# VAG 1.8T Engines: Charge Air System and Fault Diagnosis FAQ



## Guest

*1. Introduction*
This document brings together selected information from the VAG electronic parts catalogue, VAG workshop manual, Audi Self-study Programmes, the Ross-Tech Wiki and TT Forum FAQs on the charge air system of BAM & BFV 1.8T engine variants to aid in general understanding and in diagnosing possible causes of leaks. Part numbers will be similar for other engine variants (APX, AUM, AUQ, ARY, BVP, BVR). N.b. only APX engines are equipped with secondary air system. I've researched this for my own interest but I thought it would be useful to post up a FAQ for the benefit of TT Forum members because the key information is more often than not distributed about and part numbers are sometimes frustratingly difficult to pin down.

*Figure 1. Diagram of connections for charge pressure control system and vacuum control system.*








2. Activated charcoal filter (ACF) 8N0 201 805 A
3. Non-return valve for ACF 058 905 291 K
4. Exhaust gas turbocharger 06A 145 704 Q
5. Vacuum unit for charge pressure control (actuator)
6. Mechanical dump valve 06A 145 710 N
9. Solenoid valve for charge pressure control N75 058 906 283 F (ETKA illustrations 145-77 & 145-50). Superseded with 06A 906 283 E in July 2010.
10. Air mass meter (MAF sensor) G70 06A 906 461 M
11. Air cleaner 8L9 133 837 E
12. Crankcase breather pressure regulating valve 06A 129 101 D. Connecting hose 06A 103 817 D
13. Vacuum reservoir 06A 131 541
14. Charge air cooler CAC (left) 8L9 145 805 H
15. 3 barg fuel pressure regulator 037 133 035 C
16. Throttle valve control part J338 06A 133 062 BD
17. Intake manifold with IAT sender G42 06A 133 201 CD
18. Crankcase breather. Breather hose 06A 103 213 AK
19. Non-return valve 058 905 291 A
20. Solenoid air divert valve for turbocharger N249 078 906 283 A (ETKA illustration 133-35)
21. Non-return valve 058 905 291 K
22. Charge air cooler CAC (right) 8L9 145 806 B

*Figure 2. Charge air cooling system part 1*








1. Pressure hose (right upper; connects pressure pipe 5 to CAC) 8L9 145 708 G
5. Charge pipe 06A 145 731 M
10. Pressure hose (connects turbocharger to pressure pipe 5) 06A 145 832 L
11. Exhaust gas turbocharger 06A 145 704 Q
12. Breather hose 06A 103 213 AK (connects to crankcase breather, 13). Breather hose 06A 103 221 BG (connects to cylinder head & pressure regulating valve, 13)
13. Crankcase breather pressure regulating valve 06A 129 101 D. Connecting hose 06A 103 817 D (connects to air intake duct, 15)
14. Vacuum unit for charge pressure control (actuator)
15. Intake air duct 06A 133 356 R
17. Hose(s) from air divert valve for turbocharger N249 06A 133 773 E & G
18. Mechanical dump valve 06A 145 710 N
20. Solenoid valve for charge pressure control N75 058 906 283 F (ETKA illustration 145-77)

*Figure 3. Charge air cooling system part 2*








1. Pressure hose (right lower) 8N0 145 856
3. Charge air cooler (right) 8L9 145 806 B
15. Pressure hose to intake manifold (left upper) 8L9 145 790 B
18. Charge pressure/thrust sender G31 038 906 051 D
19. Pressure pipe (between left CAC and left upper pressure hose 15 to intake manifold) 8L9 145 937 A
20. Pressure hose (left upper; connects left CAC to pressure pipe 19) 8L9 145 845
23. Charge air cooler (left) 8L9 145 805 H
28. Connecting pipe/cross tube 8N0 199 521F (connects left CAC to right CAC via pipe 1 and left lower pressure hose 8N0 145 838 A)
--. Left lower pressure hose 8N0 145 838 A (unlabelled)

*2. Function of Major Components*
_2.1. Charge pressure control_
The solenoid valve for charge pressure control N75 (058 906 283 F on ETKA illustrations 145-77 & 145-50 superseded with 06A 906 283 E in July 2010.) regulates the boost pressure via the turbocharger wastegate by changing the opening time to atmospheric pressure according to the signals it receives from the engine control unit.

















This is known as the duty cycle. To achieve this it produces a control pressure by modulating the charge pressure and atmospheric pressure. This pressure acts on the pressure unit for the waste gate. The waste gate is kept closed in a depressurised state by a spring inside the pressure unit. The entire exhaust gas flow is routed via the turbine, and a charge pressure is built up.

The control pressure counteracts this spring force and opens the waste gate. Part of the exhaust gas flow is fed from the waste gate past the turbine, and the charge pressure stops rising. If there is no flow, the N75 valve is closed and the charge pressure acts directly on the pressure unit. The waste gate opens even if the charge pressure is low. If the charge pressure control fails, the charge pressure is thus limited to a basic charge pressure in order to prevent the maximum permissible charge pressure being exceeded. This results in a loss of performance. The basic charge pressure (approx. 300 - 400 mbar) is that which is achieved without regulation (mechanical charge pressure).

