Quick question for you engineering types out there: Which handles the flow of high-velocity air better: a flattened oval tube with dents and kinks in it or a straight round tube?
Dynomite Diesel's True Duramax Down Pipe is a 3.5-inch round tube that maintains its shape and diameter from the turbo outlet to the exhaust flange. Unlike the stock Duramax down pipe which is flattened to fit between the engine and the firewall and dented and shaped to fit around the trans oil dipstick tube and other components (the factory down pipe looks more like it was run over by a careless forklift operator at the Isuzu plant).
For stock tuning purposes, the factory down pipe is adequate. But, when you start putting demands on the exhaust system from added tuning and fuel, any shortcoming in the system prevents the modifications from reaching their full potential. In any turbo-back exhaust system, the shortfall is the factory down pipe since it does not get replaced with an aftermarket exhaust system-even a turbo-back kit. Getting rid of the factory down pipe and replacing it with a part that will allow the hot exhaust gasses to escape the engine faster will complete the aftermarket exhaust system package.
The True Duramax Down Pipe is made from 3.5-inch aluminized tubing that is hand-welded and has CNC-machined flanges at each end. The down pipe is wrapped with header wrap.
On the install we took part in, the down pipe went in place cleanly and matched with the turbo and aftermarket exhaust flanges without any misalignment or exhaust leaks. The 2005 Duramax with a stock turbo and some heavy tuning saw a reduction of exhaust temperatures of more than 150 degrees F on average.
Dynomite Diesel Performance
True Duramax Down Pipe