Vauxhall Z18XE Tuning

"All you need to know about tuning the Vauxhall Z18XE engine!"

We review and look at Z18XE tuning and summarise the best modifications.

Vauxhall Z18XE are fantastic to work on and with a few sensible performance parts like a remap, turbo upgrades and camshafts you will really maximize your driving opportunities.

History of the Engine

Z18XE  1.8 L (1796 cc) 120-123 hp 167 N⋅m (123 lb⋅ft)

16 valves, 4 cylinders DOHC configuration and met Euro 3 emissions standards. There is one coil per cylinder.

It uses a Simtec MS71 EMS supporting a drive by wire throttle and twin Lambda probes.


  • Chevrolet Niva


  • Saab 9-3
  • Opel/Vauxhall Astra, Corsa C, Meriva, Tigra, Vectra and Zafira

2005-2008 we saw a Z18XER
This had a cam and redesign, creating a lighter more powerful engine.

  • Opel Vectra, Merica Signum Zafira (Z18XER)
  • Fiat Croma (Z18XER)

Best Z18XE upgrades

The greatest upgrades on an engine are in our opinion the ones that give the best power gain for you spend.

We won't be swayed by popular Z18XE upgrades, they need to be cost effective.

Altering your Z18XE cam will make a dramatic difference to the engine power band. Choosing a higher performance cam profile raises the power band accordingly.

Fast road cams normally increase the performance over the rpm band, you might lose a little low down bhp but your high end rpm power will be higher.

Race cams, increase the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

For a road car should ideally to match your bhp range to your usage of the car.

I'd be surprised if you have found a Race camshaft is a pleasure to live with when driving in heavy traffic.

Some Z18XE engines respond better to less aggressive camshaft durations than others.

The engine timing and injectors and fuel pump also will make differences on the power gains you'll make.

A longer valve duration can alter the power 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.

Stage 1 mods: Drilled & smoothed airbox, Panel air filters, Sports exhaust manifold, Remaps/piggy back ECU, Intake headers, Fast road camshaft.

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

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

The Z18XE engines respond well to mods and we're happy to report there are increasing numbers of parts and performance parts out there.

The following mods took one of our members Z18XE engine to 162hp 140lbft

  • Dbilas inlet manifold
  • Vectra C intake pipe heat wraped with oversized intake pipe to throttle body
  • Enclosed carbon fibre induction kit with cold air feed
  • Kent fast road cams
  • Full 2 1/2 inch bore cat back exhaust
  • Voltage stabilizer
  • Remap

ECU flashing should help to to establish the full potential of all the mods you've done to your Z18XE.

It will usually give around 30% more power on turbocharged vehicles and 15% on NASP engines, but you mileage will vary depending on the mods you've done and the condition of your engine.

It is the main goal to any car tuning project to shove more air and fuel into the Z18XE engine

Intake flow the air during the suck phase from the air cleaner and allow it to be pulled into the engine and mixed with fuel.

The size of bore and shape and rate of flow of the Intake can make a big difference to to fuel delivery on the Z18XE.

On popular production engines headers are improved through performance upgrades, although a few manufacturers provide reasonably good headers.

Increasing the Z18XE valve size, doing some port matching and head flowing will also boost bhp and torque, and significantly will raise potential for an improved bhp and torque increase on other parts.

Turbo upgrades

NASP 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 Z18XE

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

If an engine is turbo charged modifications are going to make more power and turbo engines are built with better components.

However you'll find engines will need better parts at higher power limits

Discover these limits and install higher quality components to cope with the power.

We've seen drivers spending a loads on turbo charger upgrades on the Z18XE only to have the whole thing literally blow up just after it's been finished.

Big upgraded turbo units will usually experience a bottom end lag, and small turbo units spool up more quickly but don't have the high rpm bhp gains.

In the last 10 years the selection of turbos is always improving and we commonly find variable vane turbos, permitting the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbos divert the exhaust flow into two channels and push these at differently angled vanes in the turbo charger. They also increase the scavenging effect of the engine.

It is not unusual that there's a restriction in the air flow sensor AFM/MAP on these engines when considerably more air is being sucked into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp at a much lower level.

Adding a supercharger or additional turbo will make large power gains, although more difficult to configure. We have a twincharger power adding guide if you want to read more.


Don't miss you'll need to ramp up the fuel delivery when you are increasing the power - it makes the car more thirsty.

It is important to over specify your flow rate on the injectors.

The rule of thumb is to add 20% capacity when fitting an injector, this takes into account injector deterioration and provides 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.

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

4 Cylinder turbocharged engines

  • 58 PSI 340cc/min 200hp
  • 58 PSI 511cc/min 300hp
  • 58 PSI 682cc/min 400hp
  • 58 PSI 1022cc/min 600hp

4 Cylinder NASP engines

  • 58 PSI 285cc/min 200hp
  • 58 PSI 426cc/min 300hp
  • 58 PSI 568cc/min 400hp
  • 58 PSI 853cc/min 600hp

4 Cylinder supercharged engines

  • 58 PSI 312cc/min 200hp
  • 58 PSI 468cc/min 300hp
  • 58 PSI 625cc/min 400hp
  • 58 PSI 937cc/min 600hp


Only look to uprate your exhaust if the existing exhaust is creating a restriction in flow.

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

Don't go with the largest exhaust you can buy this will 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.

Common exhaust restrictions come around the catalyst and filters installed, so adding a freer flowing sports alternative will help avoid this restriction.

Weak spots Issues & problem areas on the

The engines are generally reliable and solid as long as they are regularly serviced and maintained.

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

For more information on Tuning your engine please join us in our friendly forum where you can discuss tuning options in more detail with our owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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

We love to hear what our visitors have got up to and which tuning parts work best for them on each model of car. Comments are used to improve the accuracy of these articles which are continually updated.

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