_2.2. Divert air control in overrun_
The solenoid divert air valve for the turbocharger (N249, 078 906 283 A, ETKA illustration 133-35) works in conjunction with the mechanical divert or dump valve (06A 145 710 N, ETKA illustration 145-77, itself often replaced by the Forge 007p aftermarket unit) to reduce air pressure in the turbocharger when the throttle is closed during gear changes and thus reduce the phenomenon of 'turbo lag'. To avoid pumping the exhaust gas turbocharger when a sudden transition from high load to overrun is made, a mechanical dump valve is activated by means of an electrically-actuated (solenoid) changeover valve, the divert air valve for the turbocharger, N249 (078 906 283 A). The N249 valve has connections to the vacuum unit and the intake air unit and simply diverts either ambient air pressure or a vacuum to the spring-loaded mechanical dump valve to actuate it open or closed. This dumps the pressurised charge air back to the intake on the overrun.
























2.2.1. Precautions and limitations
The N249 valve can be removed or bypassed to make the charge pressure dump process fully mechanical and thus eliminate any unwanted control action from the Motronic control unit.

However, controlled opening of the dump valve reduces the noise level in the induction tract and reduces fuel consumption. Additionally, SSP 337 states that electric overrun air recirculation control is much more durable than pneumatic control.
A fault with this sub-system is more likely to be as a result of an air leak or mechanical fault, not a faulty solenoid valve. Care should therefore be taken when interpreting the fault codes from VAG-COM such as 17608 because a fault with the mechanical dump valve is still reported against the N249. Note also that the part numbers for the N75 and N249 valves are very similar, are both described as a "solenoid change-over valve" in ETKA, and are only referred to by the alphanumeric designations in the workshop manual and Self-Study Programmes. Asking a parts supplier for an N75 or N249 valve would most likely result in confusion so the part number should always be quoted as this will be specific to the engine variant. A franchised dealer will be able to query the specific part number from a unique vehicle identifier such as your registration plate or VIN.

2.2.2. Relocation of the mechanical dump valve 06A 145 710 N or Forge 007p
Forge Motorsport offer an aftermarket kit to allow owners to relocate their mechanical dump valve so that it diverts intercooled compressed air back to the intake pipe rather than hot compressed air.

http://www.forgemotorsport.co.uk/conten ... FM225DVRLK

The purported benefits of this are increased longevity of the DV itself and a denser air charge being fed back into the intake. The magnitude of the power increase is not known but is expected to be marginal since the total volume of transiently dumped charge air will be small compared to the normal bulk air flow and it is dumped 'off load' in any case. Presumably, the original manufacturer's set-up was chosen to minimise the hose length between the charge pipe and the intake pipe.

_2.3. Activated Charcoal Filter (ACF) system_
The solenoid valve for the activated charcoal canister regulates the fuel vapour feed rate to the engine via the vacuum.

_2.4. Crankcase breather_
The crankcase breather controls the return of oil vapours to the engine. The crankcase breather comprises a distributor piece, a pressure limiting valve, a non-return valve and the associated hoses. The oil vapours and blow-by gases from the cylinder head and the crankcase converge in the distributor piece. The pressure limiting valve and the non-return valve control the return of these vapours and gases to the engine, depending on the intake manifold pressure:

(a) Intake manifold under vacuum:
The oil vapours and blow-by gases return via the non-return valve in the intake manifold.
(b) Intake manifold at charge pressure:
The oil vapours and blow-by gases return via the pressure limiting valve in the air distributor.

The pressure limiting valve limits the vacuum in the crankcase. If the vacuum in the crankcase exceeds a defined value, the diaphragm is drawn over the connection against the force of the spring and closes the connection. The valve is designed in such a way that it allows a small quantity to pass through when closed. This prevents the engine oil being drawn into the intake tract and has no adverse effects on engine breathing.

Part 2 continued in next post due to 15,000 character limit...


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## Guest

*3. Charge Air System Specific OBD Fault Codes*
The following notes are based on information in the Ross Tech wiki (wiki.ross-tech.com/wiki) supplemented with information from the workshop manual.

16618, P0234 Boost Pressure Regulation: Limit Exceeded (Overboost Condition)
_Possible Symptoms_
Boost pressure too high
Reduced power output
_Possible Causes_
Hoses incorrectly connected, disconnected, blocked or leaking
Malfunctioning solenoid valve for boost pressure control N75 (058 906 283 F)
_Possible Solutions_
Check charge pressure control (command versus actual boost)
Check N75 duty cycle and commanded and delivered boost profiles are normal.
Check for open/short circuit on, physical activation of, voltage supply to/electrical activation of, and internal resistance of N75 valve as specified in workshop manual

16619, P0235 Turbocharger Boost Sensor (A) Control Limit Not Reached
_Possible Symptoms_
Reduced power output
Limp mode
_Possible Causes_
Hoses incorrectly connected, disconnected, blocked or leaking
Defective solenoid valve for boost pressure control N75 (058 906 283 F)
Turbocharger defective
_Possible Solutions_
Check physical integrity and security of connecting hoses
Check charge pressure control (command vs actual boost)
Check N75 duty cycle and commanded and delivered boost profiles are normal.
Check for open/short circuit on, physical activation of, voltage supply to/electrical activation of, and internal resistance of N75 valve as specified in workshop manual
Check physical integrity of the turbocharger (turbine rotor, seals, etc.). Renew turbocharger if defects are found

