Modding upgrading and tuning the Nissan VQ25DE engine!

Tuning guide "VQ25DE Modifications"

VQ25DE Modifications Guide

How to modify and upgrade the Nissan VQ25DE

"Comprehensive guide to tuning the Nissan VQ25DE engine!"

Our friends at TorqueCars are always getting messages about how to improve the VQ25DE from people wanting to know what are the ultimate VQ25DE power upgrades. So let us look into Nissan VQ25DE modifications and outline the best modifications on this great engine and point out some problems along the way.

The Nissan VQ25DE are popular tuning projects and with the best uprated upgrades like a remap, turbo kits and camshafts you will noticeably improve your driving experience.

This pages aim is look into VQ25DE tuning and provide tips on the ultimate upgrades.

The best VQ25DE tuning parts on an engine are usually the ones that give the best power gain for your hard earned cash.

We won't be swayed by popular VQ25DE tuning parts, they need to be cost effective.

VQ25DE induction kits

Improving air intake on the VQ25DE

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 not enough air it runs rich sapping power . 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 project to get air into the VQ25DE engine but this has a knock on effect with the air flow sensor.

You'll commonly see there's a restriction in the air flow sensor AFM/MAF on the VQ25DE when loads more air is being drawn into the engine.

When tuning you may well find you need to get an air sensor or flow meter capable of upto 4 bars to cope with quite large power gains, whereas the OEM air sensor limited power at a much lower level.

Intake headers carry the on the suck phase from the filter and allow it to be sucked into the engine and mixed with fuel.

The bore size, shape and rate of flow of the Intake can make a noticeable change to fuel atomisation on the VQ25DE.

Most air intake manifolds are improved through an upgrade, although a few car makers provide reasonably well designed air intake manifolds.

Larger VQ25DE valves, doing some VQ25DE port enlargement and head flowing will also boost performance, the fantastic side effect is it will afford you increasing the performance increase on other tuning parts.

VQ25DE performance cam tips.

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

The map and fuelling also have an effect on the power gains you'll get.

A longer valve duration 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.

Altering your VQ25DE cam will make a dramatic difference to the engine bhp. Choosing a higher performance cam profile raises the bhp accordingly.

NB: Fast road camshafts commonly bump the power through the rpm band, you may sacrifice a little low end torque but higher rpm power will improve.

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.

In a daily driver you need to optimize your torque band to your usage of the car.

You'll never have found a VQ25DE Motorsport and race camshaft is a pleasure to live with when driving around busy urban areas.

Stage 1, 2 and 3 mods for the VQ25DE

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 VQ25DE parts:

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

Stage 2 VQ25DE parts:

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

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

Stage 3 VQ25DE parts:

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

The VQ25DE power trains are great to work on and we note that there are quite a few choices of upgrades and performance parts out there.

Mapping should help to release the full potential of all the tuning parts you've done to your VQ25DE.

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 may depend much on the tuning parts you've carried out and the condition of your engine.

Turbo modifications on the VQ25DE

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 VQ25DE.

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 the engine has forced induction mods are relatively easy and we find turbo engines are made using uprated components.

However most engines will have power limits

Discover these restrictions and fit stronger pistons, crank and engine components to utilize the power.

There are many mechanics spending a loads of money on turbocharger upgrades on the VQ25DE only to suffer the humiliation of seeing the VQ25DE throw a rod just after it's first rolling road session.

Large upgraded turbo units commonly experience low end lag, and small turbo units spool up much more quickly but do not have the peak rpm bhp gains.

Thanks to progress the choice of turbos is always improving and we now see variable vane turbos, allowing the vane profile is altered according to speed to lower lag and increase top end performance.

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

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large bhp gains, although more complex to install. We have this article on twincharging if you want to read more.

Tips about fuel supply on the VQ25DE

You will need to ensure that the engine is not starved of fuel so will need to look at the fuelling when you start going beyond 20% of a torque hike. Experienced mechanics will tell you to over specify your injectors flow rate.

As a rule of thumb add 20% to the flow rate when buying an injector, helps cope with injector deterioration and affords a little 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 VQ25DE performance exhaust upgrades

You may need to uprate your exhaust system with an upgraded one is if your exhaust is actually creating a flow problem.

On most factory exhausts you'll see the flow rate is 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.

Note that with the biggest exhaust you can source 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.

Usual exhaust restrictions are traced to the catalysts installed, so adding a freer 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 VQ25DE

Like most engines an VQ25DE, 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 VQ25DE, failure to do this will exacerbate engine wear, on a tuned VQ25DE 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 VQ25DE why not pop over to the forums at TorqueCars where you can chat about VQ25DE tuning options and read about others projects who may be planning to do similar modifications on their VQ25DE.

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