressure

1 - Throttle housing (electronic throttle)

2 - Pressure sensor for detecting the engine load and intake air

temperature

3 - Diaphragm cell and tuning flap on the air distributor (Carrera

S only)

4 - Resonance chamber in the intake distributor

Tuning Flap, Carrera S

The 3.8-liter engine also has a tuning flap for greater metric efficiency and a high torque at low to medium rpm

volu-as well volu-as an even torque curve The tuning flap of theCarrera S is closed by the electropneumatic switchingvalve between 3,000 and 5,000 rpm by applying avacuum to the diaphragm cell

Notes:

V8 DFI Naturally Aspirated Engines

Variable Intake System - Cayenne/Panamera

In the variable intake system used in the Cayenne and

Panamera S, four switching flaps are fitted on a steel shaft

for each bank and are encapsulated with silicon for a

reliable sealing effect A high torque curve is achieved,

depending on the position of the intake manifold switching

flap in conjunction with the optimized intake duct

geometry

1 - Electronic throttle

2 - Variable intake system

3 - Diaphragm cell for switching flaps

4 - Connecting link

5 - Shaft for switching flap for cylinder bank 1

6 - Shaft for switching flap for cylinder bank 2

The DME control unit activates an electro-pneumatic

switching valve, which switches the vacuum to the

diaphragm cell The switching flaps for cylinder bank 1

and 2 are actuated synchronously via a connecting link In

the torque setting up to approx 4,150 rpm, the long

intake manifold is effective with a length of approx 538

mm In the power setting at an engine speed of more than

approx 4,150 rpm, the short intake manifold is effective

with a length of approx 284 mm

The chart shows the torque curve with a long intakemanifold (LS - blue, 538 mm) and a short intake manifold(KS – red, 284 mm) When the engine is started, the DMEcontrol unit activates the electric switching valve and avacuum closes the variable intake system flaps in theintake manifold As a result,the engine operates with thelong intake manifold up to 4,150 rpm, thereby increasingthe torque

If intake manifold switchover fails, the intake manifoldremains in the short power position The power outputabove 4,150 rpm is retained, but there is perceptibly lesstorque at low speeds

Intake Manifold in V8 Turbo Engines

Like the V8 variable intake system, the pressure system ofthe V8 turbo engines is manufactured in a plastic shelldesign The pressure system comprises three shellelements, where the bottom shell is identical to thevariable intake system It is also made of plastic, forexample, to ensure a low weight

Unlike the V8 naturally aspirated engine, the switching

flaps are not required since the turbo charging effect is

produced by the two turbochargers As a result, the

low-loss short intake manifold lengths are effective for the

entire map For optimum efficiency, the compressed and

heated air is cooled again by the charge-air coolers

(upstream of the electronic throttle) in the turbo engines

Intake Manifold - Cayenne 3.6-liter V6 DFI MY 2008

The 3.6-liter V6 DFI engine uses operating sleeves instead

of switching flaps for adapting the intake manifold length

These move into torque position when the engine is

started and up to an engine speed of 4,200 rpm and this

is apparent from the repositioning of the operating sleeves

(at the front left of the intake manifold in direction of

travel) The vacuum unit pulls the lever to the left (in

direction of travel) The operating sleeve seals the

reflec-tion point to the power accumulator, which renders the

reflection point to the torque accumulator effective The

effective ram tube length is approx 610 mm in torque

setting

Important !

If intake manifold switchover fails, the intake manifold

remains in the short power position The power output

above 4,200 rpm is retained, but there is perceptibly less

torque at low speeds

6 - Operating sleeves (sealed)

If the engine speed exceeds 4,200 rpm, the powerposition is activated by opening the operating sleeves Theoperating sleeve opens the reflection point to the poweraccumulator, which renders the short ram tube effectivewith a length of approx 235 mm

The chart shows the torque curve with a long intakemanifold of 610 mm (blue) and a short intake manifold of

235 mm (purple)

Fuel/Ignition Diagnosis & Repair

Notes:

