LS2 Intake Manifold Porting - LS2 Stealth Mods
Though LS1-equipped '04 Goats were certainly stout, the bar was raised even further when GM rolled out the evolutionary Gen IV LS2 engine for the '05-'06 models. In addition to a host of improvements, the bore size was enlarged to 4.0-inches, resulting in an 18 cubic inch displacement increase to 364. Output was increased to 400 horsepower and 400 lb-ft of torque.
With innovation came other changes. The LS2 intake and throttle body are significantly different from previous GM LS1 offerings. While the '04 GTO LS1 engine carried an LS6 intake manifold and cable-operated 75mm throttle body, the LS2 debuted a new style of intake manifold and a 90mm electronically-controlled throttle body.
According to Pete Incaudo of Vmax Motorsports, "The LS2 manifold has a marginal increase in plenum volume over the LS6 and similar runner shapes optimized for the 6.0 liter engine. What changed, other than a 90mm throttle body opening, was the technology employed to produce the manifold. The Gen III LS1 and LS6 composite plastic manifolds were produced using a "lost core" plastic molding process that resulted in a single-piece plastic injected molded manifold."
The process involves the use of a low-melting temperature metal core, which is then loaded into a plastic molded tool, over-molded and then melted-out after the part is formed. Nylon 66 was the standard material used to produce the LS1/LS6 "composite manifold."
Pete continues, "The LS2 and LS7 manifolds utilize a more traditional plastic injected molding process that produces three different intake manifold sections, which are then fitted together and 'vibration welded' around the edges." Vibration welding, sometimes referred to as sonic welding in the industry, is simply melting the composite together after "vibrating" the materials to produce the necessary friction for a weld. Although the manifold material looks similar to an LS1 or LS6, the manifold is in fact produced using Nylon 6, a glass-filled polymer that is better able to be vibration welded.
"In short," Pete says, "a miniscule amount of air is leaking internally past the welds, costing air flow and power in the process. Although in principle it may seem simple to seal all of the leaking welds on the intake, in reality, welding the seams for a leak-free fit is extremely difficult. The liability of repairing the manifold using polymer based adhesives is unacceptable.
"Rather than repair a manifold, we developed a 'porting' program that will flow more air through it, thus raising the power potential of the head and intake manifold combination to levels typically seen only on high-dollar aftermarket intakes. On stock applications, we normally see 5-10 horsepower increases with up to 20 horsepower on engines with ported heads, higher-lift cams and free-flowing exhaust."
Sold on an exchange basis, LS2 intake porting retails for $300 shipped (carried under PN Vmax LS2 Port). For enthusiasts who are looking to purchase a new manifold, GM carries the LS2 manifold (under PN 89017648), which retails for $421.61.
In addition to porting an LS2 manifold to increase the flow, additional power can be made by improving upon the stock LS2 90mm throttle body. Shaner Performance has been specializing in porting GM throttle bodies since '99. Its latest offering is the S2 series of ported throttle bodies for the LS2.
The throttle body has been extensively modified and includes boring out the main body's restrictive ridge at the leading edge of the throttle blades. Offered on an exchange basis or as a service to your original, the throttle body runs $125 shipped. LS1 and LS6 throttle body porting is also available for the same price, and a polished finish ($159) can be ordered.
According to Mark Shaner, of Shaner Performance, "The 90mm GM throttle body is more refined and better flowing than the Gen III offerings. By eliminating the air tubes and PCV from the throttle body and designing blade screws that do not protrude into the air stream, much of the flow disruption from prior years was eliminated. Additional flow is achieved by removing material around the entrance and exits of the throttle body blades. Due to the critical tolerances of the throttle blade's movement for idle control purposes, the porting work has to be very precise or else the car will not idle properly."
Now that you know the players and their products, follow along as we perform two stealthy power-increasing LS2 modifications, while flying under the radar of both the dealer and fellow enthusiasts. Before and after dyno runs will be completed to document the power increases.
LS2 intake manifold porting was conducted at Vmax Motorsports, and Shaner Performance ported an LS2 throttle body. Testing was conducted at Real Performance Motorsports of Lewisville, Texas, on an '06 GTO owned by Bob Cook, a CNC machinist from Allen, Texas.
Dyno ResultsDyno HPHP Avg. Torque TQ Avg.A/F Avg.Baseline 348.7326.5353.2334.712.5Ported LS2/Ported TB357.8332.9363.0341.212.5Power increase9.16.4 9.86.5 0
Intake Manifold Flow TestingThe LS2 intake manifold was flow tested at 28 inches of pressure using a Superflow 600 flow bench to document the results of the porting program. A stock LS6 cylinder head was used and initially tested to document the cylinder head's flow capability using only intake port number 6 with a Vmax R&D entry for Test 1. A stock LS2 manifold was installed for Test 2 and the flow was recorded on the number 6 port with all other runners blocked. For Test 3, a ported LS2 manifold was then installed and the flow numbers were recorded as well.
Results indicate that the low and high-lift cfm benefited the most. Although the cfm increases weren't substantial, intake manifold porting isn't all just about numbers, but rather the transition and quality of air in flow. Pure cfm increases that decrease port velocity or disrupt the air flow are often counterproductive to real-world horsepower gains. LS2 intake manifold porting is very much akin to porting any Pontiac manifold. If you don't have knowledge on the subject, it is best left to the experts.
Test Lift1. Bare Head CFM2. Stock LS2 CFM3. Modified LS2 CFM0.10062.559.662.5 0.15095. .9160.90.300197.3184.7186.00.350217.5201.0205.00.4 00235.0217.5220.00.450253.0226.0230.00.500265.0233 .9238.00.550256.0*223.5*226.0*0.600257.7223.5226.0 0.650257.7223.5229.0* Port and Runner stalls at 0.550 valve lift.
For the owners of LS2-equipped GTO's, the combination of the ported Vmax Motorsports LS2 manifold and Shaner S2 throttle body are excellent alternatives to aftermarket offerings. All told, the gains from under an hour's worth of labor resulted in increases of 9 rwhp and 10 lb-ft of torque, for a total of $429.
According to Bob Cook, "after driving the car around, I am really impressed by the added power gains that the ported manifold and throttle body have provided. In addition to the gains noted during the testing session, the combination really shines from a low rpm and driveability standpoint. There is much better throttle response down low and the car just feels more responsive at every rpm level. The ported throttle body hasn't affected idle in any way and the combination feels much more powerful from stoplight to stoplight. Secondly, I really like the fact that we are using factory parts and that the subtle changes that have been made for performance increases should go unnoticed by the dealer."
For the purist looking for additional power or the individual intent on having the most powerful LS2 GTO around, the need to purchase an expensive aftermarket manifold or billet throttle bodies may have just been avoided.

Photo Gallery: LS2 Intake Manifold Porting - High Performance Pontiac Magazine

Read More | Digg It | Add to