Welcome to the MK4 VR6 Tuning Section

+ In this section, we will learn about the basics of a 2.8 12/24V 6 Cyl Engine. After reading the basics, you can learn about popular modifications done to this motor. These modifications are divided into 6 sections: 4 for extracting power, 1 for handling, 1 for weight reduction. Enjoy!

• VR6 Engine Cutaway


• Basic Engine Information:
Category: Spec
Type: Four-stroke, internal combustion engine in "Vee"/in-line 6 cylinder
Bore: 81.0 mm
Stroke: 90.0 mm
Displacement: 2.8 liter (2792 cc)
Compression ratio:10:0:1 /10:5:1
Firing Order:1, 5, 3, 6, 2, 4
Fuel/Ignition System:Bosch Motronic M2.9
Emission System: Lambda control with catalytic converter



• Modification Guide:




+ Stage 0: Free / Budget Modding

+ Looking forward to modding your dub but don't have the $$$ ? Don't worry, there are a few things you can do to get a little more out of your car. Most of the following mods can be done yourself, a repair manual (i.e Bentley) would be a good reference tool.


• Smoothing out the airbox: Free
Description:
The stock airbox has a rather restrictive path for the air traveling through. This is due to the many "notches" inside of the airbox. This mod involves "smoothing" out the inside of the box to increase flow.

+ Optional: Replace stock air filter with aftermarket (i.e K&N)





• Replace stock dogmount bushings: ~$5
Description:
The stock rubber bushings inside of the dogmount mounts are very soft. Although this equals a very smooth ride, wheel-hop is common when accelerating. This mod involves replacing the stock rubber bushings with heavy duty bushings.

+ Note: May increase cabin vibrations




+ Stage 1: Bolt-Ons

+ Ready to get the most out of your car? Stage 1 is a very nice improvement over stock. Most of the following mods can be done yourself, a repair manual (i.e Bentley) would be a good reference tool.

• Reflash your ECU: ~$250-300+
Description:
Flashing or "chipping" your stock computer will give you better throttle response as well as an increase in HP/TQ. Most programming will offer approx. 5-10+ hp and approx. 10-15+ ft-lbs of torque gained.




• Catback: ~$200-600
Description:
The factory catback (55mm) is somewhat restrictive and should be replaced with a larger, better flowing unit. 2.25 or 2.5 inch catbacks can be used. Custom catbacks are a viable option. Remember, bigger isn't always better - unlike the 1.8T, the VR6 needs some backpressure (turbo creates it naturally). Aftermarket exhausts are an enthusiast's favorite because of how good VR6s sound with them!

+ Gains: ~10hp







• Intake: ~$100+
Description:
Replacing the factory airbox with an aftermarket intake is a rewarding mod. Aftermarket intakes produce lower air intake temps which in turn = denser air = more power. Intakes also lead to better throttle response as well as more HP up top.

+ Gains: ~10hp







• Camshaft: ~$300-1000+
Description:
Camshaft: A shaft that has a series of cams at intervals along its length, for operating the engine valve mechanism. Made up of a series of egg-shaped sections, which as they rotate raise and lower part of the valve train, which in turn causes the valves to open and close.
+ Duration: Duration refers to how long a valve is opened in relation to crankshaft rotation.
+ Lift: While duration refers to how long the valve is opened, cam lift is used to determine how wide the valve is opened.
+ 256/264 popular for non forced induction usuage (12v), 264/256,252 (24v)
+ Note: Software written for aftermarket cams is recommended to receive the most gains
+ Gains: ~10-15hp







• Dogbone mount kit: ~$30-100
Description:
The stock rubber bushings inside of the dogmount mounts are very soft. Although this equals a very smooth ride, wheel-hop is common when accelerating. This mod involves replacing the stock rubber bushings with heavy duty inserts.

+ Note: May increase cabin vibrations







+ Stage 2: All Motor (N/A) Setup

+ The following guide will display common ways of getting the most naturally-aspirated power out of your VR6. Beware, most of these setups are not cheap, and a forced induction setup can be found cheaper - however - some enthusiasts appreciate and praise a very smooth and linear powerband that can be obtained in a N/A setup.


