GM Truck Engine Bolt Ons - Tow Story

Although the engine control systems used in late-model vehicles can adapt to a wide variety of mechanical changes, there are limits. Even within those limits, the systems are governed by relatively conservative factory settings that control air/fuel ratio, ignition timing, and transmission shift points. While typical bolt-on modifications don't require reprogramming of the vehicle ECM or PCM, (Engine Control Module or Powertrain Control Module) additional performance benefits can be achieved by doing so.

An obvious question related to reprogramming (or reflashing as it's commonly called) an ECM or PCM is, "If you can get better performance by changing some settings, why didn't the factory do it?" There are a number of reasons, but primarily because the factory has to consider the same type of brain-dead drivers that you encounter when towing to the races. You know the type-the guy who fills his tank with the cheapest low grade gasoline he can find, loads up the bed with a 1,000-plus pounds of whatever, and plants his right foot on the floor, while his truck struggles up a steep grade. It never occurs to these types of drivers that a gasoline engine shouldn't sound like a diesel, and they're always mystified when their engines or transmissions develop problems.

The best way to optimize ECM/PCM settings for your particular driving requirements is with a programming/scanning system such as EFILive's FlashScan. This system includes software, which will run on virtually any Windows-based computer, and the cabling necessary to connect a vehicle to a PC. The cable includes a "black box" which not only handles PC-to-vehicle communications, it can also serve as a stand-alone datalogging device.

FlashScan can be used to reprogram multiple ECMs/PCMs, so if you're inclined, you can improve the performance of other GM vehicles you or your friends own. On the other hand, there's a relatively steep learning curve associated with electronic engine controls and if you don't want to climb it, you can order a mail order tune, or have a professional tuner e-mail you a file that you can flash yourself, and use a learning tool.

Regardless of the method you select, your end goal is to optimize operating efficiency at the rpm and engine load levels that your truck encounters when it's hauling your racecar. Keep in mind that most control settings are contained in "maps"- two- and three-dimensional arrays with individual values associated with specific rpm levels and amount of engine load. Consequently, you don't have to be concerned that changes made to improve towing performance will have a negative impact when you're not pulling a trailer-or vice versa.

Ideally, reprogramming should be done after all other modifications are made, but in the real world, that's not always possible. One of the benefits of using reflashing software is that you can change settings whenever you like, as often as you like. So if you plan to make additional modifications, (such as the ported heads/cam installation we have planned for our Silverado) you can re-optimize settings as required. Some tuners also offer free or low cost "re-do's," so even if you don't have reprogramming software, you can have your truck's computer updated very economically.

The same techniques that we used on our 5.3-liter small-block can be applied to virtually any other engine. Diesels require a slightly different approach, but they are just as easy to modify. We'll cover the specifics of diesels and other gas engines in future editions of "Tow Story."