Tuning the Nissan RB25

"Comprehensive guide to tuning the Nissan RB25 engine!"

The Nissan RB25 are awesome to work on and with carefully picked motorsport tuning mods like ECU maps, turbo improvements and camshafts you will greatly maximize your driving pleasure.

We shall outline options for your RB25 tuning and highlight the best upgrades.

The best RB25 upgrades on an engine are sensibly the ones that give the biggest return for your cash.

We won't be swayed by popular RB25 upgrades, they need to be cost effective.

Significant gains on the RB25 can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

NB: Fast road camshafts tend to increase the torque over the rev band, you may lose a little low down power but the higher rpm power will be higher.

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

For a daily driver you need to optimize your engines power to your cars usage.

I'd be gobsmaked if you find a RB25 Competition cam is a pleasure to live with when driving around busy urban areas.

Some RB25 engines respond better to extreme camshaft durations than others.

The map and injectors and fuel pump also will say much on the torque gains you'll get.

Altering valve durations can alter the torque 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.

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

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

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

The RB25 power plant respond well to upgrades and we're happy to report there are plenty of parts and tuning parts around.

ECU flashing helps release the full potential of all the parts you've fitted to your RB25.

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

It is vital to any tuning task to feed air and fuel into your RB25

Intake headers flow 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 rate of flow of the Plenum can make a large change to fuel engine efficiency on the RB25.

It's not uncommon that intake manifold are in desperate need of aftermarket tuning parts, although some manufacturers provide well optimised intake manifold.

Adding a RB25 larger valve kit, getting RB25 port enlargement and head flowing will also lift bhp, this will allow you to get an improved bhp increase on other parts.

Turbo upgrades

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 RB25

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.

If an engine has a turbo already fitted modifications are relatively easy and you'll see that turbo engines will have harder and stronger components.

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

See where you'll find these limits and upgrade to higher quality components to handle the power.

We've seen people spending a lots of money on turbo upgrades on the RB25 only to experience the RB25 literally blow up just after it's been completed.

Bigger capacity turbochargers will usually suffer low end lag, and smaller turbochargers spool up much more quickly but do not have the top end torque gains.

Thankfully the range of turbo chargers is always increasing and we now see variable vane turbo chargers, where the vane profile is altered according to speed to lower lag and increase top end bhp.

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

It is not unusual that there is a limit in the air flow sensor AFM/MAP on the RB25 when considerably more air is being drawn into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped torque at a much lower level.

Adding a supercharger or additional turbo will make large torque gains, although more difficult to setup. We have this article on twincharging if you want to read more.

Fuelling upgrades and mods

Don't omit to raise the fuelling when you are increasing the bhp and torque - it makes the car more thirsty. It is important to be generous with your injectors flow rate.

The accepted safe increase is to add 20% capacity when buying an injector, helps cope with injector deterioration and gives 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.

Exhaust upgrades and mods

Only look to uprate your exhaust if your current exhaust is actually creating a restriction in flow.

On most factory exhausts you should find that the exhaust 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 balance the flow of air through the engine.

But if the exhaust is too large, ie: over 2.5 inches bore, you will lose a lot of the flow rate and end up lacking power and torque.

Common exhaust restrictions are traced to the catalyst and filters installed, so adding a freer flowing sports alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the RB25

The RB25 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the RB25, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your RB25 engine please join us in our friendly forum where you can discuss tuning options in more detail with our RB25 owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

Please help us improve these tips by sending us your feedback in the comments box below.

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 RB25 guides and tips are kept up to date.

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