GM Family II Tuning

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

Now we shall detail the best approach to Family II tuning and show the premier modifications. GM Family II have loads of potential and with the right motorsport mods like remapping, turbo upgrades and camshafts you will positively enhance your driving experience.

History, Power & Specs of the Engine


  • 16LF
    72 hp (53 kW ) @5200 rpm (Ethanol) 73 hp (54 kW) @5400 rpm (Petrol)
  • 16SH
    66 kW (90 PS; 89 hp) @5800 rpm
  • 16D
    40 kW (54 PS; 54 hp) @4600 rpm
  • C16NZ2
    55 kW (75 PS; 74 hp) @5200 rpm


  • 17D
    42 kW (57 PS; 56 hp) 105 Nm (77 lbft) @2400 rpm
  • 17DR
    44 kW (60 PS; 59 hp) 105 Nm (77 lbft) @2650 rpm
  • X17DTL
    51 kW (69 PS; 68 hp) 132 Nm (97 lbft) @2400 rpm


  • 18E
    85 kW (115 PS) @5800 rpm 151 Nm (111 lbft) @4800 rpm
  • C18LE
    70KW (95HP)
  • 18N
    62 kW (84 PS) @5400 rpm 143 Nm (105 lbft) @2600 rpm
  • 18S
    66 kW (90 PS) @5400 rpm 143 Nm (105 lbft) @3000–3400 rpm
  • C18NV
    74 kW (100 PS) @5800 rpm
  • C18NZ
    66 kW (90 PS; 89 hp) @5400 rpm 145 Nm (107 lbft) @3000 rpm
  • LH8
    63 kW (84 hp)
  • LA5
    112 kW (150 hp)


  • 20NE
    115 PS (85 kW) @5200 rpm 175 Nm (129 lbft) @2600 rpm
  • 20SE
    122 PS (90 kW) @5400 rpm 175 Nm (129 lbft) @2600 rpm
  • 20SEH
    127–130 PS (93–96 kW) @5600 rpm 180 Nm (130 lbft) @4600 rpm
  • C20NE
    115 PS (85 kW) @5200 rpm 170 Nm (130 lbft) @2600 rpm
  • LT2
    96 hp (72 kW) 160 Nm (118 lbft)
  • LE4
    110 hp (82 kW) @5200 rpm 167 Nm (123 lbft) @3600 rpm
  • LT3
    165 hp (123 kW) @5600 rpm 175 lbft (237 Nm) @4000 rpm
  • C20XE
    115 kW (156 PS) 203 Nm (150 lbft)
  • C20XE
    110 kW (150 PS) at 6000 rpm 196 Nm (145 lbft) at 4600 rpm
  • C20LET
    150 kW (204 PS) at 5600 rpm 280 Nm (207 lbft) at 2400 rpm


X20XEV 136 PS; 134 hp (100 kW) 185 Nm at 4000 rpm
X20XER 160 PS (118 kW) 188 Nm at 4300 rpm
Z20LET 147 kW (200 PS) 197 lbft (267 Nm)
Z20LEL 125 kW (170 PS) 193 lbft (262 Nm)
Z20LER 147 kW (200 PS) 193 lbft (262 Nm)
Z20LEH 177 kW (241 PS) 236 lbft (320 Nm)
U20SED (L34) 119–132 hp (89–98 kW) at 5400 rpm 126 lbft (171 Nm)



  • C22NE 123 hp
  • C22LE 116 hp
  • X22XE
    100 kW (130 hp) @ 5200 rpm, 104 kW (139 hp) @ 5400 rpm
  • Y22xe
    106 kW (142 hp) @ 5400 rpm Torque: 205 Nm (151 lbft) @ 4000 rpm
  • Z22xe


  • C24SE – 2.4 L SOHC
  • X24XF— 2.4 L
  • X24SFD 150 hp @5200 rpm 228 Nm @4000 rpm
  • Z24XE FlexPower (134–138 hp) @5200 rpm 160 lbft @2200 rpm

Tuning the GM Family II and best Family II performance parts.

Best Family II modifications

When talking about the best top for your Family II engine, we are going to concentrate on the modifications that give the best power gain for you money.

Altering your Family II cam will make a dramatic difference to the engine power band. Choosing a higher performance cam profile raises the power band accordingly.

Fast road camshafts normally bump the performance through the rev range, you could drop a little bottom end power but your higher rpm power will be better.

Race camshafts, bump the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Motorsport cam will just annoy you whilst driving in heavy traffic.

