- Designed and constructed by SEM from A365-T6 aluminum and heat-treated
- Plenum features 2.75L of internal volume for increased flow capacity to supply enough volume for higher rev limits
- Shallow profile design maintains lower CG (center of gravity); will accommodate various 1.8T swaps
- Large inside diameter and calculated runner length to support higher peak hp
- Standard stock TB and 80mm TB-sized flange openings available (custom options available upon request)
2003 Volkswagen Golf GTI 20th Anniversary
Engine 1.8L turbocharged 4-cylinder
Relevant Mods Unitronic Stage 2 software, SEM 3-inch Turboback exhaust with high- flow catalytic, AEM intake, AEM cold air
The VW community isn’t exactly touted as a bunch of performance-driven enthusiasts. Instead, most focus on ride height and wheel fitment. However, that’s not to say there aren’t individuals out there looking to go fast and hungry for power mods. The GTI lineage of Golfs has proven to itself be a real contender from our German counterparts. And with a turbocharged engine, there’s plenty of room for improvement.
Intake manifold upgrades are usually seen as hard-core mods that are only done when engines are making big power and the stock unit is choking airflow. While this rings true in many cases, a properly designed intake manifold can actually be a worthwhile upgrade to any engine.
SEM Motorsports set out to build a manifold for the 1.8T that would improve flow and throttle response while gaining horsepower and torque throughout the entire rpm range. Cast from durable, lightweight, A365-T6, aluminum metal, the SEM intake manifold is designed to replace the stock 1.8T manifold with no modifications necessary.
The plenum features a 2.75L internal volume capacity, and combined with integrated velocity stacks, the increased airflow especially helps the upper rpm range where the stock intake manifold struggles to keep up.
SEM also put a lot of thought into fuel injector placement on the runners to ensure optimal fuel atomization into the combustion chamber. To ensure equal flow of both fuel and air into the engine, a tapered plenum design is used.
The manifold is compatible with all VW/Audi 1.8T applications, and its shallow profile means it can be used in many swap applications as well. It fits the stock throttle body, however, those looking for more power can order the 80mm option. SEM also offers longitudinal intake manifolds for VW Passat/Audi A4 1.8T, which are different in design but will have similar gains.
Using Magnus Motorsports’ in-ground Dynojet, the stock manifold–equipped GTI spun the rollers to a peak whp number of 188, and torque crested at 208 ft-lb. We let the engine cool off for about 25 minutes, and then we attacked the stock intake manifold. It was off in another 25 minutes, and the new SEM intake manifold was bolted and buttoned up in no time. Having the manifold at the front of the engine makes this swap an easy one, which any novice mechanic can attempt.
The black finish of the SEM intake manifold adds a lot of style points to the engine bay, but performance is where it really shines. Power figures instantly jumped to 208 whp and an even more impressive 243 wtq. That extra volume really does pay off, and it’s not just in the high-rpm range. As the dyno plot shows, significant gains are made in the midrange and continue on to redline. Remember that this is a stock turbo, so it falls flat up top. With a better performing snail upper rpm, power production should increase significantly.
Often when air-altering modifications are made, boost pressure can increase—and that’s where the gains come from. We were careful to note max boost before and after the SEM intake manifold (23 psi), and it was within a half psi, so it’s safe to say that the design of the manifold can be credited for the extra power, not an increase in psi. It’s rare to see an intake manifold deliver more power without altering or shifting the powerband, but the SEM unit does just that. It delivers gains where they count, on both torque and horsepower fronts, therefore getting a big thumbs-up from us.
+ 20.64 whp
+ 35.19 wtq
Before 187.73 whp and 208.23 wtq
After 208.37 whp and 243.42 wtq