Ford F350 Superduty Twin Turbo - The Trouble With Twins

He also opened up the exhaust housing and added a 50:1 blow-off valve from a hot-water tank, of all things. "I was born and raised in redneck country and do things my own way, with a git-'er-done attitude," Shawn admits. "This was seat-of-the-pants engineering, right from the get go." The valve kicks open at 55 psi, about double the level of the backpressure, as a general rule of thumb.

The larger wheel is a High Tech Turbo HT3B, roughly twice the size of the other one. Overlap between the two turbos begins at 10 psi. "When that big turbo comes on, there's no lag. It starts to whistle, and the boost just wraps right around," he says. The max boost Shawn has seen is 75 psi, but he backed it down because backpressure was up to 55 psi, which was too high. So he dialed down the boost pressure to 55 psi, keeping the magic 2:1 ratio of boost to backpressure.

Running on just diesel fuel (no propane or nitrous), he claims a gain in output to 600 hp and 1,100 lb-ft of torque at the rear wheels (a stock Power Stroke produces 325 hp and 560 lb-ft at the flywheel). On the strip, he's running in the high 12s and expects to shave that down by 0.7 with a 150hp shot of nitrous. He uses the propane only for improved mileage (as much as a 6 mpg increase), not as a power-adder.

In addition to staging and tuning, another big challenge was just getting the turbos to fit. "I didn't have enough room between the firewall and the turbo, so there were some highly technical modifications to be done," he says. "I got my 10-pound sledgehammer and started beating on the firewall till I had enough room for things to fit." (Now's the time to chime in with that familiar refrain: You might be a redneck.)

With the turbos mounted, the Ellerton clan built the exhaust-manifold pipes using 2 1/4-inch pipe instead of the factory 2-inch tubes in order to increase flow and volume. They also had to route all the oil lines for the turbo. After that, they hooked up everything, and then handbuilt the intercooler pipes.

The Ellerton boys weren't done yet. The electric fans on hand were borrowed (don't forget, he's doing this on his wedding day) from a 7.3L Power Stroke, so they required some retrofitting. Also, in anticipation of a flood of power, North American Diesel Performance (NADP) beefed up the tranny with its Heavy Hauler Race Series 5R110 unit that's fitted with a triple-disc, low-stall (1,800 rpm), billet converter. NADP claims his unit is good for 650 or more horses and features new high-performance Red Alto Frictions and kolene steels (rings) along with an NADP high-performance valvebody, piston kit, and filter.

With the engine and tranny in place, Shawn was ready to go for a ride with the church bells about to start ringing. "It fired right up, but if I put my foot into more than a quarter-throttle, it went into limp mode," he says with a wince. Can't get to the wedding chapel on time that way.

Fortunately, he got a bit of help from his friends. "By this time, I had been talking with Eric from Innovative Diesel, and he was able to bypass all the emissions stuff and adjust the fueling for the big injectors. Without him tuning the truck, I would have been in trouble." (Especially with his soon-to-be wife.)

Once he had that aspect dialed in, he was ready to take things to the next level. "When the turbos lit, I still had a gray haze of smoke out the back, so I knew I was good for a 100hp shot of NOS," he points out. "I also put on dual 6-inch stacks so I wouldn't smoke out the track officials. I figured I'd better take care of the rest of the truck, so we put on a set of Mag Hytec diff covers. Now that she's working good (the truck, not his wife), we're going after NADP's Dodge."

Looking back on the whole project, Ellerton has some words of advice for anyone trying something similar: "Mock things up beforehand, and do a body lift on the cab instead of pounding on the firewall.

"And one more thing. Don't try to do it all right before your wedding day."