Dyno Tuning, Testing & Results
Dyno testing of the WS6 '00 Trans Am was performed at Real Performance Motorsports in Lewisville, Texas. Its Dynojet Model 248C dyno is optioned with the above ground kit and Commander wide-band 02 sensor so that air/fuel ratios can be charted.
Right out of the box, the PRC heads showed some real promise by registering 407.7 hp on the first dyno pull. As documented in "LS1 Power Plan," the experience and knowledge of the tuner comes into play in maximizing the combination. Although the air/fuel was on average a bit richer at 12.4:1, Brian Lohse knew there was more power lurking in the lines of code.
According to Lohse, "In general, anytime an enthusiast goes to a ported cylinder head, the combination of quality, aftermarket stainless steel valves and revisions to the combustion chamber almost always allow the tuner to increase timing and adjust the air/fuel ratio to account for variances in port flow and velocity.
"The timing was adjusted from a baseline of 24 degrees up to 26 degrees, one degree at a time. Air/fuel ratio was almost identical to the baseline except in the rpm range of 4,700-6,200. Prior to the PRC heads, the T/A would only pull to 6,200, but the extra intake and exhaust flow allowed it to generate power up to 6,400 rpm.
"To account for the increased flow, the fuel was trimmed on dyno runs two and three by 2 percent each time over the range of 4,700-6,700 rpm. On the final run, the fuel was trimmed an additional 2 percent from 5,800-6,700 rpm, and the timing remained at 26 degrees as it had in run three.
"Although there were no signs of detonation in the dyno pull, the tune was left alone to ensure that the engine would run very consistent times when bracket racing under similar heat-soaked conditions. Additional power likely can be generated by adding more timing or leaning the air/fuel mixture out, but the upside of a few more horsepower was outweighed by the risk that the compu-ter would register knock and pull timing, leading to reduced power and an early exit from competition. Achieving 417 rwhp and 385.7 lb-ft of torque through an automatic transmission with a street-friendly cam that can easily run around town or throw down low to mid-12-second timeslips speaks well for the overall combination."
Peak and average horsepower and torque are from dyno pulls recorded between 3,900 and 6,200 rpm for the baseline and 3,900 and 6,400 for the Texas Speed heads configuration.
Dyno Graph
Baseline:
Test parameters: Inlet air temperature, 77.1 degrees Fahrenheit; barometric pressure, 29.72 hg; vapor pressure 0.15 in. hg; correction factor 0.99
Texas Speed Heads:
Test parameters: Inlet air temperature, 112.2 degrees Fahrenheit; barometric pressure, 29.14 hg; vapor pressure, 0.6 in. hg; correction factor, 1.07
| Dyno Peak | HP | Torque | |
| Baseline | 381.1 | 365.8 |
| Texas Speed Heads | 417.0 | 385.7 |
| Gain | 35.9 | 19.9 |
| | | |
| Dyno Average | HP | Torque | A/F Avg. |
| Baseline | 336.2 | 351.0 | 12.5 |
| Texas Speed Heads | 361.6 | 369.6 | 12.5 |
| Gain | 25.4 | 18.5 | |
Conclusion
After installing the heads and having Brian Lohse work his magic on the tune, the T/A belted out 417 rwhp and 385.7 lb-ft of torque. Gains attributable to swapping to the PRC heads were robust at 35.9 and 19.9 respectively. Almost as impressive were the average gains in horsepower and torque, along with the fat power curve. In addition to cresting the baseline at every rpm spot, the cylinder heads really started to shine once the cam got into the mid-range and beyond. From 4,900 rpm up to redline, the horsepower and torque averaged gains of 27 and 28 respectively. Although the overall average gains were more conservative at 25.4 hp and 18.5 lb-ft of torque, all of this was done without compromising idle quality or low-rpm drivability.
Lithium grease is applied...
Lithium grease is applied to the O-ring seal; the injector is placed into the rail; and the clip is reattached. A quick look at the F.A.S.T. injectors reveals that in addition to being physically bigger, the connector is specific to the Gen III engine family (EV1/Minitimer). Gen IV engines switched over to an EV6/UScar connector, as found on the LS2, while the L76 utilizes a shorter variant of the EV6/Uscar injector specifically designed to fit within the packaging constraints of the L76/L92/LS3- and LS7-style fuel rails and intake manifolds. In addition to selling the new style injectors, F.A.S.T. also offers fuel-injector adapter harnesses to adapt to or from the EV1 or EV6/UScar-style injectors.
Once all of the injectors...
Once all of the injectors have been placed in the fuel rails, the manifold side seals are lubricated and the fuel rails are reinstalled on the SLP LS6 manifold. A small band of threadlock is placed on the four retaining bolts, and they are torqued down to 89 in-lbs.
The remaining hardware, including...
The remaining hardware, including the throttle cable, fuel-injector harness connector, fuel line, drive belt, air-lid assembly, and strut-tower bracket, was installed. The petcock on the radiator was closed and a fresh fill of Dexcool was added. After a careful check of the completed installation, the battery was connected. Before the T/A could be started, Brian Lohse adjusted the factory computer tune with HP Tuners VCM Suite and scaled the F.A.S.T. injectors to the LS1 fuel pressure of 58 psi in the "flow rate versus KPA" table. According to Lohse, "Scaling the injectors anytime that an injector and lb/hr rating is changed is absolutely critical before the car is started. Without scaling the injectors for the increased fuel supply, the engine would idle excessively rich. If driven, fuel washing past the piston rings could cause ring and/or bore problems in a very short time."
After one final check, the...
After one final check, the manifold (with the four back bolts in the holes) is carefully lifted into the engine compartment and pushed back so that the MAP sensor, brake booster hose, and vacuum lines can be attached. The manifold is then pushed into position and the remaining intake bolts are inserted and hand started. The 8mm intake bolts are snugged down with a 1/4-inch air ratchet before being torqued to 44 in-lbs on the first pass followed by a final torque to 89 in-lbs. The bolts are torqued using a specific tightening sequence: It starts on the center bolt of the passenger side and then goes in an alternating bank pattern from left to right and front to back. The SLP LS6 EGR fitting is then threaded down until is it tight and a wrench is used to put an additional 1-1/4 turns on it to ensure it seals properly.