Thursday, February 22, 2018

6.4L Ford Power Stroke Turbo Rebuild

This post was originally published on this site

Balancing Act

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.”
001 Ford Power Stroke Turbo Rebuild Opener

Photo 2/25   |   If you’re in need of a turbocharger rebuild or an upgrade, you’ll be hard pressed to find a better place than in Oceanside, California, thanks to its talented staff along with high-tech equipment not found anywhere else.

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.
002 Ford Power Stroke Turbo Rebuild Disassemble

Photo 3/25   |   Pure Turbos’ technicians wasted little time tearing apart the toasted stock ’chargers on our ’08 6.4L Ford Power Stroke engine.

“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.
003 Ford Power Stroke Turbo Rebuild Worn Blades

Photo 4/25   |   Although we previously installed new bearings and seals, this wear on the shaft and the blades surely contributed to our turbo’s problems.

004 Ford Power Stroke Turbo Rebuild Scrapecarbon

Photo 5/25   |   Pure Turbos’ tech scrapes off cooked-on exhaust gunk while inspecting every inch of the unit.

005 Ford Power Stroke Turbo Rebuild Cleaning

Photo 6/25   |   After a careful inspection during the teardown, all the bits are thoroughly cleaned in the water-based solvent tank.

006 Ford Power Stroke Turbo Rebuild More Disassembly

Photo 7/25   |   Every piece is methodically disassembled and checked for blemishes or defects.

007 Ford Power Stroke Turbo Rebuild Blast Shaft

Photo 8/25   |   Some components, like the turbines, visit the blasting cabinet, where they are cleaned so well they look new again. After the cleaning, another round of inspections is conducted to make sure the dirt and grime isn’t hiding any secrets.

Ford Power Stroke Turbo Rebuild Inspection

Photo 9/25   |   Ford Power Stroke Turbo Rebuild Inspection

009 Ford Power Stroke Turbo Rebuild Clean Components

Photo 10/25   |   How’s that for like-new condition? All the salvageable components are cleaned and blasted back to perfection before yet another round of inspections to ensure components are ready for the rebuild process.

010 Ford Power Stroke Turbo Rebuild Billet Vs Stock

Photo 11/25   |   For those who want to improve spooling and add just a little more power, Pure Turbos also has stock-sized billet-wheel upgrades that cut reciprocating weight and improve efficiency.

011 Ford Power Stroke Turbo Rebuild Vsr Balancer

Photo 12/25   |   Have you ever seen a VSR high-speed turbo-balancing machine? This piece of equipment allows Pure Turbos to spin components more than 150,000 rpm and balance them to tolerances that exceed factory specifications.

Ford Power Stroke Turbo Rebuild Tech Balancing

Photo 13/25   |   Ford Power Stroke Turbo Rebuild Tech Balancing

013 Ford Power Stroke Turbo Rebuild Low Speed Balancer

Photo 14/25   |   The turbo components are spun in the low-speed machine first to obtain rough balance specs and to look for any abnormalities with the turbine while it is in motion.

014 Ford Power Stroke Turbo Rebuild Removing Turbo Material

Photo 15/25   |   Once a part is deemed unbalanced, tiny pieces of the turbine wheel are removed until the unit comes into a proper balance.

015 Ford Power Stroke Turbo Rebuild Compressor Impellar Low Speed

Photo 16/25   |   The components are checked and rechecked throughout the entire rebuild process to ensure everything meets Pure Turbo’s tight specs. Here, the compressor and impeller are added to the shaft and introduced to the low-speed balancer.

016 Ford Power Stroke Turbo Rebuild Coaxialtorquewrench

Photo 17/25   |   Pure Turbos uses a coaxial torque wrench to tighten the shaft bolt on its turbos, creating the perfect thrust stack. A traditional torque wrench places too much side load on the fastener, which can skew the accuracy of the torque settings.

017 Ford Power Stroke Turbo Rebuild Assembly Lube

Photo 18/25   |   Pure Turbos’ technicians use liberal amounts of assembly lubricant in all the right places for each turbo build.

Ford Power Stroke Turbo Rebuild Assembly

Photo 19/25   |   Ford Power Stroke Turbo Rebuild Assembly

019 Ford Power Stroke Turbo Rebuild High Speed Balance

Photo 20/25   |   After several trips on the low-speed balancer, the turbine wheels are added to the center cartridge and spun to 100,000 rpm or more.

020 Ford Power Stroke Turbo Rebuild Balance Graph

Photo 21/25   |   This graph could be confused with dyno results. The data actually represents the turbo’s balance in relation to G-force and rpm. For reference, the light-green line with 90-degree bends represents the stock specifications of 1 g of imbalance at 50,000 rpm and 2 g at 100,000 rpm. After the low-speed balancing, the turbo is checked at two rev intervals, which produces the pink line (close to OEM requirements, but still outside those parameters at high rpm). Check out the gray line at the bottom, which was recorded after several trips to the high-speed balancer: Our turbo has no more than 0.2 to 0.3 g of imbalance. How’s that for precise?

021 Ford Power Stroke Turbo Rebuild More Assembly

Photo 22/25   |   The rebuilt compound-turbo setup goes back together after a long, involved precision rebuild.

Ford Power Stroke Turbo Rebuild Even More Assembly

Photo 23/25   |   Ford Power Stroke Turbo Rebuild Even More Assembly

023 Ford Power Stroke Turbo Rebuild Balancing Marks

Photo 24/25   |   While the small vertical lines represent the balance points from the low-speed machine, the horizontal lines equal the miniscule amounts of material removed during the high-speed balance process.

Ford Power Stroke Turbo Rebuild Finished Turbo

Photo 25/25   |   Ford Power Stroke Turbo Rebuild Finished Turbo

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