GM L3T Tuning

"All you need to know about tuning the GM L3T engine!"

We were emailed us for more information on tuning and building a modified L3T and particularly which turbo upgrades work best, so we've created this how to guide which covers our go to modifications for this engine and what we feel are the optimum value modifications you can do.

You might look straight past this 1.3 liter, 3 cylinder engine but things get interesting when you look at the specs, it has some clever cam and valve timing and is a turbocharged engine and it outputs 155hp but feels more like a 170hp engine due to its light weight, which greatly aids cornering and handling.

The GM L3T are popular tuning projects and with the right performance upgrades like a remap, turbo improvements, and camshafts you will noticeably maximize your driving pleasure.

Our aim here is to provide a guide to L3T tuning and outline the best upgrades.

History of the L3T Engine

1.3 liter, 3 cylinders & turbocharged engine, which one a number of awards, and it provides power and response and fuel economy. The bonus is that a light engine like this means the car feels like it has much more power, we would say around 170hp.

The engine has alternative designations such as...

  • Ecotec
  • L3T
  • L3Z
  • LIH
  • GM E-Turbo engine
  • L4H
  •  155hp@ 5,600 rpm& 174lbft torque @ 1,500 rpm

It was installed in the following cars and mated to a 9 speed auto transmission offering FWD and AWD output.

  • BuickEncore GX
  • Chevrolet Trailblazer
  • Chevrolet Malibu
  • Buick Verano
  • Opel Astra
  • Vauxhall Astra
  • Chevrolet Tracker
  • Buick Lacrosse

Tuning the GM L3T and best L3T performance parts.

Best L3T upgrades

The greatest L3T upgrades on an engine are in our opinion the ones that give the biggest return for your cash.

We won't be swayed by popular L3T upgrades, they need to be cost-effective. Lighter flywheels do not work very well on this engine, GM has pretty much got the flywheel weight perfectly balanced to smooth out the 3 cylinder engine.

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Best Engine Mods for your car

  1. Engine Tunes - engine tuning/remapping provides the most advantage in terms of cost savings,  aftermarket ECUs, and piggyback ECUs are all alternatives.
  2. Fast road cams are one of the most significant mechanical changes, but they must be installed by someone who knows what they're doing and they are not always easy to source but you might find a local firm to regrind a stock camshaft.
  3. Intake and Exhaust - Note that on their own these mods will NOT ADD POWER in most cases, but they can help enhance power after other mods by removing the restriction.
  4. Upgrades to turbochargers and superchargers - forced induction is the most efficient approach to increase air supply, allowing you to burn more fuel and make more power. It is one of the most costly upgrades but provides the best gains.
  5. Head work - The goals of porting and flowing the head are to get air flowing into the engine while removing flow restrictions and turbulence.
  6. Typical stage 1 mods often include: Remaps/piggy back ECU, Fast road camshaft, Panel air filters, Drilled & smoothed airbox, Sports exhaust header/manifold, Intake manifolds.

    Typical stage 2 mods often include: fuel pump upgrades, Fast road cam, Sports catalyst & performance exhaust, induction kit, high flow fuel injectors, Ported and polished head.

    Typical stage 3 mods often include: Engine balancing & blueprinting, Internal engine upgrades (head flowing porting/bigger valves), Competition cam, Adding or Upgrading forced induction (turbo/supercharger), Twin charging conversions, Crank and Piston upgrades to alter compression.

    Carefully think through your options and then buy your mods and set yourself a power target to avoid wasting your time and money.

    L3T Camshaft Upgrades

    Sporty camshaft profiles raise the higher RPM power and we generally recommend this as a primary mod on petrol engines, and secondary on Diesel to a remap.

    We've always seen top end power benefits through performance camshafts on most engines but there is not much scope for power hikes on this 3 cylinder engine from a fast road cam.

    GM have extracted the optimum amount of power leaving a very little headroom for further gains.

    On a road car, one must carefully try to match your torque band to your usage of the car.

    L3T Airflow improvements

    Different L3T engines respond differently due to the head and flow characteristics when camshafts are fitted depending on the camshaft being less aggressive camshaft durations and cam profile as unique due to manufacturing tolerances and quality variations|so set your engine up on a rolling road|check your engine on a rolling road.

    The map and fuelling also have a large bearing on the torque gains you'll hit.

    Longer valve durations can amend the torque curve, and on most engines there are some advantages to extending the intake or exhaust durations and valve lift.

