LS1 Tuning - Part 3

In Part 2 of this series we looked at entry-level upgrades for Holden/HSV LS1s. In this, the final part, we take a look at ‘next level’ modifications – naturally aspirated and forced induction...

The Naturally Aspirated Approach

Cam

Once your LS1 has been treated to headers, exhaust, air intake and management mods, the next area of focus should be the camshaft.

Sam from Sam’s Performance says the camshaft was noticeably improved in the VY series but all factory Holden and HSV (non-C4B) cam profiles are extremely conservative; this means you’ll need an aftermarket camshaft for your upgrade. Sam suggests avoiding an overly wild camshaft when using the factory intake manifold – a cam delivering about 250 degrees at 50 thou is about as big as you should to go. A slightly wilder cam might pick up a kilowatt or two but you’ll lose bottom-end and mid-range grunt.

And Sam should know - he’s dyno tested AUD$36,000 worth of cam profiles!

A cam upgrade should be installed hand-in-hand with a new timing gear set, valve springs and retainers. Sam says the factory valve springs aren’t suited for use with an aftermarket cam so it’s important to upgrade. Once the valve springs are changed it’s likely you’ll need to change retainers as well.

In a previous article (The Path to Power: 300kW LS1) we reported on the fitment of a Crow cam kit to a breathing-enhanced HSV Clubsport. This Dyno Dynamics dyno graph shows the before and after power and torque curves with the replacement cam kit – a gain of 32kW ATW gives a peak output of 220kW (on a Dyno Dyanics chassis dyno).

Cam and Heads

Interestingly, many people go straight to a cam and head package rather than installing just a cam. This is despite the fact that the cam can be replaced without removal of the cylinder heads.

Sam says the cylinder heads are the same across all Holden and HSV engines – with the exception of the C4B with its CNC ported heads and bigger valves. The standard alloy 2-valve-per-cylinder heads are said to flow around 460hp on a flowbench at a test pressure of 28 inches of water. However, with a fairly mild port job the horsepower potential increases to about 590hp.

A set of these heads together with a mild street cam typically delivers around 300kW at the wheels. The standard fuel system reaches its limit at about this point – for more power Sam suggest bigger injectors and a high-flow pump.

Multi Throttle

At power outputs of around 400kW at the flywheel, the standard LS6 intake manifold causes considerable airflow restriction.

To solve the problem, Sam has designed and developed a sexy looking set of 50mm individual throttle bodies teamed with tuned-length ram tubes. These units pose virtually zero air intake restriction and look downright sexy. The only downside is they require a hole in the bonnet and it’s not easy to install an air filter arrangement.

These individual throttle bodies play a large part in enabling one of Sam’s customer’s cars to reach 328kW at the wheels with the standard LS1 bottom-end – an amazing feat!

Stroker Kit

When the strength of the standard engine internals becomes a concern (when you’re making more than about 320kW at the wheels) it makes a lot of sense to step up to a stroker kit rather than a straightforward ‘performance’ rebuild.

Sam current sells two different stroker kits – a Lunati kit and a cheaper version. Both come with a stroker crankshaft, rods, pistons, rings and bearings. Note that Sam typically opts for a compression ratio of 10.8:1 or less for a street engine.

Sam is currently run off his feet putting together 383ci (6.3 litre) stroker engines for customers - and for good reason.

“The 383s can be easily driven every day, provide a heap of torque through the revs and easily make 360kW at the flywheel,”’ says Sam. With higher compression and a beefier cam, you can expect closer to 400kW at the flywheel.

For an absolutely all-out naturally aspirated LS1 you can’t beat a 383ci stroker engine with individual throttles. Sam has seen this combo generate more than 373kW at the wheels and a proven 630kW at the flywheel (as measured on Sam’s engine dyno).

Yes – you read it right.

Six hundred and thirty kilowatts!

The Forced Induction Approach

Supercharged

One of the easiest ways to achieve big power with the LS1 is to add forced induction – and the most popular approach is supercharging.

The biggest selling off-the-shelf supercharger kit to suit is the Vortech set-up from CAPA (Centrifugal Air Pumps Australia). The kit comes with a Vortech curved-blade centrifugal supercharger, mounting bracket, pulleys, lubrication system, blow-off valve, air intake, modified airflow meter with reprogrammed PCM, water injection and a fuel system upgrade (comprising an additional fuel pump). An optional air-to-air intercooler is also available. See Boosting the LS1 for an article covering installation of the kit.

With base boost pressure set to 7 psi, you can expect an intercooled LS1 to generate around 273kW ATW. If you’ve already got aftermarket headers and an exhaust, you’re talkin’ more like 313kW ATW.  

To run more than about 320kW ATW you’ll invariably need a bigger set of injectors to maintain safe mixtures. With bigger squirters and a different pulley to deliver 9 psi boost you should see 332kW at the wheels.

Congratulations - you’ve now virtually doubled the factory power output!

But be careful. Sam says you’re running near the limit of the standard bottom-end.

Oh and, finally, if you want a positive displacement supercharger for the fattest possible torque curve, you should consider the Starr Performance Whipple kit – see Starr Charger - Part One and Starr Charger - Part Two

Just make sure you’ve got almost AUD$18,000 in your back pocket...

Contact:

Sam’s Performance
+61 2 9772 3105