The center cartridge is often taken for granted as much of the attention when it comes to turbochargers is focused on housing sizes and wheel trims. The center section is the "durability center" of a turbo. Lubrication and cooling of the unit happens here and if things go bad, it's game over. There's no doubt that ball-bearing cartridges have been a godsend for turbo enthusiasts. Almost like cheating, tuners are using the ball-bearing design's quick spool-up to negate turbo lag and to run bigger units on smaller applications.

Garrett's dual ball-bearing turbos were originally designed for diesel engines. Diesels were known to produce throttle tip-in smoking. The smoke was the byproduct of a rich condition that occurs after the throttle is opened, but before boost is realized. Response was the goal because diesels don't rev very high. So ball-bearing turbos designed to spool-up quickly were developed that shortened the time between the pedal and the boost, which helped solve the problem. The highly responsive design was perfect for extreme motorsport applications, which eventually led to the HKS/Garrett GT lineup now seen on the street, as well as offerings from Turbonetics and other manufacturers.

In the first of this two-part article, we'll examine the inner workings of the center cartridge to develop a basic understanding of its functions. In the next installment, we'll explore the different types of ball-bearing center sections.

Learn how the center cartridge works as we assemble a conventional journal center section and outline some of the differences between journal bearings and Turbonetics single ball-bearing center sections.

The difference can be seen in the palm of your hand. It's all about stability and friction resistance; the ball bearing easily outshines the journal bearing in both aspects. Turbonetics reports that its single ceramic ball-bearing design spools 25 percent faster than a journal setup, while delivering 50 times greater thrust resistance.


Here's a conventional journal-bearing center section setup. On the left, a 270-degree thrust bearing and brass journal bearing.

This is the Turbonetics single-ball-bearing center cartridge. It features a beefier thrust bearing, a 360-degree washer and an angular-contact ceramic ball bearing.

Small but important, these retainer clips slip into ridges inside the center section and keep the bearing(s) in place within the cartridge.

Next, the bearing is dropped in the housing. In this picture, it's a journal-style unit.


Then the thrust bearing and the washer are put together. The thrust-bearing assembly is positioned on the housing. The dowels are used to properly line up the assembly with the oil passages in the cartridge housing.

The thrust bearing is one of the prime areas of failure. Ever wonder why oil changes are more frequent for turbocharged cars? Note the three oil ports and pads on the thrust bearing washer (arrows). Everything is riding on the thin layers of oil provided by these orifices.

In journal bearing applications, a retaining clip is inserted in the backing plate, which is secured with four bolts.

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Turbonetics' Tyler Tanaka was unimpressed as I throttled the company's 350Z development car around a makeshift tri-oval in the City of Industry, Calif. "Come on, drive it like you stole it," he quipped. In my experience, tearing away from a stoplight is more a test of driveline durability than the merit of a turbo kit and the tuning it takes to make it work in the real world. My M.O. is to roll onto the throttle quickly, say in third gear. This allows me to get a good feel for the spool-up of the turbo, the pull of the engine all the way through a complete powerband cycle, and I can better detect any tuning hiccups. To my credit though I did hit triple digits on more than one occasion.

The Turbonetics 350Z single-turbo kit rocks; giving the sultry 350Z a new lease on life by way of 8 pounds of boost. The spool-up characteristics of the ceramic ball-bearing center section are excellent, and the 60-1 compressor wheel deals out the boost in an authoritative manner. At cruising speeds it feels like the turbo is lurking just under the gas pedal, and with little coaxing the spooling begins. The more aggressive the right foot, the more aggressive the thrust. Be careful winding this mad dog up; the boosted VQ35DE is truly addictive.

The centerpiece of the kit is the T3/T4 60-1 hybrid turbo. But we must point to the innovative placement of the turbo and the use of the stock exhaust manifolds. Twin-turbo kits in the market for the 350Z place the turbos way down low, virtually out of sight. The Turbonetics setup positions the turbo up high, just rearward of the driver's side headlamp so you can see what you're paying for. The system utilizes the factory exhaust manifolds, which saves installation time and cuts down on the cost of the kit. Boost is routed from the passenger side header via a crossover pipe that joins with the driver's side header outlet and feeds the turbinehousing. Turbonetics reports that the factory exhaust system made more power than an aftermarket setup, but the company plans to try one or two more exhaust systems.

In our Dyno Cell testing the 350Z pumped out a generous 365.6 whp at 8 psi, the most we have seen from an "as-delivered" boost package for the Z. On the torque side we witnessed 355.3 lb-ft at peak. But looking beyond the peak we were impressed by the torque curve as it eclipsed 300 lb-ft at 3600 rpm and stayed there until the pull ceased at around 6300 rpm. Checking the power curve the VQ35DE belted out 250 hp to the wheels at a low 4000 rpm and tracked predictably to its peak. The kit is tuned well with the enhanced ECU providing a rock solid 11:1 air/fuel ratio throughout the run.

At $5,595 the Turbonetics kit is a boosted bargain that delivers big power, a reliable-looking air/fuel curve and an easy installation regime. It's a win-win scenario.
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Ask any mechanic what a fried clutch smells like and most likely they would reply that it smells somewhat like burnt toast. Unfortunately for Mitsubishi Evolution VIII owners that smell is an all too common occurrence. Hundreds of Evo VIII owners have learned the hard way about living /eating burnt toast; it's a bitter pill. Some owners with have reported clutch failure with as few as 3,000 miles on the clock. Dozens of Evo VIII forums have reports of similar occurrences. The worst part of the whole situation is that dealers will not warranty the clutch due to it being a "wear item." One clutch we removed from a vehicle only had, 3,000 miles on the odometer and it looked like a grenade was thrown at it. All the friction material on the disc disintegrated into smaller pieces.

After doing some investigation we found that one of the reasons for the failure in the clutch is the flywheel. Heat is the number one reason for clutch failure and the Evolution's flywheel does a poor job of transferring heat away from the disc. Upon closer inspection, besides the obvious blown clutch fragments, we noticed the flywheel had severe discoloration on the backside due to excessive heat buildup. Our guess is besides the overall heavy weight of the vehicle and the AWD drivetrain the driver would have to ride the clutch much more than a lighter weight 2WD vehicle for that much heat to build up in the flywheel. Add a little stop-and-go traffic into the mix and you have yourself a recipe for clutch failure. Fortunately, the after market has also recognized the need for a performance clutch for the Evolution VIII. From a simple single-disc replacement to an exotic triple-disc carbon clutch, whatever your needs are the after market has you covered.

Advanced Clutch Technology
ACT offers three different types of clutches from a basic street to full race applications. The ACT street clutch kit has a 38-percent increase in clamp load and has a torque capacity of 497 lb-ft. ACT also offers two race clutch kits: one is a four-puck disc design while the other is a six-puck disc. Both race clutch kits features a 38 percent increase in clamping load and have a torque capacity of 636 lb-ft. All three clutch kits come with a new throwout bearing and clutch alignment tool.

Centerforce
Centerforce offers their patented Dual-Friction design clutch utilizing custom carbon fiber organic facings and ball-bearing pressure plate. The carbon fiber organic material is better suited to handle the extreme heat conditions of the Evo's drivetrain. The increased clamping load does not mean a heavy pedal due to its ball-bearing design. You won't have to perform leg presses at the gym to operate the clutch. The Dual-Friction clutch has been tested on vehicles generating over 450 hp to the wheels. Centerforce also offers a billet steel flywheel that is lighter and better able to transfer heat away from the clutch disc.

Clutch Masters
Clutch Masters offers four different stages of performance clutches for the Evolution VIII, from a basic street setup to full race applications. Their street variant has a holding capacity of 70 percent over stock while the race version is capable of holding 170 percent over stock. All Clutch Master clutches come with a new throwout bearing and clutch alignment tool. The company also offers an aluminum flywheel for the Evolution VIII.



RPS Performance Products

If all-out performance is what you're after then the RPS carbon-carbon twin-disc clutch is what you need. Specially designed for high-output Evolution VIII's the RPS carbon-carbon clutch is capable of holding over 700 hp and still civil enough to be used on the street. Pedal pressure is increased only by 10 percent but the engagement is extremely smooth and comfortable to drive. However, if you want the Ferrari of clutches be prepared to fork out some dough.

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