Individual Throttle Bodies are common on many high-hp normally-aspirated race engines. This setup gives you immeasurably better throttle response and can free up some high-range hp that the stock restrictive intake manifold robs you of.
*NOTE* you will be bypassing your MAFS and as a result will need to upgrade to standalone fuel management. Instructions on setting this up can be found here. You will be removing or blocking systems necessary to pass emissions.
Time: 4-8 hours
-metric socket set and wrenches
-open-end or ratcheting wrenches in 10-14mm
-sawzall or comparable tool for cutting
-’01 and up Suzuki GSXR 750 or 1000 throttle bodies
-’01 and up Suzuki GSXR 750 velocity stacks (2 airboxes are required, this is only recommended)
-KA24DE intake manifold
-provisions for standalone fuel management. (see here for more)
-rubber plumbing couplers (clamps should be included, found at hardware stores)
-3/4″ by 3/16″ pieces of steel for brackets (hardware store)
-1-1/2″ angle iron
-throttle cable (dohc cable is very long, sohc is shorter)
-distributor block off plate
-vacuum line and plugs
Begin by cutting the runners on the upper portion of the intake manifold approximately 6″ from the flange. If there are any sharp or rough edges, filing them down would be a good idea. Use the couplers and clamps to connect the GSXR throttle bodies to the new ends of your manifold.
With that complete, use the pieces of steel to fabricate brackets for the ITB’s. although this is optional, it is recommended for extra structural security. You can bolt one side of the bracket to the ITB assembly and one under the pcv rail to attach to the manifold per side.
You can now move on to your new throttle cable bracket which you will fabricate using the angle iron. You can use the EGR’s mounting surface to attach it to.
Run the sohc throttle cable to the ITB’s throttle wheel. The end of the Nissan cable should fit in the wheel.
Mount the GSXR 750 velocity stacks you collected in order of short, long, long short. This appears to be the optimal setup for street driving according to drivers’ impressions.
The assembly of the new manifold should be complete at this point. You can bolt it in place and clear away the harness since you won’t be using it anymore.
Since your car is no longer mechanically timed, You should remove the distributor and install a block-off plate over the hole. To save some time and money, you can make the block-off plate double as a mounting surface for the EDIS ignition coil, since the plugs will reach just far enough to contact it in that location.
At this point it would be a good idea to consider installing the necessary parts for your fuel management system. If you decide to use Megasquirt, you can assemble the board and prepare the trigger wheel and ignition setup and prepare your new wire harness to your necessary sensors.
It’s simply following the diagram, running each wire to each sensor.
the only things that were not on the diagrams were the tach signal, water temp gauge and the switched ignition power supply. For the tach signal, run a wire from the clean tach uut pin on the EDIS module to the tach input on the back of the gauge cluster.
Speedo should still work. Run a wire from the second temp sensor in the intake mani to the coolant temp input on the back of the gauge cluster. The B/R wire coming from the igntion switch on the steering column needs to be tapped into to get switched power to MS, and the ignition components.
However, the wiring diagram for the ignition is slightly off. the polarity of the VR sensor wires is opposite than in the diagrams, so wire that up accordingly.
for the brake booster, you can use the stock PCV rail, and run one line from its output to the brake booster. You can also tee a 1/4″ vacuum line out of this line for the fuel pressure regulator.
the ITB’s come from the factory with a vacuum line from each port teed into one. this is used for the map sensor. Simply run a line from this to MS. the MAP sensor is inside the MS box.
Finally, plug the EGR hole in your header.
For reference, here is a stock KA24DE fuel map: