Solving ECU Options For Your LT Or LS Engine Swap With EFILive

The number of vehicles that are now receiving either LS or LT engines is amazing. You don’t have to look far to see LS-based engines winding up in Mustangs and Miatas, so there’s definitely some benefit to jumping the fence and swapping in one of these late-model powerhouses. The small-block Chevrolet engine has been the product of swaps since its inception way back in the ‘50s, and it’s nice to see that it still has the same appeal with the power-hungry.

We’re not going to get into whether someone SHOULD mix makes, models and brands when swapping engines, but rather give information and options for those who choose to make the jump. There is a seemingly deep sea of information around the modern Electronic Fuel Injection strategies used by today’s cars, and the extent that electronics control what goes on inside our car is staggering. Thanks to companies such as EFILive, enthusiasts can enter into the world of electronic engine controls and traverse the tides with great success. Just like formulating a winning combination for any engine, properly selecting from the vast offerings of slightly-used engines and controllers can be done with a little knowledge and research.

In my opinion, there are very few instances in which an aftermarket ECM is a better choice than an original equipment model – Dave Emanuel, Digital EFI

The Proper Controller

Finding a suitable late-model powerhouse isn’t too complicated, as the LS platform has been around for over 20 years and there are many variations to choose from when searching for an engine; simply choose the power level and budget that works for you. There have been several upgrades to the LSx line since they were introduced in the late-nineties, both to the engines and the controllers that drive them. Those changes allow enthusiasts to enjoy new-and-improved technologies and higher horsepower, but you need to understand what engine you have and what’s needed to make it work.

General Motors has used various controllers since the LS1 was introduced in 1997. Companies like Speartech and Howell Engine Development offer various harnesses to join both engine and ECU.

We spoke with Dave Emanuel, President of Digital EFI, a U.S. distributor for EFILive about using OEM controllers for engine swaps. He replied, “In my opinion, there are very few instances in which an aftermarket ECM is a better choice than an original equipment model – at least with the LS1 and E40 controllers. OEM controllers are available for $100-200 which is a bunch cheaper than the aftermarket units.” Although, there are instances when it makes sense, he explains, “In cases of highly modified engines, or race applications where you want to make tuning changes on the fly, an aftermarket system may be preferable. However, in my experience, the modifications have to be pretty extreme.” If you’re pulling the engine from a vehicle, many times you can also purchase it with the necessary controller to operate the engine. This ensures that you will have the necessary ECU to make the engine operate as it was designed, including the option for cam-phasing and Displacement On Demand (cylinder deactivation), if you choose to use that technology.

One thing not recommended to bring along from your take-out engine is the harness, for several reasons. Sure, it might be easier to make it part of the deal, but it also incorporates a lot of extra wiring and additional circuits that you may not use. Plus, can you really be sure that it was gently removed from the donor vehicle? Think about all of the connections and potential for hazards. Also, you’ll need to integrate the OBD-II port for computer flashing and diagnostics. If you were to go with an aftermarket harness from a company such as Speartech or Howell Engine Developments, Inc., you would get a new harness, wired out for your application, using only those circuits that you need.

An aftermarket harness allows for customization and brings new, solid connections, diagnostic port and many other required circuits that you’ll need.

But what about that take-out engine that doesn’t have an ECU with it already? How do you know which one works? That’s where the information on EFILive’s website comes into play. If you know what the engine was removed from, they have a comprehensive listing of each ECU as it was used in each application. You can simply look up the donor vehicle and see what ECU it came with. It also helps to know what you wish to do with your engine. If you plan on supercharging, then you’ll need an ECU that has provision for a two or three-bar MAP sensor.

Sorting ECUs

With over 20 years of evolution, there are a variety of ECUs to choose from to drive your LS/LT engine. Rather than make/model specific ECM/PCMs, GM began utilizing fully interchangeable ECUs in its car and truck lines. That means, while appearance and capability has changed over the years, the basic platform for how the ECU operates has been fairly stable since the LS engine was introduced. Dave explains, “With the introduction of the LS1 engine, came an entirely new generation of powertrain controllers. In addition to having the ability to handle electronic throttle control, the LS1 PCM (Powertrain Control Module) incorporated an entirely new, and significantly more sophisticated, engine control architecture. With literally hundreds of calibration tables, Gen III and later controllers offer far more precise control of engine and transmission operation than previous generations of PCMs (or ECMs).”

Whether LS or LT-based, the latest offerings from General Motors have found their way under the hoods of almost every make and model car, boat and even aircraft!

Of course, noting transmission control is important, since for the 2005 Corvette, GM scrapped the single Powertrain Control Module concept in favor of separate engine and transmission controllers. Even though separate engine and transmission controllers are used with Gen IV engines (LS2, LS3, LS7 and an assortment of truck/SUV engines), it’s best if they communicate with each other. This isn’t a problem in an original application, but with a retrofit, there’s a good chance of a miscommunication or non-communication if both controllers weren’t originally designed to talk with one another.

ECUs for the Gen III LS engines utilize a 24x reluctor wheel on the crankshaft and have the cam position sensor in the block, at the rear of the intake. Gen IV engines have a front-mounted cam position sensor and use a 58x wheel on the crankshaft (aside from a few oddball transition-year models utilizing the E40 ECM – those have a 24x but the front-mounted cam sensor). You can tell the reluctor wheel tooth count by the color of the sensor used to read it, 24-tooth wheels use a black sensor and 58-tooth versions use a gray sensor.

