Tuning the Vauxhall N18XFH

"Comprehensive guide to performance tuning the Vauxhall N18XFH engine!"

We are frequently seeing threads asking about the things we are recommending when it comes to N18XFH power upgrades. So let us look into Vauxhall N18XFH parts and outline the best mods that work on this great engine and point out some common pitfalls along the way.

The Vauxhall N18XFH are popular tuning projects and with a few sensible upgrades like a remap, turbo improvements and camshafts you will dramatically increase your driving pleasure.

TorqueCars will consider N18XFH tuning and report on the ultimate upgrades.

Just because particular parts are are common on N18XFH it doesn't mean its worth having, instead we will recommend only what we regard as the greatest parts that will give your N18XFH the biggest power gain return for your cash.

The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake and exhaust durations will alter depending on the chosen camshaft profile, so large engines power gains are on offer for camshaft upgrades.

NB: Fast road camshafts commonly increase the performance throughout the rev range, you might lose a little low end bhp but the top end will be lifted.

Competition camshafts, increase the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Motorsport camshaft won't do well if on the daily commute.

You should ideally optimize your torque band to your cars usage so for a daily driver stick with a fast road N18XFH camshaft

Some N18XFH engines respond better to less aggressive cam durations so set your engine up on a rolling road.

The ECU mapping and injectors and fuel pump also have an effect on the bhp gains you'll achieve.

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.

N18XFH Tuning Stages

Stage 1 N18XFH modifications: Drilled & smoothed airbox, Intake headers, Sports exhaust manifold, Fast road camshaft, Remaps/piggy back ECU, Panel air filters.

Stage 2 N18XFH modifications: Sports catalyst & performance exhaust, high flow fuel injectors, induction kit, fuel pump upgrades, Ported and polished head, Fast road cam.

Stage 3 N18XFH modifications: Twin charging conversions, Engine balancing & blueprinting, Internal engine upgrades (head flowing porting/bigger valves), Adding or Upgrading forced induction (turbo/supercharger), Crank and Piston upgrades to alter compression, Competition cam.

ECU mapping helps fully realize the full potential of all the tuning parts you've done to your N18XFH.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but your results usually differs on the tuning parts you've applied and the condition of your engine.

It is vital to any engine tuning job to shove more air and fuel into your N18XFH

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

Shape and flow rate of the Intake headers can make a substantial effect on to fuel mixing and power on the N18XFH.

Commonly we find the plenum chambers are needing an upgrade, although a few car makers provide reasonably well designed plenum chambers.

Adding a N18XFH larger valve kit, getting port work and head flowing will also boost torque, & importantly will permit an improved torque increase on other mods.

Turbo upgrades for the N18XFH

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 N18XFH

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

When your car is turbocharged, tuning parts are more reliable and you will discover turbo engines are built with harder and stronger components.

However engines have weakspots

Discover these limits and fit stronger pistons, crank and engine components to handle the power.

We've seen guys spending a a stack of money on turbo upgrades on the N18XFH only to have the motor explode just after it's been finished.

Larger upgraded turbo units often suffer low end lag, and low capacity turbo units spool up quickly but do not have the peak end power band gains.

Thanks to new tech the market of turbo units is always increasing and we are seeing variable vane turbo units, where the vane angle is altered according to speed to lower lag and increase top end power.

Twin scroll turbo units divert the exhaust gases into 2 channels and direct these at differently designed vanes in the turbo charger. They also help the scavenging effect of the engine.

It is not unusual that there's a limitation in the air flow sensor MAP/MAF/AFM on the N18XFH when considerably more air is being drawn into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting bhp at a much lower level.

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

Uprating N18XFH fuel injectors

When you increase the performance you will need to look at to the fuelling.

More performance needs more fuel. We strongly recommend you to be generous with your injector capacity.

The accepted safe increase is to add 20% to the flow rate when fitting an injector, this accounts for 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.

Best N18XFH performance exhausts

You only need to to improve your exhaust if your exhaust is actually creating a restriction.

On most factory exhausts you'll see your flow rate is 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 equal out the flow of gases through the engine.

But if your exhaust pipe is too big, ie: it's over 2.5 inches bore, you will lose much of the exhaust flow rate and end up sapping power and torque.

Common exhaust restrictions are traced to the emissions filters installed, so adding a faster flowing race alternative will help avoid this restriction.

Problems and issues to look out for on the N18XFH

The N18XFH engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the N18XFH, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your N18XFH engine please join us in our friendly forum where you can discuss tuning options in more detail with our N18XFH owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We really like hearing from our readers, and hearing about which upgrades were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our N18XFH guides and tips are kept up to date.

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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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