Expansion Intake Systems

The disadvantage of a resonance intake system,

particu-larly for turbo engines, is the additional air heating as a

result of compressing the air This means that the fuel/air

mixture in the combustion chamber cannot be ignited with

optimum efficiency For this reason, the 911 Turbo (997)

uses an expansion intake manifold that is designed so

that, unlike naturally aspirated engines, this effect only

occurs in the higher rev range, but is neutralized at

maximum power

At first glance, the expansion intake manifold looks much

the same as conventional intake manifolds It has no

unusual design features such as additional resonance flaps

or other moveable components Like a traditional intake

manifold, the expansion intake manifold consists of a

distributor pipe, two accumulators and six individual intake

pipes The most important difference is the geometric

tuning of the distributor pipe and the individual intake

pipes

1 - Distributor pipe

2 - Intake pipes

3 - Expansion point

Operating Principle of the Expansion Intake Manifold

Expansion intake systems can only be used for turboengines The expansion intake manifold completely turnsaround the resonance induction effect at high enginespeeds and loads The principle of air expansion is usedinstead of compression Expansion takes place at thepoint where the distributor pipe goes into the intake pipes

In contrast to compression, the air is not heated butcooled This effect results in a lower fuel/air mixturetemperature in the combustion chamber, which meansthat the mixture can be ignited in a more efficient manner.This improves engine efficiency and ensures higher enginepower and low fuel consumption with a high load and revs

The cylinders are filled with slightly less air duringexpansion than during compression To compensate forthis effect, the boost pressure is increased accordingly onthe 911 Turbo engines Despite a reduction in the flowcross-section in the distributor pipe of more than 65%,approx 4% more power has been achieved with the newexpansion intake manifold

Load Detection

Measurement of the air mass involved in combustion is avery important factor in ensuring that the air/fuel mixturecan be set accurately The mass air flow sensor, which islocated upstream of the throttle valve, measures the airmass flowing into the intake manifold and sends anelectric signal on to the engine control unit

On some new systems, the intake air mass is now lated using a pressure sensor installed at the intakemanifold in conjunction with the throttle valve position andengine speed The DME control unit determines therequired fuel mass from the intake air mass and thecurrent engine operating state

calcu-Fuel/Ignition Diagnosis & Repair

Hot-film Mass Air Flow Sensor (MAF)

Operating Principle

The hot-film mass air flow sensor (MAF) is installed

between the air cleaner and throttle valve and detects the

mass air flow drawn in by the engine The mass air flow is

actually measured inside a bypass duct, which separates

some of the air flow routed through the MAF The air flow

cools an electrically heated platinum film resistor A

control circuit feeds the heating current so that the film

resistor assumes a constant over temperature compared

to the intake air temperature The heating current is then a

measure of the mass air flow This measuring principle

also takes the air density into account as it also

deter-mines how much heat is released into the air by the

heated body

A temperature sensor is integrated as a measuring

resistor in the measuring circuit of the MAF in order to

determine the intake air temperature Long-term

measuring accuracy is retained even without burn-off, as

was necessary with older hot-wire mass air flow sensors

Since dirt is mainly deposited on the front edge of the

sensor element, the elements that are decisive for heat

transfer are arranged downstream on the ceramic

substrate

If the mass air flow sensor fails, the DME control unit uses

a substitute mass air flow model that is stored in the

engine control unit for this eventuality

MAF Versions

Different mass air flow sensors are used depending on themodel and model year and these are differentiated by theengine-specific nominal air mass and the air guide in theair duct

The above picture shows an old version of the hot-filmmass air flow sensor (MAF 5) on the left and on the right,the newer version (MAF 5 CL) with the C-shaped air ductwhich was installed for the first time in the Boxster (986)from 01/2000 onwards

Notes:

