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Common VR6 Modification Information

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This thread will contain information about commonly purchased modifications for the VR6 engine based upon past experience from my self, and other memembers.

You can also use our Rolling Road Day Results Table to estimate what power you can generally expect from different modifications, remember, that power increases are likely to be different on different engines.

BMC CDA Induction Kit

The BMC CDA filtering system replaces the stock air box with a cylindrical carbon air box containing a washable filtering element. Cold air is directly channelled through an internal airflow deflector to the filter and drawn into the engine with a very small pressure drop (patented system). System includes 2 Ft. of black alloy ducting to connect to an air intake on the front of the car.


Estimated Power Gains: ???

Estimated R.R.P: £165

Stockists: Stealth Racing

Schrick VGI (Variable Geometry Intake) Manifold

Ever wondered why Audi and VW spent time and money developing two different V6 motors of very similar displacement and horsepower and torque? One of the reasons was certainly that of the limited under-bonnet space on Golf. There was simply not enough space to fit a longitudinally mounted V6 engine in the bay.

Audi’s V6 engine actually produces more torque than VW’s VR6 because it has a dual-length inlet manifold. However, VR6 does not have to be left out! An aftermarket inlet manifold which does just the same thing is available from Schrick. VW’s accountants apparently kept the variable inlet manifold from standard production engine due to its high cost. Fitting the manifold would have negated any cost-savings from developing the VR6 with one head.


Limited by the transverse mounting of the VR6 engine, there isn't much room for generous inlet manifold. In order to achieve a good compromise between maximum power output, and adequate torque for day-to-day use, the inlet manifold runs across the top of the head. This has circumvented the shortage of space and allowed the use of an oscillating-flow tuned inlet manifold. Each cylinder has its own inlet tract that is tuned to such a length as to ensure positive inlet pressure.

A standard 2.8 litre VR6 produces 174bhp and 172lb ft of torque and the 2.9 litre engine achieves 190bhp and 184lb ft. But this achievement wasn't enough to satisfy the Wolfsburg Developers. To produce more torque lower down in the rev range, the 6 cylinders needed to breathe even more freely. The idea of the variable inlet manifold was born and developed in parallel with the assistance of Pierburg, the carburettor specialists.

That this piece of motor technology was not condemned to the depths of the Wolfsburg catacombs is thanks to the interests of Volkswagen Motorsport. They quickly realised the potential in the aftermarket industry.

How it works

The VGR manifold can be fitted to both 2.8 and 2.9 litre engines. Eventhough the VGI achieves similar aims to Audi’s switching inlet manifold, the operating principle is different.

In the Audi engine, a long, narrow inlet tract achieves high torque at low revs and maximum power is achieved using a short, wide inlet tract. For the engine to feed through the appropriate channels, inlet manifolds are switched using six individual vacuum operated flaps at 4000 RPM. In both stages, the technology is based purely on tuned oscillating-flow inlet manifolds, with the necessary switching.

In contrast, two diverse technologies are applied in the VGI. It is designed so that at low engine speeds, resonance is used to improve cylinder-charging efficiency. At higher RPM, oscillation-tuned, individual, broad tracts are used. Switching from one to the other is achieved by single flap, also vacuum operated at 4000 RPM.

The tuned inlet tract operates by the low pressure caused between the throttle valve and the inlet valve, by suction of the descending piston. Through inertia of the air in the tract, the airflow tends to keep moving towards the inlet, even after its closed, causing a slight over-pressure when the inlet valve next opens. This ensures high charge efficiency even during early stages of the induction stroke. Further during the same stroke, inlet pressure falls followed by high pressure but not before the inlet valve closes.

In order to achieve optimal control of the oscillation and reflection of the column of air in the inlet tract, it needs to be closely co-ordinated with valve timing, but this is not possible due to variation in the engine speed. Even at mid-range-rpm, the valve opening and they are out of synch. The second pressure wave arrives much too early before the inlet valve closes and a backflow reduces fuel efficiency.

Now to achieve high torque under these conditions, resonance-fuel is utilized. This is achieved by closing the connection flap between a small resonance chambers immediately before short inlet tracts above the inlet valves. These transforms the 6-cylinder engine into effectively two 3-cylinder engines with uniform firing times, which do not have overlapping inlet strokes. A resonance pulse of up to 6psi (0.4bar) above atmospheric is achieved, leading to remarkable fuel efficiency and torque increases.

