In Second gear roll-ons, the blown GT not so much exploded but wound up in a hurry. With no boost gauge, we found it impossible to tell what rpm the blower was taking practical effect, though it's not for a lack of trying. Seat-of-the-Levi's, it's simply impossible to say where the revving Coyote starts gaining from the Vortech blower because the power ramps up smoothly. (The dyno shows extra power from lower than 2,000 rpm.) Experienced as we are with Vortechs-we believe we were the first magazine to sample the then-new centrifugal in 1990-it was no surprise to feel the GT pull harder and harder in a swelling rush as rpm built. This is the big cookie in centrifugal supercharging-the building power rush-and it's definitely there in the new GT.
With all that happiness duly noted, we must also say the '11 Mustang GT is a heavy beast, and to make it a snappy street performer requires more rear gearing than the common 3.31 cog. The 3.55s should be just right with the Vortech for all-around use, while the g-junkies and smoke-'em-if-you-got-'em crowd will no doubt find the 3.73s willing partners. The smooth, linear power of the Vortech should be real treat on a road course, too. There, the constant high-rpm tempo is well-matched to the centrifugals power output, good adiabatic efficiency, and minimal weight gain.
As a street piece, the subdued V-3 Vortech blower is well-mannered. It makes a light, high-pitched gear whine that's just audible at idle, at least with stock mufflers and the radio off in the quiet '11 cockpit. There is no scream or siren-calling under boost, but there is big industrial air noise from the bypass valve with each shift and when holding some engine speed, say 4,000 rpm, at part-throttle. That's from the large volume of air being bypassed, and Vortech notes it has a quieter bypass exit arrangement it could fit. We drove with the standard K&N-type cone filter on the bypass outlet, which in our old age we thought obtrusively loud. If you're wanting a hot-rod persona, the little filter is your buddy; if preserving the '11's decorum is a goal, go with the quiet bypass.
Of course, there's always something, and when we drove Vortech's test mule, the electric power steering was mysteriously inoperative. Luckily the EPAS uses a stiff T-bar (that's a small torsion bar previously used to tune hydraulic-assisted steering feel, but a simple mechanical link with EPAS), so without assist, the steering is merely high-effort and not the rubbery, non-linear mess of a non-op hydraulic system. In fact, it reminded us of when men were men and drove vehicles like our buddy's 427 Cobra.
With the long studs ready...
With the long studs ready to act as a perch, the blower bracket assembly-complete with idler pulleys and drive belt-is lowered into place and bolted to the right front of the engine.
Here's a view of the timing...
Here's a view of the timing cover installed, with Peter holding up the drive belt to illustrate how the original drive belt routing remains unchanged except for new length to accommodate the blower.
Taking a break from the engine...
Taking a break from the engine compartment, the intercooler is installed next. Vortech master-tech Peter Waydo found that when working alone it's easier to block up the charge cooler and lower the car over it (!) using a hoist. You'll find it easier to have a buddy help prop up the charge cooler while you fiddle with the four mounting bolts.
This detail shot looks down...
This detail shot looks down on the charge cooler mounting bolts; the cooler is to the left and the bumper on the right. These long bolts and spacers double as the bumper attachment bolts, thus avoiding drilling new holes, adding bolts
Next up is the intercooler...
Next up is the intercooler air ducting. Vortech says this set of vanes in the air ducting just before the mass air gets rid of many driveability problems. It straightens and organizes the airflow after its winding trip through the charge cooler and ducting.
The air ducting is offered...
The air ducting is offered up to the intercooler from below the car and attaches only by hose clamps at the intercooler interface. There's a duct at each end of the cooler; here Peter is finishing up the second side duct. This is the last of the undercar work.
At the firewall, near the...
At the firewall, near the brake booster, a vacuum line T is installed to provide a boost reference signal. It's a simple cut-and-push on step. The fuel injectors can be swapped now, too.
We're skipping the photo of...