Pipe Hot-film Mass Air Flow Sensor

Various vehicles have a pipe hot-film mass air flow sensor

adapted to the engine With these versions, the sensor

and measuring pipe are manufactured as one unit and

must not be separated as these components have been

matched on a flow bench

Hot-film Mass Air Flow Sensor MAF 7

All MY 2009 Boxster and Cayman models, for example,

use the new hot-film mass air flow sensor MAF 7-RP (RP =

Reduced Pressure Drop) This mass air flow sensor has a

5-pin connector with a trapezoidal shape and is welded to

the measuring pipe Like its predecessor (MAF 5), it too

generates an analog voltage signal according to a thermal

measuring principle The intake air temperature is

measured at the same time There is a special bar to the

air guide at the right of the MAF in the measuring pipe to

optimize the air flow

Components:

– Measuring pipe

– Micromechanical sensor element with return-flow

detection

– Sensor electronics with signal processing and interface

– Intake air temperature sensor (NTC)

Advantages:

– Low tolerances, improved characteristic

– Less sensitive to water, particles and oil

– Compact design and reduced pressure drop

– Return-flow detection

– Flexible installation position

– Extremely robust and dynamic

– Integrated temperature compensation

Bypass Duct

The flow characteristics of the bypass duct have beenoptimized compared to the previous MAF 5 sensor Thevacuum behind a deflection edge (1) draws the partial airflow required for metering of the air quantity into thebypass duct (2) The more inert dirt particles are leftbehind by this fast motion and are returned to the intakeair via an elimination bore (3) This means that the dirtparticles cannot falsify the measurement result anddamage the sensor element

Detecting the Air Mass and Direction of Air Flow Through the Hot-film Mass Air Flow Sensor (MAF)

Current hot-film mass air flow sensors detect not only theair mass and temperature, but also the direction of airflow The mass air flow sensor is installed in the air guidebetween the air filter and throttle valve

1 - Air flow

2 - Heated micromechanical sensor element with two temperature sensors

3 - Transverse bore (air pulsations)

Design: The micromechanical sensor element is located

in the MAF sensor’s flow channel A micromechanicalmeasuring system with a hybrid circuit is used to evaluatethe measurement data in order to detect when return flowtakes place during significant air-flow pulsation

Operating Principle: A heated sensor element in the

mass air flow sensor dissipates heat to the incoming air.The higher the air flow, the more heat is dissipated Theresulting temperature differential is a measure of the airmass flowing past the sensor An electronic hybrid circuit

Fuel/Ignition Diagnosis & Repair

evaluates this measurement data so that the air flow

quantity and its direction of flow can be detected

precisely Only part of the mass air flow is detected by the

sensor element The total air mass flowing through the

measuring pipe is determined by means of calibration,

known as the characteristic-curve definition

The complete hot-film element is divided into the heating

area, which is important for detecting the air mass and is

heated to a constant temperature by the electronics and

two temperature sensors (one upstream and one

downstream of the heating element)

The air mass is calculated based on the heating current

The direction of flow of the intake air can be determined

by detecting the temperature difference using the

temper-ature sensors upstream and downstream of the heating

element The plausibility of the load signal from the MAF is

checked in the current DME systems An engine speed

and load-dependent map is stored in the DME control unit

for this purpose

The mass air flow sensor must be checked in accordance

with the guided fault finding instructions The static sensor

voltage of the MAF when the ignition is switched on (0.90

to 1.10 volts) is used as the basic check in the current

systems

This graph shows the voltage signal in volts (3) from the mass air

flow sensor while driving (1) and when the air mass (2) is flowing

back.

Output Signal from the MAF

This graph shows the increase in air mass on a 911 Carrera liter engine when accelerating at full throttle in 2nd gear from approx 1,500 rpm to maximum rpm.

