Project Nissan 240SX KA24DE Part 2 - Tech Knowledge

After weighing our options, the decision was made to install the engine into its inevitable home, a '95 Nissan S14 chassis. Naoto Negishi, owner and engine builder of NPD believed that the time spent on building a fixture and adaptor to mount the engine to a dyno could be more effectively used to install the motor into a chassis. In turn, this opened up our options for locations where we could test and tune.

Once the engine was secured to the mounts, we turned our attention to the transmission. Before fabricating anything else, the engine needed to be in its proper position. Without the transmission installed, the angle of the engine would be off. Knowing the weakness of the stock KA24DE transmission, we questioned if we should reinstall it. Looking at different options for a transmission upgrade, we realized that cost and strength have a positive relationship; the stronger the part, the most expensive it usually is. We decided to scrap the stock tranny in exchange for a gearbox from a Z32 300ZX. The VG30DETT transmission has been proven to be able to withstand more torque than that of the KA24DE. But how do we get it to mate to our KA? We called Mazworx for their KAVG S-Chassis Transmission Adaptor Kit, which includes everything you need to adapt the VG tranny to a KA or SR engine. Tested by Mazworx's in-house race program, the stronger VG30DETT transmission will ease our worries of breaking a transmission from the dyno to the track.

Since the KA24DE came as standard equipment on the stateside 240SX, we had no issues with fitment of the engine. Starting at the base, Naoto chose to use solid motor mounts from Blast Racing to keep the engine in place under high load situations. Made of billet aluminum, solid mounts are non-forgiving when it comes to vibration, but considering the car the engine is being built for, this is a small concern. In actuality, non compliance aids in keeping anything not secured to the engine in place. These mounts were originally designed for use with an SR20DET engine, and after the initial installation, it came to light that the KA24DE sat a little high, comparaed to the position of the SR20DET. Cutting the overall height of the mounts by 10 mm improved clearance of the engine to the hood.

On a standard build, a host of companies make intercooler kits for the S14 chassis. But this build is far from standard. To ensure there were no restrictions from the intercooler core, a massive GReddy R33 Spec-R core (302x710x165 mm) was used to handle the duty of cooling our intake charge. There were many aspects taken into consideration when designing the charge pipes, such as clocking of the turbo, sizing of the piping, and transition couplers. The turbo clocking (rotating) is restricted by the amount of space it is confined in, while the piping size is dictated by the outlet size of the turbo's compressor housing (76.2mm turbine side, 90mm for the compressor).

The process began by sending Mazworx the bell housing for CNC machining. They returned the machined housing with an adaptor plate, brackets, cross member, short shifter, driveshaft and all the necessary hardware. The adaptor plate was doweled to eliminate issues of misalignment between the block, plate and bell housing. Adding a Nismo tranny mount as a finishing touch, the transmission was secured into place.

Turbochargers are a compromise between response and power: a small-frame turbo delivers high response but low power capability, while a large-frame turbo develops low response but a higher power output. We knew we needed a big turbo that made power, but we were a bit surprised when Naoto came to us with his turbo of choice: an HKS T51R KAI. Usually reserved for big-power Supras, we were skeptical whether a four-cylinder KA24DE could spin this turbo, but Naoto explained that if we were aiming for 750 whp, this was the perfect turbo.

To distribute vacuum/boost throughout all the different components, a Blox Racing billet vacuum manifold chamber was used to eliminate the need to drill multiple vacuum ports into the intake manifold plenum. A single line from the intake plenum was fitted to the vacuum manifold, so vacuum could then be dispersed through machined metal nipples to the MAP sensor, blow-off valve and other accessories.

In our last installment, we had an initial mock up of the 60mm Turbosmart wastegate positioned under the power steering pump. This preliminary design proved to be problematic, as the transition from the manifold would be a tight fit. This would also radiate heat to the power steering and intake systems. Instead, Naoto decided to redirect the wastegate inlet tube towards the transmission and clock the wastegate pipe towards the back of the car. Because of the weight the pipe bears, it has to be reinforced at the manifold and under the car, to prevent cracks.

With the amount of boost needed to make 750 whp on a four-cylinder engine, intercooler pipes pulling apart was a concern. Rather than using standard silicone hoses and clamps, Naoto chose to use Adel Wiggins Flexible Tube Connectors (Wiggins clamps) on both the intercooler system, as well as the radiator pipes. Utilized by race teams, aerospace and the military, Wiggins clamps can withhold compressed air or fluids, and are tested to seal at greater than 125 psi, up to 450F and flex 3.5.

Taking into account how much boost would be running through the system, Naoto wanted to ensure that the blow-off valve would not leak under full boost, while being large enough to expel all the residual compressed air in the intercooler system. The GReddy Type-R was chosen for this build, with its stiff spring, 47mm valve and 50mm outlet that help prevent compressor surge and premature boost leakage, even under high boost pressures.

To keep up with increased engine performance, the cooling system needed to be reworked as well. The stock radiator was traded for a GReddy two-row aluminum racing radiator, designed to increase coolant capacity and efficiency. An air separator tank was incorporated into the system to remove any unwanted air in the cooling system that can lead to overheating and head gasket issues. It is important that this tank be mounted at the highest point of the system. Many times, these tanks are mounted below the plane of the radiator cap, and since air rises in liquid, this will prevent bubbles from collecting in the tank.

Unlike its RHD Japanese cousin, the steering column somewhat obstructs the turbo's area. In addition, the 60mm wastegate also shares this area with a 90mm downpipe. This made real estate a real premium. Relocated down by the subframe, the wastegate was positioned out of the way of the downpipe and the steering column.

Each Wiggins clamp set consists of a ferrule welded on each respective pipe, a hard o-ring sleeve, o-rings, and the clam shell clamp. This means that these clamps are designed to handle pressure four times the amount that we plan to run. Naoto says mistakes are often made with Wiggins clamps when choosing o-rings. The target range of temperature should dictate the hardness of the o-ring chosen. Since our purpose is to seal compressed air, the temperature range is relatively low and a softer o-ring can be used, making assembly easy. The downside? The cost of Wiggins clamps compared to standard silicone hose-and-clamp set-ups keeps it out of budget for the average consumer.

In addition to the cooling system, an oil cooler was added to further keep engine temperatures down. Using a sandwich adaptor, we mounted a GReddy oil cooler core between the intercooler and radiator. For added insurance, an Accusump oil accumulator was installed in-line with the lubrication system. After consulting Accusump, Naoto opted to mount the accumulator in the trunk, running an aluminum hard line into the oil system. The Accusump acts as a pressurized oil reservoir, to be released when there is a drop in oil pressure, and used as a pre-oiler at start-up, preventing unnecessary wear to friction surfaces due to lack of oil.

Since the power steering fluid return is under high pressure, a baffle was integrated in the center of its reservoir, with flow ports drilled around the center. The baffle acts as a shield to keep the spray to the bottom of the reservoir, yet allowing ample fluid to feed the pump. Adding a cooler keeps power steering fluid temps from soaring under high steering input, and keeps fluid from boiling over-a common problem on Nissans under constant steering input.

There is no doubt that the most effective fan is a clutch fan with a shroud. But to free up as much power and response as possible, we eliminated the parasitic drag of the clutch fan and used an electric fan in its place. Naoto built an aluminum shroud for the fan to mount to, pulling air through the entire core of the radiator. Like the intercooler plumbing, the radiator pipes were made from aluminum and sealed off with Wiggins clamps.