Modding upgrading and tuning the Vauxhall Z20LEH engine!

All you need to know about "Z20LEH Modifications"

Z20LEH Modifications Guide

How to modify and upgrade the Vauxhall Z20LEH

"Comprehensive guide to tuning the Vauxhall Z20LEH engine!"

Sites like TorqueCars are regularly getting posts asking how to improve the Z20LEH from people inquiring about getting more power from the Z20LEH and wanting to know what are the best tips on Z20LEH modifications. So let us look into Vauxhall Z20LEH parts and outline the best modifications on this great engine and point out some potential pitfalls along the way.

Let us consider Z20LEH tuning and outline the ultimate modifications. Vauxhall Z20LEH offer good returns when tuned and with the right modified upgrades like remapping, turbo kits and camshafts you will substantially maximise your driving enjoyment.

Just because particular modifications are appear in lots of Z20LEH projects it doesn't mean its worth having, we will concentrate on the top modifications that will give your Z20LEH 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'.

Z20LEH induction kits

Improving air intake on the Z20LEH

You need fuel and air for an engine to work. If there is a lack of fuel then it will run lean, if there is too little air it runs rich losing power which risks damage to the Z20LEH. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Shoving more fuel and air into the Z20LEH engine is the primary aim to any engine upgrade job.

It is common that there is a restriction in the air flow sensor MAF/MAP on the Z20LEH 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 was restricting bhp and torque at a much lower level.

Intake flow the during the engines suck phase from the filter and allow it to be drawn into the engine and mixed with fuel.

The shape and flow rate of the Air Intake manifolds can make a noticeable improvement to fuel delivery on the Z20LEH.

Most air intake manifolds are in desperate need of a performance upgrade, although a few manufacturers provide well optimised air intake manifolds.

Increasing the Z20LEH valve size, getting Z20LEH port enlargement and head flowing will also increase bhp, and as an added benefit will permit increasing the bhp increase on other tuning parts.

Z20LEH performance cam tips.

Some Z20LEH engines respond better to extreme camshaft durations than others.

The ECU mapping and fuel pump and injectors also have a large bearing on the power gains you'll make.

Altering valve durations 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.

Significant air intake, and exhaust improvements on the Z20LEH can be made from camshaft upgrades. Changing the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

NB: Fast road cams tend to push up the power through the rev range, you may sacrifice a little low down bhp but top end will be higher.

Motorsport and race cams, push up the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

In a car driven daily you must carefully try to optimize your torque band to your preferences.

You will never find a Z20LEH Competition camshaft is a pleasure to live with when on the daily commute.

Stage 1, 2 and 3 mods for the Z20LEH

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 Z20LEH parts:

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

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 2 Z20LEH parts:

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

Stage 3 Z20LEH parts:

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

Carefully think through your options and then buy your modifications and set yourself a power target to save yourself from expensive mistakes.

Mapping allows a tuner to fully realize the full potential of all the modifications you've done to your Z20LEH.

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 your results usually rely on the modifications you've done and the condition of your engine.

Turbo modifications on the Z20LEH

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 Z20LEH.

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

If your car is fitted with a turbocharger tuning parts are more reliable and most turbocharged engines use uprated components.

However every engines have weakspots

See where you'll find these limitations and install better quality components to handle the power.

We see many guys spending a lot of money on turbo upgrades on the Z20LEH only to watch the engine literally blow up on it's first outing after it's been enthusiastically driven.

Larger capacity turbo units will usually experience no power at low rpm, and smaller turbo units spool up quickly but won't have the top end engines power gains.

Thankfully the range of turbochargers is always developing and we are seeing variable vane turbochargers, allowing the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbochargers divert the exhaust flow into two channels and feed these at differently profiled vanes in the turbo charger. 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 torque gains, although more complex to configure. We have this article covering twinchargers if you want to read more.

Tips about fuel supply on the Z20LEH

Don't overlook the need to raise the fuelling when you are increasing the bhp - it makes the car more thirsty. At this point we flag up the need to over specify your flow rate on the injectors.

As a rule of thumb add another 15% when specifying an injector, which takes into account injector deterioration and affords 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 Z20LEH performance exhaust upgrades

We'd only recommend you look to replace your exhaust system with an upgraded one is if your exhaust is creating a restriction.

On most factory exhausts you'll find your flow rate is still good 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.

Do not go with the biggest exhaust you can find this will slow the exhaust rate - the best 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.

The usual suspects causing problems in your exhaust flow rate can be located the catalysts installed, so adding a higher flowing high performance 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 Z20LEH

Like most engines an Z20LEH, 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 Z20LEH, failure to do this will exacerbate engine wear, on a tuned Z20LEH 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 Z20LEH why not pop over to the forums at TorqueCars where you can chat about Z20LEH tuning options and read about others projects who may be planning to do similar modifications on their Z20LEH.

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