3.6-Depending on displacement and engine type (naturallyaspirated engine/turbo engine), the intake air mass whenthe engine is at operating temperature and no additionalloads are switched on is between approx 12 kg/h and up

to > 1,000 kg/h

The intake air mass at idle speed on a 2.5-liter engine, forexample, is approx 12 kg/h and approx 18 kg/h on a3.8-liter engine, while the intake air mass at full throttleand maximum rpm on a 2.5-liter engine, for example, isapprox 600 kg/h and approx 900 kg/h on a 3.8-literengine(up to > 1,000 kg/h for larger engines or turboengines)

Notes:

Pressure Sensor for Load Detection

The pressure sensor for measuring the mass air flow was

introduced with the Panamera This replaces the previous

hot-film mass air flow sensor (MAF) It is located at the

rear of the intake manifold (1) and also helps to increase

engine power by dethrottling the intake section The

inte-grated temperature sensor is used to measure the intake

air temperature

The actual intake air mass is calculated using the signal

from the pressure sensor The air mass is calculated in the

DME control unit using the parameters intake manifold

pressure, intake air temperature, throttle valve position

and engine speed The amount of fuel to be injected is

cal-culated based on this load signal This ensures that the

correct fuel/air mixture is always available in the

combus-tion chambers and any changes in the air pressure (due to

changes in altitude) and outside temperature are

compen-sated

The signals from the pressure sensor, e.g intake manifold

pressure, air mass, intake air temperature, etc., can be

found under the DME actual values

Advantages of the pressure sensor:

– Increased power as a result of dethrottling of the intakesection

– Greater precision with low air-flow rate– Enhanced resistance to soiling– Lightweight design (the pressure sensor replaces twoMAF sensors)

per-1 - Sensor housing

2 - Intake manifold pressure

3 - Pressure sensor chip

4 - Bonded connection

5 - Ceramic substrate

6 - Glass base

Fuel/Ignition Diagnosis & Repair

The sensor element of the micromechanical pressure

sen-sor consists of a silicon chip, in which the pressure

diaphragm has been etched A change in pressure leads

to a dilation in the diaphragm which is detected through

changes in the resistance (piezo-resistive effect) The

eval-uation circuit (including comparison value) is integrated on

the chip

Voltage Characteristic

The figure below shows the voltage characteristic of the

intake manifold pressure sensor as a function of the intake

manifold pressure

The supply voltage of the pressure sensor = 5 volts

P - Intake manifold pressure (absolute pressure in hPa)

V - Signal voltage in volts

Controlling the Air Charge (Electronic Throttle)

The supplied air mass is the decisive factor for the engine

torque output and therefore for engine power That is why

in addition to fuel proportioning, the systems that influence

the cylinder charge are also particularly important The

throttle valve, which is located in the intake duct, controls

the air flow taken in by the engine and therefore the

cylin-der charge

On conventional systems, the throttle valve is mechanicallyoperated An operating cable or linkage transmits themovement of the accelerator pedal to the throttle valve.The variable work angle of the throttle valve influences theopening cross-section of the intake duct and in this waycontrols the air flow taken in by the engine and thereforethe torque output

Electronic Throttle Valve (Electronic Throttle)

With electronic engine power control (electronic throttle),the DME control unit is responsible for activating the throt-tle valve The throttle valve, the throttle valve drive - a DCmotor - and the throttle valve angle sensor are combinedtogether to form the throttle valve control unit The throttlevalve control unit (electronic throttle) is activated bydetecting the position of the accelerator pedal using theaccelerator pedal sensor The opening of the throttle valverequired for the driver request is then calculated by the en-gine control unit taking into consideration the current oper-ating state of the engine and vehicle (engine speed, enginetemperature, PSM, PDK, etc.) and converted into activa-tion signals for the throttle valve drive

If faults are detected in the part of the system that mines performance, the throttle valve immediatelyassumes a defined position (emergency mode) The elec-tronic throttle also enables improved mixture composition,

deter-so that the increasingly stringent requirements ofemissions legislation can be met The electronic throttle isessential in meeting all of the demands that direct fuel in-jection imposes on the overall system

Notes:

Basic Principal of E-Throttle

The most significant change with electronic throttle control

is the priority in the control sequence With E Throttle

when the driver puts his/her foot down, the engine control

• Advances the ignition timing, the amount of torque the

engine produces increases so the vehicle speed

increases

The result is, the vehicle speed increases With E-Throttle

the driver becomes an input to the control system The

driver cannot open the throttle directly, instead initiates a

request that the control unit open the throttle With

E-Throt-tle, the response between the input of the pedal sensor

and the movement of the throttle valve is almost

instanta-neous

There is the possibility of the system overriding the

driver Why and when would this be done?