16620, P0236 Turbocharger Boost Sensor (A) Range/Performance
16621, P0237 Turbocharger Boost Sensor (A) Circ Low Input
16622, P0238 Turbocharger Boost Sensor (A) Circ High Input
_Possible Symptoms_
Engine management system dashpod lamp active.
_Possible Causes_
Check charge pressure sender/thrust sensor G31 (038 906 051 D) voltage supply faulty, open circuit, short to earth
_Possible Solutions_
Check charge pressure sender/thrust sensor G31 (038 906 051 D) voltage supply, open circuit, short to earth and idle/open throttle voltage signals as specified in the workshop manual.

16627, P0243 Turbocharger Wastegate Solenoid (A) Open/Short Circuit to Ground
16629, P0245 Turbocharger Wastegate Solenoid (A) Low Input/Short to ground
16630, P0246 Turbocharger Wastegate Solenoid (A) High Input/Short to B+
_Possible Symptoms_
Reduced power output because only basic (mechanical) charge pressure (approx. 300 - 400 mbar) is available
_Possible Causes_
Fuse(s) defective
Engine Motronic current supply relay (J271)
Malfunctioning or defective solenoid valve for boost pressure control N75 (058 906 283 F)
Wiring/connectors from/to solenoid valve for boost pressure control N75 faulty
_Possible Solutions_
Check fuse(s) No. 10 in fusebox & No. 4 (S134, 110 A) in main fuse box/battery
Check Motronic current supply relay (J271)
Check wiring/connectors from/to solenoid valve for boost pressure control N75
Check charge pressure control (command versus actual boost)
Check N75 duty cycle and commanded and delivered boost profiles are normal.
Check for open/short circuit on, physical activation of, voltage supply to/electrical activation of, and internal resistance of N75 valve as specified in workshop manual

17608, P1200 Boost Pressure Control Valve (N249): Mechanical Malfunction
_Possible Symptoms_
Engine management system dashpod light on
Reduced power output
_Possible Causes_
Mechanical dump valve (06A 145 710 N) defective
Connecting hoses incorrectly connected, disconnected, blocked or leaking
Solenoid divert air valve for the turbocharger (N249, 078 906 283 A) defective
_Possible Solutions_
Check/replace mechanical dump valve (06A 145 710 N)
Check physical integrity and security of connecting hoses
Check for open/short circuit on, physical activation of, voltage supply to/electrical activation of, and internal resistance of N249 valve (078 906 283 A) as specified in workshop manual. Renew if defective

17695, P1287 Turbocharger bypass valve (waste gate) open
17696, P1288 Turbocharger bypass valve (waste gate) short to B+
17697, P1289 Turbocharger bypass valve (waste gate) short to ground
_Possible Symptoms_
Reduced power output because no boost pressure is available.
_Possible Causes_
Electrical or mechanical fault with turbocharger bypass valve.
_Possible Solutions_
Renew turbocharger unit.

17705, P1297 Pressure drop between turbocharger and throttle valve
_Possible Symptoms_
Engine management system dashpod light on
Sound of escaping air when accelerating
Reduced power output
_Possible Causes_
Connecting hoses incorrectly connected, disconnected, blocked or leaking
Mechanical dump valve (06A 145 710 N) defective
Solenoid divert air valve for the turbocharger (N249, 078 906 283 A) defective
Throttle body dirty
_Possible Solutions_
Check/replace mechanical dump valve (06A 145 710 N)
Check physical integrity and security of connecting hoses
Check for open/short circuit on, physical activation of, voltage supply to/electrical activation of, and internal resistance of N249 valve (078 906 283 A) as specified in workshop manual. Renew if defective
Check/clean throttle body; perform throttle body alignment

17954, P1546 Boost Pressure Control Valve (N75) Short to B+
17955, P1547 Boost Pressure Control Valve (N75) Short to Ground
17956, P1548 Boost Pressure Control Valve (N75) Open
17957, P1549 Boost Pressure Control Valve (N75) Short to Ground
_Possible Symptoms_
Irregular behaviour (power surging)
Reduced power output
Limp mode
_Possible Causes_
Wiring/connectors from/to solenoid valve for boost pressure control N75 faulty
Defective solenoid valve for boost pressure control N75 (058 906 283 F)
_Possible Solutions_
Check wiring/connectors from/to solenoid valve for boost pressure control N75
Check charge pressure control (command versus actual boost)
Check N75 duty cycle and commanded and delivered boost profiles are normal.
Check for open/short circuit on, physical activation of, voltage supply to/electrical activation of, and internal resistance of N75 valve as specified in workshop manual

