The Lowdown on "N18XFH Modifications"

How to modify and upgrade the Vauxhall N18XFH

"Comprehensive guide to tuning the Vauxhall N18XFH engine!"

Our friends at TorqueCars are frequently getting messages about how to improve the N18XFH from people inquiring about getting more power from the N18XFH and wanting to know what are the things tuners are recommending when it comes to N18XFH mods that work. So let us look into Vauxhall N18XFH upgrades and outline the best modifications on this great engine and point out some common pitfalls along the way.

Car Tuning Tips will review N18XFH tuning and summarise the best mods that work. Vauxhall N18XFH are fantastic to work on and with a few sensible uprated upgrades like remapping, turbo upgrades and camshafts you will noticeably improve your driving enjoyment.

When talking about the ultimate parts for your N18XFH engine, we are going to focus on the parts that give the best value for money.

Improving air intake on the N18XFH

You need air matched to fuel for an engine to work. If there is insufficient fuel then it will run lean, if there is too little air it runs rich losing power which risks damage to the N18XFH. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the whole point to any engine modification task to pull air and fuel into your N18XFH but this has a knock on effect with the air flow sensor.

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

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

Air Intake manifolds take the on the suck phase from the intake filter and allow it to be sucked into the engine cylinders.

Design and flow characteristics of the Intake headers can make a large change to fuel atomisation and engine efficiency on the N18XFH.

Most intake are begging for motorsport parts, although some manufacturers provide reasonably well designed intake.

Fitting big valve kits, carrying out port matching and head flowing will also improve power, the fantastic side effect is it will give you raising the power increase on other upgrades.

N18XFH performance cam tips.

Some N18XFH engines respond better to mild camshaft durations check your engine on a rolling road.

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

A longer valve duration 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.

Significant air intake, and exhaust improvements on the N18XFH can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the engines power and power output.

NB: Fast road cams normally boost the power throughout the rpm range, you could sacrifice a little low end bhp but your higher rpm power will improve.

Motorsport cams, boost 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 won't do well if in heavy traffic.

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

Stage 1, 2 and 3 mods for the N18XFH

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

1. Suspension Upgrades - always improve your cars handling
2. Brake Upgrades - Even before adding power improve those brakes
3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
6. Fuelling - when you've increased power you'll need to match this with more fuel
7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 N18XFH parts:

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

Stage 2 N18XFH parts:

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

Stage 3 N18XFH parts:

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

A remap will help unlock the full potential of all the parts you've done to your N18XFH.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the outcome usually depend much on the parts you've carried out and the condition of your engine.

Turbo modifications on the N18XFH

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the 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 major power gains.

If an engine has a turbo already fitted upgrades are going to make more power and turbo engines are made using better components.

There are common areas of failure for every engine, with some being extremely strong and some only just able to handle stock power

It is important to find these restrictions and install better quality crank and pistons to handle the power.

It's not unheard of car owners spending a loads on turbo charger upgrades on the N18XFH only to see the engine block go up in smoke on it's first outing after it's used in anger.

Bigger turbo units often suffer a bottom end lag, and low capacity turbo units spool up more quickly but do not have the top end bhp gains.

We are pleased that the selection of turbo units is always increasing and we are seeing variable vane turbo units, allowing the vane angle is altered according to speed to lower lag and increase top end torque.

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

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large power gains, although more challenging to setup. We have this article on twincharging if you want to read more.

Tips about fuel supply on the N18XFH

You will need to ensure that the engine is not starved of fuel so should increase the fuelling when you start extending past 20% of a power hike. Most tuners we speak with say to over specify your injectors flow rate.

The rule of thumb is to add another 15% when fitting an injector, this allows for injector deterioration and allows a little spare capacity should the engine need more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended N18XFH performance exhaust upgrades

The only time you should look to boost your exhaust system with an upgraded one is if your exhaust is actually causing a restriction in flow.

On most factory exhausts you'll find your flow rate is fine even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Sports exhausts generally help improve air flow out of the engine but do not go too big or you could will reduce the flow rate. Stick to one and a half to two and half inches for best results.

Usual exhaust restrictions are in the emissions filters installed, so adding a higher flowing race alternative will help avoid this restriction.

Cat bypassing (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the N18XFH

Like most engines an N18XFH, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the N18XFH, failure to do this will exacerbate engine wear, on a tuned N18XFH this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your N18XFH why not pop over to the forums at TorqueCars where you can chat about N18XFH tuning options and read about others projects who may be planning to do similar modifications on their N18XFH.

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This entry was posted under Makes and Models. Tags: engine, vauxhall
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