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Supercharging a late model GTO

ProCharger force feeds our Goat

Nic Conley - October 27, 2011 10:00 AM

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This is what we’re working with. The LS2 already has a mild Livernois camshaft, LS6 cylinder heads, ported throttle body and intake manifold, exhaust system and cold air intake. Our initial baseline dyno pull netted 359 rwhp on our Dyno Dynamics chassis dyno, which translates into around 460 flywheel hp. Pretty respectable on any level.

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We’ll start by removing the air intake system and radiator cover. Then the cooling fans come out. They will not be reused, as ATI supplies two new fans and shroud.

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This bracket installs using existing bolts just ahead of the brake master cylinder. The power steering reservoir is moved from the front of the left head to this bracket.

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Next, the bumper cover and bumper have to come off to facilitate installation of the intercooler and ducting. Don’t let this intimidate you. This cover came off in less than five minutes.

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We opted to upgrade the harmonic balancer to this ATI Super Damper. Procharger recommends this upgrade when the boost level exceeds eight psi. Since the LS-series engines don’t use a crankshaft keyway, you need to drill and pin the balancer, which needs to be done regardless of which balancer you use. Once the new balancer is on, the special jig is attached and a hole is drilled into the balancer and crankshaft for the pin.

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The supercharger pulley is installed. Make sure the A/C belt is installed before this step. Otherwise, you will have your work cut out for you later. Don’t ask …

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The spacer block is bolted to the cylinder head.

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The blower head unit and main bracket are lowered into the engine bay. The head unit may need to be re-clocked in order to clear everything. It’s very tight in here!

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These new fans will operate exactly as the stock ones did. There’s plenty of airflow thanks to the custom aluminum shroud, which is included. The fans are lowered onto the front of the radiator and wired in. This is also a good time to install and tension the blower drive belt.

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Next, the upper radiator hose extension is twisted into position and clamped down.

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The intercooler is bolted to the bumper using factory fasteners and included brackets. Then, the bumper is reinstalled and the power steering cooler is rerouted to the front and bolted in. It really doesn’t get much easier than this.

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The ducting is tight, but it does fit. We decided to get our own T-bolt clamps since we will be making more boost later, and don’t want any blow-offs down the road. It’s best to lay the piping out to get the basic idea before starting.

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Since the GTO uses a blow-through mass air sensor, we can utilize Procharger’s Pro-Flow blow-off valve. This is a very nice high quality valve. And it fits nicely between the cooling fans and crankshaft pulley.

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Back up top, the remainder of the ductwork is installed with the MAF sensor. It’s very tight so make sure the sensor clears the belt tensioner.

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Next, we pull the fuel rails and install the new injectors. The full kit comes with 52-lb units, but since we got the tuner kit, which deletes the injectors and tune, we bought our own 60-lb injectors and will be doing our own tune.

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A must on supercharged engines is to replace the spark plugs with a colder heat range plug. We put NGK TR-6 plugs in the Goat with the gap pulled down to .028-inch to reduce the possibility of the spark being “blown out” by boost.

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The kit includes this vacuum manifold that can plumb up to four vacuum lines. We ran one to the blow-off valve, and the other to a boost gauge mounted on the A-pillar. The manifold splices right into the vacuum hose supplying the brake booster.

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We’re almost done!! The air intake tube and air filter are clamped in next. Although not mentioned here, there are changes to the PCV system that will require a vent hose being plumbed into the top of the air filter. It’s all very easy.

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Bill reinstalls the bumper cover after the hose clamps are rechecked and the engine is started to ensure clearance between the supercharger and, well, everything around it! We did take a razor knife to the radiator cover and carved out a section to clear the intake tube.

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Here’s the finished installation. Everything fits, and everything works.

CHART Vince Geglia of Trifecta Performance set us up with a custom tune for the beast. The results? Well, with a 93-octane tune, the Goat spun the rollers to 522 rwhp at 8 psi. We could’ve squeezed more out, but are a bit nervous about the durability of the stock rods and pistons, as well as the aluminum block, so we ultimately richened it up a tad for safety sake, and settled for 516 rwhp. That’s a 158 hp difference and a maximum of 201 hp over stock. What’s more, it’s a pure joy to drive with absolutely no bucking or sneezing from the motor at all.

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It really wasn’t that long ago that a 400hp street car was something special. To have that much horsepower and retain true street manners was sometimes as elusive as the mighty unicorn.

That certainly isn’t the case anymore. The big three U.S. automakers have been building cars with that much power at the flywheel for years now, and even a few trucks can produce the same results with nothing more than a dyno tune session.

The Pontiac GTO made its short comeback from 2004 to 2006, and although sales were not as aggressive as GM had hoped, they are very popular with the latest generation of hot rodders. The LS1 in the ’04 model made 350hp, while the LS2 touted 400 flywheel horsepower bone stock. We wanted to see what kind of power we could muster from the LS2 by installing Procharger’s D-1SC supercharger, all without going to an aftermarket block or rods and pistons and still run a modest amount of boost.

Our project car is a ’06 model owned by Chris Chaffin of Boise, Idaho. His car already has a few mods to the engine including a pair of LS6 heads, a mild camshaft from Livernois Performance, COMP Cams roller rockers, and a set of JBA shorty headers. We dialed in a tune with our HP Tuner’s software and strapped her to our Dyno Dynamics chassis dyno. The six-speed Goat responded with 359 rwhp, which equates to approximately 460 flywheel ponies. One thing we’ve found is that the LS engines respond very well to the right combination of parts, and this one was no exception.

Accessible Technology’s Procharger kits use top quality components, and their support is second to none. We opted to upgrade the kit from the standard P-1SC head unit to the D-1SC. It will provide more boost later, when the owner steps up with a beefier short block. All Procharger kits are intercooled, which is a huge plus when it comes to supercharging. The blower itself super-heats the air charge, sometimes as much as 100 degrees, before it enters the engine. That in itself can defeat the purpose, and cost horsepower. These ATI intercoolers drop the air charge temperature significantly, and actually help create more boost.

The GTO kit was fairly simple to install, and although tight in places, it fit like it was supposed to. All in all, the install took about 10 hours, and that included pulling the tank to install a high volume fuel pump. Performance Solutions in Boise handled the installation and dyno testing of the Pontiac as they have done the lion’s share of all the work on Chris’ Goat since the car was factory stock.

Vince at Trifecta Performance of Seattle, Washington, handled the custom tuning end and provided the ECM with just the right tune to get us what we wanted. The results? We got the supercharger to make just over nine pounds of boost and were rewarded with 522 rwhp. Just to clarify, if this car were tested on a Dynojet inertia dyno, it would have shown a tick over 570 wheel horsepower due to the difference in correction formulas. Either way, that comes out to over 650 flywheel horsepower and enough torque to move the Earth!

We can’t wait till the iron 427ci short block is finished so we can turn the wick up on the Procharger to 14 pounds and see what this force-fed Goat will dish out!

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