17958, P1550 Charge Pressure Deviation
_Possible Symptoms_
Irregular behaviour (power surging)
Sound of escaping air when accelerating
Reduced power output
Limp mode
_Possible Causes_
Hoses incorrectly connected, disconnected, blocked or leaking
Defective solenoid valve for boost pressure control N75 (058 906 283 F)
Turbocharger defective
_Possible Solutions_
Check physical integrity and security of connecting hoses
Check charge pressure control (command versus actual boost)
Check N75 duty cycle and commanded and delivered boost profiles are normal.
Check for open/short circuit on, physical activation of, voltage supply to/electrical activation of, and internal resistance of N75 valve as specified in workshop manual
Check physical integrity of the turbocharger (turbine rotor, seals, etc.). Renew turbocharger if defects are found

17963, P1555 Charge Pressure Upper Limit exceeded
17964, P1556 Charge Pressure Control Negative Deviation
17965, P1557 Charge Pressure Control Positive Deviation
_Possible Symptoms_
Reduced power output
Limp mode
_Possible Causes_
Boost pressure too high/low
Connecting hoses incorrectly connected, disconnected, blocked or leaking
Defective solenoid valve for boost pressure control N75 (058 906 283 F)
_Possible Solutions_
Check physical integrity and security of connecting hoses
Check charge pressure control (command versus actual boost)
Check N75 duty cycle and commanded and delivered boost profiles are normal.
Check for open/short circuit on, physical activation of, voltage supply to/electrical activation of, and internal resistance of N75 valve as specified in workshop manual

*4. Workshop Manual Symptom-Based Diagnosis for Boost Leaks*

Symptom A: Loss of power, or jerking when the throttle is opened and closed
Root cause A: One or more leaks downstream of air mass meter (n.b. will not show on Liquid TT gauge because power and torque are calculated from air mass flow which will be metered correctly if leak(s) is/are downstream. If intake air flow is being metered correctly but is then lost downstream through a leak, the fuel/air mixture will be too rich in fuel (low actual lambda).
Possible defective components (check security of all joints between connecting components):
A1. Hose (06A 133 356 R, ETKA illustration 129-15) connecting air mass meter to turbocharger
A2. Hoses (8L9 145 718F & 06A 133 382 K) connecting solenoid valve for charge pressure control N75 to wastegate via joint pipe
A3. Pressure control lines for vehicles with ESP (8L9 145 743 A) connecting the solenoid valve for charge pressure control N75 and the mechanical dump valve to pressure pipe 06A 145 731 M
A4. Connection hoses (06A 103 221 BG, 06A 103 213 AK) to crankcase breather
A5. Connection hose (N 103 035 04 ETKA illustration 201-94 part 21?) to active charcoal filter

Symptom B: Insufficient charge pressure
Root cause B: One or more leaks downstream of turbocharger (intake side)
Possible defective components (check security of all joints between connecting components):
B1. Rubber connecting hoses and pipes (06A 145 132 L, 8L9 145 708 G) between turbocharger and charge air coolers
B2. Hose (8L9 145 790 B) between charge air cooler and intake manifold
B3. Charge air cooler(s) (8L9 145 806 B and/or 8L9 145 805 H)
B4. Round seal/gasket (N 905 638 01) for thrust sensor G31 (038 906 051 D) in pressure hose (8L9 145 937A)
B5. Gasket (028 129 748) between throttle valve control part (06A 133 062 BD) and intake manifold
B6. Gasket (058 129 717 D) between intake manifold and cylinder head

Symptom C: Insufficient charge pressure, exhaust smell, soot deposits in engine compartment
Root cause C: One or more leaks downstream of turbocharger (exhaust side)
Possible components that might be defective (ETKA illustration 253-20):
C1. Joint/gasket (06A 253 039 H) between turbocharger and exhaust manifold
C2. Joint/gasket (058 253 039 L) between exhaust manifold and cylinder head

*5. How to Check For Charge Pressure Leaks*
A simple guide is available at http://www.turboboostleaktesters.com which also sells boost leak testing kits and at http://www.********.co.uk How To section courtesy of Tony Rigby. A summary is included here for completeness.

Remove the air cleaner to expose the air intake pipe ands securely attach the tester to the air intake pipe, marked with a yellow arrow in the top right of the picture.










To avoid pressurising the engine block during the test, isolate the charge air pipework from the block as follows:

1. Clamp or remove connecting hose 06A 103 817 D that connects the crankcase breather pressure regulating valve 06A 129 101 D to the air intake duct 06A 133 356 R and insert and securely attach a suitable bung in the exposed access hole in the air intake duct as illustrated in Tony Rigby's FAQ.

2a. Remove pressure hose to intake manifold (left upper) 8L9 145 790 B (marked with a red arrow in the bottom of the picture) and insert and securely attach a suitable bung to it. Or...

2b. Alternatively, if you wish to leave the hose attached to the inlet manifold, then remove the oil filler cap to relieve crankcase pressure. When the system is pressurised and the engine has no lubrication, some compressed air will pass into the throttle body, the intake manifold and down the piston rings to the crankcase. From here, it will pass up the valve guides into the area under the valve cover. Removing the oil cap relieves this pressure and helps keep the crank/camshaft oil seals in place.

