Article I found about the new LSXRT intake with boost
01-25-2011, 02:45 PM
#1
Article I found about the new LSXRT intake with boost
Fast LSXRT Intake Manifold Upgrade - Belittling The Competition - Tech
A Fast LSXRT Intake Manifold Provides Big Gains On A Turbocharged Trailblazer SS
From the February, 2011 issue of GM High-Tech Performance
By Dan Foley
Photography by Dan Foley
With a little help from our friends at Tune Time Performance, we were able to find a willing TrailBlazer (owner Jim Skeenes) in which to test the new FAST (Fuel Air Spark Technology) truck intake manifold (FAST LSXRT 102mm cathedral port). Let us begin by saying this was the most impressive stock replacement-type intake manifold we ever tested. Having a forced induction (turbo) combination to enhance the higher airflow volume of the FAST truck intake certainly helped make for huge power gains. However, the LSXRT intake is clearly taller and has longer runners, which enables it to move a greater volume of air than the LS3 and LS7 car intakes. We could see using the LSXRT intake on a LS-powered car (like an '80s G-body) without the hood/cowl clearance concerns to maximize engine performance on a cathedral port combo.
Recent tests with the FAST LSXR 102mm on Tune Time Performance's supercharged 2010 Camaro SS produced some great results. However, the notoriously tight engine bays on late-model F-bodies and Corvettes, which also have limited hood clearance, restricted the runner length (and shape) that FAST could design into its car-designated intake manifold, which adds high-rpm horsepower (above 5,000 rpm) without the massive mid- and low-end benefits of the truck version. We were anxious to test the FAST truck piece knowing it would boost mid-range torque like an old tunnel-ram manifold of yesteryear. Trucks and SUVs really benefit from bottom-end torque and a broadened power curve to get their added weight rolling. That's a good reason why the stock GM truck intake is taller than the car unit.
Eventually, down the road we'd like to see a four-way shootout (engine dyno) on both the stock intakes (car and truck) and the FAST units using a popular build-type LS engine. Each intake would demonstrate the gains in the power curve to help determine the right intake choice for the intended combination (gearing, converter, weight, etc). For now follow along and see how admirably the FAST LSXRT 102 intake performed in this test. As a side note, we think a naturally aspirated LS2 would have shown roughly half the gains we realized using a boosted TBSS. Still, half the gains are impressive numbers from just an intake swap.
We needed an LS-powered pickup or SUV to flog the new FAST LSXRT (Race Truck) 102mm intake manifold and thankfully Jim Skeenes, one of the many TrailBlazer SS customers of Tune Time Performance, was happy to loan us his turbocharged '07 model. His TBSS features Manley forged pistons, H-beam rods, CNC-ported 317 casting heads, Comp/Tune Time custom turbo cam (with over 0.580-inch lift and duration in the 220-230 range on the intake, 230-240 on the exhaust), SLP headers and exhaust, methanol injection, and an 82mm Precision turbo.
The stock intake is tucked tightly under the cowl/firewall of the TBSS. Fullsize pickups, Tahoe, Suburban, H2 Hummer, and Cadillac Escalades offer more underhood clearance. Before intake removal, be sure to disconnect the negative battery cable. Fuel pressure was relieved by depressing the Schrader valve, then the fuel line was disconnected from the fuel rail.
After removing the air tube, MAP, MAF, and electronic throttle body plug, fan, and serpentine belt, Tune Time's George Hatzinikitas (aka Huzzy) unbolted the alternator. Next, he unplugged the fuel injectors, vacuum lines, rear brake booster line and moved the wiring harness out of the way. To ease the R&R process he unbolted and removed the coil pack assemblies mounted on each valve cover.
Once the 10 intake manifold bolts were loosened, the stock manifold was carefully lifted and removed. The coolant was drained and the coolant crossover tube was removed to make room for the new intake.
Left to right: the FAST truck, stock truck and stock '10 Camaro intake. It's obvious the stock truck intake won't fit under the hood of a C6 or F-body, but it does what it's designed to do-help develop low-end torque to get the heavier hulks moving. The car intake with its shorter runners will usually develop better top-end power (depending on the combo). It appears the FAST truck piece is roughly an inch taller than the stocker it'll replace. It's made for GM trucks with the 4.8L, 5.3L, and 6.0L from 1999 to present with cathedral-port heads (where hood clearance is not an issue).
