STRATEGIC COOLING

EXTINGUISHING EXCESSIVE EGT ON AN LBZ TOW-RIG

EXTINGUISHING EXCESSIVE EGT ON AN LBZ TOW-RIG

Exhaust gas temperature is the single most vital parameter to monitor on any diesel. Whether your truck has been highly modified, treated to moderate power upgrades, or is completely stock, you always want to keep EGT as manageable as possible. When the owner of this ’07 Chevrolet Silverado 2500 HD—A truck equipped with an S300 turbo system, a built Allison 1000, and EFI Live tuning—saw

1,300 degrees F on the pyrometer while towing, he wanted to cool things off sooner rather than later. His urgency to shed EGT was amplified by the fact that the engine under the hood was an LBZ, the Duramax that’s (arguably) the most prone to cracking a piston due to added power and excessive heat.

The path to shedding EGT began with a thorough cleaning of the cooling stack, which yielded no change. Next, the S366 was pulled

AF TER EGT READINGS. BEFORE EGT READINGS.

The newfound power that came with scrapping the factory Garrett 3788VA VVT in favor of an S300 was cool, but the numbers showing on the Auto Meter Factory Match pyrometer weren’t. Towing at 73 mph, on flat ground, and with the Allison locked in Tow-haul, the owner saw 1,300 degrees F, sustained. Not only did this force the driver to spend an inordinate amount of time watching EGT, but with the LBZ’S track-record of cracking pistons he began to worry about bottom-end longevity, too.

After zero headway was made by separating out the cooling stack and pressure-washing the exchangers, the owner gave an exhaust housing with a tighter A/R a try. While the 1.0 A/R housing that showed up on the S366 SX-E would provide good high rpm flow for making horsepower, a slightly more restrictive .91 A/R housing would produce quicker spool up and improved transient response.