UGLY! There's no other word to describe the performance of the KA24DE engine in stock form. Nissan tunes the KA24's 2.4-liters of displacement to deliver just 155 horsepower at 5,600 RPM.
Take the KA24DE under the knife and add a turbocharger system and you'll see the "ugly" transforms into a knockout. With the KA24DE, Nissan accidently built a awesome foundation for a turbocharged four-cylinder engine. The engine's large displacment drives turbos into boost quickly. The KA24DE's connecting rods and crankshaft are also quite strong. With proper tuning and a well-engineered turbo system, 300 horsepower can be realized on the stock internals. Beyond 300 horsepower, the factory pistons often experience cracks on the ring lands and fail when a hint of detonation is encountered.
For our KA24DE build, we'll eliminate the weak links and add in some additional strength and reliability with Eagle connecting rods, JE Pistons, Clevite bearings and ARP fasteners. To maximize efficiency and produce more power per pound of boost pressure, we'll also address the cylinder head and valvetrain to improve the engine's volumetric efficiency.
One of the biggest advantages the KA24DE engine has over the SR20DET is its iron block. Iron is significantly stronger than aluminum although it suffers a significant weight penalty. For the purpose of containing the extreme pressures in the combustion chamber, there is nothing better than a strong cast-iron block. Our KA24DE shortblock was sent to Cosworth USA for preparation. The block was resurfaced prior to assembling the BHJ deck plate with ARP fasteners. The BHJ deck plate simulates the distortion the piston bores exhibit when the cylinder head is secured to the block. This ensures the cylinder bores are absolutely perfect circles when the pistons are installed. The KA24DE was only overbored to 89.5mm, leaving plenty of material remaining between the bores. We selected 9.5:1 JE Pistons with the optional thermal barrier crown and anti-friction skirt coatings. The reduction in heat transfer from the thermal-barrier coating helps increase the engine's performance by utilizing all of the combustion gasses to push down on the piston during the power stroke. The anti-friction coating on the piston skirts also reduces power loss as the piston moves up and down the cylinder bore. The pistons connect to the factory crankshaft by way of Eagle forged connecting rods. Cosworth performed a high-speed balance on the entire rotating assembly (pistons, rods, crankshaft, crank pulley and clutch/flywheel) for smooth operation.
Heading in the Right Direction
Port Flow Design treated our KA24DE head to a port-and-polish before fitting the oversized Supertech stainless-steel valves and complementary valvetrain. Higher-tension Supertech valve springs and titanium retainers keep the valves on the seat. A pair of BC Brian Crower Stage-3 camshafts were selected to increase lift and duration for more power in the mid-to-high RPM range. Proper cam-to-bucket clearances were set by Port Flow Design after installation of the Supertech bucket-over-shim conversion kit.
Pain is the Name of the Game
As we cinch the Cometic MLS head gasket between our built bottom end and upgraded cylinder head, there' are just a few more hours of work that need to be completed to have the engine ready to drop in our 240SX. According to Jeren, he's getting ready to deliver a heap of hurt to Richard's SR20.