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xcrazydx and myself have dedicated some time in the past month to assembling the following MKV guide for the general public out there on myfastgti.com. This is a rough draft. Please provide commentary: what you like, what you dont like, what you would like to see added, what should be removed, why our army of two is excellent or otherwise. Thanks ladies and gentlemen.

North-American '06-'09 Volkswagen GTI - So that you don't do it wrong

Introduction

Disclaimer
Be advised, the following information is provided for educational purposes only. It is not meant to accurately diagnose any vehicle malfunctions, serve as an exact step-by-step DIY guide, or force You to do anything at all. Visit an authorized auto-repair facility for that. If You chose to use any of the provided material, You do so at Your own risk. None of the authors, editors, or referenced sources assume any financial or legal responsibility for any potential vehicle damages or bodily harm that may come as a result. However much time was spent on piecing this document together and every attempt was made to provide You with the most accurate and proper facts. This material is uploaded as freeware but if You wish to duplicate or reproduce any portion of it, please be decent and give us credit.

General Info
This guide assumes that You are willing to do additional thorough research if any of the particulates become increasingly interesting to You. Same goes for the terminology and DIY procedures. Please follow provided links, it will save us all much time and improve faith in humanity.
Basic information on Your GTi: http://en.wikipedia.org/wiki/Volkswagen_Golf_Mk5.
Depending on the production year, the MKV comes with either an FSI or a TSI engine. FSIs were installed in early '06-'08 models and starting with '08.5 TSI engines were implemented. TSI engines do not have some of the issues, which are inherent to the FSI design (explained in "Content" section). A MKV GTi may come equipped with either a 6-spd manual transmission or a twin-clutch robotic manual transmission otherwise known as the DSG. Although a DSG is a faster way of getting to 60mph (from here-on Empirical system is assumed), gets better MPG, and provides for a smoother commuting experience, it is extremely expensive, fragile, and requires costly maintenance. Various drivers will argue that the manual is more engaging and no other transmission should even exist in the GTi line-up as the 6-spd is impressively smooth and rewarding to operate. Interior equipment varies between vehicles and will not be discussed although a sun-roof is massively advised.
If You are about to purchase a MKV, please make sure to take the vehicle to a certified technician for a thorough inspection BEFORE making any promises to the selling party. Also, it is vital to test-drive your potential ride. These vehicles are often driven hard and it takes special attention and care to maintain them in good health.

Content

1. MKV
'06-'09 GTi model generation. There are also MKI, MKII, MKIII, MKIV, and MKVI generations.

2. DV
A compressor bypass valve (CBV), also known as a pressure relief valve or diverter valve, is a manifold vacuum-actuated valve designed to release pressure in the intake system of a turbocharged vehicle when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake (before the turbo) but after the mass airflow sensor. Early versions of the DV often rupture, even in stock GTis, resulting in massive loss of power as they start to leak boost as well as a lit-up CEL. (read sections "Modifying Your GTi", "Typical Malfunctions")

Figure 1 - Intact "G"-Revision Diverter Valve

The above figure is an intact DV of the "G" variety removed from a late '07 MKV to be replaced by an electric piston-operated "D"-revision, which is known to hold boost better.

3. PCV
A crankcase ventilation system is a way for gases to escape in a controlled manner from the crankcase of an internal combustion engine. A common type of such system is a positive crankcase ventilation (PCV) system, the heart of which is a PCV valve-a variable-restriction valve that can react to changing pressure values and intermittently allow the passage of the gases to their intended destination (which nowadays is the engine's intake stream). All FSI GTi models come with a very weak and poorly designed PCV and when malfunctioning, allow for undetermined quantities of blow-by accumulation on the cylinder valves in the form of carbon-build up. It is important to remember that direct-injected engines, FSI and TSI included, do not benefit from fuel additives, which allegedly act as a valve-cleaner. This holds true due to the fact that the fuel never comes in contact with the valves themselves as it follows the route of injectors straight into the cylinders. (read sections "Modifying Your GTi", "Typical Malfunctions")
You may hear others mentioning a "front" PCV and a "rear" PCV. They are parts of the same system although the "rear" one connects to the valve cover on the right back side unlike the "front", which can easily be seen in Figure 2.

