The secondary section of the...
The secondary section of the exhaust downpipe was set in position.
Installation of the kit was straightforward, requiring only that the exhaust manifolds (in this case, headers) be removed and replaced with the tubular exhaust manifolds and crossover pipe. It was also necessary to tap into the extension for the oil-sending unit to provide oil to the turbo. A hole was drilled into the oil pan to serve as a drainback for the turbo. The down tube featured a Y-section to connect the turbo exhaust to a conventional after-cat. After running the various inlet tubing to and from the turbo, intercooler, and factory throttle body, we were ready for the dyno.
Before getting to the power numbers, a quick lesson on horsepower and torque might be helpful. From the formula that dictates the mathematical relationship between horsepower and torque values (HP=TQxRPM/5,252), we see that gains in horsepower below 5,252 will show a greater increase in torque. Conversely, improvements in torque above 5,252 will show more dramatic changes in horsepower.
An example works well here. Using the formula, we see that increasing the power by 50 hp at 3,500 rpm will result in a jump in torque of 75 lb-ft. Increasing the torque output by 75 lb-ft at 6,000 rpm will improve the power output by more than 85 hp. Since the stock 5.0 motor has always been a torque motor (it produces a higher peak torque number than horsepower) and does so at a relatively low engine speed, adding boost to the equation is likely to exaggerate this relationship. Basically, adding a turbo kit to a motor that makes peak power at just 4,800 rpm will provide huge torque gains. If the peak torque number was higher than the peak power number in normally aspirated form, we should expect things to remain the same once we install the turbo.
True to form, adding the turbo kit from HP Performance offered not only a sizable jump in peak power, but a huge jump in peak torque. Where the normally aspirated motor produced 243 lb-ft of torque, the turbocharged 5.0 thumped out a diesel-like 493 lb-ft of torque at just 3,700 rpm. Running 10 psi of boost, the peak power output of the turbocharged 5.0 checked in at 433 hp.
We've always been amazed at the power offered by a good turbo system, and this single-turbo kit from HP Performance certainly continued the trend. The great thing about this torque monster was the immediate gratification that came from sticking our foot into the throttle. Having 493 lb-ft to play with at just 3,700 rpm means this thing builds speed like nobody's business. Even down at just 3,000 rpm, the torque output was 360 lb-ft. What this avalanche of torque means is that this Mustang gets moving, right now. Of course traction is in short supply, but it's always better to have too much power and not enough traction than the other way around.
While 433 hp and 493 lb-ft of torque was certainly impressive, naturally we couldn't leave well enough alone. Despite the high mileage, we decided to crank up the boost at least a few more pounds to see how it responded. To hedge our bets and prep for the upcoming trip to the strip, we poured in some 114-octane Rockett Brand race fuel. At this combination of timing (18 degrees total), air/fuel (11.2:1) and boost level (13 psi), the 114-octane fuel was probably overkill on our part, but we wanted to make sure we still had a healthy candidate for Part 2.
It was necessary to install...
It was necessary to install the downpipe before bolting the passenger-side exhaust manifold in place.
Next came the crossover pipe....
Next came the crossover pipe. Since the turbo kit for the 5.0 featured a single turbo, it was necessary to route the exhaust energy from both banks of the motor to a single outlet. The crossover tube joined the right and left side exhaust manifolds to feed the T4 turbo.
Since the turbo was capable...
Since the turbo was capable of considerable boost and power, it was controlled using a Tial 44mm wastegate initially set at 10 psi. This was later turned up to 13 psi for track use.
The 60mm turbo was installed...
The 60mm turbo was installed onto the awaiting exhaust-manifold mounting flange. Larger turbos are available, but the 60mm was more than adequate to feed the needs of our stock 5.0.
With the turbo in place, Nathan...
With the turbo in place, Nathan from HP Performance installed the primary downpipe running from the turbine side of the turbo to the secondary pipe positioned below the passenger-side exhaust manifold.
Completing the exhaust system...
Completing the exhaust system was the Y-pipe designed to bolt to a production or after-cat exhaust.