2003 VW GTI 1.8T - Getting A Head - Tech - Eurotuner Magazine

Our MK4 VW GTI Gears Up For More Power With A Ported Aeb Head And New Intake Cam

After seven consecutive years of daily-driving our '03 VW GTI 1.8T, the most power we achieved was 195whp and 233 lb-ft of torque. Plenty of juice for a daily street car, but it was time to take our project to another level. So last month, we began preparations for more boost by calling Integrated Engineering (IE). They presented us with their 2.0L stroker kit.

In case you missed last month's issue, IE's stroker kit includes 83mm Mahle pistons, H-Beam rods and a 2.0T FSI crank. All the parts allow the 1.8T to withstand more abuse while enhancing its efficiency and ability to make torque.

The larger pistons give a capacity of 2008cc from the standard 1781cc, while the bigger diameter helps reduce cylinder pressures and stress on the engine.

IE's rods are regarded as some of the strongest in the business thanks to a robust H-beam design with wider beams. They've also been heat-treated and shot-peened for strength.

The final component is the 2.0T FSI crank that's been modified to drop into the 1.8T block. The stroke is increased from 86.44mm to 92.88mm and it's also a stronger forged piece compared to the 1.8T's cast part.

With the stroker kit in our hands, we were ready to dismantle our motor. Project Silverstone was entrusted to Raven Motorsports in Long Beach, CA because of their expertise with VW and Audi platforms. They had also just wrapped up their own big-turbo Audi A4 1.8T that competed in eurotuner GP (see et 2/11).

So Raven put our GTI on the lift and removed the motor in half a day. The next week entailed removing the stock engine internals, then cleaning the block for the stroker kit.

It occurred to us that we weren't taking advantage of another opportunity. It's not everyday we have the motor disassembled, so we brainstormed some ideas to make the new setup flawless. As a result, Javad Shadzi of 034Motorsport recommended a proven strategy for big-turbo 1.8Ts - upgrading to a high-flow cylinder head.

For newbies, the head sits above the cylinder block. It contains the valves, spark plugs, inlet and exhaust ports plus cams. Since Project Silverstone is a '03 model, it was manufactured with an AWP engine, which had the later-style cylinder head. However, the earlier AEB 1.8Ts were blessed with a high-flow head with larger ports.

Now you might be wondering why VW would make the later 1.8T more restrictive. After chatting with Javad, he had some insight to offer: VW and Audi stopped using the high-flow heads because the larger ports weakened it. The valve seats tended to move around, causing the valves to break. Hence, the AEB head was ditched in '00 and went to a smaller port head with added material for strength. "But we found if you take a used AEB head, one that's been heat cycled for years, then re-cut the seats and lock it back into place, the head is more stable. This prevents the problems of the lack of material," Javad explained.

With our aspirations to build the most complete package, 034 had an AEB head available in their inventory. Their machinists performed a stage 3 porting job to improve both the quality and quantity of air flow. "It's not the most aggressive job. We can pull out more material, but if you get too aggressive you lose a lot of velocity on the lower valve lifts, which would cause power loss on a street car. A good porting job involves more than just removing material," he said.

Every inch of the combustion chambers and ports were smoothed and shaped to optimize flow, preventing hot spots and carbon buildup. 034 installed 1mm oversized stainless steel intake and inconel exhaust valves to aid airflow in and out of the head. Bigger valves required the seats to be enlarged, as well as the bowls between the valves and ports.

Along with the new valves, Supertech high-rate valve springs and titanium retainers were fitted. The retainers are important because they weigh less than half the stock ones. This helps the valvetrain react faster at higher RPM. In a stock valvetrain, revving above 7000rpm is stressful, so the retainers also feature a stepped design. This allows a longer, stiffer valve spring that lessens the chance of the spring becoming coil-bound, giving the valvetrain more travel.

Finally, 034 replaced the valve guides and stem seals with OEM parts to ensure they were fresh. The AEB head was surfaced, smoothed and washed before it was shipped for installation.

With a ported AEB and stronger valvetrain parts, our 1.8T motor will be capable of exceeding 9000rpm. "Ultimately, this will give you a faster spooling and a more responsive setup," Javad explained. "It will give good power between 4000-8000rpm. It's a must if you want to rev over 7000rpm and make good peak numbers."

Horsepower and torque gains with an AEB head vary depending on the turbo and cam setup. But it was reassuring to know 034 uses the same head on its Time Attack Audi A4 1.8T from eurotuner GP (et 2/10).

With the new cylinder head ready for Project Silverstone, we sourced a high performance drop-in intake cam from Autotech. It's not aggressive like a race cam that tends to have rough idling. The Autotech cam is intended for street cars and has shown to gain power in tuned or stock 1.8Ts.

The cam isn't a reground factory part either. The stock factory cam duration is 184° at .050" lift. Whereas the Autotech part makes it slightly more aggressive with 195°. The longer duration keeps the valves open longer, increasing airflow. The lobe centers that operate the valves were also moved to create more mid-range power that extends into the top-end.

Next month we'll show you the engine re-assembled and hope to bring you our initial dyno figures before we go big-turbo.