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Our six-speed '01 Trans Am's LS1 had already been upgraded with SLP's air lid, mass air, and Y-pipe, along with a 180-degree thermostat and B&B TriFlo exhaust. With the stock computer tune in place, it made 318.2 hp and 329.6 lb-ft at the wheels--good enough for low-13-second quarter-mile times. |
The F.A.S.T. LSX Polymer Intake Manifold, PN 30-54001 is equipped with a 78mm throttle body opening and is advertised as adding 15-20 horses on a stock engine. Like the stocker, this sucker is polymer, and therfore will stay far cooler than aluminum aftermarket manifolds, creating a more dense incoming charge of air. This version will set you back $933. Choose PN 30-54003 for a 90mm throttle body opening. |
Over the years, nitrous has been given a bad rap. It blows motors, melts pistons, and sends the hoods of cars flying skyward. It even blew up an entire car in that Hollywood abomination, The Fast and the Furious. Come on, the stuff isn't even flammable!
The truth is nitrous can be used quite safely, and that's exactly what we are about to do here. Play it safe and you'll get power increases otherwise available only through extensive engine mods or forced induction. The rules of the game are as follows: 1. Watch your mixture. 2. Retard your ignition timing. 3. Monitor nitrous bottle pressure. 4. Use quality fuel. 5. Don't engage the system below 2500 rpm or at less than full throttle. Do all of this, and your motor will stay intact. As you'll see, the components we selected made our system virtually foolproof. Before getting to the details of our kit, one other important point that all nitrous sprayers need to be aware of is spark-plug concerns. Factory platinum plugs generally aren't nitrous-friendly because their wide gap makes it difficult to light a dense nitrous-fuel mixture. In addition, such a spark plug does not conduct heat out of its ground strap quickly enough, which can melt it and also cause a detonation condition. Bad news. The good news is spark plugs designed for nitrous use are readily available, with colder heat ranges and shorter ground strap designs to get the heat out of the plug quicker. We selected NGK's V-Power TR6, a relatively inexpensive and widely used spark plug for LS1s. The only downside to these plugs is that we'll need to change them about every 10,000 miles which, on these cars, can be a bit of a hassle.
As nitrous systems go, direct-port systems are king. Delivering the exact same amount of nitrous and fuel to every cylinder, they offer the ultimate in engine safety. This distribution issue is especially key on a typical non-symmetrical EFI manifold with the throttle body located at one end. While significantly more difficult to install than traditional "wet" or "dry" systems, the peace of mind with direct port can be well worth the time. The ZEX system tested offers a wide variety of power levels to choose from. As this Trans Am's engine is essentially stock, it was decided that 125 hp would be an appropriate value. As you'll see, our results leave some power on the table with a somewhat rich mixture. Safe may be a four-letter word, but it's music to my ears, and I wasn't about to alter the ZEX system's recommended jetting. Going to smaller fuel jets would most certainly have freed up a few ponies, but at the moment, over 500 hp at the motor is good enough for this author's daily driver. Incidentally, it turned out that with the as-installed recommended jetting, the nitrous added almost exactly the ZEX-promised 125 hp at the engine.
True, it may not sound as cool as a blower or turbo, and it can only be used during full-throttle, higher-rpm blasts, but nitrous-oxide injection is cheaper; total dollars spent for everything in this article (including the throttle body and other non-nitrous-essential items) was a bit over $4,000. And as currently jetted, this nitrous kit produced essentially the same performance increase a typical intercooled turbo or blower would.
Perhaps most importantly of all, the intimidation factor of purging a cloud of nitrous into the air is second to none.