On the road

The effect of the manifold is immediately apparent – you won’t need any test equipment! A new urge is sensed almost right from the idle. There is markedly better acceleration up to 4,000rpm, followed by a strong surge to the redline. The switchover of the flap is almost undetectable from inside the car.

The new low to mid-range power is particularly useful in the higher gears. The 50-70 sprints in fourth is reduced by almost a second! Fuel consumption is also improved, as higher revs don’t need to be used as much.


Estimated Power Gains: ???

Estimated R.R.P: £???

Stockists: Stealth Racing

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here is a section on the Exhausts...



One of the first things you are going to want to do is get the car sounding right. AS you can see from the lists below there are a few options for you. Most guys seem to go for the CAT back systems and they tend to have ok things to say on most. As you would expect there are favourites. But if you have had a good experience before then why not go with that.

Costs can vary so surf away and you'll find a deal. If people have had issues they will let you know as this thread progresses.

Of course you could go for as large a pipe as you want. However you have to get it over the rear axle. Once you are above 2.5" then you will have issues. Turbo guys have gone up to 3" but I am fairly sure they will have to oval the pipe through the space. (Let us know chaps(esses) !!)

The Standard system has 3 boxes the middle one known as the suitcase. This is the main one that needs the work/removal.

People tend to go for 2 box systems but that will increase the volume. 3 Box systems give the tone with out the volume. When selecting any system, some will give more of a crusing drone in car than others, so think about this when chosing. If you can - pop along to a meet and you will soon hear and get the chance to sak the owners.

Made to order these can be the same or cheaper than some of the cat back options. shop around and you must visit the place and see examples of their work. Everything should be at .304 rated Stainless as a basic level and TIG welded. The bends should be mandrel formed so as to ensure the diameters and steel are supported. Thus no breaks later on or flow restrictions. The guarentees are worth looking into as well. There is one company who franchises their kit and have good and bad reviews. It is ALL about the individuals who fit them.

If you are going the FI route then high flow CATs are essential and I would personally then suggest that the made to order is the way forwards as the "off the shelf" solutions are not ideal for these environments.

If you are going to go for the 6-Branch then you will need to use some form of heat protection. It is already warm enough under there. The wrap is easy to do by yourself but powder coating is much sexier.

So CAT Back systems...

1. Scorpian

2. Jetex (throaty)

3. Magnex (seem to have rust issues sometime with the welds rotting)

4. Miltek (A VR6OC Fav..)

5. Remus

Made to measure

1. Longlife (Lifetime G with no service visit)

2. Powerflow (Subject to the fitter)

3. Hayward and Scott ( really good but ££££ )

4. Mercat (Scotland)

Sport Cats

1. Longlife

CAT Bypass

1. Miltek

2. Hot tuning

3. Longlife


1. Raceland (heat wrap required)

2. Hottuning

3. Longlife

Other Stuff


Cheers folks

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engine mounts to add and discuss....

VT are the origional option and they suggest the following:-

"got my quote from Vibra and their recomendations were as follows for my charges car with the stainless 6-branch mani:

"We make both Fast Road and Competition mounts but some people prefer to use Comp mounts on the road - and put up with the extra harshness. However what we have found is that VR6 is not too harsh with a Comp front mount. Stealth regularly fit Comp front mounts to VR6's. Therefore we would suggest using a Comp front mount (especially in view of the mod you are intending to carry out) with Fast Road mounts at the rear and gearbox end. Part Nos. and prices for Mk3 mounts : -

Font mount VAG960MX £137.09

RH Rear mount VAG885M £65.67

LH G/Box mount VAG875m £67.16

Prices are plus carriage and VAT


Some people suggest only the rear needs changing however it is mounted to the subframe it can induce harshness into the car, if a full comp is fitted here!

prices were 2006...

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can i add that i was using an ashley 2 box system and although the fit was terrible and needed modification to get it to stay in place the sound was nice and deep but not to loud and made the car feel much more responsive.

secondly i now run a 2.5 inch straight through from cat to back box single box system, and that is extremely loud and totally changes the feel of the car, losing low end torque round town but turning into an animal when it comes into the power band

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can i add that i was using an ashley 2 box system and although the fit was terrible and needed modification to get it to stay in place the sound was nice and deep but not to loud and made the car feel much more responsive.

secondly i now run a 2.5 inch straight through from cat to back box single box system' date=' and that is extremely loud and totally changes the feel of the car, losing low end torque round town but turning into an animal when it comes into the power band


i can totally agree with you Gav.....

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