SCT Makes Your Late-Model Engine Swap Run In A Flash

Many performance enthusiasts already know about the late-model tuning company,  SCT and its line of performance tuners for many vehicles. We recently spoke with the folks at SCT to discussed how its line of tuners and tuning software can help enthusiasts who are swapping engines into their vintage vehicles.

Of course, mixing and matching various decades of performance comes with its own pitfalls and disclaimers – so here’s ours. The EPA has very strict guidelines for late-model engine swaps. We strongly suggest that you check out the EPA’s Engine Switching Fact Sheet, to verify you are not running afoul of any federal, state or local laws with your vehicle.

That said, any swap will run up against some hurdles and there are a few things you can do to stack the cards in your favor. Some of them should be considered long before you turn a wrench or key.

ECUs come in various shapes and sizes, and it's what's inside that can make all the difference. You need to know how your ECU is configured before attempting to run your engine. Later-model vehicles used both an ECU and a TCU for the transmission.

Off To A Good Start

We reached out to SCT about options for those swapping engines and how its products can make the engine’s operation optimal. As with any engine swap, you need to make sure that all of the electrical components are designed to work together. Items like Engine Control Units (ECU) and Transmission Control Units (TCU) need to be designed to communicate correctly. Also, components such as the engine’s crankshaft and even the camshaft need to speak the same language as the engine’s computer.

Long story made short, GM changed the number of reluctor “teeth” on both the crankshaft and camshaft of its engines over the years. You not only need to know that the ECU can count the right number of teeth on the crankshaft but also, that the number of teeth on the crank and cam are in sync with what the ECU is intending to see.

Whether your engine is a salvage-yard jewel or one of Chevrolet Performance's latest crate engines, you'll need to make sure that the ECU speaks the same language.

A lot of this information can be had by knowing the year, make, and model of the engine in question. From there, the ECU’s operating system can be established. If the engine/trans is a complete take-out with the accompanying ECU and TCU (if necessary), it is fairly reasonable to assume it will communicate appropriately in the new vehicle.

Many enthusiasts will purchase an entire running vehicle to ensure that everything works as intended. This is a great option, but many folks will also opt for a crate engine or purchase an engine from the back of a pickup at a swap meet. In these situations, SCT’s Calibrations Lead, David Griffin has some very sage advice.

The engine's ECU must be able to read both the crankshaft reluctor-wheel tooth count as well as the number of "teeth" on the camshaft sprocket. Notice the one, solid raised area (left) compared to the four, individual raised areas on the cam sprocket (right). These areas are detected by the Cam Position Sensor to let the ECU know exactly where the engine is in relation to firing the injectors and spark plugs.

“You need to make sure your ECU’s operating system matches your TCU’s operating system,” he says. “Around 2005, GM began switching to separate ECU and TCU controllers rather than a single, integrated unit. If you are running the incorrect TCU, you will have shifting issues or the transmission may not shift at all.”

There is more at stake than simple gear selection,” David explains. “It is important to make sure your ECU is the proper ECU for your setup. Items such as Drive-By-Wire (DBW) as compared to Drive-By-Cable (DBC) throttle bodies are all part of the ECU’s base configuration. If you have an electronic DBW throttle body, you will need the correct ECU to make it all work.”

Whether you plan on keeping it simple with a cable-driven throttle body (left) or have the newest technology like the Drive-By-Wire in this swapped LT4 (right), today's ECUs can make the most of your application. You need to know upfront which one you'll be using and make sure the ECU matches.

How big of an issue is the crankshaft and camshaft’s communication with the ECU? David puts it all in perspective. “It is important both the crank- and cam-sensor settings — along with the reluctor wheels — match the ECU’s operating system. I see a lot of people make the mistake of using a 24x-based ECU with a 58x reluctor wheel,” he says. “Up until the Gen III LS-based engines, the 24x crankshaft reluctor wheel was used. When the Gen IV platform was introduced, GM switched to a 58x reluctor wheel. I see people mix this up quite often.”

Luckily, Lingenfelter Performance Engineering has a 58x-24x Crank Sensor Trigger Conversion box which converts the signal. Just remember, this does allow you to convert the 58x crankshaft trigger signal to a 24x signal, but it will not convert the 24x signal to a 58x signal. In this instance, you need to obtain the proper ECU, or swap out the reluctor wheel on the crankshaft.

