The second generation VW Golf GTI 16V, referred to be devotees of the marque as the A2 or MKII, is a terrific second-hand car. The 8-valve GTI won Car and Driver's Car of the Year award in 1985, the year it was brought to the U.S., and things just got better from there: In 1987, VW introduced the 16V GTI. Initially it made 123 horsepower, but by 1991 was producing 134hp. Do the right modifications and this practical hatchback can easily be made as fast as many full-on sports cars and sports sedans from the same era, such as Porsches and BMWs.
What is Turbocharging?
Turbocharging is a form of forced induction that forces more fuel and air into the motor. The turbo works off the exhaust. As exhaust gases exit the motor, they are forced through the fins of the compressor inside the turbocharger, increasing the horsepower by forcing more air and fuel into the motor. The fact that the turbo works off the exhaust is also why lag can be a major issue, where there is a moment before the turbo kicks in and increases horsepower. The great thing about turbocharging is that you can take a relatively small motor and make it much more powerful.
The 16V Engine and Turbocharging
Either a 1.8-litre or a 2.0-litre motor can be turbocharged, but the 1990 and later 16-valve GTIs featured a 2.0-litre, DOHC inline four that even in stock form puts out an impressive 134 horsepower. The exterior also featured more modern-looking bumper treatment.
Something to consider when turbocharging a GTI motor is the compression ratio, which can be a limiting factor in turbocharging, since turbocharging increases the motor's compression ratio when under boost. In stock form, the 16-valve GTI has a relatively aggressive compression ratio of 10:1. This is suitable for boost pressures of up to five pounds, which can deliver around 40 horsepower. Anything beyond that, though, will require rebuilding the motor with a lower compression ratio. This can be done with aftermarket pistons or pistons from a supercharged VW Corrado. You can also start with an 8V 8.6:1 compression ratio block, which already has a turbo-friendly compression ratio, and mate that to the 16V head.
Along with the turbo unit itself, turbocharging a car requires other components. Since the motor is getting more air, larger fuel injectors are recommended to provide adequate fuel. Heat is the enemy of horsepower, so to keep things cool, an intercooler helps. Once the turbo and associated plumbing is installed, a free breathing 2.5-inch exhaust is recommended for getting the most from the turbo. You'll also need to install some type of engine management system or at least a boost controller to control the amount of boost from the turbo.
Sourcing the Parts
Since the GTI is such a popular car for tuning, there are companies that offer turbo kits. Kinetic Motorsports offers a ready to install kit for the 16-valve GTI. You can also source the parts yourself. You will need a manifold for the turbo conversion, available from various sources like APTuning. The turbocharger to use is a Garrett T3 turbo, which can be sourced new or acquired from a junk yard. Do some research and you'll find a lot of mass-produced cars used this turbo, such as Saab 900 Turbos.
The Complete Package
With the addition of more power comes the need for added control. A successfully turbocharged Golf will be a blast in a straight line, but with only a front-wheel-drive platform to control all that power, it's a good idea to sort the chassis to balance the performance and keep things safe. What this means is a lower, stiffer suspension to reduce squat and dive and possibly wider wheels, so you can install stickier tires to control the power. As well, a high-quality limited-slip differential, such as a Quaife, is suggested for the front end. This will ensure that the horsepower is distributed properly to the front tires, allowing you to really use that newfound horsepower and torque. Extra braking, to slow the car from the higher speeds it can now attain, is also highly recommended.
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