It’s no secret that rebuilding an engine or transmission requires using specialty tools and plenty of expertise, but few gearheads consider the complexity of rebuilding a turbocharger. Modern turbos are made with much more than seals, a turbine, and housing. These pieces must also be assembled with ultra-tight, precise tolerances. If they aren’t, catastrophe could be imminent.
If you have any doubts, consider this fact: Modern turbochargers for diesel engines can spin up to 150,000 rpm, velocities so high that accurate balance is an absolute must. Anything less often results in shrapnel entering your engine thanks to a turbine blade contacting the housing.
“Balancing a turbo that spins that fast requires a lot of knowledge and the right machinery, since the balancing process involves removing miniscule portions of the turbine that only weigh a couple of grams and are about the size of the lead tip on a pencil,” says Jesse O’Hara, founder and CEO of Pure Turbos in Oceanside, California., “It’s very common for the turbochargers on Ford’s 6.4L engine to develop problems at around 100,000 miles,” Jesse says. “And, in most cases, those issues start with the seals and bearings and quickly progress to shaft-play, which, if not caught early enough, can result in severe damage to the turbo.”
The 6.4L Power Stroke is boosted by a stock compound-turbo setup that’s sized at 64 mm on the high-pressure side and 53 mm on the low-pressure side. What’s a compound-turbo system? Without breaking into an engineering dissertation, it’s basically a pair of turbochargers running in series, unlike twin turbos, which work in parallel. Compounds use two different-sized turbos, a low pressure and a high pressure. The low-pressure (the larger of the two) ’charger ingests atmospheric air that then feeds into the high-pressure turbo (the smaller one), which then sends the air into the intercooler or engine. This process compounds the charge, producing big boost and minimal lag, a combination that is generally unobtainable with traditional turbocharger systems.
After installing a rebuilt 6.4L engine in an ’08 Ford F-250, we decided to also rebuild the Power Stroke’s turbos.
Although we thought the engine and ’chargers were assembled correctly, it wasn’t until the engine had 100 miles or so that a howling sound straight from a Star Wars movie started trickling into the cab near the firewall. Some investigative work revealed it was in fact, our newly rebuilt turbos. So the cab was removed yet again, and we paid a visit to Pure Turbos for help with getting everything straightened out.
“Unfortunately, this scenario is all too common when it comes to turbo rebuilds, since the tolerances have to be extremely precise, especially the balance,” Jesse says. Apparently, our unit’s new internals weren’t balanced correctly, and the resulting imbalance created a resonance that sounded like a howl. Had we continued to ignore the problem, it would have eventually knocked the bearings and seals out, and ultimately, the turbine would have contacted the housing.
Although a stock rebuild is more than sufficient for our project, Pure Turbos recognizes that many diesel owners want more power than the stock equipment can create. So it has devised a stepped performance program for most engines. If stock isn’t enough, the company offers a billet-wheel upgrade.
“The billet wheels are the same size as the stock units but can add up to 50 hp and improve spooling response thanks to a more efficient design and less weight—all without breaking the bank,” Jesse explains.
And for Super Duty owners who demand even more, Pure Turbos also offers its 73mm LP Billet Turbo that’s good for 700 hp, without any sacrifices like additional lag. “Because the 6.4L engines use a compound-turbo setup, we were able to upgrade to billet compressors and get away with a larger 73mm wheel,” Jesse says.
“While other companies make a 71mm upgrade, as we always have with our upgraded factory turbos, we got creative. And thanks to some internal tricks, we were able to modify the stock housing to accept and even larger 73mm wheel,” Jesse adds. All rebuilt turbos and upgrades are backed by a one-year warranty against defects.
If there were a few takeaways from all of this, it’s that one can’t afford to take the cheap route on a turbo or fly-by-night rebuild, as boost is too important to a diesel engine. Turning to a company like Pure Turbos ensures you’ll get quality components that work. In the spirit of keeping things on the level, we initially considered the process of rebuilding stock turbos a casual affair. But having gone the DIY route only to be rewarded with pulling the cab and the turbo an additional time, we fully understand that sometimes things are better left to the experts.