• Common All-motor nomenclature:
Terms: What does it mean?
1) Bore & Stroke

1a) Bore is a measurement of the diameter of the holes bored into the engine block for use as cylinders. The stroke is the length that piston travels.

Generally, bigger bore yields fast-revving engines with low rotational mass and therefore higher rev limits with later torque peaks and overall higher top end power at the expense of torque throughout the operating range. Smaller bore with longer stroke tends to make more torquey engines with lower rev-limits, with the increased rotational mass leading to slower revving.

2) Displacement

2a) Engine displacement can be defined as the total volume of air/fuel mixture an engine can draw in during one complete engine cycle; it is normally stated in cubic centimetres, litres or cubic inches.

Engine power is dependent on the quantity of air/fuel mixture ingested and the efficiency of its combustion and conversion into power. To increase the quantity of mixture combusted, the engine displacement can be increased (we will see in this guide), the speed of operation of the engine can be increased, or the mixture quantity (volume) can be delivered at a higher pressure (stage 3, forced induction).

Formula for displacement


3) Crankshaft

3a) The crankshaft or crank, is the part of an engine which translates reciprocating linear piston motion into rotation.


4) Air / fuel ratio

4a) The A/F ratio defines the amount of air consumed by the engine compared to the amount of fuel. Proper A/F tuning is crucial to guarantee long engine life as well as promote better performance. Leaner setups result in higher combustion temperatures which means more power, but at the expense of higher EGT (exhaust gas temps) as well as a higher likelihood of knocking (bad!). Richer setups less prone to knock.

Thus, tuning the A/F between too lean / too rich is very important to ensure RELIABLE power.


5) Compression Ratio

5a) The CR is the degree to which the fuel mixture in an internal-combustion engine is compressed before ignition. It is defined as the volume of the combustion chamber with the piston farthest out divided by the volume with the piston in the full-compression position. A high ratio promotes efficiency but may cause engine knock (bad!).


6) Valve

6a) A valve, whether it is intake or exhaust, is used to open and close the intake and exhaust ports in the cylinder head. The valve is usually a flat disk of metal with a long rod known as the valve stem out one end. The stem is used to push down on the valve and open it, with a spring generally used to close it when the stem is not being pushed on.






• How to increase power with the VR6:
Method:
+ Increasing the engine displacement: This can be done by "boring" - increasing the diameter of the cylinders and pistons, or by "stroking" - using a crankshaft with a longer stroke or both.

+ Cost Scale: 5/5 ($2500+)
+ Port and Polish: Porting and Polishing (P&P) is the removing of material from the intake/exhaust ports as well as the combustion chambers for the reason of improving flow both in AND out of the combustion chambers. If done correctly (i.e using air flow bench), this can translate into impressive HP gains. Doing the P&P yourself can be done, but is generally not recommended.

+ Cost Scale: 4/5 ($1000+)
+ Big Valve Head (BVH)(12V): One of the few weaknesses of the 12v VR6 is the head design. There is much room for improvement in air flow. One solution for opening up the VR6 head and allowing it to 'breathe' more efficiently is by installing bigger intake and exhaust valves along with the port and polish (see above). Bigger valves can ultimately flow more air. The biggest gains in power are found using a big valve VR6 head.

+ Cost Scale: 4/5 (~$1500+)





+ Stage 3: Forced Induction

+ By far the most envied VW setup is the VR6 turbo / supercharger, also known as the VRT. Forced induction on the VR6 will put out some serious power, however, a proper setup will cost some money. Let's begin by learning what forced induction is.

+ Forced induction is simply the term given to devices that feed the intake of the engine with more compressed air, thereby increasing the quantity of oxygen available for combustion. This compressed air is normally referred to as Boost or charge air. The two types of forced induction discussed in this guide are superchargers and turbochargers.

• Turbo vs Supercharger: An Age-Old Debate
+ Turbo Information http://en.wikipedia.org/wiki/Turbocharger
+ Supercharger Information http://en.wikipedia.org/wiki/Supercharger




Turbo Advantages:
+ Easier to target a desired boost with a turbocharger as there are many forms of boost controllers that allow a user to adjust to desired boost fairly easily.
+ Uses wasted exhaust gases to produce boost.

