Discover "QG18DD Modifications"

How to modify and upgrade the Nissan QG18DD

"Comprehensive guide to tuning and performance parts on the Nissan QG18DD engine!"

Popular tuning sites like TorqueCars often are getting posts asking how to improve the QG18DD from people inquiring about getting more power from the QG18DD and wanting to know what are the best tips on QG18DD power upgrades. So let us look into Nissan QG18DD mods and outline the best upgrades on this great engine and point out some frequent tuning mistakes along the way.

The Nissan QG18DD provide a fun base for your project and with the optimum performance upgrades like remapping, turbo improvements and camshafts you will greatly maximise your driving enjoyment.

Car Tuning Tips will review and look at QG18DD tuning and summarise the premier modifications for your car.

Just because particular mods are are common on QG18DD it doesn't mean you should fit it, we will focus on the best mods that will give your QG18DD the best power gain for you money.

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 QG18DD

You need air and fuel for an engine to work. If there is not enough fuel then it will run lean, if there is not enough 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 the aim to any tuning task to push air and fuel into each cylinder but this has a knock on effect with the air flow sensor.

It is common that there's a limitation in the air flow sensor (AFM/MAF/MAP) on the QG18DD when considerably more air is being pulled into the engine.

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

Engines intake headers take the air during the suck phase from the filter and allow it to be sucked into the engine and mixed with fuel.

The size of bore and shape and flow rate of the air Intake manifold can make a noticeable difference to to fuel engine efficiency on the QG18DD.

It's not uncommon that plenum chambers are ripe for motorsport parts, although some manufacturers provide reasonably good plenum chambers.

Big valve conversions on the QG18DD, carrying out 3 or 5 angle valve jobs and porting and head flowing will also improve power, & more importantly will permit increasing the power increase on other parts.

QG18DD performance cam tips.

Some QG18DD engines respond better to more aggressive cam durations so set your engine up on a rolling road.

The engine timing and fuel pump and injectors also have an effect on the power gains you'll get.

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 QG18DD can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

NB: Fast road camshafts usually push up the power throughout the rpm range, you may lose a little low end bhp but your top end will be higher.

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

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

You should ideally optimize your bhp range to your typical driving style so for a daily driver stick with a shorter duration QG18DD camshaft

Stage 1, 2 and 3 mods for the QG18DD

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 QG18DD parts:

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

Stage 2 QG18DD parts:

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

Stage 3 QG18DD parts:

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

Remapping will help fully realize the full potential of all the mods you've done to your QG18DD.

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 may vary depending on the mods you've done and the condition of your engine.

Turbo modifications on the QG18DD

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 QG18DD.

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.

When your motor has a turbocharger upgrades are going to net you a larger power gain and you'll see that turbo charged engines will have strengthened components.

However every engines have limits

Research these restrictions and install better quality components to handle the power.

We've seen drivers spending a loads on turbocharger upgrades on the QG18DD only to have the QG18DD go up in smoke on it's first outing after it's completed.

Larger upgraded turbochargers tend to experience no power at low rpm, and low capacity turbochargers spool up much more quickly but won't have the top end power band gains.

In the last 10 years the world of turbo units is always developing and we are seeing variable vane turbo units, where the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbo units divert the exhaust gases into 2 channels and feed these at differently designed vanes in the turbocharger. They also improve 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 challenging to configure. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the QG18DD

Don't dismiss the need pay attention to the fuelling when you are increasing the power - it makes the car more thirsty. Experienced tuners recommend to over specify your flow rate on the injectors.

The rule of thumb is to add 20% to the flow rate when specifying an injector, this accounts for injector deterioration and gives 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 QG18DD performance exhaust upgrades

Only look to uprate your exhaust system with an upgraded one is if the existing exhaust is actually 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.

Please dont run with the biggest exhaust you can source you'll slow up the exhaust flow 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.

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

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

Faults issues and things to look out for on the QG18DD

Like most engines an QG18DD, 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 QG18DD, failure to do this will exacerbate engine wear, on a tuned QG18DD 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 QG18DD why not pop over to the forums at TorqueCars where you can chat about QG18DD tuning options and read about others projects who may be planning to do similar modifications on their QG18DD.

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