    ECU Mapping Improvements for the L3T

    ECU flashing allows a tuner to establish the full potential of all the parts you've installed on your L3T.

    (Sometimes flashing the ECU is not an option, so an aftermarket ECU is a route to take, and many of these will outperform factory ECU's but ensure it has knock protection and that you get it set up properly.) It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NA (naturally aspirated) engines, but your mileage usually differs on the parts you've carried out and the condition of your engine.

    Air Flow improvements on the L3T

    Pushing fuel and air into each cylinder is the whole point to any engine performance tuning job.

    Intake manifolds take the air from the air cleaner and allow it to be sucked into the engine cylinders with fuel for the squish phase.

    The design and flow rate of the Air Intake manifolds can make a substantial improvement to fuel delivery on the L3T.

    I usually find intake manifolds are in dire need of motorsport parts, although a few OEM provide fairly well-optimized intake manifolds.

    Adding a L3T big valve conversion, doing some 3 or 5 angle valve jobs, and porting and head-flowing will also improve power, & importantly will permit a better power increase on other mods.

    L3T Turbo upgrades

    The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes major power gains.

    When your motor has a turbocharger mods are giving better power gains and turbo engines use uprated components.

    However engines have weakspots. Research these restrictions and install better quality crank and pistons to handle the power.

    It's not unheard of mechanics spending a lot of money on turbo upgrades on the L3T only to have the motor literally blow up when it's used in anger.

    Large turbochargers tend to experience no power at low rpm, and small turbochargers spool up much more quickly but don't have the peak rpm torque gains. As this is a small 3 cylinder it works best with small turbochargers, and to introduce lag on this engine would be just WRONG.

    Thanks to progress the market of turbos is always moving on and we are seeing variable vane turbos, permitting the vane angle is altered according to speed to lower lag and increase top end torque.

    It is common that there is a restriction in the air flow sensor (AFM/MAF/MAP) on the L3T when a lot more air is being pulled into the engine.

    We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting performance at a much lower level.

    Adding a supercharger or additional turbo will make large performance gains, although more difficult to get working. We have this in depth look at twinchargers if you want to read more.

    L3T Fuelling Upgrades

    You will need to ensure that the engine is not starved of fuel so need to ramp up the fuelling when you start going beyond 20% of a power increase. Boosting the fuel pressure provides a more snappy acceleration responsiveness.

    Don't forget to over specify your flow rate on the injectors.

    As a rule of thumb add 20% capacity when fitting an injector, helps cope with injector deterioration, and allows a little spare capacity should the engine need more fuel.

    We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

    L3T Performance Exhausts

    You may need to boost your exhaust if the current exhaust is actually causing a restriction in flow.

    On most factory exhausts you'll see the flow rate is ok even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

    Sports exhausts balance the flow of gases through the engine.

    But if your exhaust pipe is too large, ie: over 2.5 inches bore, you will lose a great deal of the flow rate and end up sapping power and torque.

    Usual exhaust restrictions can be located in the catalysts installed, so adding a higher flowing race aftermarket catalyst unlocks that lost power, and without resorting to doing an illegal catless mod, will keep the car road legal. We should explain that performance catalysts and filters perform comparably to cat removal and have the added benefit of keeping your car street legal, as decat or catalyst removal is not a street legal modification.

    Weak spots, Issues & problem areas on the L3T

    The L3T engines are pretty solid and give little trouble as long as they are regularly serviced.

    Service time oil changes are vital on the L3T, especially when tuned and will help maintain the long life of the engine.

    To find out more about mods and upgrades, or just get some friendly advice on Tuning your L3T engine please join us in our friendly forum where you can discuss L3T tuning options in more detail with our L3T owners. It would also be worth reading our unbiased GM tuning articles to get insights into each modification and how effective they will be.

    Please help us improve these tips by sending us your feedback in the comments box below.

    We love hearing what our members have got up to and which mods work best for them on each model of car. We use your comments and feedback to improve the accuracy of these L3T tuning guides which get regular updates and revisions.

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    One Response to “L3T Tuning”

    1. Dan Dudek says:

      Well, performance aside, I was thinking of putting this engine into my classic (well, not too classic) type 1 Beetle, 1965. I will be having an actual frame built for this one, versus just the original Pan.
      These Beetles came with only a 60-hp air-cooled engine. Can the 1.3 (or 1.2) be reconfigured to suit a longitudinal drivetrain? I see that you mention using a new CPU as a possibility for setting this up… is this readily available? Are turn-key crate engines available? Is this something you might want to configure?

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