A new harness is always a good idea. It eliminates gremlins caused by poor connections and excess wires for systems that you’ll not be using. They also offer the necessary OBD-II port so you can configure your ECU and run diagnostics once up and running.

Starting From Scratch

Does that mean the LS on a bed of a truck is a veritable Pandora’s Box of electronic issues? Not necessarily. Thankfully, the aftermarket has embraced the LS/LT-based engine market and offers many products to fill in the gaps. We have suggested before that enthusiasts swapping complete engines should strongly consider installing a custom-built harness for their application. This removes many of the issues that could arise from unnecessary components or cut wires, or connectors that were less than gently removed.

Also, many companies that offer harnesses can also supply the necessary ECU and TCU (if needed) for your application. Many can even install a base tune to get your application up and running. From there, you can use the SCT tuner of your choice to optimize the engine’s operation to your liking. At that point, SCT’s software and hardware open up a world of tuning for your late-model engine.

Finding Your Tune

Since the mid-’90s, GM ECUs have all been EEPROM types which can be re-flashed by using the OBD port in the wiring harness. All OEM and aftermarket harnesses for LS and LT engines will have an OBD-II port that serves as the portal into the mind of the computer. The OBD-II port is useful for diagnosing and tuning the ECU, and all SCT’s hardware is designed to integrate with the OBD-II port. After that, the end-user has several options for how they wish to modify their engine’s operation.

SCT’s latest tuning devices are the GTX (Left) and the BDX (Right). Both are cloud-based tuners, able to send files via WiFi. The GTX also has a 5-inch touch-screen that serves as a great customizable gauge display.

David mentions, “Typically the end-user will use their SCT device (X3, X4, BDX, etc.) and read the calibration from the ECU. Then, they can email it or send the calibration through the cloud to one of SCT’s approved calibrators to build the initial tune.”

Once the engine is up and running, the end-user can then utilize their SCT device to transfer data to their calibrator via data logs so that the calibrator can finalize the tune for their application.

LiveLink is a Windows-based data-logging software available from SCT.

Many enthusiasts know SCT as a tuning hardware provider. But, another way that SCT enables end-users to modify their ECU is through its software offerings. The LiveLink software enables enthusiasts to view, data log, record, and playback their vehicle’s PCM data on a laptop computer. This can be extremely beneficial when troubleshooting or finalizing a tune for a specific application.

Another software option that really opens the doors to effectively tuning an engine’s operation is SCT’s Advantage III software. A powerful option used by SCT’s calibrators, this program is also available to enthusiasts who choose to take on the task of trimming the fat from their engine’s operation. SCT’s Advantage III is a Windows-based, custom-tuning software that offers control of hundreds of vehicle PCM parameters and offers on-screen help files for each area being tuned.

As an added benefit, SCT offers regular training courses about the software in its dyno-equipped facilities in Florida. For those unable to attend a training session in person, SCT also offers online-training courses to get you up to speed.

SCT’s Advantage III software opens the door to the powerful realm of ECU tuning. There are hundreds of parameters available to modify within this software.

The Advantage III software is designed to work in conjunction with one of SCT’s hand-held tuners and can transform that take-out engine into the powerhouse it was always intended to be — even if it no longer resides in its OE vehicle. One of the benefits of using SCT’s BDX or GTX tuners is the cloud-based transfer of data files and tunes via WiFi. The GTX also serves as an excellent data point with gauges and readouts of real-time data on its configurable 5-inch touch-screen display.

Today’s engine controls are powerful systems that not only keep our engines running, but also provide the performance and economy that we’ve come to expect from today’s fuel-injected engines. With SCT’s software and hardware offerings, tuning your late-model swap can be as easy as contacting SCT. That way, you can make sure your engine systems are operating at peak performance no matter what vintage chassis they might find themselves powering.

Article Sources

About the author

Andy Bolig

Andy has been intrigued by mechanical things all of his life and enjoys tinkering with cars of all makes and ages. Finding value in style points, he can appreciate cars of all power and performance levels. Andy is an avid railfan and gets his “high” by flying radio-controlled model airplanes when time permits. He keeps his feet firmly grounded by working on his two street rods and his supercharged C4 Corvette. Whether planes, trains, motorcycles, or automobiles, Andy has immersed himself in a world driven by internal combustion.
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