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Do I need a tune for my LS swap?

Almost always, if it's fuel-injected. Here's what needs a tune and why.

What does my tune need? →

Your swap or mod	Tune?	Why
EFI swap with the factory computer	Yes, always	Every donor PCM needs reprogramming: delete VATS (or the engine will not start), match injector size and MAF scaling, and match transmission settings; emissions monitors and speed limiters from the donor are also present.
Aftermarket cam	Yes	Idle, fuel, spark and torque-model changes; on AFM engines, the deactivation must be turned off too.
Bigger injectors	Yes	The injector size in the tune has to match the injectors installed.
Headers	Recommended	On EFI engines, tuning adjustments help get the full benefit from headers.
Heads, intake, stroker or power adder	Yes	Speedway: a custom tune is crucial after modifications, and upgrading the ECM or going standalone is paramount past factory airflow, displacement or with a power adder.
Turbo or supercharger	Yes, carefully	Air/fuel ratio, timing and boost have to be balanced across the rpm range; Speedway recommends an experienced calibrator or dyno tuner.
Electronic transmission swap	Yes	The computer controls shift timing and line pressure, so its transmission settings must match.
Standalone EFI (e.g. Terminator X)	Yes	Self-learning helps, but Speedway says even self-learning systems should be tuned properly.
Carbureted LS	No engine tune	Carb tuning plus an LS ignition controller with preloaded timing curves (a laptop fine-tunes it).

PCM must be recalibrated to stop commanding deactivation; aftermarket cams also need idle, fuel, spark and torque-model changes.

What the sources say

Paraphrased from the linked sources (30 points). Specifics depend on your computer and operating system.

Show all

• GM LS, LSA: Aeroflow states tuning is required for its fly-by-wire throttle body because it uses a different heavy-duty motor with different parameters than the standard unit. Aeroflow Performance
• GM LS, LSA: The replacement throttle plate is 102 mm compared to a standard GM LS 87 mm unit, so intake manifolds may need clearancing for full throttle opening. Aeroflow Performance
• GM LS, LSA: On the GM E38 computer, installing the 102 mm drive-by-wire throttle body requires adjusting the ETC area scaler plus throttle-position and airflow-correlation diagnostics. Aeroflow Performance
• GM LS, LSA: Aeroflow recommends dyno tuning with the throttle body to ensure no engine damage occurs. Aeroflow Performance
• GM; most GM vehicles up to 2018 model year: Changing tire size or differential gear ratio can make the speedometer, odometer, and transmission shift points inaccurate, so the vehicle needs gear/tire recalibration. HP Tuners
• GM; most GM vehicles up to 2018 model year: On GM vehicles, gear and tire changes are corrected with the Gear/Tire Wizard in VCM Editor, which recalibrates the speedometer and scales the transmission tables. HP Tuners
• GM; most GM vehicles up to 2018 model year: The Gear/Tire Wizard's Auto Scale option automatically adjusts transmission tables to preserve similar shift RPM after a gear or tire change. HP Tuners
• GM; most GM vehicles up to 2018 model year: Skipping recalibration after a gear or tire change can cause poor shift quality, incorrect mileage tracking, and trouble codes. HP Tuners
• GM; most GM vehicles up to 2018 model year: The Gear/Tire Wizard function is supported on most GM vehicles up to the 2018 model year. HP Tuners
• In a VE-based fuel model, incorrect injector characterization data degrades the accuracy of the entire tune, especially the VE table and the ECU's ability to hit lambda targets. High Performance Academy
• Injector setup is one of the first steps in the tuning process; without good injector data the whole fuel model is flawed. High Performance Academy
• The fuel-pressure reference type (atmospheric vs manifold-referenced) must be set correctly because injector flow and dead time vary with differential fuel pressure. High Performance Academy
• The fuel's stoichiometric AFR and specific gravity are key inputs to a VE-based fuel model and must be entered correctly. High Performance Academy
• Gen IV LS, Gen V LT: After a DOD/AFM/DFM delete, the PCM or ECM must be recalibrated so it no longer commands cylinder deactivation. LSX Magazine
• Gen IV LS, Gen V LT: With a stock-spec non-DOD cam, the main calibration change for a delete is generally disabling the deactivation function and its related diagnostic logic. LSX Magazine
• Gen IV LS, Gen V LT: An aftermarket cam in a delete build requires adjusting idle airflow, fueling, spark, torque modeling, and other drivability tables, beyond simply switching deactivation off. LSX Magazine
• Gen IV LS, Gen V LT: A software-only disable is not a mechanical delete: it leaves the original deactivation lifters and oil-control hardware inside the engine. LSX Magazine
• Gen IV LS, Gen V LT: Installing conventional lifters while keeping the original deactivation cam can create uneven compression, misfire codes, and poor engine operation. LSX Magazine
• GM P01 0411; Gen III LS: Combined changes in displacement, injectors, ethanol fuel, boost, and MAF removal required comprehensive changes to the 0411 (P01) computer rather than a minor tweak. LSX Magazine
• GM P01 0411; Gen III LS: On early controllers, scaling the MAF signal for boost loses important resolution, which is a reason to convert to speed density instead. LSX Magazine
• GM P01 0411; Gen III LS: A 3-bar speed-density custom operating system allows running up to 30 pounds of boost in this application. LSX Magazine
• GM P01 0411; Gen III LS: The MAP sensor must match the selected custom operating system; a mismatched sensor severely corrupts global fueling. LSX Magazine
• GM P01 0411; Gen III LS: The VE table tells the computer how much air enters the engine by RPM and MAP, so a speed-density conversion requires recalibrating that table from scratch. LSX Magazine
• GM P01 0411; Gen III LS: A large cam typically lowers volumetric efficiency at low RPM and raises it at higher RPM, so the stock idle-region VE values become wrong after a cam swap. LSX Magazine
• GM P01 0411; Gen III LS: Swapping to 1,000cc injectors required entering the supplied flow rate, offset, and short pulse adder data into the tune. LSX Magazine
• GM P01 0411; Gen III LS: Converting to speed density required forcing the MAF to fail (0 Hz fail frequency) and reconfiguring the P0101, P0102, and P0103 diagnostics so no check-engine light is set. LSX Magazine
• GM P01 0411; Gen III LS: Turbocharged engines can make boost at partial throttle and low RPM before ordinary RPM-based power enrichment activates, which is dangerous if boost enrichment is not calibrated. LSX Magazine
• GM P01 0411; Gen III LS: Timing should be pulled in any table region that may see boost for safety, then walked back in on the dyno. LSX Magazine
• GM P01 0411; Gen III LS: A displacement change requires correcting the cylinder volume in the tune; the example used 370 cubic inches divided by 8, giving 46.25 cubic inches per cylinder. LSX Magazine
• GM P01 0411; Gen III LS: A custom OS's initial maximum VE values guard against lean damage but prevent the engine from starting until baseline VE values are transferred in. LSX Magazine

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