Figure 2 - Faulty PCV system on a late '07 MKV GTi

4. Cam
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel (e.g. an eccentric wheel) or shaft (e.g. a cylinder with an irregular shape) that strikes a lever at one or more points on its circular path. The cam can be a simple tooth, as is used to deliver pulses of power to a steam hammer, for example, or an eccentric disc or other shape that produces a smooth reciprocating (back and forth) motion in the follower, which is a lever making contact with the cam. Two cam versions exist for the MKV Gti - The "A"-version, which is bad, and the "B"-version, which is better. The "A" is known to wear down the cam follower to the point of complete disintegration, which causes multiple pieces of shrapnel to travel through the engine, allowing the fuel pump to come in direct contact with the cam-shaft, and otherwise creates for thousands of dollars worth of damage (read sub-section "typical malfunctions").

Figure 3 - HPFP-side of late '07 MKV GTi's cam

Figure 4 - Cam follower (circular outline and absence of black coating are signs of premature wear)
 

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5. Intake
A stock air intake on a MKV is a rather restrictive system which is built into the engine cover in FSI engines and is separate from the cover in TSI engines. Upgrading the intake will provide small increases in the MPG, horsepower, and engine responsiveness although the most noticeable effect is noise amplification. It is generally a good idea to get rid of the stock intake in exchange for a short-ram intake, which will allow the engine to breathe the way it was meant to.
A short-ram intake is not the same as a cold air intake otherwise known as a CAI. A CAI will sit lower to the ground (few inches away) and, in a highly modified GTi, will provide colder air for the engine resulting in more power and responsiveness. Installing a CAI on a daily driver will not yield any of the benefits expected to be seen in track cars. However it increases the chances of hydro-lock if the filter becomes submerged in water. Although not officially required, a short-ram is a recommended upgrade for those wanting to purchase ECU-tuning software.
It does not matter which SRI you chose to install as all perform identical functions. Some may be louder, some may be made of a more aesthetically pleasing material, but the result is the same. Look on youtube J

Figure 5 - A red Neuspeed P-Flo SRI installed on a late '07 MKV GTi
6. ECU and aftermarket software
Visit this link if You do not know what an ECU is: http://en.wikipedia.org/wiki/Engine_control_unit.
A tune for the ECU of a MKV GTi is without a doubt the most cost-efficient method of obtaining additional power from the engine. Think of it as an operating system on Your computer (windows, linux, unix, Mac OS). MKV's ECU is a programmable computer which can be flashed with aftermarket software via an OBDII port (variations exist) at a professional shop. Typical positive results include increased MPG, significant raise of horsepower and torque (up to 50%), increased engine responsiveness, and increased intake and DV noise; although obviously the most important and desired is the power increase. Keep in mind that tuning Your vehicle will increase load on many of the vehicles systems so increased attentive care will be required.
Some of the most reputable companies which provide aftermarket ECU software are APR, GIAC and Unitronic. Other companies exist but are not as respected. APR typically provides for a smoother power-curve, doesn't require an external device to switch through programs (cruise-control stalk operated) and has annual sales. GIAC is more aggressive and gives you slightly more power than APR but requires an external controller device and the price is fixed.
Tunes take advantage of support mods, such as intakes, to produce more power. It is in their nature to slowly adapt to the vehicles configuration as they are learning programs.
Flashing a stock MKV will upgrade You to Stage 1. Further bolt-ons are required for Stage 2 and higher. (see section "modifying your gti").

7. Catch Can
This is arguably the first upgrade a MKV owner should purchase, especially if plans for further modifications exist or You care about Your ride at all.
An oil catch can is an aftermarket replacement for the PCV serving the purpose of extracting unwanted blow-by contaminants such as oil particles and condensation. It will typically consist of a face plate, canister, and hoses. The stock PCV system on pre-'08.5 MKVs is known to be weak and allows for excessive blow-by which slowly builds combustion by-product residue on the intake valves of an FSI engine. Eventually enough carbon build-up accumulates resulting in rough idling, decreased power, and increased fuel consumption. Installing a catch-can will prevent or stop carbon build-up.
Although typically a catch-can will extract contaminants from the passing air via a wire-mesh complex and will require timely drainage, vent-to-atmosphere versions exist. The VTA type is 100% effective versus 95% for the sealed type. VTAs will not pass emission tests in some regions of the world. The benefits of zero-maintenance for VTAs can be countered by installing a self-made drain-valve on a sealed-type catch can meaning that the CC will no longer have to be unclipped in order to be drained into a container. It is important to remember that when temperatures drop below freezing, the 95% H2O content of the blow-by extract will freeze inhibiting CCs functionality almost completely. In other words, empty the CC more often in the winter.

