The first stage of tuning any engine is always the initial breathing aspects. If the engine doesn`t need to work as hard then it`ll produce more power and torque.
So to help the engine we can do a number of things. The easiest are known as bolt on performance parts, namely air filters and exhausts.
These work by increasing air flow and reducing resistance. The most popular for Scirocco's is probably the K&N panel filter, which is a direct replacement for the standard paper filter. It has a few advantages over the standard filter,
it`ll last the lifetime of the car as it`s cleanable (with the correct cleaning fluid and oil)
it will allow a greater airflow due to the design of it`s construction.
Now, the panel filter on it`s own won`t really gain the engine extra power (not noticeably so anyway) but it should make the engine feel more responsive.
The only thing to watch out for when doing this type of modification is that the fuel air mixture will alter slightly, this is ok on the fuel injected models but the carbs may well need to be richened slightly.
Induction kits work in a similar way, they are not actually available for the Scirocco, however, a Golf mk2 K&N 57i kit can be modified to fit.
Theoretically the induction kit will work slightly better than a panel filter because of less air resistance and a shorter path for the air to flow along. However, a lot of applications that I`ve seen will probably be loosing power over the standard filter, this is due to the location of the filter itself. Unless the filter is shielded from any heat source it will suck in the hot air from the engine therefore lowering the combustion ratio which equals less power. The air getting into the cylinders needs to be as dense as possible therefore as cold as possible.
Drilling the airbox will have the same problem, more noise, but less power. I know – I`ve had tests on a rolling road done which show approx 6bhp (@wheels) loss on the drilled air box.
In summary the best way to feed the engine air will be through a panel filter, unless you provide adequate shielding for the cone type filter.
The airbox can be modified of course, look at Davids GTX page for details and pictures on the modification.
The exhaust is the first place most people start, it provides an instant change to the car in looks, performance and mostly noise.
There are many systems available for the Scirocco, the two most popular are the 2.5” Jetex and the 2” Supersprint. Both are good systems, well made and fairly easy to fit. The Jetex is rumored to be more awkward to fit due to it`s larger bore, I personally had no problems at all. In fact I had more problems with the Supersprint, but that was probably just me...
Exhaust systems help the engine in much the same way as induction modifications, the less the engine has to work in pushing the gasses out then the more it can work on producing power. Before you start thinking “great, I`ll just take my exhaust off then” you will need to know that the engine really needs an exhaust. As the gasses cool down in the exhaust they expand which helps suck the exhaust gasses out at the other end.
Without an exhaust pipe at all the engine will have no back pressure and therefore more power but the torque produced will be very much lower resulting in a very undriveable car. This is where you need a matched exhaust system for your engine size and power output.
For more standard and mild-tune engines the 2” Supersprint is fine, but if you are after more power, say over 135-140bhp then a larger bore exhaust is recommended.
To really benefit from an exhaust it is advisable to fit a 4 branch manifold. They do tend to be expensive, but are worth the money. They are lighter than the standard cast-iron manifolds allow much better breathing and get rid of the nasty manifold to downpipe clips which everyone hates! After fitting one slightly more noise may be noticed, but also more torque at lower rev ranges and more power further up.