The perfect complement to the LSX manifold is how ZEX markets this LSX Direct Port Nitrous System, PN 82032. Featuring one nozzle per cylinder, the system allows for reliable horsepower increases between 75 and 300 hp. The unique nozzle technology ZEX uses helps keep the same ratio of nitrous to fuel no matter what the nitrous bottle pressure happens to be, ensuring a consistently safe operation. MSRP is $1,593. | 
To begin the installation, remove the airbox and intake tubing and start disconnecting all of the plugs, cables, and hoses going to the intake manifold and throttle body. This canister purge line on the driver's side just aft of the throttle body has a tricky clip on it that requires one to press on its semicircular side in order to disengage it from the manifold. | 
Further back on the manifold is this sensor, which is attached to a bracket that slips into a recess on the stock manifold. The bracket will not be reused with the LSX manifold, nor will most others; however, this sensor does not need to be disconnected from the vacuum lines that attach to its aft portion. Just unplug it and leave it hanging there. Since you'll be working under the cowl, it helps a bunch if you take some dykes and clip all of the plastic fastener tips hanging down from the leading edge of the cowl. Otherwise, they'll constantly stab and scratch you and you'll look like a rabid cat attacked you. |
Since we did not have a J37088-- a quick-connect separator tool--handy (but you have one, right?), we had to take the fuel rails off of the manifold before removing the manifold from the engine. Four bolts are all that hold it down. | 
The fuel rails and attached injectors pop off of the manifold using just a bit of upward force. The rails were then laid aside in the passenger side of the engine compartment. Had we had the above-mentioned special tool, we could have disconnected the fuel lines from the rail and not had the rails and injectors lying partially in our workspace--no biggie though. | 
The only things keeping the manifold on now are the 10 manifold bolts. The ones beneath the cowl need to be held up out of their bores about an inch so that they are away from the cylinder heads; the bolts are of sufficient length that it is impossible to get them out while the manifold is still on the engine. Duct tape works well enough. |
Hot tip: don't even try to disconnect the brake booster hose from the back of the manifold as you are taking the manifold out. Save yourself a headache by pulling the hose off the brake booster itself. This way the hose will come along with the manifold as it is removed rather than obstructing manifold removal and possibly breaking its plastic fitting in the process. | 
As the manifold is pulled out, there are two more hidden connections at the rear that need addressing. One is a vacuum line going to the back rear of the passenger side of the manifold, and the other is the MAP sensor that sits in the top rear of the manifold. Just pop the MAP sensor up and out of its hole; don't bother unplugging it from the wiring harness. Be sure to lift the rear of the manifold before coming forward in order to clear an oil pressure-sending unit hidden back there. | 
It's outta there--finally! Taking a moment to compare the two manifolds side by side, it's clear the LSX intake port design (right) has been exposed to some design changes over stock. The most obvious is the amount of material left to be removed if the owner ever desires manifold porting (easy, thanks to the manifold's multi-piece design). It's worth mentioning here that although the LSX manifold is made of polymer, its polymer type allows it to be 30 percent stronger than the stock manifold. |
To help make room for the LSX manifold atop the engine, the lifter valley plate bolts are replaced with low-profile button head cap screws. This is necessitated by the LSX manifold's larger outside dimensions, requiring the manifold to be both taller and situated closer to the valley plate than stock. We were also told to remove the plastic clips from the knock sensor wires seen here, but our vehicle didn't have any to begin with. If your car is a pre-'01 F-body, you'll also have to replace your rear coolant crossover pipe. | 
Using a flat-blade screwdriver, the LSX intake must now be popped in half. See how easy porting this intake would be? The two halves of the manifold are sealed by a factory-type rubber seal running along every junction; check it to make sure it is in place correctly before putting the two halves back together. We won't do that just yet because we have some nitrous burst panels that need installing. | 
Using a 13/64-inch drill bit and 1 3/8-inch hole saw, the burst panel guides molded into the bottom of the lower half of the LSX intake are bored out. The purpose of having the ability for these passages to open up is that if a nitrous backfire were to ever occur, they would vent the excess pressure below the manifold instead of the manifold being exploded into so many plastic pieces. This scenario is far less likely with a direct-port system than with a "wet system" (where enrichment fuel is supplied within the manifold itself). One can never be too safe though. |
The LSX Nitrous Burst Panels (PN 30-54002, $187) install into the holes with a backing plate on the inside, which the cap screws thread into from the outside. This way, if these burst panels were to ever come loose, the screws could not get sucked into the motor. To avoid this "getting loose" scenario entirely, use some red Loctite on the screws. The stamped stainless steel burst panels are designed to open around 38 psi, saving the manifold (and possibly motor) from certain damage. | 
It's now time to install the nitrous nozzles into the LSX manifold. The manifold does not come pre-drilled for the nozzles, but does have bosses where the holes are to be made. After drilling with an 11/32-inch drill bit, the holes are tapped with the ZEX-supplied 1/8 NPT tap. The tap can be started by hand, and this is suggested to avoid going in crooked. | 
As each hole is being tapped, it's important to make sure that the nozzle is often test-fitted into the hole so that when it gets threaded in all the way, it tightens in the correct orientation (seen here). The nitrous and fuel need to be shot down the port to the intake valve in as direct a manner as possible. With the holes tapped correctly and all plastic shavings cleaned from inside the manifold, the nozzles can be installed for good. Use some Loctite on the nozzle threads. |