Recalibrations Pay Big Dividends In Smoothness And Performance

Published: 09 October 2002

Pictured: HSV.

In line with the strong emphasis on refinement, HSV embarked on an extensive Y Series engine recalibration program.

A full 12 months before the Y Series launch HSV's calibration engineer, Gerry Bechet, began the massive task of totally recalibrating every parameter of the Electronic Control Module (ECM) used on the 5.7 litre HSV enhanced LS1 and 300kW C4B V8s.

Since the ECM is essentially a mini computer whose job is to control all aspects of engine operation, Gerry concentrated on ensuring it was precisely programmed.

He began by delving into what's called 'Torque Modelling'. Basically this comprised an exhaustive series of controlled dynamometer tests conducted at the Holden Racing Team HQ, to measure exact engine torque output. The test was repeated for a wide range of variable operating parameters - throttle positions in 5% steps up to 100% open, engine revolutions in 200rpm steps from 800rpm to 6200rpm, eight different air fuel ratio steps and friction at each point.

The result is a series of complex three dimensional Torque Models. Gerry explains that since the ECM doesn't physically know the amount of torque the engine is developing it uses these Torque Models to predict it.

"The Torque Model says I'm getting so much air, so much fuel and so much spark advance and if I take off friction that should equal the torque I'm actually producing. The number it predicts should equal the torque the dynamometer is showing."

When mismatches occur between the electronic brain's predictions and actual engine torque, performance suffers. By recalibrating the Torque Models to exactly match actual torque output, every Y Series now delivers an immediately noticeable lift in drivability and refinement, particularly when coupled to the recalibrated automatic transmission.

For example, when upshifting there's a maximum torque threshold at which the auto can shift without damaging internal components. If the engine output is too high it asks the ECM to momentarily retard the spark to reduce torque during the shift. Now, because the ECM's Torque Modelling is exactly accurate, shift torque is spot on and every gear change is smooth and refined.

Part of the brief was also to enhance engine performance across the rev range, for which you need more spark advance and leaner air fuel ratios. For the HSV enhanced LS1, remapping the spark advance table and applying lessons learned from the 300kW calibration has raised maximum power by 5kW to 260kW.

For both engines Gerry targeted the knock sensors which 'listen' for engine knocking and retard the spark accordingly.

"The knock sensors were a bit over sensitive - they'd hear one little knock and retard the spark which means you lose engine performance. We remapped the sensitivity and now they're working hard to give you maximum performance and efficiency all the time."

In the search for leaner air fuel ratios the catalytic converter protection function was found to be a little over sensitive.

"We looked at what air fuel ratio we could run without damaging the catalyst. We discovered we could tone that down, still protect the cat and run a little leaner which is closer to maximum power."

A non-electronic recalibration has also been incorporated in the form of a snail shaped cam where the throttle cable acts on the throttle body. It provides a more progressive throttle action which promotes smoother low speed driving and improved 'drive away' feel.

"It's taken one year of solid work to recalibrate and the result is a subtle but discernable difference when driving."

HSV's trademark has always been exhilarating engine performance and that hasn't changed with Y Series. What has changed is the smoother more refined manner in which that performance is delivered on the road with the welcome bonus of improved fuel economy in everyday driving.

Optimising the ECM's programming for Y Series ensures that in every imaginable situation HSV's legendary powerplants are delivering their very best in terms of drivability, power, and fuel efficiency.

Recalibrations Pay Big Dividends In Smoothness And Performance

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