[It looks like there is still a path to the intake manifold via the mechanical dump valve 06A 145 710 N and non-return valve 058 905 291 A (if passing) or through the N249 valve so a further bung might be required.] When the system is pressurised, all joints and hoses between the marked points can still be properly tested for leaks.

Start by applying a low pressure (e.g. 5 psi), listen for boost leaks and check to see whether the applied pressure is maintained. Increase the applied pressure in 5 psi increments up to the maximum commanded boost level attained on your vehicle.

A couple of videos demonstrating this technique (worth skipping to 4m 00s in the second one):










*6. Product Recommendations*
Mikalor Supra Heavy Duty stainless steel hose clamps are suitable for high pressure applications and are widely available, including eBay, but expensive. They are wider than standard jubilee clips too so might not fit in the recessed end channels of the OEM hoses.

_Product Specifications_
http://mikalor.it/english/pdfs/alta2.pdf
http://mikalor.it/english/pdfs/alta3.pdf
http://mikalor.it/english/pdfs/alta4.pdf

_Technical information_
http://mikalor.it/english/pdfs/polar7.pdf

An alternative:

http://www.irrigationuk.com/hose-clips- ... _1529.html

_BAM & BFV Engines' Charge Air System Hose End Diameters & Clamp Quantities_

Mass air flow housing (80 mm, 1 off)
Intake pipe (85 mm, 1 off)
Hoses connecting the mechanical dump valve (35 mm, 1 off) & (32 mm, 1 off)
Pressure hoses between turbo & intake manifold: (72 mm, 4 off) & (67 mm, 8 off)
N75 valve hoses (14 mm, 2 off)
Hose (06A 103 817 D) connecting the crankcase breather pressure regulating valve to intake pipe (28 mm, 2 off)
Hose (06A 103 221 BC) connecting the crankcase breather pressure regulating valve to cylinder head (28 mm, 2 off)
N249 Valve clamps (14 mm, 4 off)
Pipework associated with N249 valve (12 mm, 4 off)
Non-return valve clamp. (8 mm, 1 off)

*7. Acknowledgements*
1. Tony Rigby for reviewing the first draft without savaging it and for helpful advice and suggestions.
2. The TT Forum community for getting me interested in the first place.

Revisions List
Rev. 0. Saturday, 11th December 2010.
Rev. 1. Tuesday, 14th December 2010. Tony Rigby's comments included. Deleted reference to N249 "allowing Motronic to intervene in the event of an overboost fault condition." Added product recommendations as new section.

Doug Short
PM me with any suggestions for improvement or further information you would like to see and I'll update as necessary. A link to the FAQ in Microsoft Word 2003 format is in another post below:


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## TT51

Very good indeed Doug and as I have suffered a faulty N75 in the past which I did eventually diagnose after some trial and error (but originally thought it was the DV) and when I asked Audi for a new 'N75' was presented with the N249, I would have found this write up very very useful indeed.

Neil


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## Grahamstt

Not much to do at work at the moment eh Doug :lol: 
No seriously tho an excellent write up

Graham


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## Guest

Thanks guys. Just hope it's not too late in the day to be of assistance to new owners. I learned summat anyway.

Aye well, we were away in the Lakes for a week and were unable to venture far due to the weather so there was plenty of opportunity then. I'd rather dig into some sort of technical manual than a good novel. 

Doug

This must have been posted elsewhere, but I found an archive of hundreds of VAG Self Study Programs (SSP) here:

http://hotfile.com/dl/84605314/063c53b/ ... k.z01.html
http://hotfile.com/dl/84603628/315b685/ ... k.zip.html

You need to download both files as it's a split ZIP file. I used WinRAR to extract the archive. There's some fabulous technical reading in there covering the stuff listed below. Once you've deleted all the duplicates it's down to 397 Mb. I've highlighted ones that might be of interest to the TT Forum community in bold. Also the Volkspage site:

http://www.volkspage.net/technik/ssp/index_eng.php/

has the PDF files individually listed but I did find a few errors and dead links (typically, the one I was looking for (SSP 305) on the 2.5 TDi 5 cylinder engine! Also, most of the SSPs before 200 are in German and are just scans of a printed document. If you're struggling to find any, I have all the ones listed below extracted from the zip file so if you want them, just PM me your e-mail address.

