Free (And Low-Buck) Mods: * Descreen MAF - Screen is removed from MAF in theory to increase airflow, $0. Real Performance Motorsports and many other shops do not recommend this mod* Cut EGR Tube in LS1 Manifold - EGR tube is cut down in intake manifold to increase airflow, $0* Airbox Mod - Factory lower airbox and airdam are modified to pull more air in from underneath the car, $0* Throttle-Body Coolant Bypass - Engine coolant is not routed to throttle body, thereby allowing for a cooler charge, $5-15* Ported Throttle Body - Throttle body either home ported and polished or sent out to a service provider, $0-$300
Recommended Tools: * Metric socket set* Metric wrenches* Flat-bladed screwdriver* Schrader valve tool* Fuel-line disconnect tool
Dyno Testing: The '99 T/A, as tested in the baseline configuration already had a few of the "free or cost-effective" modifications done to it, including an aftermarket K&N air filter and a descreened MAF. With just a swap of the LS6 intake manifold, the car picked up a total of 7 hp from peak to peak, but more importantly, gains showed all across the rpm range. For the owner of an LS1 manifold-equipped Firebird, the LS6 manifold is highly recommended if the owner plans to add additional modifications such as an aftermarket camshaft or headers, as the LS6 manifold supports a combined head and intake flow above the LS1 intake manifold's nominal flow of approximately 285 cfm. Higher-flowing heads and camshafts that produce high lift will see big power gains with the LS6 manifold.
For the owner of an LS1-equipped Bird who doesn't plan to do more modifications or doesn't have the budget necessary for the LS6 manifold, the modification where the LS1 intake manifold EGR tube is cut down has proven to provide gains in the 3-5hp range on stock vehicles.
After spending less than five minutes swapping out the stock throttle body, the Shaner S2 unit produced an outstanding gain of an additional 5 hp and 5 lb-ft of torque. If you can stand to have your beloved Firebird down a few days, or utilize the replacement core policy that S2 Performance has, you will be rewarded with additional power.
The final dyno test involved removing the stock airbox assembly and installing the MTI carbon-fiber-look airlid. When the rollers stopped spinning, the MTI lid pulled down an additional 8 hp and 5 lb-ft of torque.
Total gains from an afternoon's worth of work added up to a tick under 19 hp and 14 lb-ft of torque. Had the car been baseline dyno'd with a stock MAF and factory paper air filter, it may have crested the rear-wheel-horsepower goal of 20.
The important thing is that you look at the gains from a system perspective versus just what the individual parts netted. It's entirely possible the order in which the dyno pulls were made may have increased or decreased the individual contributions of each part. In the final analysis, HPP has shown you how to gain a minimum of 15 rwhp for a very low entry fee.
Free mod! Throttle body coolant...
Free mod! Throttle body coolant bypassThe EVAP tube, PCV line grounding strap, and EGR valve are connected. Rather than route the coolant hose that comes off the front bypass hose to the throttle body, a brass connector with barbed ends is inserted into the line, and after slipping on two factory hose clamps, the other end of the throttle body coolant line is attached and tightened. The throttle-body coolant bypass mod was just completed. This procedure is the same on an LS1 intake, so if you don't need the extra heat that might keep your throttle body from icing up in the winter months, this modification may take you five minutes with a cool engine. Using a large crescent wrench, the EGR tube is connected to the LS6 EGR fitting that we installed earlier. The stock throttle body is then reinstalled with the three 10mm bolts, and the PCV hose was connected to it (not connected in picture).
Cost-Effective Mod! Shaner...
Cost-Effective Mod! Shaner S2 Throttle BodyThe LS6 intake manifold and throttle body bypass modification were dyno tested, and the car picked up power all the way across the powerband. With that test out of the way, we quickly swapped the stock throttle body for a used ported throttle body from S2 Performance. After sending in your throttle body for modifications, the Shaner S2 ported throttle body (on the left) is extensively reworked, including boring out the main body's restrictive ridge at the leading edge of the throttle blades. The air chamber is filled with epoxy, and brass air tubes are added to retain proper idle and PCV operation. Blade screws are ground flush with the shaft, and then the inside of the throttle body is hand sanded and smoothed. A ported throttle body will run you $119.95 in a satin finish or $139.95 polished. With the car loaded back on the dyno, the S2 throttle body was tested.
Free Mod! Maf Descreen, Or...
Free Mod! Maf Descreen, Or NotBefore installing the MAF and airbox assembly to the car, the MAF is inspected. Since the owner's car already had a MAF that had the screen removed, Real Performance Motorsports reached into its parts cabinet and pulled out a factory MAF. According to RPM and many other shops we spoke with, an enthusiast should never descreen the MAF or polish the MAF ends. As can be clearly seen in this photo, constant effective air filtration is a must if the MAF screen is deleted. Bugs and wood chips don't flow well through a throttle body. For those reasons alone, the mod isn't recommended. The only time a stock MAF will reduce horsepower is when it becomes incapable of either properly reading the signal to provide the PCM with an accurate analysis of how much air is flowing through it, or the MAF is maxed out (more air flowing through it than it can read). If the MAF ever needs cleaning, electrical contact cleaner is the only liquid that should touch the center electrical sensors. Back to our T/A, the MAF and airbox assembly are installed, and the key is cycled a few times to get fuel into the injectors and to check for leaks. After verifying there are no leaks, the car is started and then loaded back up onto the chassis dyno.
MTI was the originator of...
MTI was the originator of the aftermarket airbox lid. In addition to both black and clear units, the company offers this attractive carbon-fiber-look lid for the '98-'02 F-bodies. The airbox lid retails for $129 and includes a rubber connection hose and band clamp from the airbox lid to the MAF. The smooth underside of the lid that is free of ridges flows cleanly into a round opening that optimizes airflow. A K&N replacement air filter was already installed when the stock configuration was tested, but you can pick up the filter as part of an air induction package with any of the lids, or separately from MTI for $49. After removing the factory air lid, the MTI lid is slipped into place and the band clamps are attached. The connection hose is retained with two band clamps that are tightened with a flat-bladed screwdriver to attach the lid to the MAF. Remember to swap the IAT sensor from the factory airbox over to the MTI lid and to purchase the optional K&N breather filter ('01-'02 models only) to keep your AIR pump functioning properly. When the rollers stopped spinning, the MTI lid increased power as well.