audi r8 part1 .pdf



Nom original: audi r8 part1.pdf
Titre: audi r8 part1
Auteur: lionel

Ce document au format PDF 1.4 a été généré par PDFCreator 2.0.2.0, et a été envoyé sur fichier-pdf.fr le 12/05/2015 à 21:55, depuis l'adresse IP 82.237.x.x. La présente page de téléchargement du fichier a été vue 763 fois.
Taille du document: 206 Ko (7 pages).
Confidentialité: fichier public


Aperçu du document


Engine Component Damage (UK TPI)(2029773/4)

Page 1 sur 7

Connection offline
Technical product information
Engine Component Damage (UK TPI)

Transaction No.: 2029773/4
Release date: 04-Sep-2012

Customer statement / workshop findings
Poor idle, rough running, knocking noise, lack of power, oil leak, excessive smoke

Technical background
Although areas such as improved fuel consumption and reduced exhaust emissions are at the
forefront of powertrain development, it is also important to any manufacturer to understand the
reasons behind mechanical engine failure. In all cases, external influences must be considered and
where possible, investigated further.
Where warranty claims are made, please ensure that you assist with on-going quality analysis by
attaching clear images of the failure to a DISS quality report (not technical enquiry unless a reporting
obligation is set).
Once the engine is stripped to the point of understanding the failure, please use the guide below to
help understand what might have been the initial reason for the failure. As such, this guide will ensure
that items that caused the failure are considered prior to installing a new unit – possible fuel quality,
non-approved additives or leaking injector etc.
Care should be taken during each stage of the engine disassembly to ensure that the cause of the
failure is not overlooked – incorrect valve timing for example.
Always ensure that relevant TPIs are referred to when considering specific failures. The following
serves purely as a general guide and does not replace targeted TPIs that outline known damage
causes. It is also a non-exhaustive guide that does not cover every eventuality and scenario

Production change
---

Measure
1.0 Ring Land Fractures

Although this type of damage is often dismissed as a mechanical failure caused by the material itself,
in reality, the material is never the cause.
In order to understand why this type of damage has occurred, there are a few indicators that can help

file:///D:/ElsaWin/docs/hs2/A/en-GB/src/2b/714283/master.htm

12/05/2015

Engine Component Damage (UK TPI)(2029773/4)

Page 2 sur 7

with diagnosis.
In the first instance, the shape of the fracture can determine the direction of force. The following
diagrams show the direction in which the ring land moved as a result of excessive pressure from
either above or below. In the first image, as with the example above, it’s clear from the shape that the
piece moved in the downward direction – whereas the second image shows overstressing in the
upward direction (usually during installation).

There are three possible reasons for piston land fractures
1.

Knocking combustion

2.

Hydraulic locks

3.

Installation errors

1.1 Knocking Combustion
This means that the octane rating of the fuel is not capable of covering the entire operational needs of
the engine. In which case, either the compression ratio has increased or the octane rating of the fuel
has decreased. Although the former is more common in the development phase, for service
workshops in the aftersales environment, the likely cause is that the octane rating of the fuel is not
correct (diesel mixed in with the fuel). This is usually confirmed by the fracture being evident on the
pressure side of the piston.

When considering a diesel engine, the only reason for this type of damage is ignition delay.
1.2 Reasons for knocking combustion on petrol engines:


The anti-knock properties of the fuel are not suitable to cover the engine’s octane requirements
across the entire operating range. Therefore, the fuel does not correspond to EN228 standard



Diesel in with the petrol which lowers the octane rating – even a small amount will lower the
octane rating dramatically



Engine oil in the cylinder due to excessive oil consumption



Excessively high compression ratio caused by incorrect head gasket, build-up of carbon on the
piston crown/head or a machined cylinder head in the service workshop



Ignition timing too advanced



Mixture too lean which leads to high combustion temperatures and pre-ignition



Excessively high intake air temperatures caused by poor ventilation or high exhaust backpressure

1.3 Knocking combustion on diesel engines

file:///D:/ElsaWin/docs/hs2/A/en-GB/src/2b/714283/master.htm

12/05/2015

Engine Component Damage (UK TPI)(2029773/4)

Page 3 sur 7



Atomisation of the injectors is not correct or leaking injectors



Injection pressure too low



Compression pressure too low – possibly caused by incorrect head gasket, piston rings etc



Use of starting aids (start sprays)



Use of non-approved fuel additives

1.4 Hydraulic Locks
Hydraulic locks can be caused by fluid entering the combustion chamber. This can be attributed
mainly to one of the points below:


Water from flood damage



Coolant entry due to other external influence (EGR cooler, head gasket, cracked bore etc)



Engine oil – customer may have expressed excessive oil use



Fuel – faulty injector for example

1.5 Installation errors
When the engine builder inserted the piston, they did not compress the rings correctly or knocked the
piston in rather than slid it into place. In this case, the ring land fracture is the opposite shape and
clearly indicates that it has moved in the upwards direction.

