A little technical information regaring the popular throttle body install on the zx L28 engine family.
The 60mm throttle body in most applications is a nice thing to do, meaning it will not make your car any faster. What the bigger 60mm unit will do for your car is to give you a quicker throttle response, meaning for less pedal movement you will feel like the car is going better. The facts are that the bigger throttle plate will let more air into the engine with less pedal movement and that is why the car feels faster. The 50mm stock unit for many applications is good to go until you start really pushing some hp with engine upgrades. So there you have it.
The Nissan 240SX, 60mm throttle body is a must for applications above 350Hp. The stock throttle body is a 50mm unit and will not flow easliy without creating back pressure in the system, the required air to develop in the 450-500Hp range. I looked at the Webber throttle body, and the 240SX throttle body and decided the 240 throttle body would be a better fit to my application. The Webber throttle body has a 70mm inlet and necks down to 60mm with a 60mm butterfly plate. I did not want to go to all of the trouble of adapting a 2 1/4" pipe to the 70mm inlet on the webber. One good thing about the webber throttle body was the bypass air screw in the unit. The Nissan throttle body has no such bypass air screw, so I was required to install my own bypass air needle valve unit in the intake manifold. I had to make a 1" spacer plate to make the shorter 240 T/B the same length as the stock 280zxt T/B. I also wanted to keep the fast idle hardware on the car for cold days and the spacer plate worked excellent for that install. I used 70mm 8X1.25 allen bolts to mount the assembly. The throttle linkage was taken apart and parts from the 280zxt T/B along with parts from the 240SX T/B were used to make a very nicely modified throttle linkage assembly, very clean install. I used the nut, lockwasher and the throttle linkage from the 280ZXT T/B and the small spring from the 240SX T/B. I tapped the throttle shaft to the correct depth and hack sawed off the excess shaft. The threaded shaft is 10mmX1mm pitch threads (that die cost me 20.00, a little expensive, but worth the investment). The 280zxt linkage installed just like the stock T/B did and with a slight pedal adjustment the job was complete. I also blocked off the water passage through the T/B to help keep the air charge cooler. I used 1/2"X13 thread pipe plugs in both ends of the passage and that looks very clean also. I ran the water hose from the thermostat into the fast idle simply bypassing the Throttle body. The TPS was not a problem, as the 240SX TPS has the three prong switch just like the 280ZXT TPS. I just had to find which pins were the switch with the aid of a multimeter. The automatic 240SX TPS also has a three wire potentiometer that can be cut close to the body of the unit, also, SDS units can use this on their systems so if you are thinking of going that way it will work well on the SDS system. I also found a quick release connector on a Volvo 740 (not off my Volvo, but a junker) and have a quick disconnect on my TPS. I always had a hard time with the stock connectors and their retaining clips. I broke a number of connectors trying to get them off the various sensors and the injectors. I decided to take care of this problem and went with quick disconnects on all my ECU engine connections, sure makes taking the parts off again so much easier.