• When the torque produced would induce unstable

han-dling (wheel spin caused by torque – excessive torque

breaks wheels loose)

• When downshifting while decelerating and too low a

gear is selected – causing the wheels to break loose

The throttle is opened to reduce the engine braking

effect

• When the lateral acceleration is so high that the PSM

cannot maintain vehicle stability if torque rises any

fur-ther

• When the engine is unloaded and high RPMs might

dam-age the engine (Over revving)

In normal operation, the E-Throttle functions like a throttle

cable vehicle (The throttle follows the pedal position)

Inter-vention is only initiated when it is necessary to maintain

vehicle stability or to protect the engine

The E-Throttle system eliminates the idle stabilizer The

E-Throttle system controls idle with the throttle plate The

E-Throttle also eliminates the cruise control servo and

con-trol unit

System Operation

The E-Throttle system consists of three main nents.

compo-• Accelerator Pedal Position Sensor

• Engine Management Control Unit

• Throttle Valve Control Module

When the driver depresses the accelerator pedal:

1 The pedal position sensor potentiometers send a pedalposition signal to the engine management control unit

2 Based on this signal, the control unit determines the desired throttle valve position

3 The control unit sends current to the motor connected

to the throttle plate, and it moves

4 The motor moves the throttle plate until the signalsfrom the throttle plate potentiometers indicate that thedesired throttle valve position has been reached

1 - DME control unit

2 - Pedal value position (sensor)

3 - Monitoring unit for diagnosis

4 - Electronic throttle (actuator)

5 - Other input signals

6 - Other output signals

Throttle Valve Control Module Self Test and Monitor

The E-Throttle system performs a self- test of the throttlevalve control module each time the ignition is switched on,

if the time before the engine is started is longer than 10seconds

The following items are checked:

• Closing spring test

• Opening spring test

• Emergency position test (where the throttle plate parkswhen the electric motor is not energized)

Fuel/Ignition Diagnosis & Repair

An adaptation can also be performed with the tester.

• When the adaptation is performed the engine

manage-ment control unit closes the throttle plate completely to

determine its “mechanical stop”

• It then remembers this position and establishes an

“electrical stop”

• Afterward the throttle is not closed beyond the electrical

stop

• This prevents the throttle from wearing a groove in the

throttle body that the throttle would bind in

There is a wide open throttle electrical stop, however; this

is not set during an adaptation, it is established by the

engine control unit The control unit can find wide open

throttle by monitoring air mass

This is how the engine control unit determines wide

• The throttle has just gone beyond wide open throttle

• The wide open throttle point is just before the air mass

began to fall

Throttle Valve Control Unit

The throttle valve control unit (electronic throttle)essentially consists of the following parts:

• Throttle valve with reset spring

• Drive unit with position sensing, integrated in one ing

hous-• Drive

It is driven by a DC motor that is connected to the throttleshaft via a two-stage drive The position of the throttlevalve is sensed by two potentiometers that are mounteddirectly on the throttle shaft

1 - Housing with throttle valve

2 - Throttle valve drive

3 - Housing cover with electric drive

4 - Position sensing via two potentiometers

Notes:

The graph below shows the voltage range (5) of

poten-tiometers 1 and 2 in the throttle valve control unit from

throttle valve closed (3) to full throttle (4) The voltage of

potentiometer 1 and potentiometer 2 goes in opposite

directions The sum of the two voltages must always be 5

volts

The mechanical operation range is 5 and voltages below 3 or

above 4 are used for fault detection.

