Modding uprating the Volvo B6304S engine!

All you need to know about "B6304S Modifications"

How to modify and upgrade the Volvo B6304S

"Comprehensive guide to tuning the Volvo B6304S engine!"

The Volvo B6304S engine – a powerplant that embodies Volvo's commitment to performance, sophistication, and a smooth driving experience.

The B6304S, introduced in the 1990s, is a six-cylinder engine that found its place in various Volvo models, including the 960 and S90. As part of the Volvo Modular Engine family, the B6304S carries the legacy of Volvo's dedication to safety, reliability, and refined power.

In terms of specifications, the B6304S boasts a 3.0-liter displacement, showcasing Volvo's emphasis on providing a balanced combination of power and smoothness. The engine is equipped with Double Overhead Camshafts (DOHC), contributing to precise control over the valvetrain for optimal performance.

The B6304S is recognized for its smooth power delivery, a characteristic that aligns with Volvo's commitment to delivering a comfortable and refined driving experience. The use of advanced engineering features, such as the DOHC setup, enhances the engine's ability to provide power across the RPM range.

Volvo's emphasis on safety extends to the B6304S, with features like robust construction and meticulous engineering designed to meet the brand's stringent safety standards. This aligns with Volvo's holistic approach to vehicle design, where power and safety coexist seamlessly.

As we explore the intricacies of the Volvo B6304S engine, we gain insight into Volvo's commitment to creating vehicles that excel in both performance and safety. The B6304S series represents a chapter in Volvo's history where the brand sought to deliver an elevated driving experience, combining power, precision, and safety.

The Volvo B6304S engine stands as a testament to the brand's dedication to crafting vehicles that offer a harmonious blend of performance and sophistication. Its role in various Volvo models contributes to the legacy of engines that prioritize smooth power delivery and safety, making each Volvo ride a refined and enjoyable experience.

Sites like TorqueCars are regularly getting messages requesting info on how to improve the B6304S from people inquiring about getting more power from the B6304S and wanting to know what are the best B6304S mods that work. So let us look into Volvo B6304S parts and outline the best modifications on this great engine and point out some common pitfalls along the way.

We shall look into B6304S tuning and provide tips on the ultimate upgrades. Volvo B6304S offer good returns when tuned and with a few sensible enhancements like a remap, turbo upgrades and camshafts you will really increase your driving fun.

The best B6304S tuning mods on an engine are in our opinion the ones that give the best power gain for your hard earned cash.

We won't be swayed by popular B6304S tuning mods, they need to be cost effective.

B6304S induction kits

Improving air intake on the B6304S

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

So the primary aim to any engine upgrade task to force more air into your B6304S 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 B6304S when loads 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 was restricting torque at a much lower level.

Headers take the on the suck phase from the filter and allow it to be drawn into the engine cylinders.

The size of bore and shape and rate of flow of the Intake can make a large change to fuel atomisation and engine efficiency on the B6304S.

Commonly we find the air intake manifolds are begging for an upgrade, although a few manufacturers provide decently flowing air intake manifolds.

Big valve conversions on the B6304S, doing some port matching and head flowing will also improve bhp, and importantly will give you increasing the bhp increase on other tuning parts.

B6304S performance cam tips.

Different B6304S engines respond better to more aggressive cam durations than others.

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

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.

The cam profile plays a big part in the engines power output so cam upgrades make quite a large difference. The intake & exhaust durations will alter depending on the chosen cam profile, so large power band gains are on offer for cam upgrades.

NB: Fast road cams usually increase the bhp and torque across the rpm range, you might lose a little low down power but high end rpm power will be lifted.

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

On a daily driver you need to match your torque band to your typical driving style.

I would be surprised if you have ever thought a B6304S Motorsport and race cam is a pleasure to live with when on the daily commute.

Stage 1, 2 and 3 mods for the B6304S

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

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 B6304S parts:

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

Stage 2 B6304S parts:

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

Stage 3 B6304S parts:

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

The B6304S engines are great to work on and we're pleased to see that there are increasing numbers of mods and performance parts around.

Remapping will help release the full potential of all the tuning mods you've done to your B6304S.

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 results may vary depending on the tuning mods you've carried out and the condition of your engine.

Turbo modifications on the B6304S

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 B6304S.

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.

When your car is turbo charged mods are going to net you a larger power gain and most turbo charged engines already contain strengthened components.

There are reliable 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 higher quality crank and pistons to survive the power.

We see many people spending a loads on turbocharger upgrades on the B6304S only to suffer the humiliation of seeing the engine block literally blow up soon after it's used on the roads.

Bigger upgraded turbos often experience a bottom end lag, and small turbos spool up more quickly but don't have the peak rpm bhp gains.

We are pleased that the market of turbos is always increasing and we are seeing variable vane turbos, permitting the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbos divert the exhaust flow into 2 channels and push these at differently angled vanes in the turbo. 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 bhp and torque gains, although harder to setup. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the B6304S

You will need to ensure that the engine is not starved of fuel so will have to pay attention to the fuelling when you start extending past 20% of a torque hike. Care modifiers usually say to over specify your injector capacity.

The rule of thumb is to add 15% capacity when fitting an injector, this accounts for injector deterioration and provides a bit of 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 B6304S performance exhaust upgrades

The only time you should look to boost your exhaust system with an upgraded one is if the current exhaust is actually creating a flow problem.

On most factory exhausts you should find that the exhaust flow rate is ok 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 will certainly help air flow through the engine but avoid an exhaust that is too large or you could will reduce the flow rate. Stick to one and a half to two and half inches for best results.

The usual suspects causing problems in your exhaust flow rate are traced to the catalyst and filters installed, so adding a better flowing performance alternative will help avoid this restriction.

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

Faults issues and things to look out for on the B6304S

Like most engines an B6304S, 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 B6304S, failure to do this will exacerbate engine wear, on a tuned B6304S 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 B6304S why not pop over to the forums at TorqueCars where you can chat about B6304S tuning options and read about others projects who may be planning to do similar modifications on their B6304S.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We want to know your experiences with tuning mods on your B6304S, it helps us improve our tips and keeps us current so please use the comments box to drop a tip.

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Check out TorqueCars new YouTube channel, and see their awesome new content...


Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article