Bosch CAN Specification 2.0 (1991).pdf
Cambelt Change Intervals - Diesel Engines.pdf
Cambelt Change Intervals - Petrol Engines.pdf
Controller Area Network (CAN) A Serial Bus System - Not Just For Vehicles.pdf
ElsaWin 3.2 Self Study Course.pdf
Service Intervals from Model Year 1986 to Model Year 2005.pdf
*SSP 175 OBD II.pdf*
*SSP 186 CAN-Bus.pdf*
SSP 190 Adjustable Turbocharger.pdf
SSP 195 2.3 V5 Engine.pdf
SSP 196 1.4 ltr 16v 55Kw Engine with Roller-Type Cam follower Design & Function.pdf
SSP 198 2.7 litre V6 Biturbo Design & Function.pdf
SSP 199 Radio Navigation System Design & Function.pdf
SSP 200 Part 1 Golf 1998 Construction and Operation.pdf
SSP 200 Part 2 Golf 1998 Construction and Operation.pdf
SSP 200 Part 3 Golf 1998 Construction and Operation.pdf
SSP 201 Lupo Design & Function.pdf
SSP 202 Vehicle Diagnostic, Testing and Information System VAS 5051 Design and Functions.pdf
SSP 203 The 1.0-ltr. 37 kW petrol engine with Camshaft in Block Design & Function.pdf
*SSP 204 ESP Electronic Stability Programme Design & Function.pdf*
SSP 205 6-Speed Manual Gearbox 02M.pdf
*SSP 206 Four-Wheel Drive with Haldex Coupling.pdf*
*SSP 207 Audi TT 8N Coupe Design & Function.pdf*
*SSP 208 Part 1 Air Conditioner in the Motor Vehicle.pdf*
*SSP 208 Part 2 Air Conditioner in the Motor Vehicle.pdf*
SSP 209 1.9-ltr. TDI Engine with Pump Injection System.pdf
SSP 210 Electronic Power Control.pdf
SSP 211 Part 1 New Beetle Design & Function.pdf
SSP 211 Part 2 New Beetle Design & Function.pdf
SSP 211 Part 3 New Beetle Design & Function.pdf
SSP 212 Variable Intake Manifold in VR Engines Principles & Description of Operation.pdf
*SSP 213 New Technology 1999 Design & Function.pdf*
SSP 218 Lupo 3L Design & Function.pdf
*SSP 220 Audi TT 8N Roadster Design & Function*
SSP 221 Electronic Manual Gearbox Design & Function.pdf
SSP 222 Electronicall Mapped Cooling System Design & Function.pdf
SSP 223 1.2 & 1.4l TDI Engines with Pump Injection System Design & Function.pdf
*SSP 224 Service Interval Extention - Basics for LongLife Service.pdf*
SSP 225 Electro-mechanical Power Steering Design & Function.pdf
SSP 228 Variable Automatic Gearbox Multitronic 01J Design & Function.pdf
*SSP 230 Motor Vehicle Exhaust Emissions Composition, Emission Control, Standards, etc. - Basics.pdf*
SSP 231 Euro On-Board Diagnostic System for Petrol Engines Design & Function.pdf
SSP 232 5-Speed Automatic Gearbox 09A-09B Design & Function.pdf
SSP 233 2.0-Litre Engine Design & Function.pdf
SSP 235 Part 1 Multi Function Wheel Design & Function.pdf
SSP 235 Part 2 Multi Function Wheel Design & Function.pdf
SSP 237 Manual Gearbox 02T.pdf
*SSP 238 Data exchange on the CAN Bus 1 - Basics.pdf*
SSP 239 Audi A2 - Body Construction & Function.pdf
SSP 240 Audi A2 Technology Design & Function.pdf
SSP 241 Audi Allroad Quattro with Additional Shift Stage Design & Function.pdf
SSP 242 Pneumatic suspension system Part 1 - Selflevelling suspension in the Audi A6 Design and Function.pdf
SSP 243 Pneumatic suspension system Part 2 - 4-level air suspension in the Audi Allroad Quattro Design and function.pdf
SSP 246 Variable Valve Timing with Fluted Variator Design and Function.pdf
SSP 247 Audi A2 Engine & Gearbox Design & Function.pdf
SSP 248 The W Engine Concept Design & Function.pdf
SSP 249 Engine Management of the W8 Engine in the Passat Motronic ME 7.1.1.pdf
SSP 250 Engine Management for the Phaeton W12 Engine Design & Function.pdf
SSP 251 Passat Model Year 2001.pdf
SSP 252 1.4 l 77 kW Engine with Petrol Direct Injection System in the Lupo FSI Design and Function.pdf
SSP 253 Direct Petrol Injection System with Bosch Motronic MED 7 Design and Function.pdf
SSP 254 Audi A4'01 Technical Features Design & Function.pdf
SSP 255 The 2.0l R4 & 3.0l V6 engines.pdf
SSP 256 VAS 5052 Design & Function.pdf
*SSP 257 Electric Vacuum Pump for Brake Servo Unit Design & Function.pdf*
SSP 259 EPHS - Electrically Powered Hydraulic Steering Design and Function.pdf
SSP 260 1.2 ltr. 3-cylinder petrol engines Design and Function.pdf
SSP 261 Passat W8.pdf
SSP 263 Polo Model Year 2002.pdf
*SSP 264 Brake Assist System Design & Function.pdf*
SSP 265 Vehicle electrics in Polo Model Year 2002.pdf
SSP 268 6.0 l W12 engine in the Audi A8 part 2.pdf
*SSP 269 Drivetrain CAN Data Bus Convenience & Infotainment CAN Data Bus.pdf*
SSP 270 Phaeton.pdf
SSP 271 Phaeton Heating and Air Conditioning System Design & Function.pdf
SSP 272 Phaeton Onboard Power Supply.pdf
SSP 273 Phaeton Convenience and Safety Electronics Design & Function.pdf
SSP 274 Phaeton Infotainment System Design & Function.pdf
SSP 275 Phaeton Air Suspension with Controlled Damping Design & Function.pdf
SSP 276 Phaeton Proximity Control (APC) Design & Function.pdf
SSP 277 Phaeton Chassis Design & Function.pdf
SSP 278 Audi A4 Cabriolet Design & Operation.pdf
SSP 279 2.0L 110kW engine with petrol direct injection FSI.pdf
SSP 280 Part 1 Phaeton Auxiliary Heater Thermo TOP C and Supplementary Heater Thermo TOP Z Design & Function.pdf
SSP 280 Part 2 Phaeton Auxiliary Heater Thermo TOP C and Supplementary Heater Thermo TOP Z Design & Function.pdf