2.0 Removal of material from the piston crown and ring zone

In the case of material being removed from the piston crown and down to the piston rings (sometimes
behind the rings), this is caused by glow-ignition within the combustion chamber. Ultimately, parts
within the combustion chamber are glowing hotter than the flash point of the air/fuel ratio. These
components are likely to be the spark plugs, exhaust valve and areas of carbon build up on the piston
crown.
In this situation, it is often found that material has also been removed from the exhaust valve (intake
valve is fine due to the cooling effect of incoming air).

file:///D:/ElsaWin/docs/hs2/A/en-GB/src/2b/714283/master.htm

12/05/2015

Engine Component Damage (UK TPI)(2029773/4)

Page 4 sur 7

2.1 Summary of possible causes – Petrol Engine


The heat range of the spark plugs is too low (check service history and parts fitted)



Mixture too lean which results in higher combustion temperatures



Unsuitable fuel with an octane rating that is too low for the compression ratio (potentially diesel
fuel in the petrol) or not EN228 standard



Non-approved fuel additives used or incorrect levels



Damaged/leaking valves or poor valve clearance



Excessive oil in the combustion chamber caused by valve guide seals or piston rings



High engine or intake air temperatures



Engine overheating due to a fault with the coolant system

2.2 Summary of possible causes – Diesel Engine


Fuel does not conform to EN590 standard



Use of non-approved fuel additives



Damaged/leaking valves or poor valve clearance



Atomisation of the fuel incorrect



Excessive oil in the combustion chamber caused by valve guide seals or piston rings



High engine or intake air temperatures



Engine overheating due to a fault with the coolant system

It is also possible to see signs of glow ignition in the centre of the piston crown.

3.0 Impact damage to the piston crown and cylinder head area

file:///D:/ElsaWin/docs/hs2/A/en-GB/src/2b/714283/master.htm

12/05/2015

Engine Component Damage (UK TPI)(2029773/4)

Page 5 sur 7

In the case of impact marks on the piston crown and cylinder head, it’s important to check the vehicle
history and observe areas of the intake system that may have had parts dislodged (turbo/EGR/throttle
valve etc).
In some cases, it’s found that there is material washout around the ring groove area. This is a result
of debris becoming lodged in the ring groove which causes abrasion to the area surrounding the
piston ring.

3.1 Possible causes


New engine fitted but parts of damaged engine not cleaned out of the intake/exhaust system



Parts of the intake system have broken off and entered the combustion chamber
(turbo/EGR/throttle valve etc)



Parts within the combustion chamber broken off (glowplug/spark plug/injector)



Incorrect valve timing



Incorrect valve clearance (wrong cylinder head gasket or excessive piston protrusion)



Engine over-revved (valves no longer close in time and impact on the piston crown)



Excessive clearances in the conrod bearings leading to excessive piston protrusion

4.0 Erosion of material from the top of the piston land and crown

The top of the piston land and crown show evidence of material being carried away in an erosion type

file:///D:/ElsaWin/docs/hs2/A/en-GB/src/2b/714283/master.htm

12/05/2015

Engine Component Damage (UK TPI)(2029773/4)

Page 6 sur 7

process. No other damage or signs of seizure marks are evident on the piston.
The reason for this type of material erosion is caused by extended time periods of knocking
combustion. Pressure waves are generated during the knocking which spread across the combustion
chamber and down to the first compression ring. At the reversal point of the pressure wave, small
parts of the material are removed through kinetic energy. The small parts of the eroded material could
potentially cause glow-ignition which accelerates the process.
4.1 Possible causes


Use of fuel with inadequate knock values – octane rating too low or fuel does not conform to
EN228



Diesel in the fuel which lowers the octane rating



Diesel fuel does not conform to EN590 standard



Excessive amounts of oil in the combustion chamber (worn piston rings etc)



Compression ratio too high (large carbon build up, incorrectly machined cylinder head)



Ignition timing too advanced



Mixture too lean which causes very high combustion temperatures (consider injectors/fuel
pressure etc)



Intake air temperature too high – possible exhaust back pressure or poor ventilation of intake
air

5.0 Erosion and build-up of sulphur within the combustion chamber

The customer’s complaint could be ‘reduced power’ or ‘poor running’. When removing the cylinder
head or checking with a bore scope, a large amount or discolouration is noted and often sulphur build
up is evident.
5.1 Possible causes


Using fuel that does not conform to EN228 standard (Petrol)



Using fuel that does not conform to EN590 standard (Diesel)



Using fuel with high levels of ethanol/biomass blends



Using non-approved fuel additives

Always consult the owner’s manual for guidance about fuel additives and types of ethanol/biomass
blends suitable for use in the vehicle.

file:///D:/ElsaWin/docs/hs2/A/en-GB/src/2b/714283/master.htm

12/05/2015

Engine Component Damage (UK TPI)(2029773/4)

Page 7 sur 7

If you suspect that the fuel is the cause of the engine damage, it is the responsibility of the authorised
repairer to investigate this further. Fuel analysis suppliers operate regionally and should be utilised
where necessary.
Note: Volkswagen Group would always advise that fuel chemical analysis is used as a last resort. In
the first instance, always use your own ability through smell/appearance to make a judgement. Where
necessary, address your suspicion with the customer and ask that fuel receipts are inspected.
Special tool VAS 6774 can also be used for analysis of the diesel fuel. However, this tool does not
replace laboratory testing. Please contact tools.equipment@vwg.co.uk for questions about this
special tool.

Warranty accounting instructions
Claims where the failure is not caused by a manufacturing defect will be debited. This includes repeat
failures as a result of not considering the advice within this TPI.
Do not refer to this TPI when considering a warranty claim – this is a workshop guide only.

Parts information
Refer to ETKA

Customer information
---

file:///D:/ElsaWin/docs/hs2/A/en-GB/src/2b/714283/master.htm

12/05/2015




Télécharger le fichier (PDF)

audi r8 part1.pdf (PDF, 206 Ko)

Télécharger
Formats alternatifs: ZIP







Documents similaires


audi r8 part1
audi r8 part2
ssp 87 1
moteur diesel
cryotechnic2
akrapovic slip on exhaust aprilia shiver75020082009

Sur le même sujet..