A compact, SUS exhaust manifold is crammed in between the chassis and the cylinder head. Space is at a premium but fortunately the parts are engineered in such a way where clearance issues are minimal.
The Emissions
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.
The Dyno
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.
The Drive
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.
The T518Z turbocharger is manufactured by MHI to GReddy's specifications. The T518Z is available with either an 8cm2 or 10cm2 turbine housing; the S2000 makes use of the larger housing, which contributes to it not running out of steam until around 400-plus hp. | 
About the only thing different between the AP1 and AP2 turbo kits is the eManage Ultimate. Actually, the eManage Ultimate is the same; it just comes with a slightly different plug and play wiring harness between the two vehicles. Either way, the system comes pre-tuned to work with the RC Engineering 550cc/min fuel injectors. No tuning required. | 
Right from GReddy, the kit is good for 299.8 hp and 227.83 lb-ft of torque as measured on MD Automotive's chassis dynamometer. |