Looking at both the truck intakes from behind, it's simple to see the FAST unit is taller. Vacuum nipples are present for the brake booster and MAP sensor. It's designed with longer, straighter runners to deliver a stronger average power range. This two-piece manifold can easily be taken apart to be ported and polished.
Tune Time Performance mid-mounted this large 82mm Precision Turbo. It provides the well-worked, meth-injected, intercooled LS2 with 11 psi of safe boost. This TBSS has run a best of 11.7 with Third gear slipping (and transmission failure). A fresh rebuild of the trans was performed right before we began the intake swap. Check out GMHTP's website for an update once we have a chance to get the TBSS back to the track.
01-25-2011, 02:45 PM
#2
In order for the FAST intake to fit, the stock lifter valley plate (hex-headed) bolts need to be replaced. Button-head cap screws are provided with the FAST intake and are tightened to 18 ft-lb.
Knowing clearance issues were ahead of us, first we trial fitted with and without the heat insulation pad. In the picture without the pad the intake still couldn't clear since the cowl slopes down towards the firewall. We did some measuring before we began to massage the area for the necessary clearance (3/8-inch minimum).
We hammered away at the area we marked and measured until we had the proper clearance. The intake was placed in position many times until we measured the right amount of clearance. Without enough clearance, the intake could get damaged from engine movement. We spray painted the hammered area white. Once the intake was mounted it was hard to tell the cowl was ever beat on.
The upper half was removed so we could drill a couple of vacuum holes and prevent the shavings from getting inside the intake. Notice the long, straight runners, which aim straight at the intake valve. These long, straight runners add airflow velocity for more power throughout the curve. Each individual runner is removable for servicing and/or porting, polishing.
The provided screws hold down the MAP sensor (shown being tightened) and the purge valve nipple (above the 102mm inlet). Not shown, but Huzzy fabricated new hold-downs to reuse the stock fuel rails with the Racetronix 60 lb/hr injectors. FAST offers a Billet Fuel Rail or a hold-down kit for the stock fuel rail to simplify the swap.
Once in place, the FAST manifold sat under the cowl with over 3/8-inch clearance! Notice the alternator/power steering pump bracket was moved aside, absent of the coolant crossover line and upper radiator hose. This was necessary to ease the install. Before the intake was placed all the way rearward, we had to attach the brake booster and MAP sensor hose to their nipples. The 10 provided intake bolts were tightened in sequence according to the instructions in two passes, first pass [45 in-lb] and final pass [89 in-lb].
With everything reconnected and reinstalled we fired it up and noticed a smoother running motor. Fortunately no fluid leaks were present-that says a lot for the Tune Time Technicians. The FAST intake is not only much cooler-looking than stock, it helps the LS engine to run stronger.
Any type of engine changes will require tuning changes. With the wideband O2 sensor in the tailpipe of the TBSS, on the initial pulls the A/F was too rich (10.3 to 10.5) and we lost 2 psi of boost (baseline 11 psi, now 9 psi) for the duration of the pull. Loss of boost pressure is a common occurrence when swapping to headers, or high-flow heads and even a high-flow/volume intake manifold (like here). In our case the forced induction was flowing more easily into and through the motor. Even with the too-rich A/F and 2-psi loss of boost we saw a power increase. Gains at the wheels were 5 hp and 9 lb-ft of torque, quite impressive when considering the pig-rich A/F and loss of boost.
Matt went to work and performed his tuning magic (leaning out the tune), while Huzzy reached under and turned the adjustable wastegate actuator to equalize the boost to be the same as baseline boost (11 psi).
For the final pulls, the A/F was a perfect 11.5 to 11.7 and the boost held at 11 psi just like the baseline run. In all fairness, the boost was at times spiking to 14 psi (where it did 13 psi on the baseline) at peak torque (4,500 to 4,700 rpm). Still, boost was holding the same 11 psi as the baseline at 5,000 to 6,200 rpm where gains at the wheels averaged 30-50 hp (see the charts). Peak gains were 50 hp and 66 lb-ft of torque (baseline 558 hp, 633 lb-ft now 608 hp, 699 lb-ft). Wow, what an intake!