We're skipping the photo of lowering the blower onto its bracket to save space, but now's the time for that. There's nothing trick to this step except Vortech ships its superchargers pre-filled with oil, and to keep it from leaking out during shipment, a solid plug is fitted to the blower vent. With the blower in-place replace the plug with the blower vent. It's an easily overlooked step if you don't follow along with Vortech's excellent installation instruction manual.
Stuffing the fan shroud assembly...
Stuffing the fan shroud assembly back into position takes patience. Numerous hoses and wires like to grab this snug-fitting part while you're trying to get it into position, so take your time, gently pushing and pulling the offending hoses as you go. It's a rather snug fit going in, so don't despair; it all fits nicely once in position. Racers running the bolt-in YSi and Novi 2200 blowers with their 4-inch outlets will want to move to an aftermarket low-profile fan because it leaves ample room for giant 5-inch air ducting between the radiator and engine. The standard Si-trim has a 3.5-inch blower outlet.
Refit the throttle body, this...
Refit the throttle body, this time inverted and with its spacer. There's nothing trick about this, and curiously, the wiring seems to fit better than with the throttle body in its stock location.
All of the discharge air ducting...
All of the discharge air ducting can be installed now. It's all simple-if tight fitting-duct and clamp work using roto-molded ducts and rubber hose sections. Use WD40 as a lube, and just snug the connections at first, tightening all clamps only after adjusting the tubing to best fit.
Finish the duct work by reinstalling...
Finish the duct work by reinstalling the stock airbox and inlet air duct to the blower. Vortech is building the inlet duct to work with draw-through or blow-through (the mass air) systems. Street cars use the blow-through design and vent their bypasses to the atmosphere. Racier arrangements benefit from a draw-through (allows a larger mass air) and must vent bypass air into the intake upstream of the blower. The small bent hose shown here on the inlet is for those draw-through systems. It is clamped shut on street systems, such as we're installing.
The stock engine cover interferes...
The stock engine cover interferes with the supercharger, so you can either trim it in the location Peter is noting, or leave it off.
Looking like it grew there,...
Looking like it grew there, the finished Vortech street installation seems a 5.0 natural. CARB exemption is allowed by keeping the stock airbox with its hydrocarbon trap intact. True, the stock airbox is slightly restrictive right at redline rpm, preliminary guesses hover around 10-15 hp, but it's nothing you can feel on the street.
For non-CARB legal, off-road...
For non-CARB legal, off-road applications Vortech is offering an optional open-element air-filter arrangement. This hand-fabbed, 3.5-inch-diameter prototype aluminum tube approximates the 4-inch rotomolded production off-road inlet; it will extend all the way to the left front corner of the engine compartment and have an air dam around the filter.
On The Dyno
Vortech uses its in-house Mustang Dyno for development, a test rig notorious for lower readings than the ever-popular Dynojet. In fact, while we often guestimate flywheel horsepower as 15-percent lower than that reported by a typical Dynojet, 24 percent is a more accurate multiplier with Vortech's Mustang Dyno. As it is, we saw 450 rwhp on Vortech's dyno during the run we're presenting here.
Note how the rpm, boost, and horsepower are linear. The torque wanders some, with the Coyote's characteristic dip around 4,000 rpm-it must be the variable cam timing causing this.
Vortech intelligently aims for a conservative tune, using 10.7:1 as the air/fuel ratio target and timing set for 91-octane fuel. This is necessary to cover the real-world variables, and lets East Coasters custom-tune an extra 30-40 hp with their readily available 93-or-better-octane pump premium.
We can also see how boost really doesn't get out of the 7-psi range on this development run. Vortech's goal is 8 pounds of boost and 500 rwhp using the off-road inlet pipe.
Of course, the racers are already far ahead of all this. Tuned into the low 11:1 air/fuel range, spinning the supercharger to 10 pounds with a T-Trim and the engine well into the 7,000-rpm zone, racers had already run an automatic '11 GT as quick as 10.73-second e.t.'s using East Coast premium pump gas at press time for this issue.