Total tuning is a philosophy that involves putting parts together that will work well as a whole to net the maximum performance intended. The ultimate goal of our KA24DE build is to yield extreme power yet keep it within a reasonable realm of reliability. With the completion of our long-block assembly, we ensured that we had a strong core for our KA24DE. Next, we will go over the external engine accessories and parts to seal up our motor, preparing for its installation into our donor vehicle.
Since Naoto was going to build a KA24DE project long before we approached him about it, he had already begun making appropriations for an intake and exhaust manifold. By the time we got to our build, the basic construction of both pieces was already done. All that remained was for it to be adjusted for final fitment.
You can see the preliminary...
You can see the preliminary fitting process here. Only when the pipe is properly fitted can it be welded.
The KA24DE intake manifold is similar in design to its S13 SR20DET brother in that it also has a two-piece design and runner path. After analyzing the overall design of various SR20DET aftermarket surge tanks, Naoto came up with his own design, using a SR20DET surge tank and the factory KA24DE as a base. The surge tank is a five-piece design that's constructed of a 3mm die-pressed aluminum sheet. That means that each sheet is cut to fit, inserted into a die mold, and pressed to shape. Each of the pieces are fitted together like a jigsaw puzzle to give it the overall shape. To promote a smoother, even flow of air, Naoto added velocity stacks at the end of each runner. The entire assembly is welded together after careful fitment.
To get more injector choices, collars are machined and inserted into the injector bosses. Usually an O-ring would be used here to seal between the boss and the collar, but to prevent leak under high boost, Naoto chose to weld them instead. A GReddy fuel rail then feeds each injector. As for throttle body choices, initially we thought about going with a Pulsar N15 70mm (OD 80mm) throttle body, but after thinking it over Naoto didn't want to take any chances with choking the motor off, so we chose to use a Q45 83mm (OD 90mm) throttle body.
This is the final overall...
This is the final overall shape of the intake manifold. We will be using top-feed injectors rather than the factory side-feed style.
To flow enough air to hit our power goals we knew a big turbo was in order, but we didn't think that NPD would go with a turbo this big. The weapon of choice is an HKS T51KAI turbo. Our initial reaction was: "No, that is way too big," but after the shock, we realized it made a lot of sense. This turbo is rated to make power in the 800bhp range, a hair over our target of 750 bhp. A heavy-duty turbo needs an equally heavy-duty wastegate to keep up with it. We called on Turbosmart for its new Power-Gate60. Newly released, it's 30 percent lighter, 20 percent smaller, and has 40 percent more flow than its previous Power-Gate50.
The design of the exhaust manifold is pretty straightforward. The key criterion is the same as any high-performance exhaust manifold: be able to adequately flow, be rigid enough to not crack, and be serviceable. The base flange is a 19mm CNC-machined piece designed by NPD. Exhaust moves out of the flange into 42.7mm ID, 3mm thick runners. Each runner meets at a 4-1 merge collector and is finally pushed out through a HKS v-band turbo inlet. Waste pressure is sent through a double-slip fit wastegate outlet tube. The wastegate tube is plumbed right at the base of the merge collector to maximize efficiency. The combination of wall thickness, pipe size, design, and slip fit joints work together to meet all of our criteria.
 The velocity stacks aid in...  The velocity stacks aid in the smooth flow of air. Without them the abrupt transition of the adaptor flange would inefficiently move air into the runners. |  The Q45 throttle body (83mm...  The Q45 throttle body (83mm ID) is a 23mm increase over the stock KA24DE (60mm). |  We used a top-mount style...  We used a top-mount style exhaust manifold to make room for our massive turbo. |