Understanding Ls Engine Tuning: Stock Ecu Limits

Tuning a stock ECU is possible, but it can be challenging and may require specific tools and knowledge. Some people prefer to use a stock ECU with minimal tuning requirements, while others opt for aftermarket solutions like Holley, FAST EZ-EFI LS, or MegaSquirt for more control and customization. It's important to consider your goals, budget, and technical expertise when deciding between a stock or aftermarket ECU for your project.

Tuning a stock ECU

When making modifications to the engine, such as changing the camshaft or adding performance parts, tuning the ECU becomes even more important. Failing to tune the ECU after making modifications might result in running the engine too lean, which could lead to performance issues and potential damage.

There are different methods for tuning a stock ECU. One method is to use a piggyback ECU, which does not replace the stock ECU but instead works alongside it to make adjustments. Another method is to chip the ECU, which involves replacing the ROM with an EEPROM or adding a daughterboard with an EEPROM. This allows the ECU to be flashable, meaning you can load new fuel and timing maps, adjust the rev limiter, and make other changes.

It is important to note that ECU tuning can be complex, and it is easy to make mistakes that can negatively impact performance or cause damage. Therefore, it is recommended to seek professional help or at least consult with experienced individuals before attempting to tune a stock ECU.

LS engine stroking methods

Stroking an LS engine for more power is a popular modification, and with good reason. The LS engine is already a powerful engine, but its stock crate engines have a lot of upside potential. Swapping to a more aggressive cam will get you more power, but if you want to up your game, you should consider stroking the engine for more displacement.

Internal combustion engines are glorified air pumps, and the more air you can move through them, the more torque and power they will make. This is why big-block engines with larger displacements have traditionally been associated with more torque. Increasing the displacement of an engine is one of the easiest ways to boost its performance, and with the recent influx of affordable aftermarket crankshafts and connecting rods, it has become cheaper than ever.

Two Ways to Increase Engine Displacement

There are two main ways to significantly increase the displacement of an engine:

• Increase the bore size: This involves increasing the diameter of the cylinders.
• Increase the stroke: This is done by lengthening the throw on the crank, which increases the distance the pistons travel in the cylinders.

LS Engine Stroking Considerations

When stroking an LS engine, it is important to consider the following:

• Room in the block: A longer stroke means the pistons will be pulled farther down the cylinder, so you need to make sure there is enough room in the block and the length of the cylinders is not too long.
• Parts compatibility: Changing the stroke of the crank usually means you also need to change the length of the rods and the height of the pistons. It is important to choose parts that are compatible and will not cause interference issues. Buying a stroker kit can ensure that all the parts work well together.
• Balancing: The bigger the stroke, the more critical and difficult it is to balance the rotating assembly.

LS3 Stroking Example

Let's take the example of stroking an LS3 engine. The LS3 comes with a 4.065-inch bore, 6.098-inch rods, and a 3.622-inch crank, resulting in a displacement of 6.2L or 376 cubic inches. Here are the steps to increase its displacement:

• Keep the stock bore: You don't need to increase the bore size to get more displacement.
• Increase the stroke: Add a 4-inch stroke crank, along with some 6.125-inch rods, to get a new displacement of 415 cubic inches.
• Honing the cylinders: Honing out the cylinders to 4.070 inches will give you an even greater displacement of 416 cubic inches, an increase of 40 cubic inches!
• Choose the right camshaft: While increasing the stroke adds power, you should also consider upgrading the camshaft. A Stage III cam from Brian Tooley is a good option for this build.
• Check for clearance: When installing the crank, it is imperative to check for clearance by installing it with at least one pair of rods/pistons.
• Choose the right bearings: Check everything over to make sure you have the right bearing tolerances. Clevite bearings are a good option for this build.
• Choose the right crankshaft: Make sure to order the crankshaft with the correct reluctor wheel needed for your ECU (either 24x or 58x).
• Choose the right connecting rods: To compensate for the new 4-inch stroke crank, add a set of forged H-beam SCAT rods that come with ARP 2000 cap hardware.
• Choose the right pistons: Forged 4.070-inch JE pistons with a comp height of 1.115 inches will give you a compression ratio of 10.9:1 with LS3 heads.

Stroking an LS engine is a great way to increase its displacement and, ultimately, its power output. By following the steps and considerations outlined above, you can safely increase the performance of your LS engine while maintaining its reliability.

LS ECU options

The stock ECU, also known as the OEM (Original Equipment Manufacturer) ECU, is the one that comes with the LS engine from the factory. It has been designed and programmed by the vehicle manufacturer, such as General Motors, to specifically control the engine and its various functions. The stock ECU has the advantage of being robust and sophisticated, as engineers have put extensive effort into optimising its performance. It is also usually cheaper than aftermarket options, typically costing around $100-200. However, it may not offer as much customisability as aftermarket ECUs.

