We purchased our ’01 Trans...
We purchased our ’01 Trans Am new that model year. Equipped with the WS6 Ram Air and Handling Package and a six-speed manual transmission, it is completely original and has just 18,000 miles on its odometer. We decided it was time for a custom computer tune to maximize its performance.
I can’t recall ever meeting a performance enthusiast who doesn’t enjoy going fast on the cheap and easy. If you’ve spent any time driving a ’98-’02 Formula or Trans Am, or ’04 GTO, you’re familiar with how capable the LS1 is. Rather pricey when new, all of these models are now used cars as they approach or exceed a decade old. You can find several in local auto listings on any given weekend and most with an asking price of $12,000 or less, depending on mileage and condition.
The LS1 engine motivating these late-model Pontiacs is a hot rodder’s dream. With a factory rating of at least 300 hp, the performance they provide makes them seem grossly underrated, yet they are capable of delivering 25 mpg or more on the open highway. Heavily supported by the aftermarket, myriad bolt-on components are available from a host of specialty manufacturers and they improve performance to more than impressive levels. Custom computer tuning is required to maximize those efforts. But how much power can be unleashed by tuning an otherwise stock LS1?
Computer tuning consists of tapping into the vehicle’s Powertrain Control Module (PCM) and adjusting such tables as fuel and spark to improve performance. Some companies offer handheld tuners containing a generic tune, while others can email a more specific tune that’s downloaded using that same tuner. Though noticeable improvements are possible, nothing can replace the performance gains associated with professional custom tuning that uses a chassis dyno to maximize performance. Follow along as Tom VanVugt of C&S Dyno Shop in Omaha, Nebraska, extracts 18 hp from the LS1 in our ’01 Trans Am without even turning a wrench!
The all-aluminum LS1 was the standard Firebird V-8 beginning in ’98. Initially rated at 305 hp, a new camshaft and a revised intake manifold boosted that to 310 for 2001. The WS6 option added 15 hp taking it to 325.
The PCM receives input from various sensors located throughout the engine. It processes that information countless times each minute and then refers to preprogrammed fuel and spark tables to determine how much of each are required to reliably maintain peak performance in a particular condition. With the ability to reference thousands of cells representing any possible scenario, the engine is able to operate extremely efficiently at idle and part throttle to maximize fuel economy in light-load conditions and very aggressively in Wide Open Throttle (WOT) conditions for greatest overall performance.
To quell chronic detonation...
To quell chronic detonation issues, we sought the tuning experience of Tom VanVugt at C&S Dyno Shop in Omaha, Nebraska. We hoped he might be able to improve performance and driveability in the process. Strapped to the roller drum of the Mustang Dyno chassis dyno, the LS1 generated 301 hp and 317 lb-ft at the rear tires on the stock tune. That equates to more than 360 hp and 375 lb-ft at the crankshaft when factoring driveline loss.
A stock PCM tune must be liberal enough to account for the manufacturing tolerances that occur during normal LS1 production. The PCM uses various multipliers that consider such engine parameters as speed, load, temperature, and fuel and air consumption to provide reliable operation and peak performance in all possible conditions. While all engines tend to operate within a reasonable range, some perform noticeably better on the stock tune than others. Though extremely minute, engines with tolerances closer to perfect generally run a bit better than those further out.
The stock LS1 tune is rather rich, and that’s purposely intended to protect the engine from detonation or overly-lean conditions that can burn components. By adjusting the fuel tables, the Air/Fuel (A/F) ratio can be leaned in certain conditions, which generally improves full-throttle performance. The spark tables can also be optimized to further improve performance on the available amount of fuel. That includes advancing it in certain areas and retarding it in others, while safely staying away from detonation.
Knock sensors “listen” for detonation and retard timing whenever the slightest amount is detected. “We’ve found most LS1s have at least some inaudible detonation in stock form, whether it’s real or false knock,” says VanVugt. “The knock sensors tell the PCM to pull a certain amount of timing, and that negatively affects performance. You wouldn’t expect it to see knock retard with as rich as stock LS1 tune is, but it’s clearly visible when data logging PCM activity. We desensitize the sensors in our tune so they only react to real detonation.”