Diesels like boost, and unfortunately, pushing absurd amounts of air isn’t usually too healthy for the turbochargers that have to produce the pressure. In most factory applications, about 20 psi is all one will see as far as boost pressure goes. Diesel enthusiasts can (carefully) push the factory hardware to 30 psi or more, but at these levels the turbo will eventually fail.
However, as fueling increases and power climbs, boost pressures will need to be in the 50-, 75-, or even 100-psi range, and the stock turbocharger just won’t survive. But there is a solution—and it can even be found in junkyards.
In compounding, a larger turbocharger blows air into a smaller one, which pressurizes the air twice before it enters the engine, allowing for much higher boost pressures and much greater power production. One of the coolest examples of this type of system using some junkyard ingenuity is found on Harvey Grant’s ’51 Chevy rat rod. The turbo system uses three 50mm Holset HC1 turbos found on ’89 to ’93 Dodges to compound boost (two into one) into a 5.9L Cummins 12-valve with a VE injection pump. While horsepower is yet to be determined, the system is theoretically capable of 600 to 700 hp at the wheels, and about 75 psi of boost pressure. Since it’s a rat rod, the whole assembly was built as cheaply as possible, using leftover parts and pieces from other projects, which means the total cash outlay for the system was only about $400! Keep in mind, however, that there’s also about 30 hours of labor in the project, not to mention a good amount of welding ability to start out with.
“Although not yet finished, the ’51 Chevy has already garnered a lot of attention at local shows. Built starting with a rusted-out cab, half a Dodge frame, and a seized-up 5.9L Cummins engine, the fact that the rat is running now for just a few grand is impressive, to say the least.”
With a grinder and a lot of patience, the two 3-inch downpipes were mated to a single 4-in
Junkyard Turbo Tips
If you’re planning on MIG-welding your piping, make sure no loose slag is leftover to rattle around in the intake or exhaust tracts.
Any 2- to 2.4-inch-inducer turbo should work well in a triple setup, with ’89 to ’02 Dodge Rams being a good source of turbo options (HC1, WHC1, HX35, and HY35 turbos). In theory, these turbos should work with the factory turbocharger in Duramax and Power Stroke engines as well.
Spend a lot of time mocking up the turbos before you start going nuts with a welder. Triples take up a lot of space, and it’s better to think first and cut once. Also, make sure the turbos are mounted above the top of the oil pan, so the oil will drain correctly.
There’s no mistaking the intimidating nature of triple turbos, but what is surprising is t
Harvey Grant built the turbo setup with what he had laying around, which meant two HC1s we
Oiling is all-important for the life of turbochargers, so some money was spent here. High-
Because of the rat rod theme, Harvey got creative with the drain tubes, using �-inch coppe
The intake piping was first mocked up using pre-heater hose from NAPA (the stuff that’s us
Because of the extreme amount of boost, the intake discharge tube is a simple up-and-over
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