SSP 281 New Beetle Cabriolet.pdf
SSP 282 Audi A8-03 Technical Features.pdf
SSP 286 New Data Bus Systems LIN,MOST,Bluetooth.pdf
SSP 291 6-speed Automatic Gearbox 09G Part 1.pdf
SSP 291 6-speed Automatic Gearbox 09G Part 2.pdf
SSP 292 Adaptive Air Suspension in the Audi A8.pdf
SSP 294 VAS 5051 On Line Link.pdf
*SSP 295 Part 1 Diagnosis with VAS 5051, VAS 5052 and VAS 5053 Procedures & Function.pdf*
*SSP 295 Part 2 Diagnosis with VAS 5051, VAS 5052 and VAS 5053 Procedures & Function.pdf*
SSP 296 1.4 & 1.6l FSI Engines with Timing Chain.pdf
SSP 297 Touareg.pdf
SSP 298 Touareg Electrical System Design & Function.pdf
SSP 299 6-Speed Manual Gearbox 08D Design and Function.pdf
SSP 300 Part 1 6-Speed Automatic Transmission 09D.pdf
SSP 300 Part 2 6-Speed Automatic Transmission 09D.pdf
SSP 300 Part 3 6-Speed Automatic Transmission 09D.pdf
SSP 301 Touareg Heating and Air Conditioning System Design & Function.pdf
SSP 302 Touareg Chassis & Four Wheel Drive Concept Design & Function.pdf
SSP 303 Part 1 The V10-TDI Engine with Pump-Jet Fuel Injection System Design & function.pdf
SSP 303 Part 2 The V10-TDI Engine with Pump-Jet Fuel Injection System Design & function.pdf
SSP 304 Part 1 Electronic Diesel Control EDC 16.pdf
SSP 304 Part 2 Electronic Diesel Control EDC 16.pdf
SSP 304 Part 3 Electronic Diesel Control EDC 16.pdf
SSP 305 2.5l TDI Engine Design & Function.pdf
SSP 306 Touran.pdf
SSP 307 Part 1 Touran Electrical System Design & Function.pdf
SSP 307 Part 2 Touran Electrical System Design & Function.pdf
*SSP 308 Direct Shift Gearbox 02E.pdf*
SSP 315 European On-Board Diagnosis for Diesel Engines Design & Function.pdf
SSP 316 The 2.0 ltr. TDI Engine Design & Function.pdf
SSP 317 Electro-mechanical Power Steering with Dual Pinion Design & Function.pdf
SSP 318 Part 1 Golf 2004.pdf
SSP 318 Part 2 Golf 2004.pdf
SSP 319 Part 1 Golf 2004 Electrics Design & Function.pdf
SSP 319 Part 2 Golf 2004 Electrics Design & Function.pdf
SSP 321 Golf 2004 Running Gear Design & Function.pdf
*SSP 322 The 2.0L FSI engine with 4-valve Technology Design & Function.pdf*
SSP 323 Audi A6 - 05.pdf
SSP 324 Audi A6 - 05 Running gear.pdf
SSP 325 Audi A6 - 05 Assemblies.pdf
SSP 326 Audi A6 05 - Electrics.pdf
SSP 327 Part 1 Audi Engines - Chain Drives.pdf
SSP 327 Part 2 Audi Engines - Chain Drives.pdf
SSP 328 The 2004 Caddy.pdf
SSP 329 Volkswagen California Camper 2004.pdf
SSP 330 The Diesel Particulate Filter System With Additive Design & Function.pdf
SSP 331 Part 1 Variable Anti-roll Bars on the Touareg Design & Function.pdf
SSP 331 Part 2 Variable Anti-roll Bars on the Touareg Design & Function.pdf
SSP 332 Audi A3 Sportback.pdf
SSP 333 4MOTION with Haldex Coupling Model Year 2004 Design & Function.pdf
*SSP 334 Fuel System in FSI Engines Design & Function.pdf*
SSP 335 Cornering Light System Design & Function.pdf
SSP 336 Catalytic Coated Diesel Particulate Filter Design & Function.pdf
*SSP 337 2.0l FSI Engine with Turbo Charger Design & Function.pdf*
SSP 338 Part 1 Golf Plus 2005.pdf
SSP 338 Part 2 Golf Plus 2005.pdf
SSP 339 Passat 2006.pdf
SSP 340 Part 1 Passat 2006 Electrical System Design & Function.pdf
SSP 340 Part 2 Passat 2006 Electrical System Design & Function.pdf
SSP 342 Radio Systems 2006 Design & Function.pdf
SSP 343 New Audi A4-05.pdf
SSP 344 Part 1 The New Audi A6 Avant 05.pdf
SSP 344 Part 2 The New Audi A6 Avant 05.pdf
SSP 345 Universal Mobile Phone Preparation Design & Function.pdf
SSP 346 Electromechanical Parking Brake Design & Function.pdf
SSP 349 Fox 2006.pdf
SSP 350 3.0l V6 TDI Engine Design & Function.pdf
SSP 352 Unit Injectors with Piezo Valves Design & Function.pdf
SSP 359 1.4l TSI Engine with Dual-charging Design & Function.pdf
SSP 361 Audi Q7.pdf
SSP 362 Audi Q7 - Running Gear.pdf
SSP 363 Audi Q7 - Power Transmission Transfer Case 0AQ.pdf
SSP 364 Audi Q7 - Electrical System.pdf
SSP 365 Audi 4.2 V8 with Common Rail Injection System.pdf
SSP 366 Audi Infotainment Systems `05 Bang & Olufsen Audio System, Digital Radio Tuner & Television Hybrid Tuner.pdf
SSP 369 Crafter 2006.pdf
SSP 370 Crafter - Electrical System Design & Function.pdf
SSP 372 Shiftmatic Gearbox 0B81 Design & Function.pdf
SSP 373 Part 1 EcoFuel Natural Gas Drive in Touran and Caddy 07 Design & Function.pdf
SSP 373 Part 2 EcoFuel Natural Gas Drive in Touran and Caddy 07 Design & Function.pdf
SSP 375 Audi Q7 - New Driver Assistance Systems- Audi side assist, Optical Parking System (OPS) & Reversing Camera.pdf
SSP 377 Audi 4.2-litre V8 FSI.pdf
SSP 378 Audi Open Sky Sunroof Systems.pdf
SSP 379 Part 1 Eos 2006 Electrical System Design & Function.pdf
SSP 379 Part 2 Eos 2006 Electrical System Design & Function.pdf
SSP 379 Part 3 Eos 2006 Electrical System Design & Function.pdf
*SSP 380 Audi TT Coupe 8J '07.pdf*
*SSP 381 Audi TT Coupe 8J '07 - Suspension System.pdf*
*SSP 382 Audi TT Coupe 8J '07 - Electrical and Infotainment Systems.pdf*
*SSP 383 Audi TT Coupe 8J '07 - Body.pdf*
The New Passat 2006 - Launch Training Information.pdf
Transporter 2004 Heating and Air Conditioning Trainer Information.pdf


