Tuning the Vauxhall C18NZ

"Comprehensive guide to performance parts and tuning the Vauxhall C18NZ engine!"

We often are seeing threads requesting information on the best C18NZ power upgrades. So let us look into Vauxhall C18NZ parts and outline the best upgrades on this great engine and point out some potential pitfalls along the way.

Now we will outline options for your C18NZ tuning and point out the ultimate modifications. Vauxhall C18NZ have loads of potential and with the optimum modified parts like remaps, turbo upgrades and camshafts you will really enhance your driving pleasure.

When talking about the greatest parts for your C18NZ engine, we are going to focus on the ones that give the biggest return for your cash.

Altering your C18NZ camshaft will make a dramatic difference to the engine power band. Choosing a higher performance camshaft profile raises the power band accordingly.

NB: Fast road camshafts usually push up the bhp and torque throughout the rpm range, you may lose a little low down torque but high end rpm power will be better.

Motorsport camshafts, push up the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

In a car driven daily you need to match your engines power to your cars usage.

I would be surprised if you have found a C18NZ Motorsport camshaft is a pleasure to live with when in heavy traffic.

Different C18NZ engines respond better to more aggressive camshaft durations so set your engine up on a rolling road.

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

Longer valve durations can alter the bhp 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.

C18NZ Tuning Stages

Stage 1 C18NZ modifications: Sports exhaust manifold, Fast road camshaft, Panel air filters, Remaps/piggy back ECU, Intake headers, Drilled & smoothed airbox.

Stage 2 C18NZ modifications: induction kit, Fast road cam, Ported and polished head, Sports catalyst & performance exhaust, fuel pump upgrades, high flow fuel injectors.

Stage 3 C18NZ modifications: Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Competition cam, Twin charging conversions, Internal engine upgrades (head flowing porting/bigger valves), Crank and Piston upgrades to alter compression.

ECU mapping should help to release the full potential of all the upgrades you've done to your C18NZ.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but your mileage may rely on the upgrades you've carried out and the condition of your engine.

It is vital to any engine modification job to pull fuel and air into your C18NZ

Intake manifold take the air during the suck phase from the intake filter and allow it to be drawn into the engine cylinders.

The size of bore and shape and flow characteristics of the Intake can make a big improvement to fuel engine efficiency on the C18NZ.

Commonly we find the intake headers are begging for an upgrade, although some car makers provide reasonably good intake headers.

Fitting big valve kits, doing a bit of 3 or 5 angle valve jobs and porting and head flowing will also improve power, and significantly will allow you to get increasing the power increase on other parts.

Turbo upgrades for the C18NZ

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 C18NZ

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

When your car has a turbo already fitted parts are simpler to install and most turbocharged engines will have uprated components.

However most engines will need better parts at higher power limits

It is important to find these limits and fit better quality components to handle the power.

It's not unheard of tuners spending a loads of money on turbocharger upgrades on the C18NZ only to experience the engine explode on it's first outing after it's been completed.

Big upgraded turbo chargers tend to experience no power at low rpm, and low capacity turbo chargers spool up more quickly but won't have the high rpm engines power gains.

In recent times the world of turbos is always moving on and we are seeing variable vane turbos, allowing the vane angle is altered according to speed to lower lag and increase top end bhp.

Twin scroll turbos divert the exhaust gases into two channels and flow these at differently profiled vanes in the turbo. They also improve the scavenging effect of the engine.

It is common that there's a limit in the air flow sensor (AFM/MAF/MAP) on the C18NZ when considerably more air is being sucked into the engine.

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

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

Uprating C18NZ fuel injectors

When you improve the bhp you will need to look at to the fuelling.

More bhp needs more fuel. We strongly recommend you to be generous with your flow rate on the injectors.

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

Best C18NZ performance exhausts

You only need to to upgrade your exhaust if the existing exhaust is actually causing a restriction.

On most factory exhausts you should find that your flow rate is still good 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 will certainly help air flow from the engine but do not go too large or you could will reduce the flow rate. Stick to 1.5 to 2.5 inches for best results.

Common exhaust restrictions typically happen through the catalyst and or DPF filters which manufacturers fit, especially as they start to get worn and carbon builds up, so adding a higher flowing performance alternative will help avoid this restriction.

Problems and issues to look out for on the C18NZ

The C18NZ engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the C18NZ, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your C18NZ engine please join us in our friendly forum where you can discuss tuning options in more detail with our C18NZ 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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This article is flagged for an update, so please pass on specific tips below that I can include. All articles, and content was written by me, Waynne Smith TorqueCars founder. Some outlines are just too general so I appreciate your feedback and suggestions. This entry was filed under Vauxhall. You can leave a response below or join our forum to discuss this article and car modification in detail with our members.

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