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Fox Turbo Upgrade - Sleeper Hit
HP's Bolt-On Turbo System Turns A '92 Fox Into A 'Stang To Be Reckoned With On The Street
For years, centrifugal supercharging has been the way of the street-Mustang world when it comes to bolting power adders on '86-'93 versions of our favorite ride. Sure, nitrous oxide ranks a close second to the blowers-it's first in some enthusiasts' opinion based on its less expensive initial cost and excellent performance gains. For this tech venture, we're focusing on exactly where a bolt-on turbo setup for a 5.0-powered EFI 'Stang fits in the best-bang-for-the-buck mix.
The turbo system we're working with ('79-'95 Intercooled Stage 1; $4,495) comes from HP Performance of Roswell, New Mexico. Jimmy Hittle and Nathan Paige co-own HP and readily admit that developing turbocharger applications for all three genres of popular late-model 'Stangs has always been one of their main priorities. For example, WFCX Wild Street winner Frank Varela uses an HP system on his eight-second street/strip '91 Fox; Mike Palugi's '05 King of the Street-winning '03 Terminator sports HP's twins; and Matt Snow's S197 GT ("Snow Stormer," July '07, p. 122) benefits from the rush of an HP turbo kit's wind.
In our search for the right candidate for this project, we stood firm about finding and using a bone-stock Mustang. We also decided to include nearly stock LX or GT Mustangs. They were only allowed basic bolt-ons so we could get a true understanding of what-if any-influence HP's turbo and intercooler has on a 5.0's power output at the rear tires of a street 'Stang.
Our up-close interactivity with turbo-chargers is largely relegated to hearing the 106mm, 94mm, or 88mm hairdryers whoosh by us when Pro 5.0, Super Street Outlaw, or Drag Radial Mustangs make their way down the dragstrip during NMRA race weekends. A turbocharged race Mustang in action is a sight to behold. It leaves a lot to the imagination when thoughts of applying a turbocharger on a milder Mustang enter the brain.
Through a process of elimination, we selected the Mustang GT of GTR High Performance's co-owner Ricardo Topete to be the recipient of HP's Fox system. Ricardo purchased his Pony new in 1992, and it's in great shape despite its 150,000 miles. The car is equipped with short-tube headers/catted X-shape crossover exhaust, underdrive pulleys, a cold-air system, a 76mm MAF, a 70mm throttle body, lowering springs, and 3.90 gears. Although it's also equipped with a stock automatic transmission, we think it best represents the type of '86-'93 'Stang this kind of power adder will thrive on. We're keenly aware that whatever remaining life there is on our test 'Stang's stock automatic will more than likely be shortened if power gains eclipse 360 rwhp and Ricardo lets those horses run every time he leaves a stoplight.
Power adders are often touted as bolt-on ready and applicable to stock Mustangs without any mention of additional equipment or accessories. HP Performance bills its Fox kit as an everything-included, bolt-on, no-weld experience needed. Determining whether or not the claim is true is something we had to do. The system is highlighted by a 60mm Garrett turbocharger and HP's own 3.5-core intercooler. The kit also features ceramic-coated, 131/44-inch mild-steel tubular headers; a massive 311/42-inch down-pipe; 3-inch exhaust tubing with a Y-pipe, a T-bolt, and V-band clamps; a Walbro 255-lph fuel pump and new 42-lb/hr injectors; a TiAL 44mm wastegate; a Spal electric cooling fan; and every fastener you can think of needing for this type of install. Materials for an oil change (FL-300 filter is recommended), fresh spark plugs, and a new, shorter serpentine belt are the only parts that must be purchased separately.
There's also no need to reinvent the 'Stang as occasionally must be done in order to achieve proper fitment of its components. On our application, we used a 75-inch belt, underdrive pulleys on a crank and water pump, and we removed the smog pump.
We always enjoy having company owners or their representatives visit us to personally take part in a tech project. Such is the case this time, as we were fortunate to have Jimmy Hittle with us to provide expert assistance with the turbo installation. Of course, he was also there to get a first-hand look at how his company's Fox 'Stang turbo system performed in our evaluation on the chassis dyno at GTR.