ECUs in 1997-2004 LS engines utilize a 24x reluctor wheel on the crankshaft and have the cam position sensor in the block, at the rear of the intake. Gen IV engines have a front-mounted cam position sensor and use a 58x wheel on the crankshaft (aside from 2005s utilizing the E40 ECM). Gen IV engines also used a one-tooth, and four-tooth cam positioning indicator on the cam gear.

With Gen IV engines, it’s best to stick with the same type of controller as used originally, either E40, E38, E67 or E78. It is possible to control a Gen IV engine (LS2, LS3 and LS7) with a Gen III (LS1-style) controller if the 58x reluctor wheel is swapped out for the Gen III’s 24x reluctor wheel and adapter harnesses are used for the cam position sensor and throttle body, since throttle body operation is reversed between the two generations. [Lingenfelter also offers this handy conversion module.] Also, some sensors may need to be replaced, depending on application.

The LS1 (a and b) controllers were found in 1997 Corvettes and 1998 Corvette and Camaro.

The Gen III controller (LS1a) started in the 1997 Corvette and found its way into the 1998 Corvette and Camaro. GM revised the ECM in 1999 (LS1b) with a newly-designed case and updated circuitry. This means that a ’99 ECU cannot be substituted for an earlier unit unless the wiring harness is modified to work with the later ECU. Also, ECUs for 2000 are similar to the ’99 version but some re-wiring again is necessary to retrofit them into the earlier version.

Even though ’99 and later PCMs can be found under a host of different part numbers, they are all essentially the same and most can be interchanged so long as you know what you’re starting with. Also, between 2000 and 2005, GM used both mechanical and drive-by-wire throttle control. A cable-throttle ECU can be used on a Drive-By-Wire engine only if the complete operating system of the ECU has been re-flashed. Dave advised us that, “it would be unwise for someone to attempt to start any engine with an ECM if its programming was unknown.”

This E38 is a Gen IV controller and only dictates engine operation. It uses a separate controller for the transmission, like all Gen IV controllers. Note the two connectors.

Also, the ’03 and ’04 ECUs had 500K memory, while later models have a 1-meg memory. The 500K PCMs have blue and red connectors, the 1-meg PCMs have red and green connectors. Dave reports, “I’m not aware of any problems using one style PCM with an engine that was originally controlled with the other, except for the obvious need to have the correct connectors. In some cases, some sensors or controllers may need to be changed.” Model year 2005 brought the E40 ECU and ’06 through ‘14 or ‘15 used the E38 or E67, while the E92 unit utilized Direct injection.

The E40 (left) and E67 (right) controllers both have three connectors, but they are not the same as the number of pins is different in the connectors.

The E67 controller has a wider range of capabilities than the E38 and while it is similar, the proper harness and sensors must be used for the specific controller. E38 and E67 ECUs add a layer of complexity because they don’t have traditional VE tables, so you have to work with a virtual VE table. Not a huge hurdle, but something to know when considering a controller. Also keep in mind that the E38, E67, E78 and E92 controllers were also used on engines besides V8s. While they all can be reprogrammed appropriately for a Gen IV (aside from the Gen V E92), you need to know the programming inside the box before trying to start any engine for the first time.

The E92 controller also has three connectors but appears totally different from the others and is designed for Direct-Injection applications.

Build Your Own

EFILive can program all relevant ECMs through the 2017 model year and can auto-detect to tell what ECM is installed, so long as the ECM has power. EFILive’s FlashScan V2 interfaces with the car’s ECU and is both a scanning tool and a tuning tool. Flashscan V2 offers stand-alone data logging from the PCM, ECM and/or TCM, and you can also log up to four external analog inputs and an external serial data input (from dyno, WBO2 etc.).  FlashScan V2 can also read and flash any supported vehicle without the need for a laptop, and because the V2 also supports SD Card storage, the number of tunes you can store is almost endless.

EFILive’s software and FlashScan V2 can tune a vast list of ECUs. A comprehensive list is available on EFILive’s website. The number of parameters that can be adjusted with a FlashScan V2 is incredible. But, just because you can, doesn’t mean you should.

EFILive is not a tune, but rather a means to create a tune specific to your vehicle. The only drawback to using an OEM controller is that it can’t be programmed on the fly. While that may discourage some, others will enjoy the depth of control that comes from using the system as designed by the manufacturer. The tuning capacity of the OEM controllers is staggering and we have to echo Dave’s words when it comes to this level of power, “Keep in mind that the ability to access a variable DOES NOT mean you should alter it.” Restraint is sometimes the most important tool to have.

This OEM level of control was created by GM and EFILive gives access to all the benefits through their FlashScan V2. These are simply the extent of parameters that can be modified with the ignition timing. Many other areas deal with diagnostics, driveability, idle control and any other imaginable part of engine operation.

EFILive is supplied with a number of default dashboards showing gauges configured for either metric or Imperial data. Data logs created by the scan program can be used by the flash program to locate data cells that relate to specific operating conditions. This allows highlighting the cells in a specific table that correspond to the operating conditions selected on a graph of logged data, allowing them to be targeted and adjusted as necessary. Highlighting only those areas that need tweaking greatly streamlines tuning operations.

The dashboard interface is also configurable to relay pertinent information for any task as well as to cater to your individual preferences.

As mentioned, the OEM controllers have a vast amount of inputs pertaining to the operation of the engine and most LS controllers can be properly programmed for boost or nitrous. Beyond that, EFILive offers custom operating systems which specifically address those requirements. Some of these systems also allow engines to be converted from mass air to speed density and some offer a “valet mode,” which functions in conjunction with a switch mounted in the vehicle. If you would like to try out EFILive, you can download a free program and check it out before purchasing a FlashScan V2 and license. It will be time well-spent.

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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