6.7L Compound-Turbo Cummins Engine - Engine Builder Magazine

6.7L Compound-Turbo Cummins Engine

Ross Dunagan and his team at Flyin Diesel Performance recently finished a compound-turbo 6.7L Cummins build that was more than three years in the making. Customer Erik Santana wanted to go all out, so they did, and the result was worth the wait!

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They say persistence pays off. Ross Dunagan knows it. The co-owner of Flyin Diesel Performance, a 7,000-sq.-ft. shop located about an hour northwest of San Antonio in Kerrville, Texas, and his team recently wrapped up a compound-turbo project more than three years – and two separate trucks – in the making. Judging by the finished product, the juice was well worth the squeeze.

Dodge Ram

To be fair, the job seemed straightforward enough when longtime customer Erik Santana initially brought in his 2012 Ram 2500 Mega Cab with a blown-up motor and asked Dunagan and co-owner Jon Morris to whiteboard an upgrade.

“He wanted to pretty much go all out,” Dunagan recalls. “We ended up swapping the truck to a 48RE conversion with bigger injectors, bigger turbo, etc.” 

Originally, Santana’s target for the new build was 750 horsepower. But power goals have a way of ballooning over time. Before long, that 750-hp mark jumped to 1,000. In response to the customer’s ask, Dunagan and his crew upgraded from a single turbo to compound turbos, went to dual fuel pumps and 150% over injectors. Despite their efforts, the team’s revised horsepower goal remained just out of reach.

Dodge Ram

“We got the truck right at 950 hp, and then we started hitting ECM limits,” Dunagan says. “The truck should have done over 1,000, but we just couldn’t break that barrier on the 2100 ECM.”

This was also a big, four-door, 4WD truck that was regularly stressing its transmission and suspension components beyond the limits. But it was the ECM that was giving Dunagan’s team the most trouble.

“We kept on battling, trying to break the 1,000-hp mark in that truck for about three years,” he says. “It just wasn’t getting the power that we were hoping for out of that 2012 ECM. We finally said [to the customer], ‘Look, you want to go fast, we want to get more reliable, and we want to try and really compete with this thing. We need to do something different. Why don’t we put this in a single cab.’”

6.7L Cummins engine

Santana was on board. They found a donor motor for the 2012 Ram, converted everything else back to factory, and sold it. After some searching, Santana was then able to locate a 2005 Ram 2500 Regular Cab.

“We literally swapped everything from the 2012 over,” Dunagan notes, “other than running a 2006 849 ECM, which gave us more control over what we needed control over, which was injector timing. And, we didn’t have near as many map tables and whatnot that we had to jump through hoops on to try to get this truck to perform like it should.”

Starting in July 2023, with its compound turbo setup and ‘06 ECM on board, the next six months were spent dialing in the new engine program. Finally, earlier this year, the single-cab Ram did what its predecessor couldn’t – and then some – by delivering an eye-popping 1,200 hp to the wheels.

6.7L Cummins engine

Dunagan tells us his customer “is absolutely stoked with this thing now. It’s still a street-driving truck. He does drive it around, takes it to the gym and whatnot – we just had it at a local Cars & Coffee in San Antonio. It is still every bit a street truck, with full interior, headlights, tail lights, full bed, A/C, heat, etc.

“The biggest thing that draws the attention is that it’s still a factory style-appearing truck, as far as on the outside,” he adds. “Granted, it’s got custom wheels and tires, but it can still drive down the road; it can do its normal driving functions, but it’s got 1,200 horsepower on tap.”

Generating all that power is a factory bore 6.7L block with upgraded valve springs and pushrods, coated factory pistons, CP-Carrillo connecting rods, and 12mm block girdle.

Dodge Ram

“We had Parks Engine Service in Seguin (TX) build the short block for us,” Dunagan says. “But it’s still a factory cam motor with a factory head. For those two things to flow 1,200 hp is pretty phenomenal.”

Elsewhere, the build features a single 14mm S&S Diesel pump, S&S 350% injectors, and those 72/88 turbos – the compound kit provided by Dallas-area supplier EvilFab Performance. Pitching in, too, was San Antonio-based Truck Source Diesel

“They’ve got an awesome fabrication guy down there. He did all the fab work on the intercooler piping itself,” Dunagan says, adding that “as crazy as this is going to sound, it also has one of our custom-made engine dipsticks and transmission dipsticks. We’re the only ones that manufacture them for the Cummins platform – and all diesel platforms, actually. It also has a custom billet valve cover.”

Dodge Ram

The 48RE transmission was put together in-house by the Flyin Diesel team using Goerend parts. The truck also sports some traction bars and QA1 shocks, but other than that it’s almost a factory-style setup as far as the suspension.

While Dunagan certainly appreciates his customer’s determination in seeing this project through to completion, he did reveal that the ‘05 Ram was likely to undergo additional enhancements down the road.

Dodge Ram

“Future plans would be to add the dual injection pump setup to it,” he says. “Try and see if we can push this truck closer to 1,500 horsepower. We’re going to upgrade the large turbo probably to a 91 or 92mm and try and get some more airflow out of it. But our goal right now is to just try to get the truck some more exposure, and now that he’s got a little bit of seat time in it, start racing this thing more competitively. But then, also, to still be able to keep it to its daily driver use. Not towing or anything like that, but just being able to still fire the truck up, take it down the road, and not worry about it. If you want to take an hour-long trip with it, you can do that.”

After three-and-a-half years and a full body swap, something tells us Santana will very much enjoy piloting this rig wherever he goes.

Diesel of the Week is sponsored by AMSOIL. If you have an engine you’d like to highlight in this series, please email Engine Builder Editor Greg Jones at [email protected].

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