"This system was designed for Fox owners who are looking for a bolt-on turbo kit that will easily bring 550 hp to the rear tires of a street car, but is capable of making up to 1,000 rwhp, providing all the variables to do so are in place-the engine, transmission, and so on," says Jimmy. "All a 'Stang's accessories are retained with this base kit, and with its CNC-bent down-pipe and tubing, fitment in a stock Fox is spot-on perfect."
We're not going to spoil the suspense. Look at the photos and captions first, then see what HP Performance's turbo does to our high-miles/low-mods Mustang. Keep your credit card nearby.
Ricardo and Chris loosen the bolts and dislodge only the upper intake manifold. The lower plenum remains in place, but fuel injectors can also be taken out at this time, as HP-provided 42-pounders will be installed when everything comes together. The intake is removed with the Jamex strut-tower brace still intact. HP Performance prefers that this piece be ditched prior to installing the Fox system. Ricardo's brace was reluctant, so improvisation was necessary.
The engine must undergo a partial disassembly with most of its top pieces coming off in order to accommodate the new turbo components. After removing the stock clutch fan and shroud, the fan bolts are used to resecure the water-pump pulley.
Did we mention that HP's turbo kit doesn't affect any of a Mustang's factory accessories except the clutch fan? There's no sacrificing cold A/C for the sake of having turbo power. Jimmy bends the stock A/C hard line slightly. The turbo-charger assembly sits in the front-most corner of the engine compartment's passenger side. The hard line is tweaked just enough to allow the necessary clearance without compromising its factory appearance. A/C lines can remain connected during this installation process because there's no need to discharge the system.
If oil is the lifeblood of a turbo system, exhaust is its lifegas. Our test 'Stang's X-shape crossover and short-tube headers are taken out and discarded. The all-inclusive turbo system provides more-than-suitable replacements in its 131/44-inch headers with 3-inch collectors, a 3.5-inch down-pipe, and the new 3-inch, Y-shaped tube that mates cleanly with most after-catalytic muffler systems.
In turbocharger parlance, the "hot side" refers to all the exhaust-related portions of a turbo system-headers, crossover, and down-pipe. HP's mild steel headers and tubing carries a limited lifetime warranty and the ceramic coating is protected for three years. The company prefers to use mild steel for high-heat applications such as this. Steel can withstand thousands of heat cycles and is much less susceptible to cracking than stainless steel.
New 42-lb/hr fuel injectors are provided and will feed a more-than-sufficient amount of fuel to the 5.0 in Ricardo's GT.
At this juncture, removing the serpentine belt, smog pump, and all the Mustang's emissions equipment (hoses, tubes, and so on) are the last tasks before the install process begins. This kit doesn't have an Executive Order number from the California Air Resources Bureau (the 50-state-legal blessing). Depending on where you live, drive, or register your Mustang, an aftermarket turbo may not be permissible for street use. It's important to consider all the legal variables involved with a turbocharged 'Stang because you don't want to get busted.
Jimmy disconnects the factory O2 sensors, which are retained and reused once the turbo system is fully installed.
Although HP has thoroughly scienced out every aspect of its Fox turbo system, it's always a good idea to mock-fit critical pieces, especially if your 'Stang has ever sustained front-end or frame damage. With the hot-side header in place, Jimmy checks the position of the turbine housing in relation to the frame. Keep a marker handy to indicate areas accordingly, should there be any reason to modify.
Have you ever wondered what the science is behind the turbo inlet dimensions when you see racers discussing turbo sizes on Internet forums? HP's Fox setup uses a 60mm turbo, meaning the distance between two tips of its inducer (blade-like pieces on the compressor wheel) measures 60 millimeters.
Bench assembly is a small part of a turbo installation. Jimmy mounts the inducer inside the compressor housing and attaches an oil-supply fitting that will feed the compressor and turbine housings with engine oil. As we mentioned earlier, oil is the lifeblood of a turbo system. It cools and lubricates the internal components of both housings.
