All you need to know about "VQ25DD Modifications"

VQ25DD Modifications Guide

How to modify and upgrade the Nissan VQ25DD

"Comprehensive guide to tuning the Nissan VQ25DD engine!"

TorqueCars are always getting emails asking about how to improve the VQ25DD from people wanting to know what are the things tuners recommend when it comes to VQ25DD upgrades. So let us look into Nissan VQ25DD upgrades and outline the best mods that work on this great engine and point out some potential pitfalls along the way.

Now we shall detail the best approach to VQ25DD tuning and highlight the premier modifications. Nissan VQ25DD make awesome project engines and with the best modifications like ECU maps, turbo upgrades and camshafts you will dramatically maximise your driving enjoyment.

When talking about the ultimate parts for your VQ25DD engine, we are going to concentrate on the parts that give the best power gain for you money.

VQ25DD induction kits

Improving air intake on the VQ25DD

You need air matched to fuel for an engine to work. If there is little supply of fuel then it will run lean, if there is a lack of air it runs rich losing power which risks damage to the VQ25DD. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So it's important to any car tuning project to shove more fuel and air into your VQ25DD but this has a knock on effect with the air flow sensor.

You'll commonly see there is a restriction in the air flow sensor AFM/MAF on the VQ25DD 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 sapped torque at a much lower level.

Headers take the air during the suck phase from the air filter and allow it to be pulled into the engine cylinders.

Shape and flow rate of the Intake can make a substantial improvement to fuel mixing and power on the VQ25DD.

Most plenum chambers are crying out for motorsport parts, although some car makers provide well optimised plenum chambers.

Increasing the VQ25DD valve size, carrying out port matching and head flowing will also improve performance, & importantly will raise potential for a better performance increase on other parts.

VQ25DD performance cam tips.

Different VQ25DD engines respond better to more aggressive cam durations check your engine on a rolling road.

The engine timing and injectors and fuel pump also have a large bearing on the bhp gains you'll make.

Extending exhaust or intake 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.

Significant air intake, and exhaust improvements on the VQ25DD can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

NB: Fast road camshafts commonly increase the performance through the rev range, you could drop a little low down bhp but high end rpm power will be higher.

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

A Race cam is not great driving in heavy traffic.

You should ideally match your bhp range to your typical driving style so for a car driven daily stick with a shorter duration VQ25DD cam

Stage 1, 2 and 3 mods for the VQ25DD

Stage 1 VQ25DD parts:

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

Stage 2 VQ25DD parts:

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

Stage 3 VQ25DD parts:

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

The VQ25DD engine blocks respond well to mods and we see that there are plenty of parts and tuning parts out there.

A remap will help release the full potential of all the modifications you've done to your VQ25DD.

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 figures achieved usually depend much on the modifications 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 VQ25DD

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 VQ25DD.

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

If the engine has a turbo already fitted upgrades are relatively easy and turbo charged engines are made with stronger components.

There are practical limits for every engine, with some being very over engineered and some only able to handle stock power

It is important to find these limitations and upgrade to stronger pistons, crank and engine components to cope with the power.

We've seen people spending a lot of money on turbo charger upgrades on the VQ25DD only to have the engine explode just after it's used in anger.

Bigger turbo chargers will usually experience no power at low rpm, and low capacity turbo chargers spool up quickly but won't have the top end power band gains.

Thankfully the range of turbo units is always increasing and we are seeing variable vane turbo units, permitting 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 two channels and feed these at differently angled vanes in the turbo charger. They also help 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 difficult to setup. We have this article covering twinchargers if you want to read more.

Tips about fuel supply on the VQ25DD

Don't overlook the need to uprate the fuel delivery when you are increasing the torque - it makes the car more thirsty. At this point we flag up the need to be generous with your injector capacity.

As a rule of thumb add 15% capacity when buying an injector, this takes into account 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 VQ25DD performance exhaust upgrades

You should look to upgrade your exhaust system with an upgraded one is if the current exhaust is creating a restriction in flow.

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

Sports exhausts balance the flow of air through the engine.

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

Usual exhaust restrictions are in the emissions filters installed, so adding a higher flowing 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 VQ25DD

Like most engines an VQ25DD, 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 VQ25DD, failure to do this will exacerbate engine wear, on a tuned VQ25DD 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 VQ25DD why not pop over to the forums at TorqueCars where you can chat about VQ25DD tuning options and read about others projects who may be planning to do similar modifications on their VQ25DD.

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