Figure 6 - A BSH Stage 2 Street CC on a late '07 MKV GTi

From left to right: canister, hoses, face-plate. Notice that a CC removes the "front" PCV.
A catch-can is different from a "PCV-fix". A PCV-fix may be an updated version of a stock system or an after-market block-off plate, none of which resolve the issue and simply delay the inevitable.

8. Stage 1
Only requirement is a re-flash of the ECU. APR, GIAC, and UniTronic are popular.

9. Stage 2
A downpipe is required, and also a re-flash of the ECU. An intake is recommended, but not necessary. However, with an FSI engine, I highly recommend it.

10. Stage 2+
A downpipe, an upgraded High pressure fuel pump (HPFP), and an ECU re-flash. An intake is highly recommended.

11. Stage 3
GT2871R Turbo, Oil/Coolant lines, Intake, Front Mount Intercooler and hoses, Turbo inlet hose, Compressor outlet hose, Pancake pipe, HPFP, Injectors, Exhaust manifold, downpipe, and ECU re-flash.

12. BOV
A BOV performs the same function as the DV, except it releases the air to the atmosphere instead of back into the system. These work well for most turbo vehicles, but have problems on the MKV GTI. CELs and limp-mode are typical.

13. Spark Plugs
A spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as aerosol, gasoline, ethanol, and liquefied petroleum gas by means of an electric spark. Chose Bosch or NGK. Don't cheap out. Colder-range go well with an ECU tune.

Figure 6 - NGK Spark Plug

14. Ignition Coils
An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system which transforms the battery's 12 volts (6 volts in some older vehicles) to the thousands of volts (20 to 30 thousand volts or more) needed to spark the spark plugs. Some coils have an internal resistor to reduce the voltage and some rely on a resistor wire or an external resistor to reduce the voltage from the cars 12 volt wiring flowing into the coil. The wire which goes from the ignition coil to the distributor and the wires which go from the distributor to each of the spark plugs are called spark plug wires or high tension leads. In modern systems, the distributor is omitted and ignition is instead electronically controlled. There is a recall out for early-versions of MKV spark plugs. If You are experiencing a flashing CEL or misfires, this is likely the culprit.

Figure 7 - "F" Coil packs for MKV GTi at ECS Tuning
 

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15. Brake pads
Brake pads are a component of disk brakes used in automotive and other applications. Brake pads are steel backing plates with friction material bound to the surface that faces the disk brake rotor. A good set of pads (better than OEM) are HAWKS or RedStuff.

Figure 8 - Brake pads for MKV GTi at ECS Tuning












16. Brake Lines
They simply are the hoses that brake fluid is pushed through to depress the pistons on brakes. Lots of folks use these to enhance brake performance for street use as well as track days. The brake pedal feels stiffer and more responsive. Nice touch if You are servicing the brakes on Your MKV.

Figure 9 - ECS-made brake lines (front and back)










17. BT
A turbo that is much bigger than the stock. Such as this, KO4 or Figure 10 GT3071R.

Figure 10 - GT3071R turbo




18. Intercooler/FMIC
An intercooler, or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged (forced induction) internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric (constant pressure) cooling, which removes the heat of compression (i.e., the temperature rise) that occurs in any gas when its pressure is raised or its unit mass per unit volume (density) is increased. A decrease in intake air charge temperature sustains use of a more dense intake charge into the engine, as a result of supercharging. The lowering of the intake charge air temperature also eliminates the danger of pre-detonation (knock) of the fuel air charge prior to timed spark ignition. Thus preserving the benefits of more fuel/air burn per engine cycle, increasing the output of the engine. Intercoolers increase the efficiency of the induction system by reducing induction air heat created by the turbocharger and promoting more thorough combustion. They also eliminate the need for using the wasteful method of lowering intake charge temperature by the injection of excess fuel into the cylinders' air induction chambers, to cool the intake air charge, prior to its flowing into the cylinders. This wasteful practice (when intercoolers are not used) nearly eliminated the gain in engine efficiency from supercharging, but was necessitated by the greater need to prevent at all costs the engine damage that pre-detonation engine knocking causes.


