Back in March, we started our engine tuning series with go-faster upgrades for the S50/S52 BMW E36 M3. We then followed up with guides for VW VR6 12v, M50/M52 E36 BMW 325i/328i, Audi/VW 1.8T and Audi S4 2.7-liter twin-turbo. This month, we're back down to earth for the two liter engine found in Volkswagen's Mk4 Golf and Jetta.
The more popular VR6 and 1.8T engines in the Mk4 were available between 1999 and '05, while the base models sported a normally-aspirated 2.0 8v rated at 115hp.
Today, even the most inexpensive cars (like Ford Focus, Chevy Aveo, Kia Rio and Toyota Yaris) develop that type of power. So if you drive a stock Mk4 2.0, be sure to pay close attention so we can bring your engine up to speed.
Keep in mind, we'll be assuming a baseline of 100hp to the front wheels (whp) on a chassis dyno, which is what an average car will produce on a given dynamometer. Diverse cars and dynos will vary, but we prefer not to use any flywheel guesstimates since they're usually quoted with a different assumed percentage loss and are rarely backed by engine dynos.
Although there are many parts available for the earlier 2.0 version of the Mk3 Golf and Jetta, we chose the Mk4 because more of our readers own them. However, we've added a section at the end for the older engine, so contact the companies listed to see what's available.
Note: The quoted prices don't include labor costs; they're simply prices for parts.
$0-1000:
Autobahn Designs (ABD) sells its Quick Flow air intake system at the retail price of $190, providing 4-6whp and ideal in wet climates. For dry weather areas there's a $230 LAN pipe air intake with a stainless pipe and ceramic-coating to keep heat out. Expect 6-8whp on a stock car. ABD also has a $165 stainless steel Big Bore intake to replace the stock plastic unit. Although an improved throttle response and a slight performance gain may be noticeable, it's more about system reliability.
APR offers the Carbonio's carbon fiber intake for $279. It has a thermal barrier to keep air cool and can be combined with APR's stainless steel cat-back exhaust for $789 ($769 without tips).
Autotech's cold-air intake (CAI) uses a 3" polished aluminum intake tube and K&N conical filter for $200. Its $130 peg-vernier adjustable cam gear is forged in anodized aluminum, with an alloy steel hub and cover plate, allowing timing in 1.5min increments.
C2 Motorsports is known for its software. It sells a software upgrade at $375, with extra software for forced induction applications. C2 also sells a low-compression head gasket for $150, dropping compression one point over stock.
ECS Tuning's $170 XAS Xtreme air system is a 3" CAI which comes in a variety of powder-coated colors. It draws air from the bumper and reportedly sees a 30-60 air temp reduction. However, it isn't recommended for extreme weather areas. ECS also carries Ansa Silverline 2.25" cat-back exhausts, which seem like a bargain for stainless steel at $300. The ECS lightweight underdrive pulleys come in a variety of colors and reduce weight by 73%, cutting parasitic drag on the engine through the alternator, power steering and alternator pulleys. For a refundable deposit, ECS will even lend you its alternator pulley removal tool.
Euro Sport Accessories (ESA) sells two intakes; its Cool Flow series retails at $200 and includes an ITG filter, rubber-sealed heatshield, hose and hardware. Its $220 Cool Flow Race series uses a mandrel-bent tube with laser cut bracket, setting the filter away from engine heat. It's not recommended for wet weather. On the exhaust side, ESA's $400 cat-back is an aluminized and stainless combo to cut costs. There's also a stainless version for $675. Both systems include a center resonator and are good for 5-8whp. The $160 ESA pulley under-drives the crank 23%, decreasing drag and unleashing up to 3-5whp. It includes a bracket and hardware to adjust the power steering pump and belt tension.
British-based Kent Cams offers a vernier cam gear allowing up to 7 advance or retard to the stock or an aftermarket cam. A Kent 260 cam with 11.2mm lift is available but may set off a check engine light (CEL). There are 266, 270 and 280 cams available as well from suppliers like Euro Sport Accessories and NGP Racing.