1 - Potentiometer 1

2 - Potentiometer 2

3 - Throttle valve closed

4 - Throttle valve open fully

5 - Voltage range

If there is a lack of engine power, the throttle valve actual

value can be used to check whether the throttle valve

opens fully The adjustment range is from 0 - 100%, or

from 0 - 80° (100% and 80°= open fully), depending on

the system If one potentiometer sends an implausible

sig-nal, a substitute value is used, whereby throttle valve

open-ing is delayed (10%/second) and the throttle valve only

opens by max 30%

If both potentiometers send implausible signals,

emer-gency mode is activated As a result, the electronic

throttle servo motor is no longer supplied with power and

spring force keeps it slightly open at the start gap

Throttle Valve Adaptation

The ignition must be switched on for 1 minute and then

switched off again for 10 seconds in order to adapt the

electronic throttle (the accelerator pedal must not be

pressed during this time) There is also a function for

direct adaptation of the electronic throttle under

Maintenance in the newer DME systems

During electronic throttle adaptation, the throttle valve isclosed electrically as far as the mechanical stop after ap-prox 35 seconds and then opened by >10% The mechan-ical stop “Close” is re-taught during this adaptation

Accelerator Pedal Sensor – 911 Carrera/S (997) and

Boxster/S (987)

The new electronic pedal sensor operates without contactand is therefore wear-free The sensors on the printed cir-cuit board (1) are inductively activated by a metal plate,which is moved mechanically behind the printed circuitboard by the pedal The electronic pedal sensor (alsocalled accelerator pedal module) has an accelerator pedal,

a spring-loaded unit for kickdown simulation (only with tronic), a printed circuit board (1) with the electronic pedalsensors 1 and 2 and an electric plug connection

Tip-This picture shows an open pedal sensor.

Important !

The pedal sensor must not be opened

The pedal sensor sends the input signals for the drivertorque request to the DME control unit

Fuel/Ignition Diagnosis & Repair

1 - Potentiometer 1

2 - Potentiometer 2

3 - Throttle valve closed

4 - Throttle valve open fully

5 - Voltage range

The gray area below idle 3 and above full throttle 4 are

shown The voltages in these areas are not possible (they

are mechanically inaccessible) If a voltage in these ranges

is sent to the engine management control unit, a defect in

the pedal position sensor is detected and a fault is

indicated

The graph shows the voltage range (5) of pedal sensors 1

and 2 in the accelerator pedal module from throttle valve

closed (3) to full throttle position (4) The voltage of

poten-tiometer 2 is always 50% of potenpoten-tiometer 1

The supply voltage for the pedal sensors is 5 volts

(poten-tiometer 1), and 2.5 volts (poten(poten-tiometer 2)

Pedal position 1: approx 0.6 V to approx 4.0 V

Pedal position 2: approx 0.3 V to approx 2.0 V

Accelerator pedal module in the Cayenne

Emergency Operation and Monitoring

The accelerator pedal position sensor, and the throttle

valve control module; are continuously monitored by the

engine control unit for electrical defects and plausibility

If a defect is detected, operation in a limited mode will be

initiated Some defects, for example; a total failure of both

potentiometers in the pedal position sensor will render the

vehicle inoperative The same would be true of both

poten-tiometers in the throttle valve control module

The system cannot operate if the position of the

accelera-tor pedal or the throttle plate cannot be determined

3 - Characteristic in Normal mode (green)

4 - Characteristic in Sport mode (violet)

Example of 911 Carrera (997) and Boxster (987)

When the Sport Chrono function is activated, the

accelera-tor-pedal characteristics become more dynamic and the

rev-limiter is adjusted to a hard setting These

adjust-ments, along with other interventions relating to Tiptronic

and Porsche Doppelkupplung (PDK) or PSM, for example,

enable the driver to achieve even faster lap times during

sporty driving

Notes:

Fuel/Ignition Diagnosis & Repair

Subject Page

Timing the Spark 2

Electronic Digital Ignition 3

Fuel/Ignition Diagnosis & Repair

Ignition System

In gasoline engines, the air/fuel mixture is ignited at the

correct ignition point by the ignition system via a spark

between its electrodes which in turn initiates the

combus-tion process

In addition, the electronic systems of today have done

away with the breaker points and control the current flow

in the primary with a transistor These electronic systems

use electronic sensors to detect crankshaft speed and

position Systems without a distributor use a second

sensor on the camshaft to identify which stroke the

crank-shaft is on, this assures that the ignition spark is sent to

the correct cylinder

Timing the Spark

The goal of ignition timing control is to produce effective

pressure (defined as a gas pressure in the combustion

chamber high enough to move the piston) at exactly top

dead center

Because it takes a brief amount of time for the bustion process to produce effective pressure (approx-imately 2 milliseconds which remains invariable as long asthe mixture ratio remains fairly constant), we have to shiftthe ignition point of the mixture forward of top dead center

com-to produce effective pressure at com-top dead center Theamount of change in this shift becomes progressivelylarger as engine speed increases

If we achieve effective pressure before top dead center,the gas pressure will act against the rising piston anddestructive knock will occur If we achieve effectivepressure after top dead center, we lose power and torque.For best output, achieving effective pressure very close totop dead center is very important Take a look at theIgnition angle vs combustion chamber pressure graph,you can see the effect of early and late ignition timing oncombustion chamber pressure

Ignition angle vs combustion chamber pressure graph

1 Ignition (Za) at correct time ––––––

2 Ignition (Zb) too soon (ignition knock)

3 Ignition (Zc) too late

Electronic Digital Ignition

Porsche vehicles use a digital electronic ignition system

With this system, Porsche can create, optimize and store

“electronic maps” with the best ignition point for every

load and speed combination

Graph 1 – This illustration shows a electronically optimized

ignition point map which is used in today's Porsche electronic

digital ignition system.

The map above (Graph 1) shows ignition timing on the

vertical axis, load and engine speed on the horizontal

axis’ So, if we move to the right on the engine speed axis

about half way, and then half way to the left on the load

axis you end up in the middle of the map The amount of

timing advance is the height of the graph at that point The

bottom of the graph, low load and low speed, is idle, the

top corner is highest load and highest speed at wide-open

in relation to system voltage and engine speed creatingthe optimum amount of dwell for each operating condition

Dwell vs Battery Voltage and RPM

Dwell

In a breakerless ignition system, the time during which theelectronic control unit allows current to flow through theprimary winding of the coil

Notes:

Ignition Driver

Task and function

The DME control unit assumes the role of the distributor,

in other words the calculated timing angle (based on

engine speed, engine load and various correction factors)

is forwarded by the processor to the ignition drivers

inte-grated in the control unit or the Ignition coils as a function

of the firing order These ignition drivers switch current to

the ignition coil’s primary windings on and off For a long

time now, multi-stage power transistors (ignition drivers)

have replaced the circuit breakers know as points that

were previously used as a standard in an ignition system

The ignition driver also limits the primary winding current

and voltage Limiting the primary winding current restricts

the energy in the ignition system to a predefined value and

helps control component temperatures Limiting the

primary voltage prevents an excessive increase in the

available high voltage and thus prevents damage to

components

Generation of High Voltage

The DME control unit switches the ignition driver on during

the calculated closing time (dwell angle) The primary

winding current in the ignition coil increases to its nominal

value during this closing time The primary winding current

level and the primary winding inductance value of the

ignition coil determines the energy created in the magnetic

field The ignition driver then interrupts the flow of current

in the primary winding at the ignition point As the

magnetic field of the primary winding collapses it induces

a voltage in the secondary winding of the ignition coil,

ulti-mately initiating the combustion process via the spark

plug In the case of static high-voltage distribution with

individual ignition coils, a diode in the high-voltage circuit

prevents switch-on sparking

1 - Ignition driver (with activation signal)

in directing and building the magnetic field The energycreated in the magnetic field of the primary winding isinduced into the secondary winding as a result of theprimary current being interrupted The amount of energycreated as a result of the magnetic induction principal is afunction of the ratio between the number of windings in theprimary and secondary circuits (turns ratio) Interruptingthe primary winding current at a defined crankshaft angle(timing angle) results in the necessary ignition voltagebeing transferred to the spark plug were a spark isdischarged, resulting in ignition of the air/fuel mixture

Fuel/Ignition Diagnosis & Repair