Figure 11 - Forge TwinterCooler





19. Turbo-Back Exhaust (TBE)
A TBE is a full exhaust system that connects to the turbo flange and follows all the way to the exhaust tips. A TBE is a DP and a cat-back (CB) together. Remember that the widest part of the exhaust is determined by its narrowest component.

Figure 12 - TBE









20. Down-pipe (DP)
The first piece in a turbo exhaust system, also the most important for hp gains. It connects to the turbo flange and mates to the CB. An O2 spacer or ECU software is required to prevent the sensor from telling the on-board computer that the engine is running rich.

Figure 13 - 3 inch DP










21. Resonator delete
Refers to removing the resonator on the CB section of the exhaust.

It removes this piece:


And replaces with this pipe with no resonator:







22. S3 Injectors
Fuel Injectors from the Audi S3, commonly used when upgrading to a bigger turbo. They offer 13% more flow than the factory MKV 2.0 injectors.




23. S3 Cam
Cams from the Audi S3. They have been reported as having no performance gain on stock head and valves. However there is debate that they prevent premature cam follower wear. At this point this is all speculation.


S3 intake-manifold
TSI roller-cam kit for FSI engines
Tail-lights
Side-markers
Suspension
-coil-overs
-cup-kit
-air-bags
-struts
-bushings
Wastegate actuator
ECU Tuning (Stage 1)
Blacked out emblems
Gauges
Euroswitch
Engine mounts
Transmission mounts
Flywheel
Clutch



Content


Typical Malfunctions/Must-do replacements and procedures

DV
PCV
DSG (problems, fluid flush)
Cam follower
Stereo
Ignition system
A/C
Burning oil
Seafoam
Valve cover gasket
cv


Shopping




Recommended Resources
 

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Fixd Ur Typo .... Other Than That O0
 

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Good write up for noobs and others that may not know a lot about their car and what they may be getting into. It is not cheap to fix a dub but it can be prevented with proper maintenance and love. O0
 

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I was wondering about that but just thought it was my computer that wasnt loading something again. A couple of us should make one of these for MKIV's and MKVI's with known problems and normal maintenance. O0
 

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I was wondering about that but just thought it was my computer that wasnt loading something again. A couple of us should make one of these for MKIV's and MKVI's with known problems and normal maintenance. O0
There is supposed to be a pic everywhere it says figure xx. Just so everyone knows, post helpful comments and additions only, cuz all these posts are gonna be deleted and then this will be stickied and locked.
 

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Very nice.

I know I'm a noob but I find it interesting that there is no mention of any suspension issues or mods.

I understand that this is a work in progress so maybe that's coming.
 

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Very nice.

I know I'm a noob but I find it interesting that there is no mention of any suspension issues or mods.

I understand that this is a work in progress so maybe that's coming.
Yeah I guess you could add a cup kit, coils, springs, and bags to the list of stuff to do to a MKV but there are no real problems with the stock suspension going out or anything like that. Only thing is if you put aftermarket springs on with stock shocks then they will wear faster or vise versa. O0
 

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The only thing I see is the Stage setups for a TSI are different than an FSI... Other than that its a good read.
 

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Very good stuff!

Just some things that caught my eye, but not really important

DV: " is a manifold vacuum-actuated valve"
its actually electrically actuated

INTAKE: Needs SRI added to the original mentioning or short ram intake

CATCH CAN: needs CC added to the original mentioning of catch can

also fixed a typo in the OP
 

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ahem, a little biased towards the manual over dsg? I wouldn't call it fragile, it just a had a recall because of a crappy component. I beat the crap out of mine, it's rugged for any auto, especially compared to any noram one.

Anyways, good job, you guys have way too much time on your hands, lol
 

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ahem, a little biased towards the manual over dsg? I wouldn't call it fragile, it just a had a recall because of a crappy component. I beat the crap out of mine, it's rugged for any auto, especially compared to any noram one.

Anyways, good job, you guys have way too much time on your hands, lol
We both have dsg's, they are very fragile and I would never recommend one.
 

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Thanks for putting this together. This is a great resource for us new to the GTI. I thought it would be appropriate to add the recent warranty extension (I just got the letter last week) info for the 06-07 TFSI covering the Intake Camshaft, Camshaft Follower, and High Pressure Fuel Pump.
 
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