Turbo Disadvantages:
+ Turbo Lag: The amount of time that it takes a turbocharger to reach the onset of boost is referred to as lag. Differs from a Supercharger, which is always "on".
+ Harder to install


Supercharger Advantages:
+ A supercharger is 'on' all of the time, meaning that it is capable of producing a linear increase of boost up until redline.
+ Easier to install

Supercharger Disadvantages:
+ In order to achieve desired boost with a supercharger, a larger or smaller pulley must be installed.
+ Use belts driven by crank shaft to increase boost to the engine. It takes horsepower away from the engine to drive the supercharger = less efficient than a turbo.




• Turbo / Supercharger nomenclature:
Terms: What does it mean?


1) Wheel trim

1a) Trim is a term used to express the relationship between the inducer and exducer of both turbine and compressor wheels. It is an area ratio of the turbo. The trim ratio is equal to: (inducer^2 / exducer^2) * 100
Illustration


2) A/R (area / radius)

2a) The A/R describes the relationship between the area of the intake (where fresh air enters) and the radius of the turbo compressor/turbine wheel.
Illustration

Larger A/R means more flow at the expense of more turbo lag. Basically, more top end at the expense of low end spool.


3) Log vs Tubular manifold

3a) Cast log manifolds are typical on OEM setups. They are usually dedicated to one type of turbo setup. Tubular manifolds are usually seen on serious race setups because they allow maximum flow with equal tube lengths. They are usually custom


4) Air / fuel ratio

4a) The A/F ratio defines the amount of air consumed by the engine compared to the amount of fuel. Proper A/F tuning is crucial to guarantee long engine life as well as promote better performance. Leaner setups result in higher combustion temperatures which means more power, but at the expense of higher EGT (exhaust gas temps) as well as a higher likelihood of knocking (bad!). Richer setups less prone to knock.

Thus, tuning the A/F between too lean / too rich is very important to ensure RELIABLE power.


5) Compressor Map

5a) A compressor map graphs a turbo’s performance characteristics, including efficiency, mass flow range, boost pressure capability, and turbo speed.
Example


6) Roots, Lysolm, Scroll

6a) Types of superchargers: click here for more info


7) Intercooler

7a) Used to improve volumetric efficiency by increasing the amount of charge in the engine and lowering charge air temperature thereby increasing power and reliability.




• Purchase a complete turbo / sc kit or go custom?
Advantages of a kit:
- You are getting a genuine product that has been engineered to work in your car and work at roughly the same OEM specs.
- You will receive all parts needed for the install, as well as software and the backing of a company (including warranty).


Advantages of piecing together a custom kit:
- Usually cheaper than most kits.
- More options
- More enjoyable to some


Disadvantages of a kit:
- Usually more expensive than custom kits
- Limited options

Disadvantages of piecing together a custom kit:
- No company backing or support
- May have to deal with unforseen problems
- Limited software tuners




• Turbo parts list:
Required parts:
- Turbo: ~$1100+
- Exhaust manifold
- Uprated fuel pump (i.e Walbro): ~$150
- Downpipe
- Oil feed/return lines, charge pipes
- Turbo Inlet
- Diverter / Blow-off valve: $100-150
- Exhaust manifold gasket< $100
- External wastegate (if turbo is not internally gated)
- Lower compression via headgasket spacer or low-comp pistons
- Proper cams
- Correct chip tuning or standalone (dyno tune recommended): ~$700+
- Appropriate sized Fuel pressure regulator: ~$150+
- Correct Injectors: ~$275

Recommended parts:
300-500 WHP: Stronger internals

Limited slip differential:
+ With much more power on tap, putting it down will be a problem. LSDs ensure that torque will be transmitted to both wheels, even if one is slipping. This will reduce the likelihood that only one wheel will spin while your vehicle remains stationary. Benefits: better acceleration, better track times, etc.
- Quaife LSDs
- Peloquin LSDs

3" turboback exhaust




[/b]

I dont know how old is this information but the prices are off. The turbo kit for vr6 actually is one of the most faster spulling. Software for the DIY in this engines there is a few very good, compeared to a headech stand alone (this is not for everyone). This should be updated. MPO.