Tuning Feature: Nissan VQ25DET Modified

"Comprehensive guide to tuning the Nissan VQ25DET engine!"

We are always getting emails inquiring about getting more power from the VQ25DET and wanting to know what are the best VQ25DET mods that work. So let us look into Nissan VQ25DET parts and outline the best mods that work on this great engine and point out some common pitfalls along the way.

This engine is a V6 and evolved considerably over it's production run and cc ranged from 2.0 to 4.0 litres. Nissan produced a motorsport version the VQ30DETT showing what this platform is capable of. Some of the 3.5 liter engines have pretty strong internals and can withstand up to 1000hp in ideal conditions, and parts from these high spec engines are often sourced and fitted into others accross the range.

The Nissan VQ25DET are fantastic to work on and with a few sensible modified tuning mods like a remap, turbo improvements and camshafts you will substantially improve your driving pleasure.

TorqueCars will look into VQ25DET tuning and point out the best upgrades.

The greatest VQ25DET upgrades on an engine are usually the ones that give the biggest return for your cash.

We won't be swayed by popular VQ25DET upgrades, they need to be cost effective.

Significant power increases can be made on engines, and the VQ25DET is no exception, with cam upgrades. Altering 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 commonly boost the power through the rpm range, you could sacrifice a little bottom end power but the higher rpm power will be higher.

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 Race cam will just annoy you whilst driving in heavy traffic.

You should ideally optimize your engines power to your typical driving style so for a typical daily driver stick with a mild fast road VQ25DET cam

Each engine responds better to different cam durations than others.

The ecu map and injectors and fuel pump also will make differences on the bhp gains you'll make.

Longer valve durations can alter the bhp 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.

VQ25DET Tuning Stages

Stage 1 VQ25DET modifications: Sports exhaust manifold, Fast road camshaft, Intake headers, Panel air filters, Drilled & smoothed airbox, Remaps/piggy back ECU.

Stage 2 VQ25DET modifications: Ported and polished head, induction kit, fuel pump upgrades, high flow fuel injectors, Fast road cam, Sports catalyst & performance exhaust.

Stage 3 VQ25DET modifications: Twin charging conversions, Crank and Piston upgrades to alter compression, Adding or Upgrading forced induction (turbo/supercharger), Competition cam, Internal engine upgrades (head flowing porting/bigger valves), Engine balancing & blueprinting.

A remap should help to fully realize the full potential of all the mods you've done to your VQ25DET.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the end result will rely on the mods you've applied and the condition of your engine.

It is the main goal to any engine modification job to shove more air into your VQ25DET

Intake manifold transmit the air from the intake filter and allow it to be drawn into the engine and mixed with fuel.

The bore size, shape and flow rate of the Plenum can make a noticeable difference to to fuel delivery on the VQ25DET.

On popular production engines headers are in desperate need of motorsport parts, although a few makers provide reasonably well designed headers.

Increasing the VQ25DET valve size, carrying out port matching and head flowing will also raise power, & more importantly will permit a better power increase on other upgrades.

Turbo upgrades for the VQ25DET

NASP engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your VQ25DET

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

If your motor is fitted with a turbo mods are giving better power gains and most turbocharged engines use harder and stronger components.

There are tuning limits for every engine, with some being over specified and some only able to handle stock power

See where you'll find these limits and upgrade to stronger pistons, crank and engine components to handle the power.

We've seen people spending a loads on turbo upgrades on the VQ25DET only to have the motor catastrophically fail on it's first outing after it's used on the roads.

Bigger turbochargers tend to experience no power at low rpm, and low capacity turbochargers spool up quickly but do not have the peak rpm torque gains.

Thankfully the range of turbos is always improving and we now see variable vane turbos, where the vane profile is altered according to speed to lower lag and increase top end power.

Twin scroll turbos divert the exhaust gases into two channels and direct these at differently profiled vanes in the turbo. They also boost the scavenging effect of the engine.

It is not unusual that there's a limitation in the air flow sensor (AFM/MAF/MAP) on the VQ25DET when a lot more air is being pulled into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp and torque at a much lower level.

Adding a supercharger or additional turbo will make large bhp and torque gains, although more complex to install. We have this feature on twinchargers if you want to read more.

Uprating VQ25DET fuel injectors

Don't omit to improve the fuel system when you are increasing the bhp and torque - it makes the car more thirsty. It makes sense to over specify your injectors flow rate.

The rule of thumb is to add another 20% when buying an injector, helps cope with injector deterioration and gives you some spare capacity should the engine need more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

Best VQ25DET performance exhausts

Only look to replace your exhaust if the current exhaust is creating a restriction in flow.

On most factory exhausts you'll see your flow rate is still fine even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Sports exhausts can help equal out the flow of air through the engine.

But if your exhaust pipe is too big, ie: over 2.5 inches bore, you will lose much of the exhaust flow rate and end up lacking power and torque.

Typically exhaust restrictions can be located in the catalyst installed, so adding a faster flowing performance alternative will help avoid this restriction.

Problems and issues to look out for on the VQ25DET

The VQ25DET engines, if regularly serviced and maintained, are generally very reliable and have few issues. {But if neglected they can cost a small fortune|When neglected they get very expensive to run|They can however be quite expensive if neglected| }

Regular oil changes are vital on the VQ25DET, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your VQ25DET engine please join us in our friendly forum where you can discuss tuning options in more detail with our VQ25DET owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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We really like hearing from our readers, and hearing about which tuning mods were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our VQ25DET guides and tips are kept up to date.

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This article is flagged for an update, so please pass on specific tips below that I can include. All articles, and content was written by me, Waynne Smith TorqueCars founder. Some outlines are just too general so I appreciate your feedback and suggestions. This entry was filed under Nissan. You can leave a response below or join our forum to discuss this article and car modification in detail with our members.

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