Installing Industrial Injection’s 69mm Turbo For a Whopping 85 Horsepower Gain on our 12 Valve

We had made some great initial gains on our 12-valve project dubbed “The Green Monster,” but we had a ways to go before it was anywhere near the “fast” category. Our homemade intake, Power Driven Diesel lift pump, and Scheid Diesel injectors (along with a timing bump to 18 degrees) had us topped out at 390rwhp, a far cry from the 134rwhp we had started from. Our funky remote control nitrous system busted through the 500rwhp mark with a 506 reading, so we knew more air needed to be our next step to making more power.

Factory Turbocharger Limitations

The stock turbos on Cummins engines are wonderful pieces of engineering from Holset. More often than not, they can handle twice their original boost settings without breaking a sweat, and our wastegated HC1 turbocharger (HX35’s came on later 2nd Generation trucks) was able to crank out 38psi on the dyno. We had heard (and seen) that 35-40psi was pushing things though, and with our wastegate wide open we didn’t have any more room for advancement, boost-wise. The only way to go up, was to replace our factory turbo.

DIY’ing Our Own Turbo Kit

There are literally dozens of options out there for turbochargers for 12-valve trucks, but unfortunately there isn’t really a “kit” like there is for later Dodges. So we made our own. It started with the exhaust manifold. Most popular turbochargers from BorgWarner and Garrett have a T4 exhaust flange, while the factory Cummins is a T3, so we either had to use an adapter (which might mess up the downpipe) or find a T4 exhaust manifold. Fortunately, Stainless Diesel and Steed Speed still make them, and we were able to get a deal on one off of the Competitiondiesel.com web forums for about 2/3 the price of new. This would give us a wide variety of “out-of-the-box” turbo choices in case we wanted to go up or down in the spooling or power department.

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Turbo Selection

A few years ago when they were first released, a BorgWarner engineer told us that its new 69mm S300-frame SX-E turbo spooled like a 66mm, but made power like a 75mm, and that stuck with us. We were eventually shooting for 10s, but 11s in the quarter mile would be a good start, and also get us around those newer Mustangs, Camaros, and Chargers, most of which are rooted in the low 12-second zone. This meant we would need somewhere around 650 to 700rwhp to meet our goal, which meant the 69mm would be just about perfect. The S369 flows 95 lb/min of air, and at roughly 8hp per lb/min, that meant we’d have a ceiling of around 760 hp…..give or take. This definitely looked like the turbo for us.

Installation

Part of the reason we went with this turbo and manifold selection was that (in theory) the setup would be a direct bolt-on. We got our S369 from Industrial Injection, which had several advantages. Since Industrial is a huge distributor they almost always have turbos in stock, and they also were able to machine the outlet of the turbo for an HX40 flange, which meant that a standard 4-inch downpipe could be used. It came in one big box all shipped to our door, and would complement our manifold perfectly. The installation would be handled by Rex Gully of Allied Diesel Performance, who is familiar with hot-rodded 12-valves.

Performance

On the dyno, we finally got a chance to see what kind of numbers our shmedium-sized 69mm could put out. For the sake of consistency we dynoed at Brown’s Diesel in Riverdale, California–the same place we had made 390rwhp with our stock HX35. The difference would now be way more air, and a lot higher boost, at least that’s what we hoped. As soon as we took our first test drive, we knew there was a big difference. The truck now would light up the tires on a second-gear roll, and while boost was a little slower to roll in, the turbo still built boost at 1,900rpm, and was at peak boost by 2,500rpm. We rigged up a boost gauge, and our tests confirmed a huge increase, with 52psi up from 38psi. With that boost came a huge power increase, as the truck put down a whopping 475rwhp. Remember, this is still with a stock 160hp pump, and only 18 degrees timing. Our real-world performance also improved accordingly, as our quarter mile time went from 14.40 at 94 mph to 13.90 at 98 mph.

Wrapping it up

Honestly, a power gain of 85hp is more than we could have expected, and we’re luckier in more ways than one. Our head gasket still hasn’t made an early exit (a definite possibility at 50psi) and our factory intercooler boots (another weak link) are still holding strong. The fact that we have basically two major modifications (a 69mm turbo and Schied 5×18 injectors) and made the power we did is a testament to the fact that the old Cummins-powered Dodges may have a chip in the performance game after all. Stay tuned for more!