Aftermarket ECUs, on the other hand, are produced by third-party manufacturers and offer a wide range of features and capabilities. For example, the FiTech Ultimate LS ECU & Harness Standalone Kit is a self-learning ECU that is designed for LS engines with crank and cam sensors. It offers features such as sequential fuel and spark control, a 3 BAR MAP sensor for boost support, programmable fan control outputs, and compatibility with car and truck coils. Aftermarket ECUs are often more expensive than stock ECUs, but they can provide more flexibility and advanced features for performance enthusiasts.

When choosing an ECU, it is important to consider the specific requirements of your vehicle, such as the type of engine, transmission, and desired level of customisation. For instance, if you are planning to use a 4L80E transmission, a '99 or newer computer with IAC control circuitry is recommended. Additionally, for Gen IV engines, it is advisable to use the same type of controller that was originally used, such as the E40, E38, E67, or E78.

In some cases, it is possible to use a stock ECU with minor modifications. For instance, when using a Gen III controller with a Gen IV engine, you can swap out the 58x reluctor wheel for a 24x reluctor wheel and use adapter harnesses for the cam position sensor and throttle body. However, it is crucial to ensure that you have the correct connectors and that all necessary sensors and controllers are compatible.

Ultimately, the choice between a stock and an aftermarket ECU depends on your specific needs and budget. Stock ECUs offer reliability, sophistication, and affordability, while aftermarket ECUs provide customisability, advanced features, and enhanced performance capabilities.

LS swap ECU options

When it comes to LS swap ECU options, there are several factors to consider, including the type of throttle body, transmission, and desired features. Here are some options to consider:

Stock ECU

The stock ECU is often recommended as the easiest and best option for LS swaps. It requires minimal tuning and is more robust and sophisticated than aftermarket computers. Engineers have fine-tuned the stock ECU, resulting in better performance and driveability. To control a 4L80E transmission, a '99 or newer computer is needed, and it should have IAC control circuitry, typically found in "6.0 van" ECUs. The stock ECU is a good choice unless you're doing something radical with your LS swap.

GM ECU

A GM ECU is another option and can be tuned to match your specific needs. The GM 24X ECU is compatible with both drive-by-cable and drive-by-wire throttle bodies, while the GM 58X ECU only works with drive-by-wire. The GM 24X ECU has been a popular choice for hot rodders, but the GM 58X ECU offers higher processing power and more precise tuning.

Holley ECU

Holley offers ECU options such as the Holley Dominator, which supports 24X, 58X, drive-by-cable, and drive-by-wire configurations. It also offers flexibility and additional features such as wideband, boost control, and speed-based traction control. However, the Holley option can be more costly.

FiTech ECU

FiTech offers a standalone self-learning ECU specifically designed for LS swaps. It is compatible with LS or similar engines with crank and cam sensors and supports power adders such as boost or nitrous. The kit includes a touchscreen controller for easy setup and configuration. However, it does not work with drive-by-wire throttle bodies and variable valve timing.

Megasquirt ECU

The Megasquirt ECU is an option, but it may not be favoured by some dyno shops due to its complexity. It can be used in parallel with the stock ECU to retain certain features when swapping an LS motor into an older chassis. Megasquirt does not currently support drive-by-wire systems.

Other Options

Other ECU options include Haltech, which is known for its high price, and Redline ECU-882C-1-H-TTL, which has been used successfully in racing. Additionally, there are free tuning software options like TunerPro and LS Droid, which can be used with certain ECUs.

Turbocharging a stock ECU

Turbocharging a stock engine control unit (ECU) is possible but not recommended. The ECU controls many functions beyond the engine, and when turbocharging, a remap or custom ECU is ideal. The stock ECU will not know how to handle the extra air from the turbocharger, and the engine will run worse.

A remap or custom ECU will allow you to tune the vehicle with a turbocharger. Without this, the ECU will automatically change aspects of the engine, such as spark timing and fuel injection, to compensate for the change in air density and temperature. This will result in the engine running poorly or not at all.

There are a few options for a custom ECU, such as a Megasquirt or a Haltech 550, which can be repinned for the factory loom. However, these will require additional hardware, such as a wire for the wideband.

If you are set on using a stock ECU, there are some workarounds. One option is to do a carburettor conversion, putting the carburettor before the turbo. However, this will not allow you to use an intercooler. Another option is to add an extra injector near the throttle body and connect it to a wire from the closest injector, along with a relay setup. This will allow you to also connect a boost or RPM trigger. However, this method is not recommended, as it will just dump extra fuel and may flood the engine.

It is also important to note that before adding a turbocharger, you should perform a compression and leak-down test on the engine to ensure it is healthy enough. If the engine is not healthy, it will need to be rebuilt.

Additionally, larger fuel injectors are necessary when adding a turbocharger to match the increase in air density. Without these, the old fuel injectors may cause a lean condition, which could overheat and wear the engine cylinders.

Finally, when considering the amount of boost you want to run, it is better to think in terms of horsepower rather than pounds per square inch (psi) or boost pressure. Horsepower is a more universal and constant measure, as it is what engines are rated for power.

Frequently asked questions