Tuning guide "Z18XE Modifications"

How to modify and upgrade the Vauxhall Z18XE

"Comprehensive guide to tuning the Vauxhall Z18XE engine!"

TorqueCars often are getting posts asking about how to improve the Z18XE from people wanting to know what are the things tuners are recommending when it comes to Z18XE modifications. So let us look into Vauxhall Z18XE modifications and outline the best mods that work on this great engine and point out some frequent tuning mistakes along the way.

The Vauxhall Z18XE provide a fun base for your project and with the best upgrades like ECU maps, turbo improvements and camshafts you will certainly maximize your driving fun.

Our aim here is to provide a guide to Z18XE tuning and report on the optimum modifications for your car.

Just because particular tuning parts are are common on Z18XE it doesn't mean it is good, instead we will concentrate on the ultimate tuning parts that will give your Z18XE the best value for money to power increase.

Without us subscribing to the misaprehension of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

Improving air intake on the Z18XE

You need air and fuel for an engine to work. If there is a lack of fuel then it will run lean, if there is little flow of air it runs rich sapping power and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Forcing air into your Z18XE is the main goal to any engine modification job.

It is common that there's a restriction in the air flow sensor (AFM/MAF/MAP) on the Z18XE when a lot more air is being drawn into the engine.

We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting power at a much lower level.

Headers take the air during the suck phase from the air cleaner and allow it to be drawn into the engine cylinders.

Structure and flow characteristics of the Intake headers can make a noticeable improvement to fuel engine efficiency on the Z18XE.

We often see intake headers are improved through an upgrade, although some car makers provide well optimised intake headers.

Fitting big valve kits, getting port work and head flowing will also lift power, & importantly will allow you to get a greater power increase on other mods.

Z18XE performance cam tips.

Different Z18XE engines respond better to less aggressive camshaft durations check your engine on a rolling road.

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

Altering valve 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.

Significant air intake, and exhaust improvements on the Z18XE can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the power band and power output.

NB: Fast road camshafts normally raise the bhp through the rev band, you may lose a little low end bhp but high end rpm power will be better.

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

On a road car you should ideally to optimize your torque band to your preferences.

I'd be gobsmaked if you have found a Z18XE Race camshaft is a pleasure to live with when on the daily commute.

Stage 1, 2 and 3 mods for the Z18XE

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 Z18XE parts:

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

Stage 2 Z18XE parts:

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

Stage 3 Z18XE parts:

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

ECU flashing will help release the full potential of all the tuning mods you've done to your Z18XE.

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 end result usually vary depending on the tuning mods you've applied and the condition of your engine.

Turbo modifications on the Z18XE

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 Z18XE.

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 the engine has a turbo already fitted tuning mods are relatively easy and turbo charged engines already contain harder and stronger components.

However most engines will need better parts at higher power limits

It is important to find these limits and install higher quality crank and pistons to handle the power.

We've seen mechanics spending a a stack of money on turbo charger upgrades on the Z18XE only to see the whole thing go up in smoke just after it's been enthusiastically driven.

Big capacity turbos often suffer no power at low rpm, and small turbos spool up more quickly but don't have the peak end engines power gains.

In recent times the selection of turbochargers is always increasing and we commonly find variable vane turbochargers, permitting the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbochargers divert the exhaust flow into 2 channels and push these at differently designed 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 performance gains, although more complex to install. We have this article covering twinchargers if you want to read more.

Tips about fuel supply on the Z18XE

Don't overlook the need to boost the fuelling when you are increasing the power - it makes the car more thirsty. It makes sense to over specify your injector capacity.

The accepted safe increase is to add 15% to the flow rate when fitting an injector, this accounts for injector deterioration and affords you some spare capacity should the engine require 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 Z18XE performance exhaust upgrades

Only look to upgrade your exhaust system with an upgraded one is if the current exhaust is actually creating a restriction.

On most factory exhausts you should find that the exhaust flow rate is still ok 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.

Note that with the largest exhaust you can find you'll slow up the exhaust flow rate - the best exhausts for power gains are usually between one and a half to two and half inches. Your exhaust design, the bend angles and construction are what have more effect on flow rates than your pipe width to a certain extent. So the exhaust design is a big factor.

Typically exhaust restrictions can be traced to the catalysts installed, so adding a freer flowing race alternative will help avoid this restriction.

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

Faults issues and things to look out for on the Z18XE

Like most engines an Z18XE, 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 Z18XE, failure to do this will exacerbate engine wear, on a tuned Z18XE 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 Z18XE why not pop over to the forums at TorqueCars where you can chat about Z18XE tuning options and read about others projects who may be planning to do similar modifications on their Z18XE.

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