1996 Dodge Ram 2500 Turbo Dyno Tech - The Ultimate Single
Combining BD’s Turbine Diverter Valve with a Garrett GTX4202R
Almost nothing can beat compound turbos in performance applications. While a big single can make plenty of power, compounds will spool quicker, tow better, be more driveable, and are capable of surviving at higher boost pressures.
With this in mind, we set out to configure a single turbo arrangement that would perform just as well as a compound-turbo setup, but with the simplicity, reliability, and cost advantages of a single turbo.
The truck we would be doing the turbo testing on was Ace of Spades, owned by Richard E. Brown (REB for short) of Brown’s Diesel. It’s a ’96 Dodge Ram 2500 that’s a sand drag, sled pull, and general hooligan truck, so he wasn’t afraid in the least of putting it through its paces. Out in the dunes of Pismo Beach, Ace of Spades is known for racing other trucks, buggies, and even quads, thanks to a healthy dose of nitrous. For this type of usage, throttle response and quick spooling is all-important, so it was the perfect candidate. “It feels like a 1,000-rwhp truck,” said REB, before the test ever started, “so now that we finally have it on the rollers, we have to break a thousand.”
"“We think this single setup beats compound turbos in both price and performance.”"
When we were looking for a turbocharger, our goal was to find something as quick-spooling as possible and still make it to the 700 to 800hp range without nitrous. After blowing up one S471 with spray, the decision was made to step up to a Garrett GTX4202R ball bearing turbo, because of its quick-spooling nature, ball-bearing design, and 120 pounds per minute of airflow capability.
Because the truck runs nitrous on a regular basis, a Steed Speed exhaust manifold was already installed, along with a Tial water-cooled wastegate. The 48mm gate would not only relieve excess drive pressure, it would be able to withstand the abuse of drag racing, sled pulling, and playing in the sand.
The Ace Up Our Sleeve: BD’s Turbine Diverter Valve
One of the main reasons compound-turbo setups work so well is how soon in the rpm range the smaller turbocharger gets going, which lights everything else off. But there’s a way you can make a larger turbo spool quicker: by using BD Diesel Performance’s Turbine Diverter Valve. The valve sends all the exhaust gases through one side of a divided turbine housing, effectively cutting the A/R in half. In common terms, that means our 1.0 A/R housing (roughly 14cm2) would be reduced to a 0.50 A/R (7cm2). This drastic reduction in area makes a larger turbo (like the 75.8mm Garrett we’d be running) spool much quicker than it would without the diverter valve, which would create more torque and better response, and even achieve better fuel economy. To avoid excess drive pressure, the diverter valve partially opens at 12 psi and is fully open at 22 psi, which means our Garrett would be back to a 1.0 A/R, as exhaust gases would now be equally flowing through both ports on the turbine housing.
On the Street
Given enough rpm and load, almost any size turbo will build boost. The real test of responsiveness, however, comes in how quickly an engine can come into boost under low-rpm, low-load situations. So, we drove the truck on flat ground at 2,000 rpm and compared the boost level to the set of ATS towing twins (57mm and 71mm turbos) we had on Project Triple Threat (our ’95 Dodge Ram). The result was surprising. At a steady state speed, with almost no load, the twins came in at 8 psi of boost. The Garrett single and Turbine Diverter Valve registered 10 psi of boost, indicating that even under light load conditions (and at the same rpm) the single was every bit as responsive as the compounds.
On the Dyno
The truck we’d be testing this setup on had all the fuel in the world, thanks to a set of 5x25 injectors and a 13mm Columbus Diesel Supply injection pump, but our first fuel-only runs would be mainly to see how the combination responded and how much torque it produced. When the truck made its runs, it was clear how hard the combination hit on the dyno. Wastegated at 50 psi, the truck made 654 rwhp and 1,080 lb-ft, which is a particularly good torque number for a big single turbo on an intertia dyno. But there was still nitrous to add into the mix.
The first dyno run on nitrous was performed with the same setup the truck sees in the sand: a 20-pound bottle and -8AN line feeding three solenoids on Hobbs pressure switches set up to trigger at 20 psi, 30 psi, and 40 psi. On this run, three 0.080 jets were used, which was the most a -3AN line (solenoid to nozzle) can flow. With the diverter valve ramping up boost right until the first stage hit, the truck went from 200 rwhp to more than 800 rwhp in less than a second. Power peaked at 884 rwhp and torque at 1,591 lb-ft, but there was still more left in it.
1,000 rwhp or Bust
“Alright, let’s get this thing done,” said REB, who went over and started robbing the nitrous system (bottle and all) from his other truck, an ’06 Dodge. Some quick wiring mirrored the second nitrous system with the first, but instead of one nozzle per stage, there would be two. With the truck on six 0.080 jets, it nearly leapt off the rollers, and a scary 3-foot flame instantly appeared out of the stack. One thousand rear-wheel horsepower was broken by 2,700 rpm, and the power curve carried all the way out to 4,100 rpm before it dropped off. The peak number was 1,110 rwhp, while torque checked in at an unreal 2,133 lb-ft.
After our testing, we can definitively say the combination of the ball-bearing Garrett turbo and BD’s Turbine Diverter Valve made for a combination that did indeed rival a compound-turbo setup. We were a little disappointed by the fuel-only numbers, but another 5 to 10 degrees of timing and ramping the boost up to 60 psi would have easily put the truck in the mid 700s, horsepower-wise. All in all, we think this single setup beats compound turbos, in both price and performance.
|1996 Dodge Ram 2500|
|Engine:||5.9L Cummins, 0.020-inch-over industrial pistons, ARP 625 head studs, O-ringed head, F1 Diesel Camshaft|
|Air:||Steed Speed exhaust manifold with external Tial wastegate, Garrett GTX4202R turbo, custom nitrous system with three stages and six nozzles using NOS parts|
|Fuel:||Columbus Diesel Supply 13mm P-pump, Industrial Injection 5x25 injectors, AirDog 200-gph lift pump|
|Horsepower:||1,110 hp (dyno)|
|Torque:||2,133 lb-ft (calculated)|
|Transmission:||47RE with 48RE parts, built by Brown’s Diesel, billet shafts, Goerend manual valvebody, 2,000-rpm-stall torque converter|
|Tires:||Baja Claws 395/60R16 (front), 285/80R17 (rear)|
|Wheels:||Pro Comp/third-gen Dodge|
|Suspension:||Revtek leveling kit|
|Axles:||4.56 gears, Dana 80 rear axle, ARB air lockers front and rear|
|Fun Fact:||At the sand drags, Ace of Spades took on a 572ci Chevy on alcohol in a 3,800-pound C10… and won!|