above : Our Bolt-on Stage 1 GTi turbokit (200hp)
In this article we will give you a overview of turbo theory and then tell you what you should look for in a GTi turbo kit
Turbocharging the GTi is one of the best ways to make additional power. The g13b is amazing engine, it's the GTi's best asset. For a 1.3 dohc 16v it produces an amazing 100hp @ 6500rpm. Also it takes well to turbocharging more than other engines due mainly to it's four valve pentroof combustion chamber design, which is very effective at breathing deeply and resisting detonation. Plus throw in the fact it has a great cylinder head design, forged pistons and crank and you've got a excellent foundation to build upon.
Ok first some basics. Turbocharging uses a turbine driven compressor to increase the pressure of the air making its way into the cylinder. By increasing the pressure of air entering the cylinder the density of the air in the cylinder is increased. When you add more fuel to this increase in air, power is increased greatly.
The turbocharger itself is actually two components in one assembly sharing a common shaft. On the shinny end, its a compressor housing with an inlet occupied by the compressor wheel. However on the opposite end, it's a turbine with an outlet occupied by a turbine wheel. The turbine is provided with a steady supply of high energy exhaust gases which pulse out of each exhaust manifold runner and blows against the turbine wheel.
The advantages on turbocharging are : A) Increased horsepower and torque. B) Not much of a loss in Fuel economy (low boost system)
The disadvantages to the turbo route are : A) Cost. Things can start to get expensive, depending on what components you choose.
Turbocharging your GTi
Low Boost Turbo Systems - Stage 1
The simplest turbo setup would be a stage 1 low boost turbo system. This type of system is fairly easy to install and you will get good off-boost performance and quick turbo spool up with a minimum of turbo lag. This type of bolt-on kit consist of a gt25 turbo , Cast iron/mild steel manifold, front mount intercooler, fuel controller, 2.5" downpipe, fifth injector, pipework, brackets, bolts, hoses. When selecting your turbocharger, choose a ceramic ball-bearing turbo, since this will enable even faster turbo spool up and higher boost pressure per engine rpm. Expect an additional 7-10hp just by using this type of turbo. Another thing you will also need to be using is an exhaust system that utilizes a diameter of 2.0-2.25", to reduce back pressure and boost spike. When getting the exhaust done ask for mandrel bent tubing, it'll keep the tubing diameter consistent. A blow off valve is also needed. This is to prevent compressor surge when the throttle plate is closed. An added benefit is the 'pfft' sound you'll hear. Generally with this type of system you can run a max of 12psi of boost with a high efficiency intercooler. With the low boost setup and stock 10:1 compression ratio you must use premium fuel to avoid pinging/detonation. The power you can expect to make ranges from 130-200hp with this setup. Torque will also almost double, giving you great pickup even in 4th and 5th. Quarter mile times will be in the mid 13's to mid 14's depending on your setup/driving skills.
One modification you will have to make when installing a turbo is modifying the oil pan for a return oil line. The way you want to do this is first remove the GTi's oil pan, then drill a hole to mount the oil return fitting near the top at the front of the pan. Make sure the fitting is above the oil full line, so that returning oil flows steeply downhill. After you drill the hole, use a 5/8-inch fitting and make sure the fitting is welded to the pan. In contrast getting oil to the turbo is relatively simple, as a "T" fitting can be used from the engine oil pressure gauge sending unit. Make sure you use hi-temp braided-stainless steel line designed to carry oil.
Another thing to consider is the type of deltagate you will be using to control your boost pressure. You can use a internal or external one. The internal deltagate is easier to work with since you have less plumbing fabrication work to do.
After you install your turbo system make sure you are using very cold spark plugs to fight detonation and use race gas when you tune the system on a dyno.
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chill.
