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Nissan 350Z: Exhaust and Air Intake Mods Andrew Totolos makes a few enhancements that help a new-generation Z-car breathe easier — and go faster. From "Tricked Out" episode DTRK-407

(Continued from page 3)

The 350Z stock engine, before the plenum and strut tower bar are modified.

Mod #2: Install Intake Plenum Spacer and New Strut Tower Bar

For the second modification, Andrew installs a plenum spacer, which will open the factory plenum all the way around by 5/8 of an inch. This will give a higher volume of airflow and allow more power for the car's cylinders. Andrew also installs a modified strut tower bar for better hood clearance with the modified plenum.

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Plenum spacer

Materials and tools:

intake plenum spacer
aftermarket strut tower bar
standard shop tools
sealant
putty knife
rag

	Figure A
	Figure B

Plenum Physics 101 — or — Is Your Z-Car Experiencing Shortness of Breath?

The intake plenum is basically a fancy term for the big open chamber in an intake manifold (figure A). Its job is to take the air from our intake pipe and distribute it into the cylinders (figure B). Like most stock parts on this Nissan, it's well designed and pretty efficient. But it does have a weakness that we can fix.

The stock plenum is mounted at an angle so it's a little higher in the back than it is in the front. Nissan did this so they could put in a front strut tower bar and allow the hood to close as well. But this angled design restricts airflow somewhat, thus robbing us of potential power. By installing a simple spacer, we can open up the plenum all the way around by about 5/8 inch, thereby increasing air flow and allowing the engine to run cooler, thus furthering the benefits we began with the installation of the cold-air intake. As an added benefit, the spacer helps insulate the plenum, thus adding slightly to the cooling effect. The net result of all this should be, what else, a bit more power.

And what about the plenum clearance with respect to the strut? That's easy. We just install a specially modified one that designed to work wiuth the spacer but still allow the hood to close.

Figure C

Install Intake Plenum Spacer

• In order to remove the factory intake plenum, the existing strut tower bar needs to be moved out of the way. Pop loose a couple of wires, and loosen the pre-load on the bar. Remove the two bolts on each side that hold the strut tower bar in place.

• Once the strut tower bar is gone, disconnect the cold air intake from the intake manifold at the silicone throttle body coupling.

• Remove the bolts that hold the two halves of the intake plenum together around the edges, and also the ones in the center of the plenum top (figure C) before popping off the crankcase ventilation line.

• With the top section removed, you can take a look inside the intake plenum.
  

  	Figure D
  	Figure E

• To install the spacer, unscrew the studs from the old spacer and replace them with the new longer set of studs that come with the kit (figure D).

• Any air leaks at the plenum would be bad, so clean the surface before dropping the spacer down over the new studs (figure E).

• Apply a thin layer of sealant on the upper edge, and drop the upper plenum half down onto the studs.

• Replace all of the fasteners. Everything should be tightened up in a star pattern to keep from warping the parts.

• Once the pieces are sandwiched together, use a putty knife and a rag to remove the extra sealant that squeezed out around the edges. The remaining sealant will need to cure for approximately one hour.

• Replace the cold air intake pipe.

Figure F

Modified Strut Tower Bar

• To go along with the new system, Andrew installs an aftermarket tower bar that will run in front of the plenum instead of over it, therefore it will not interfere with the closing of the Z's hood.

• In order to fit the new strut tower bar in place, a wiring harness has to be moved out of the way.

• Once the wiring harness is out of the way, the new strut tower bar can be installed. It works the same as the old one, so simply replace the bolts at the top of the towers, and tighten them down (figure F).

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