We drained fuel prior to beginning the installation, so Ricardo and Eli have an easy go at lowering the fuel tank. With the tank down, replacing the filler-neck rubber gasket (PN F4ZZ-9072-DA) is a good idea. Original pieces with as much time on them as Ricardo's has are probably going to look as bad as this one does.
Chris handles wiring on the HP-provided Walbro, high-pressure 255-lph fuel pump and drops it into the tank. Once this is done, the fuel tank can be reinstalled.
We've covered the position logistics and reason for punching the hole in the oil pan ad nauseam. Oil supply for the turbo is taken from a fitting ported into the 5.0's oil-sender's log and returned via an oil drainback into the pan in many Mustang forced-induction applications. This photo details the importance of coating your 11/42-inch tap with heavy grease before threading the pan. The grease will catch most of the metal shavings and prevent potential damage to the engine. As an additional safety measure, we suggest you drain the pan and change the oil before calling your turbo installation complete.
This front-mount intercooler measures 311/42 inches thick by 27 inches long by 10 inches tall. It will chill things down to a point where it easily supports 1,000 hp.
The 'cooler mounts up front, between the bumper and the A/C condenser. HP set up this piece for easy installation in a position where it will receive the consistent airflow through openings in the GT's bumper cover.
A coating of Permatex Ultra Copper is the preferred method of sealing turbo headers. Gaskets are prone to burning out due to the high temperatures and pressures created by the turbocharger's exhaust side.
Since Ricardo's 'Stang will now be free of pollution controls, the air-injection tube is removed and cut. Each end is then flipped over and coated with Ultra Copper before being bolted down and used as block-off plates at the back of each cylinder head.
HP Performance designed headers for its Fox turbo system to allow plenty of access to spark plugs, making for easy maintenance. The number-two plug is probably the toughest to negotiate in and out of the head, but it's doable with patience.
The slip-fit crossover tube links the output of the passenger- and driver-side headers, and routes exhaust gasses into the tubine housing. HP provides a complete host of T-bolt and V-band clamps that ensure all the hot-side and cold-side connections are tight and leak free.
TiAL's 44mm wastegate keeps boost regulated by controlling the amount of exhaust that actually gets to the turbocharger. It's regulated at no more than 10 pounds with this system. HP also includes a bypass valve, which diverts excess intake pressure away from the throttle body whenever the throttle is closed. It vents the pressure to atmosphere and creates the whaaaCHEW-CHEW-CHEW-CHEWWW sound that's music to any Pro 5.0 fan's ears.
While we said there's no welding involved, there's a small amount of cutting that must be done as part of the turbo installation. After mock-fitting the complete turbocharger assembly, the areas of the passenger-side inside fender panel are marked and a reciprocating saw is used to create the necessary clearance for the turbo and its inlet tubing, as well as the discharge tube to the throttle body. A 311/42-inch hole is also drilled in the framerail to allow the crossover tube to reach the flange on the header.
Jimmy mounts the 31/44-inch oil-return hose before installing the turbo assembly in the engine compartment.
A liberal smearing of Ultra Copper is also used on the header-to-turbo collector flange. This union is critical, so once the turbo is positioned, it's important that each bolt is secured evenly and is maxed out for tightness.
HP's massive 311/42-inch down-pipe connects to the back of the turbine housing and sends remaining exhaust to a Y-shaped tube that's attached to an after-cat exhaust system. The choice of mufflers is up to a 'Stang's owner, but we found that running the system through open pipes sounds mean and is possibly low enough to make it passable in certain areas.
A 76mm MAF tube is one modification that came to us on our test 'Stang. Since we upgraded fuel injectors to 42-lb/hr units, the original tube (on the right with its sampling tube calibrated for 24-lb/hr injectors) is replaced with the 76mm tube HP supplies, which has a sampling tube sized for the larger injectors. They adjust the airflow over the mass air sensor, changing signals sent to the EEC IV to calculate the engine's fuel requirement.
