GReddy's Mike Chung reassured me that his coworker wouldn't mind my positioning his turbo S2000's tach needle somewhere in the neighborhood of nine grand. At over 10 pounds of boost. On a local stretch of road just around the corner from GReddy's suburban headquarters. In the middle of the day. At first I thought maybe Mike didn't care for the guy. But I soon realized there were two more likely explanations. One: GReddy's S2000 turbo kit does little in terms of sacrificing Honda reliability and as such makes no qualms when it comes to revving the F-series full song. And two: visiting the upper part of the tachometer is a definite prerequisite for feeling all of what the T518Z turbocharger is worth.
Own an AP1 or AP2 S2000? Here're seven reasons why you should, at the very least, consider GReddy's newest Honda turbo kit.
Honda should be commended for developing the F20C/F22C S2000 engine. It is, after all, the most powerful Honda four-cylinder we can get our hands on from the dealer. And it should be, seeing as how the whole point of the S2000 was of a celebratory nature, recognizing Honda's half-century of efforts. Horsepower per liter figures and the engines' engineering are both exceptional. Even the smaller F20C pushes 240 hp and 153 lb-ft of torque, and has an 11.0:1 compression ratio and factory forged pistons, a rarity in terms of Hondas. Sure, a respectable engine, but it always falls short when compared to turbocharged 4G63s and Boxers of smaller displacement making more power. Fortunately that can be taken care of.
GReddy's S2000 turbo kit is based off of a Mitsubishi Heavy Industries (MHI) manufactured TD05H-18G turbocharger, the compact T518Z. A couple of turbine housings are offered for this turbo, 8cm2 and 10cm2. The 2.0L, F20C and 2.2L, F22C both benefit from the 10cm2 exhaust housing's larger scroll area and inlet. The larger housing makes for a negligible amount of low-end lag but makes up for it in its ability to ultimately outflow the smaller housing, something you'll appreciate once the boost is turned well past 10 psi and backpressure becomes more of an issue. Boost is controlled by a 7psi internal wastegate. This speeds up installation time and allows everything to fit within the confines of the engine bay; the longitudinally mounted F-series affords little room on the exhaust side. Like all MHI turbochargers, the GReddy-spec T518Z has one of the most durable center cartridges available, featuring a large-diameter center shaft and free-floating bushings. Such bearing designs have been shown to outlast even some of the lower end ball bearing housings not to mention most other journal bearing cartridges. The compressor wheel measures in with a 50.5mm inducer and 68mm exducer, translating into a 55.1 trim piece. The turbine's 76.87 trim comes from a 56mm inducer and 49.1mm exducer. This means that the T518Z is good for roughly 420 hp when matched with either of the F engines. Of course, upgraded internals and proper tuning will be necessary at that point.
Hondas typically don't respond well to forced induction without the proper foresight. Honda MAP sensors are not designed to increase fuel output at the sign of positive pressure and the high-compression internals found on most Honda engines make tuning a delicate matter. GReddy's solution begins with their eManage Ultimate-a piggyback computer that alters the signals between the ECU and various engine sensors like fuel injectors. RC Engineering 550cc/min fuel injectors are supplied with the kit and provide a generous amount of fuel for what the S2000/18G combination can push. But pairing such injectors with most any Honda and an OEM ECU will result in an overly rich condition in which the engine likely won't fire up. This is where the eManage comes into play. GReddy pre-tunes the piggyback with each kit to de-tune the injectors at idle, at lower engine speeds and when boost isn't being applied. The results make for an extremely smooth idle and exceptional driveability. The eManage Ultimate also alters ignition-timing maps to decrease timing as boost increases. This is especially useful when dealing with high-compression engines, such as the F20C and F22C, where detonation can happen relatively easily even without the turbocharger-just mix in some low-octane fuel and await the pinging.
The kit also includes a GReddy Type 31V front-mount intercooler. The V-spec core uses a tube and fin design and measures in at 195mm by 600mm by 76mm. Also matched with the 31V are all of the appropriate sections of tubing that contribute to making this kit a true bolt-on experience. The aluminum tubing is polished with bead-rolled ends to help secure the provided silicone hose couplers and clamps securely in place. An Airinx filter delivers air to the compressor side of the T518Z and a compact, stainless steel GReddy exhaust manifold supplies the turbine with what it needs. GReddy also provides a bolt-on downpipe that mates up with the factory-issued catalytic converter and features a separate section of tubing that allows the wastegate to breathe uninterrupted from the exhaust stream.
GReddy makes installation fairly easy. Typically, the most challenging part of turbocharging a non-turbocharged vehicle is sorting out the oiling system. The process generally involves a series of adapters for the feed side and at the very least a bit of welding on the return portion. Not the case here; the GReddy kit comes with a bolt-on solution. The oil pan still needs to be removed, but instead of welding on some sort of bung or adapter, all that's required is to drill the appropriate-sized hole and bolt the adapter and gasket in place. We mentioned how space is at a premium under the S2000's hood. As such, GReddy needed to find a way to make everything fit. Yes, the turbo itself is compact and so is the exhaust manifold. But no matter how compact the manifold design, little room is left over for the oil filter. The solution is included with the kit and comes in the form of a remote filter adapter. Changing the filter on an F-series has never been this easy.
The kit is CARB (California Air Resource Board) legal; what more can we say? And whether or not you happen to live in the state with the most stringent emissions regulations, CARB legality should matter to you. Why? Because if California says it's OK, then you can bet the kit will pass emissions tests just about anywhere else. GReddy's turbo system achieves such status for a number of reasons. First, it works with the OEM-issued catalytic converter. Second, GReddy provides all of the appropriate provisions on the intercooler piping for all of the necessary breather tubes, which is one of the first things emissions technicians look for when performing visual inspections. To conform to emissions codes, the GReddy kit does not include any type of blow-off or bypass valve. The vehicle we tested did have one, but we've found in testing that the MHI turbos are among some of the strongest and show little signs of fatigue in terms of compressor surge.
Horsepower figures peak at just over 299 to the wheels and torque is bumped up to a healthy 227 lb-ft. Both are considerable increases, 84 hp and 77 lb-ft at just 10 psi, respectively. It's interesting to note the abrupt torque jump just after 2,000 rpm. The split becomes considerable around 4,000 rpm where the turbo's 10 psi begins to come on strong. The torque predictably tapers off soon after but shoots up just after the 6,000rpm VTEC point. Power tapers off prior to the 8,000rpm mark but isn't apparent on the road. The results are an extremely linear power curve free of any significant traction-inhibiting torque spikes.
Driving the GReddy turbo-powered S2000 is another story. It seems as though there are two paths to take in terms of Honda turbocharging. You can either strap on the largest, oversized beast of a turbo you can find in hopes of attaining unworldly peak horsepower figures, little of which is actually usable, or you can err on the realistic side and fit something smaller. The second choice almost always makes for more usable power, which translates into a more enjoyable drive. This is exactly what GReddy achieves with the T518Z. Torque is applied out back gradually enough so as not to light the rear tires up in a storm of smoke, yet remains broad enough to outrun most any of the T-too-big Honda's not outfitted with slicks.