SLP Performance- Take The Money & Run

Now that the buzz surrounding the simple pushrod design, the big-lift cam, the truly high-performance ignition and the race-ready heads has died down, the 1998-present LS1-powered F-bodies are adding to their solid reputations as affordable used hot rods '98-up F-cars can be had with high miles for as little as 10 grand at the popular auto trader web sites, finally allowing the budget-minded to own a world-class powerplant. Of course, the fun really starts once that alloy screamer is in the driveway. The LT1's successor had no trouble putting tons of power to the ground in factory form, but the Gen. III engine has such a hunger for airflow that it soon became known for making big power with even the cheapest mods. The people buying these suckers used aren't exactly Rockefellers, so it stands to reason that they will be as creative as possible in squeezing the most power out of them with the least amount of money. But how cheap can you be while still picking up usable power? Can the thermoplastic fantastic LS1 respond favorably to a no-bucks mod-fest?

Ex-staffer and reigning wordmeister Jay Heath, who recently purchased a 40,000-mile '99 Trans Am, was brainwashed into wondering the same thing, and we've talked him into a before-and-after dyno thrash/track bash starring his box-stock baby. Only five simple modifications would be performed: cutting the airbox, porting the throttle body, cutting the EGR tube, bypassing the throttle body coolant line, and de-screening the MAF. All of these changes could be done at home with basic tools and a grinder-the question was, would they add power without adversely affecting driveability?

Track TestingBaseline-April 1, 2003, Englishtown, N.J.Temp: 56 Humidity: 40% Barometer: 30.35 Density Altitude: -725 feet a.m.

Free mods--June 17, 2003, Englishtown, N.J.Temp: 80 Humidity: 35% Barometer: 30.32 Density Altitude: 920 feet a.m.

Accurate Dyno Testing--How SLP Does ItSLP Performance Parts spared no effort in creating a first-rate engine and chassis dyno test facility at its home base in Toms River, NJ. The four-room testing complex offers a SuperFlow SF-901 engine dyno and a SuperFlow SF-840 dual eddy-current chassis dyno. The two dynos are each set in an independent test cell split between both a customer observation lobby and a dual-purpose control room. While in the observation lobby, an enthusiast will not bore easily when offered a view of each dyno cell through four-foot windows, a snack and soda machine, a thorough selection of car mags like GMHTP, and of course a full line of SLP's latest catalogs. Looks aren't everything though, especially when it comes to dyno testing. There really is no point to testing if the results are inaccurate or inconsistent. SLP understands this well.

SLP goes to great lengths to ensure as accurate of testing as possible, starting with setup. An experienced and knowledgeable dyno operator will recognize that every setup procedure will impact testing and should be completed in a ritualistic, prescribed, consistent manner. At SLP, it all starts with something as simple as driving the vehicle onto the dyno. When positioning drive wheels on the dyno rolls, the car is set perpendicular to the rolls and tires are properly centered on the rolls (not biased to the front or rear of the roll). The drive wheel tire pressure is always set and equalized. The vehicle is strapped down both from the front and from the rear. Strap tensions are equalized and always consistent. Strap down points are also consistently the same and at the same angles. All this effort is made because the tire-to-roll contact is critical. Most importantly, the tire-to-roll contact is the transmission point for generated torque. However, a certain percentage of power will be lost to tire friction so it is best to minimize the loss by carefully following the aforementioned steps. Consistency in vehicle setup on the dyno is absolutely critical for repetitive testing consistency. A significant difference in vehicle strap down can incorrectly erase or amplify any power gain from a modification that is being tested. Poor contact can cause tire slippage, erroneous dyno loading, and inaccurate dyno results. Additionally, several other undesirable side effects are possible, including safety hazards, tire wear, differential wear, and vehicle or dyno damage.

Precision vehicle setup is just the beginning of good dyno testing at SLP. Setting up and calibrating the dyno itself is just as important. Testing accuracy can only be as good as the calibration accuracy. The two most critical calibrations are the dyno load cell and barometer. Other calibrations and specifications are also important and must be correctly set as well.

The dyno load cell is calibrated by checking the measured load when a precision weight is applied. The calibration of the load cell is checked on a weekly basis at least--more often if needed. In the case of the SuperFlow chassis dyno at SLP, the calibration is never off by more than 0.5 percent. The barometer is the most critical atmospheric condition requiring measurement. Barometer readings (along with the rest of the atmospheric conditions) are used to 'correct' the torque and power measurements at WOT (Wide Open Throttle).

All testing results should be corrected to SAE standards. This allows a fair apples-to-apples comparison between tests completed at different times (and therefore under different atmospheric conditions). For absolute numbers, stick to SAE (Society of Automotive Engineers) corrections as opposed to STP (Standard Temperature and Pressure) corrections. SLP only uses SAE corrections, unless specifically requested to use STP by a customer. STP corrections will yield higher numbers than SAE corrections-be cognizant of this when comparing results.