The last time we hit the dyno, our 5.9L Cummins picked up a whopping 140 hp at the wheels with a relatively small 0.078-inch nitrous jet. It was obvious that our '89 Dodge, known as Project Rust Bucket, needed more air, and it needed it badly. Now that its engine has an upgraded cylinder head and a beefed-up fuel system, it's time to wage an all-out war on airflow restrictions.
| The first step of our turbo install involved removing the upgraded original unit-a process that couldn't be easier. The downpipe clamp was loosened on the exhaust side, the turbo intake was removed, and the stovepipe was taken off. After that, the four bolts that held the turbo to the exhaust manifold flange were removed, the oil lines were taken off, and our engine was now turboless.
Tricked-Out Turbo
We upgraded our stock non-wastegated turbo to a super-trick 62mm S300 turbocharger from Majestic Turbo. Not only does Majestic Turbo sell all sorts of turbochargers, it builds them, too. So our S300 came with a wastegated housing and a 360-degree thrust bearing upgrade for ultimate reliability. This turbo has been used on customers' trucks to make more than 500 hp and 1,000 lb-ft at the rear wheels, so we felt it was perfect for our project truck. We also opted for a wastegated 14cm2 housing (or 0.80 A/R) and 65mm turbine wheel so we could make it spool like a stocker. At $1,350 with all the goodies, it was the perfect turbo for our budget build.
| Although the compressor side of our new 62mm S300 turbo (left) looks about the same size as our High Tech Turbo 60mm upgrade, that 2mm-larger compressor wheel makes quite a bit of difference. Remember that small turbocharger size increases correspond to large airflow changes, because the compressor wheel will be spinning more than 100,000 rpm!
More Intake, More Exhaust
While our turbo upgrade was the heart of the project, we also improved all our associated hardware. The external wastegate on the truck was fitted with an updated unit from Turbosmart, our downpipe went from 3 inches to 4 inches courtesy of Source Automotive, and our stovepipe intake was replaced with a custom unit built by J&H Performance.
| On the exhaust side, Majestic Turbo's S300 (right) features a 65mm turbine wheel and a 14cm2 exhaust housing. Stock '89 Dodge turbos came with a 60mm turbine wheel, and an 18cm2 exhaust housing (left). What does all this mean? It means the larger 65mm turbine wheel should flow a lot more exhaust gases than the Holset turbo, while the 14cm2 exhaust housing should give it excellent spooling characteristics.
In Theory
After these latest airflow upgrades, Rust Bucket will be ready to hit the road again. We feel confident our O-ringed head with ARP studs will take any power level we can throw at it, and with our airflow upgrades, we expect a 30 to 50 hp improvement, along with a big drop in EGT when we hit the dyno.
