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Starr Charger - Part One

We check out Starr Performance's twin-screw blower kit for LS1s.

Words by Michael Knowling, Pix by Julian Edgar

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At a glance...

  • Starr Performance LS1 supercharger kit
  • Whipple blower
  • Water-to-air intercooling
  • Water injection
  • MAF-less tune
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People love go-fast bolt-ons - and with good reason. Bolt-ons are easy to install, easy to remove (and then resell) and don't require expensive engine disassembly.

If the benefits of bolt-ons appeal to you, then an aftermarket supercharger kit must be a near performance panacea. There's simply no other bolt-on mod that comes close to matching the extra kick in the pants.

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Now meet the Starr Performance positive displacement supercharger kit for the LS1.

Peter Starr and the guys at Starr Performance are proud to offer their bolt-on blower kit that comprises a twin-screw supercharger, water-to-air intercooler, cast intake manifold, upgrade fuel system, reprogrammed ECU and all other necessary components.

This is one of the nicest aftermarket blower kits we have seen.

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Peter started this project with some clear goals in mind - he wanted around 400kW at the flywheel, excellent reliability, factory-like driveability and everything had to be kept below the bonnet. Another important requirement was instant boost response and strong performance from just 1000 rpm.

In essence, the engine had to be as impressive in the cut-and-thrust of traffic as it was on the open road.

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The weapon chosen for the task is the latest Whipple twin-screw supercharger (Starr Performance is the Australian distributor of Whipple superchargers). Peter says there are other twin-screw superchargers on the market, but none has the capacity to deliver the anticipated power. The Whipple is up to the job, thanks to its huge 2.3 litre per revolution displacement.

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The supercharger is mounted in the valley of the LS1 V8. Installation involves removing the standard intake manifold and fitting Starr's beautifully cast replacement manifold and alloy adaptor plate. The supercharger bolts directly to the adaptor plate.

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This photo shows one of the O-rings that seal the cast manifold to the cylinder heads. Peter says every joint in the induction system is sealed with an O-ring. No gaskets are used.

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The supercharger is driven using a sophisticated remote drive arrangement that allows everything to remain beneath the standard bonnet line. A replacement pulley is fitted to the crankshaft nose and a serpentine belt drives the factory accessories as well as the front pulley for the remote drive coupling. Peter says the front pulley on the remote drive coupling is easily large enough to avoid problems with belt slip. The rear pulley on the remote drive coupling spins the supercharger via a high-strength toothed belt.

Peter estimates the supercharger drive loss is up to around 40 horsepower.

The Starr kit delivers a peak boost pressure of 10 – 11 psi when fitted to a stock engine. The full 10 – 11 psi hit is available from about 3000 rpm all the way to redline.

Note that Peter considers intercooling essential when boosting the standard-compression LS1.

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The kit uses a compact – and patented - water-to-air intercooler arrangement that's integrated into the cast supercharger manifold. The core is V-shaped to promote laminar airflow into the intake ports. We're told that the core reduces charge-air temperature up to 50 degrees Celsius and causes only a small pressure drop.

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The rest of the water-to-air intercooler system uses an aluminium front heat exchanger (which nestles in front of the OE coolant radiator) and a Davies Craig booster pump to circulate the fluid. Note that the pump is run at a constant voltage when the engine is running – there's no variable speed control strategy. Oh, and a genuine Holden power steering reservoir is used as the filler for the water system – this helps maintain a factory-style under-bonnet appearance.

Interestingly, a water injection kit is fitted in addition to the water-to-air intercooler system.

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The water injection system serves as a safety feature to further reduce the chance of detonation. We're told that the water injection also helps seal the inter-meshing supercharger rotors and, as a result, provides about 1 psi extra boost.

A Spraying Systems brass nozzle injects water upstream of the throttle body at boost pressures above about 6 psi. Water is drawn from the factory washer bottle and is pushed through the nozzle by a washer-type electric pump. The pump is switched from a specially configured pin on the ECU.

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On the atmospheric side of the supercharger, the Starr kit employs custom cast elbow with a 94mm throttle body. Peter emphasises the importance of allowing the supercharger to draw air without restriction. A 4 inch diameter pipe leads to a custom airbox containing a K&N pod filter.

And what about fuelling and engine management, you ask?

Starr Performance is experienced at tuning the factory management system and has taken this approach for their supercharger kit. This means all the fail-safes and engine protection strategies remain in place. Closed-loop fuelling and active knock sensing are also retained. There are also dual spark tables – the ECU reads the conservative timing table whenever there is heavy knock sensor activity.

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The retune involves removal of the factory airflow meter and installation of a 2 Bar MAP sensor. Note that the intake air temperature sensor is located post-intercooler to give a 'real world' signal to the ECU.

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The modified engine management system fires a set of eight 43lb/hr upgrade injectors. A standard fuel pressure regulator is used in conjunction with an electronic device that boosts the voltage to the factory fuel pump, so increasing its flow.

Using another specially configured pin on the ECU, the voltage booster is triggered at above 5 psi boost. Fuel pump voltage then increases from 14 to 21 volts. Note that, in a street application, you're unlikely to hold high load for any more than a few seconds at a time. This means the pump is operated at high voltage for only short durations and pump life is not sacrificed.

Ignition hardware is left standard.

With the standard exhaust system in place, the Starr blower kit is capable of generating 300kW at all four wheels in the company's demo Holden Adventra. That's more than double the stock ATW figure! Peter calculates the initial goal of 400kW at the flywheel has been exceeded by approximately 20kW...

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With a high-flow exhaust yet to be fitted, Peter is expecting the Adventra to kick out an easy 320kW at all four wheels. Note that an upgrade exhaust is not supplied in the kit - Peter assumes by this stage most customers will already have an aftermarket exhaust fitted.

In Part Two we'll be firing up the supercharged Starr Performance Adventra for a drive!


Starr Performance +61 3 9894 8860

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