Modding upgrading and tuning the Nissan VQ38HR engine!

Modifying and improving: "VQ38HR Modifications"

VQ38HR Modifications Guide

How to modify and upgrade the Nissan VQ38HR

"Comprehensive guide to tuning and performance parts on the Nissan VQ38HR engine!"

Our friends at TorqueCars are regularly getting emails about how to improve the VQ38HR from people inquiring about getting more power from the VQ38HR and wanting to know what are the best tips for VQ38HR modifications. So let us look into Nissan VQ38HR parts and outline the best mods that work on this great engine and point out some problems along the way.

We shall consider VQ38HR tuning and highlight the greatest modifications. Nissan VQ38HR are fantastic to work on and with the optimum sports enhancements like remaps, turbo upgrades and camshafts you will improve your driving pleasure.

When talking about the best parts for your VQ38HR engine, we are going to focus on the modifications that give the best value for money.

VQ38HR induction kits

Improving air intake on the VQ38HR

You need fuel and air for an engine to work. If there is too little 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 performance tuning job to feed fuel and air into each cylinder but this has a knock on effect with the air flow sensor.

It is common that there's a limit in the air flow sensor AFM/MAP on the VQ38HR 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 limited bhp at a much lower level.

Intake manifolds carry the air flow during the suck phase from the air filter and allow it to be fed into the engine cylinders with fuel for the squish phase.

Shape and rate of flow of the Headers can make a large change to fuel atomisation and engine efficiency on the VQ38HR.

We often see air intake manifolds are crying out for aftermarket parts, although a few car makers provide reasonably well designed air intake manifolds.

Big valve conversions on the VQ38HR, doing some port matching and head flowing will also boost bhp, & more importantly will make space for a better bhp increase on other mods.

VQ38HR performance cam tips.

Each engine responds better to more aggressive camshaft durations check your engine on a rolling road.

The engine timing and injectors and fuel pump also will make differences on the power gains you'll make.

Extending exhaust or intake 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 VQ38HR 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 commonly bump the bhp and torque across the rev range, you could drop a little low end torque but your higher rpm power will be better.

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

A Race cam makes it harder when driving around busy urban areas.

You should ideally optimize your bhp range to your driving style so for a car driven daily stick with a shorter duration VQ38HR cam

Stage 1, 2 and 3 mods for the VQ38HR

Stage 1 VQ38HR parts:

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

Stage 2 VQ38HR parts:

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

Stage 3 VQ38HR parts:

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

Carefully think through your options and then source your tuning parts and set yourself a power target to avoid costly mistakes.

A remap will help fully realize the full potential of all the tuning parts you've done to your VQ38HR.

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 mileage often rely on the tuning parts you've applied and the condition of your engine.

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

Turbo modifications on the VQ38HR

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 VQ38HR.

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

When the engine is turbo charged upgrades are simpler to install and most turbo engines use strengthened components.

However you will find an engines will need better parts at higher power limits

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

We've seen people spending a loads on turbocharger upgrades on the VQ38HR only to have the VQ38HR catastrophically fail on it's first outing after it's been enthusiastically driven.

Large turbo chargers often experience no power at low rpm, and little turbo chargers spool up more quickly but won't have the top end bhp gains.

In recent times the world of turbo chargers is always developing and we now see variable vane turbo chargers, allowing the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbo chargers divert the exhaust flow into two channels and feed these at differently profiled vanes in the turbo charger. 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 power gains, although more complex to setup. We have this guide to twinchargers if you want to read more.

Tips about fuel supply on the VQ38HR

When you increase the bhp you will need to look at to the fuel system.

More bhp needs more fuel. Experienced mechanics will tell you to be generous with your injector capacity.

As a rule of thumb add 15% when specifying an injector, this accounts for injector deterioration and gives 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 VQ38HR performance exhaust upgrades

You should look to increase your exhaust system with an upgraded one is if the existing exhaust is actually creating a flow problem.

On most factory exhausts you'll find the flow rate is still 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 increase the flow of air through the engine.

But if the exhaust is too large, ie: it's over two and a half inches diameter, you will lose a lot of your flow rate and end up sapping power and torque.

Usual exhaust restrictions come around the catalyst and filters installed, so adding a faster flowing high performance alternative will help avoid this restriction.

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

Faults issues and things to look out for on the VQ38HR

Like most engines an VQ38HR, 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 VQ38HR, failure to do this will exacerbate engine wear, on a tuned VQ38HR 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 VQ38HR why not pop over to the forums at TorqueCars where you can chat about VQ38HR tuning options and read about others projects who may be planning to do similar modifications on their VQ38HR.

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