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## TTCool

Very interesting but hope I never have to refer to it.

Well sourced indeed. Ive got this thread bookmarked 

Joe


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## Ruaraidh_Gamma

Re: N249



> and allows Motronic to intervene in the event of an overboost fault condition


This is incorrect. In the event of an overboost condition ME7 closes the throttle to control the boost pressure. If the bypass (dump) valve were opened, the compressor load would be removed and the turbocharger would overspeed and be destroyed.

Removing the N249 removes the predictive opening function of the ME7 bypass control by reverting to pneumatic only operation but it does not affect overboost control.


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## Guest

Ruaraidh_Gamma said:


> Re: N249
> 
> This is incorrect. In the event of an overboost condition ME7 closes the throttle to control the boost pressure. If the bypass (dump) valve were opened, the compressor load would be removed and the turbocharger would overspeed and be destroyed.
> 
> Removing the N249 removes the predictive opening function of the ME7 bypass control by reverting to pneumatic only operation but it does not affect overboost control.


Thanks Ruaraidh, that was an assumption on my part. Post updated. Do you know if the N249 has any safety function at all?

Doug

Link to FAQ as Microsoft Word document on Microsoft Skydrive:
http://cid-a5095b3331915f32.office.live ... 01%5E6.doc


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## stevebeechTA

Wow thanks! mate, That must have took a min or two.

I know its meant to help us understand how things work etc but i think i need to read that a few times. Got a bloody headache now.


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## Ruaraidh_Gamma

N249 is for surge noise prevention and turbo thrust bearing protection only.


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## antcole

Top write up Doug!!

That ones saved to favorites! :wink:


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## Guest

Additional Section for other FAQs & threads of relevance.

1. Inspection & replacement of 3-piece breather hoses underneath the inlet manifold (ETKA illustration 103-80):
viewtopic.php?f=2&t=192260

Doug


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## mikesimbo

Hi Doug, I don't suppose you still have the pictures/diagrams to go with all of that information on these pages as the images don't seem to loan and it would be really useful to me! Cheers, Mike.


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## tricklexxx

Doug no longer with us mate...

He's not dead or anything, just closed his account... Something to do with spending too much time on here.


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## mikesimbo

tricklexxx said:


> Doug no longer with us mate...
> 
> He's not dead or anything, just closed his account... Something to do with spending too much time on here.


Damn! Poor him!


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## percolated

This looks like it was the most comprehensive thread on the breather/ PCV hoses.

Now that Doug has gone, is there a similar one with pictures?

I have spent hours and hours trying to find more information with pictures on this topic.

If anyone has a bookmark to it, or a pdf or something, kindly post it here!

cheers


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