Tapping into the vehicles PCM is as easy as connecting a laptop to the under-dash computer
Detonation not only hinders performance as the computer pulls timing, persistent detonation can also severely damage engine internals. It seems that better running LS1s are always very close to detonation, however. An experienced tuner knows just how far he can take fuel and spark tuning before detonation occurs, and the result is significantly improved performance and driveability at every rpm.
The Test Subject
Our ’01 Trans Am was delivered to us in September of that model year. With the optional WS6 Ram Air and Handling Package, a six-speed manual trans, and a 3.42 rear, its 346-cubic-inch LS1 was factory rated at 325 hp at 5,200 rpm and 350 lb-ft at 4,000 rpm. After a reasonable number of miles for typical break-in, its performance in stock form always impressed, and we’ve been hesitant to modify it because of that. It simply ran as well or better than most other stock LS1s on the road at the time. It seemed to be one of those cars that was “just right.”
Always fed a strict diet of premium grade fuel, the LS1 would sometimes detonate audibly at higher rpm in wide-open-throttle (WOT) conditions. We reported the condition to the Service Department of our local Pontiac dealer and everything appeared to be operating normally during a routine check. We were offered the opportunity to re-flash the stock PCM, but had heard horror stories about owners losing performance after a re-flash and decided against it.
Knowing how damaging detonation can be to stock internals, we routinely added a slight amount of 100-octane unleaded racing fuel when driving spiritedly. That certainly quelled the detonation, but we knew it was a crutch instead of a solution. Once our local supplier quit carrying unleaded race fuel, we decided to take permanent action, and that was in the form of a complete dyno tune.
Tom VanVugt owns C&S Dyno Shop in Omaha, Nebraska. and he’s been tuning late-model vehicles for several years. Considered by many as one of the area’s best tuners, we were confident that he could correct our detonation issues, and possibly extract even more power from our already-potent LS1.
A complete dyno tune at C&S Dyno Shop typically requires 6 to 8 hours and generally retails for about $500. “We begin by measuring the vehicle’s output in stock form and reviewing its operating parameters,” VanVugt explains. “Once we unlock the PCM and tune it we generally see an increase of 20-25 rwhp and 25-30 rwtq from an otherwise stock LS1 car. It’s usually a bit less with better running cars like this Trans Am, but I was confident we could eliminate the detonation, and improve performance and drivability at the same time.”
Speed Density (SD) programming calculates fuel requirements in various conditions.
The stock programming (top) dips severely after 4,000 rpm, at which point MAF programming
The Dyno Session
Bearing in mind that our Trans Am is bone stock with 18,000 miles on its odometer and its LS1 is completely original and retains its factory air lid and paper filter, and stock WS6-specific muffler, we expected rear-wheel horsepower numbers on the C&S Dyno Shop’s Mustang Dyno somewhere around 285 to 290. That might seem lower than those recorded on a DynoJet chassis dyno. That’s because DynoJet uses a fixed-weight roller drum, while that of the Mustang Dyno varies resistance based on vehicle weight.
With our Trans Am’s rear tires firmly planted on the Mustang Dyno’s roller drum, the LS1 generated 301 rwhp at 5,300 rpm and 313 rwtq at 4,100 rpm, and average horsepower and torque between 2,500 and 6,000 rpm measured 243 and 298, respectively. According to VanVugt, the result was consistent with a mildly-modified LS1, but admits he has seen similar numbers from other very-fast stock LS1 cars, of which he considers ours. When considering a driveline loss of at least 20 percent for his particular dyno, that equates to 360 hp and 375 lb-ft at the crankshaft—a clear indication of how grossly underrated the LS1 truly is.
Purchasing a license from HP Tuners through C&S Dyno Shop adds $125 to the cost of the tune. “We use HP Tuners software to unlock and modify the factory computer because it’s the best available for what we do’” he says. “It gives us almost unlimited capability when tuning a stock LS1 or one with bolt-on modifications. HP Tuners offers additional support for heavily-modified or boosted applications at extra cost, but the $125 license is all that’s needed in this instance.”