VAG-Tools: MK4 VR6 Tuning Guide: Stage 2

+ 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:	Description / Links / Info
+ 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+)	Eurospec 12v 2.9/3.0/3.2 Stroker parts Eurospec 24v 3.0/3.2/3.3 Stroker parts
+ 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+)	General Image 24v P&P 12v Gain poll
+ 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+)	EIP Kit WRD BVH BVH Discussion

• All Motor Dynos: http://www.vr6dynos.com/allmotor.shtml

• Continue on to Stage 3