Wednesday, November 22, 2017

From the beginning wortec, have been heavily involved in the tuning of General Motors engines. Our experience is focused on the later generation of GM engines starting with the "LS1 continuing to the LS3 and beyond!".

The LS1 was a heavily revised version of the long standing small block Chevrolet. This update arrived in the late nineties and took the form of a 5.7ltr displacement with single camshaft in block design and two valves per cylinder.

A key part of this design was the new engine management system which allowed us to extract all of the OEM calibration and then allow us to make alteration to the tune that would give better optimisation of performance parts that may be fitted. The OEM control unit is very powerful and has been proven to be able to support some very high powered cars with a refinement not seen on most after market systems. Horsepower figures of over 1000bhp are possible and can be supported by the standard controller (with suitable calibration)  Power adders like superchargers and turbo's are also easy to incorporated into the ECU (GM refer to the controller as a PCM which means Power train Control Modual)

LS1 engines show very good gains in torque and horsepower from simply adjusting fuelling and spark advance. Added to these changes various revisions to other maps produce a very smooth and capable engine. LS1 engines installed in GM product like the Holden Commodore and Monaro show gains of 30-40hp over the OEM calibration with better drivability. The gains in other GM cars of the same age all show similar or in some cases better gains.

As part of the re calibration of the PCM wortec also data log the engines performance via the cars "On Board diagnostics Port". This port allows us to read and record all the cars sensors in real time and with the addition of various extra sensors, like wide band Air Fuel sensors we are able to check and refine the calibration until the performance goals for the car are reached.

The tuning process is performed in the environment the car is designed for. This means Road cars are tuned on the road and test circuit to provide the perfect tune. Once the calibration is completed the car can be dyno tested to provide a finished set of figures for that car. No changes are made on the dyno as this is an environment that the car is not designed to preform in. If any concerns are found during the dyno test the car is rechecked on the test circuit to identify the problem and then re-tested if required.

For race car tuning and other motor sports the cars are calibrated at the race track or drag strip to make sure the car is preforming at its optimum. Via the data logging system we can equate results to real world performance date to ensure upgrades are bringing real benefits.

The follow on from the LS1 was the LS2. The revised engine hand some important changes due in most part to emissions regulations. LS2 was a 6.0ltr engine following the tradition dimensions of the small block Chevrolet. The performance was up to 400-420hp in most cars that use the engine. The OEM calibration is much closer to the maximum for the engine and power gains from re-calibration are smaller than the LS1, gains of 10-15hp are more common. An area that does show gains is that of drivability where changes produce a better drive and can be tailored to the driver. These changes in fact don't add power but they do mean you can drive the car closer to its optimum for more of the time so in fact point to point speed is increased.

To extend the LS2 more after market parts are required, good gains from exhaust system changes are common, tubular headers and enlarged cats and cat back systems are a very good start. Intake optimisation helps but does not yield big gains. The next step is an uprated camshaft to increase lift, duration or both on exhaust and inlet valves. The limitations for cams are either emissions or driveability. If neither are of concern power can move well past 500hp but to maintain both emission and drivability 480hp is a realistic power goal.

All naturally aspirated combinations can be controlled by the OEM PCM which for LS2 has been made faster and more powerful. One calibration change which has a place in cars with large cam shafts is the the ability to remove the "Mass Air Flow meter" and run the car in "Speed Density". In simple terms the "MAF" calculates the amount of air coming into the engine and then applies the correct fuel to that number. This is a very good design on modern cars and allows the car to adapt to changing conditions well. But some times the MAF is not a suitable way of running an engine. In this case we run the car in "Speed Density! again in simple terms this means the car is calibrated in a way that a table is produced inside the OEM controller that provides a individual number of the cars efficient at any given rpm and engine load. From this table the engine can add required amount of fuel.

The use of "Maf" or "Speed Density" is always dependant on engine set-up, use and customer requirement no one is better than the other they both are vital to tuning and are both supported by the OEM GM controller.

Power adders such as Superchargers and turbo's are easily controlled by the GM PCM and once again go to prove how good the OEM unit is. Some controllers from GM come with built in tables to run superchargers as they are used on cars like the Cadillac CTS-V and Corvette ZL1 which have forced induction from the factory. It is not a requirement to have a supercharger specific PCM as all GM controllers once re calibrated can run superchargers or turbo's.

LS3 is the current engine from GM and is an evolution of LS2. This engine forms the base for most GM V8 performance cars and is the focus of our calibration engineers who are looking to optimise the aftermarket being designed at the moment.

LS3 will be superseded by the LT1 (new version with no reference to the LT engine from the early nineties) These engines continue the extremely efficient and powerful V8 engines from General Motors and now incorporate displacement on demand and direct injection. Performance from standard engines will be 450bhp with the possibility of 500bhp from mildly tuned ones and also 30+mpg from cars equipped with the latest versions of GM gearboxes.

 GM automatic gearboxes are also part of wortec's tune packages and can be recalibrated to provide a very performance biased drive whilst maintaining a relaxed drive when required. The controller for the automatic gearbox has now become very complicated and easily rivals the complexity of the engine controller. This complexity has meant progress on new calibration options has been slow but the results are now being supplied to our dealers and feed back is excellent.