You should ideally match your engines power to your cars usage so for a daily driver stick with a mild fast road Family II cam

Some Family II engines respond better to less aggressive camshaft durations so view each engine as unique.

The engine timing and fuelling also will make differences on the torque gains you'll hit.

Extending exhaust or intake durations can alter the torque band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.

Please watch our video which covers the 5 principles of tuning your car. Be sure to keep up with our latest YouTube content and subscribe.

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.

Typical stage 1 mods often include: Panel air filters, Sports exhaust header/manifold, Fast road camshaft, Remaps/piggy back ECU, drilled & smoothed airbox, Intake manifolds.

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

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

Plan your options and then buy your tuning mods and set yourself a power target to avoid wasting your time and money.

ECU mapping should help to establish the full potential of all the modifications you've fitted to your Family II.

(In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

It will usually give you around 30% more power on turbocharged vehicles and you can expect to see around 15% on NA (naturally aspirated) engines, but your mileage usually vary depending on the modifications you've fitted and the condition of your engine.

Shoving more fuel and air into the Family II engine is the main goal to any engine upgrade job.

Intake take the air from the filter and allow it to be fed into the engine cylinders with fuel for the squish phase.

Design and flow characteristics of the Intake manifolds can make a noticeable difference to fuel mixing and power on the Family II.

I usually find plenum chambers are in dire need of an upgrade, although some OEM provide well optimised plenum chambers.

Larger Family II valves, doing some port matching and head flowing will also lift torque, and significantly will afford you a greater torque increase on other parts.

Turbo upgrades

NA (naturally aspirated) engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your Family II

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

When an engine is fitted with a turbo tuning parts are going to net you a larger power gain and we find turbocharged engines already contain many forged and stronger components.

However every engines will have power limits

Research these limitations and upgrade to better quality crank and pistons to cope with the power.

It's not unheard of drivers spending a lots of money on turbocharger upgrades on the Family II only to watch the engine catastrophically fail on it's first outing after it's been enthusiastically driven.

Larger capacity turbochargers commonly experience no power at low rpm, and smaller turbochargers spool up really quickly but don't have the top end bhp gains.

In recent times the selection of turbo units is always improving and we are seeing variable vane turbo units, permitting the vane profile is altered according to speed to lower lag and increase top end power.

Twin scroll turbo units divert the exhaust flow into 2 channels and push these at differently designed vanes in the turbo. They also boost the scavenging effect of the engine.

It is common that there's a limitation in the air flow sensor AFM/MAP on the Family II when considerably more air is being pulled into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited torque at a much lower level.

Adding a supercharger or additional turbo will make large performance gains, although more complex to get working. We have this article covering twinchargers if you want to read more.


You will need to ensure that the engine is not starved of fuel so will need to pay attention to the fuelling when you start going beyond 20% of a torque increase.It is important to be generous with your flow rate on the injectors.

As a rule of thumb add 20% when fitting an injector, this accounts for injector deterioration and affords some spare capacity should the engine require 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.

All the following flywheel power targets will assume an injector duty cycle of 80% and a base of 58psi of fuel pressure at idle.

4 Cylinder turbocharged engines

  • 58 PSI 340cc/min 200hp
  • 58 PSI 511cc/min 300hp

4 Cylinder NA (naturally aspirated) engines

  • 58 PSI 285cc/min 200hp
  • 58 PSI 426cc/min 300hp

4 Cylinder supercharged engines

  • 58 PSI 312cc/min 200hp
  • 58 PSI 468cc/min 300hp


You only need to upgrade your exhaust if your exhaust is actually creating a flow problem.

On most factory exhausts you'll find the exhaust 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.

Do not go with the largest exhaust you can get you'll slow up the exhaust flow rate - the best exhausts for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

Typically exhaust restrictions can be located the catalyst installed, so adding a higher flowing high performance aftermarket one will improve air flow, and rather than doing an illegal decat, will keep the car road legal.

Weak spots, Issues & problem areas on the Family II

The Family II engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

Regular oil changes are vital on the Family II, especially when tuned and will help extend the life and reliability of the engine.

If you would like to know more, or just get some friendly advice on Tuning your Family II engine please join us in our friendly forum where you can discuss tuning options in more detail with our Family II owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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We love hearing about our website visitors projects, especially the mods done and which work best for you on your car. Which helps us keep our guides and tips up to date helping others with their modified car projects. Your feedback and comments are used to keep this page up to date, and help improve the accuracy of these Family II tuning guides which get regular updates and revisions.

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