HP suggests you lose the strut-tower brace in order to make installing the discharge tube a lot easier.
Clint Anderson is our wiring specialist, and he handles extending the GT's mass air harness. With the turbo system, the mass air meter is incorporated into the cold-side plumbing and is relocated into the passenger-side fender.
A Novice's Guide to Turbocharging: Basically, the engine's spent exhaust gasses enter the turbo through the volute on the turbo housing and spin the turbine wheel. As the wheel spins, the compressor wheel-connected to turbine wheel via compressor shaft-also spins at wickedly high speed and draws in/compresses the incoming air charge. The air charge passes through an intercooler and shoots through a tube in the mass air into the throttle body. It's really that simple.
This Spal fan is another included feature of HP Performance's Fox-Mustang turbo system. This unit whips up a serious wind that will keep coolant temp in check. This is necessary for our kind of application, especially in SoCal.
This is the knob. Jimmy is fond of this Holman manual boost controller ($100 optional upgrade), which runs from a vacuum source in the intake manifold to the side of the wastegate. Once the wastegate is maxed at 9 psi, the controller overrides it, allowing those who want more power to crank it in. An electronic version of the same device is also available ($380). Ricardo's 'Stang will need more engine and a lot more transmission before it's ready to test one.
Here's a look at Ricardo's newly turbocharged 5.0. HP Performance does this system right, as everything fit well. True to the company's claim, there was no welding necessary, nor did we need to purchase any additional parts or hardware. HP says the system is designed around stock '86-'93 Mustang geometry. Aftermarket K-members may present alignment challenges with some of the tubes. The kit is complete, and it looks at home in the engine bay of this '92 Fox.
|ON THE DYNO|
HP TURBO W/MSD
With the install tasks handled, we fired up the freshly turbocharged 'Stang for the first time and took in the sound of a dramatically different exhaust note. Despite having a straight-through/open exhaust-Ricardo was undecided on mufflers at dyno time-the 'Stang's engine sounded much quieter at idle than it did in naturally aspirated trim.
Jimmy set fuel pressure at HP's recommended 27 psi, and Ricardo locked timing out at 16 degrees total. The Autolite 24s were gapped at 0.030 and a fresh batch of California's 91-octane pump gas was loaded in the tank for our dyno tests.
We were all curious to see how the Mustang's stock auto trans and torque converter would react to the influence of increased power and torque. Jimmy says most five-speed and AOD turbo 'Stangs are in boost by 2,900-3,000 rpm on the street. Since we're testing on the dyno and have to start our pulls in Third gear, we won't see boost until about 3,300 rpm, and there may not be enough time for the turbo to achieve full boost before the run time expires. While we realized there might be a few horsepower left on the table because of this, we forged ahead with our evaluation.
The result of the first dyno hit was a pleasant surprise. Our automatic 'Stang put 361 hp and a stellar 446 lb-ft of torque down on the dyno, and the tranny didn't miss a beat. That's a 185hp increase over our baseline with 209.48 lb-ft of additional torque.
Although this early showing was phenomenal, the dyno graph exposed a distinct break in the power and torque curves at 4,400 rpm and a full 9 psi of boost. After brainstorming, it was determined that spark was being blown out inside the cylinders, and we needed to address that issue right away if we wanted to continue testing with any more success. The data doesn't lie. It was obvious there was more power and torque to be made as long as the transmission hung in there.
We secured a new MSD 6AL unit, thanks to the efforts of Extreme Speed and Peterson Performance of Upland, California. GTR had one of MSD's plug-and-play harnesses for the ignition box (PN 8874), and Jimmy had everything connected in a hurry.
For our final hit, we decided to see how more timing and closing the spark-plug gap to 0.027 would work in conjunction with the enhanced spark provided by the MSD. We'll let the numbers speak for themselves from this point, but if we had to sum up our opinion of the impact an HP Performance turbocharger has on a daily driven, 5.0-powered, automatic Fox in one word, that word would be "whoa!" Check out the video on our Web site www.50mustangandsuperfords.com.