Low-end torque, top-end performance, less weight and sound. Exploring your choices through our demonstrator’s specification.
Part of our Honda S2000 Restoration & Tuning Journal Series
1. Do Your Intake and Exhaust Choices Work Together?
Fit a K&N air filter. Replace a tired original catalytic converter with a Berk high-flow cat. Choose an exhaust after hearing one you liked in a video.
There are plenty of ways to begin modifying an S2000’s intake and exhaust.
While researching parts, you will often encounter the term “high flow”. If air and exhaust gases can pass through more easily, that sounds promising.
But what would you actually like to improve?
More pull at lower revs? Better top-end performance? A different response to the accelerator? Or the sound you have been looking for?
This article is about choosing intake and exhaust components for an S2000 with standard engine internals, and bringing them together to suit your preferences.
Our yellow demonstrator provides the example.
Our demonstrator combines aftermarket components with original Honda parts. Each has a place in the specification.
2. Why Modify an Already Well-Engineered Standard System?
The S2000 is a remarkably satisfying car in standard form.
Replace wear items at suitable intervals, clean away accumulated deposits and maintain the car towards its original condition, and there is already a great deal to enjoy.
For me, that is one of its strengths.
When choosing modifications, I want to understand what the standard components do well. Changing parts and losing the balance that made the car enjoyable would be a disappointing result.
With that in mind, let us consider what high-flow modifications are intended to achieve.
Put simply, “high flow” means making it easier for air or exhaust gases to pass through, allowing a greater quantity to flow.
An engine produces power by taking in air and burning fuel with it. If more air can enter the cylinders when needed, and an appropriate quantity of fuel can be burned effectively, there is potential to increase torque and power.
That is the main performance aim behind improving intake and exhaust flow.
So how do we get more air into the engine?
In the naturally aspirated S2000 we are discussing, there is no turbocharger or supercharger forcing air into the intake. Start by considering how the engine draws air in for itself.
As a piston moves down during the intake stroke, pressure inside the cylinder falls. Air then flows in because of the pressure difference between the cylinder and the air outside.
That is what we mean when we say the engine “sucks” air in.
Before reaching the cylinder, that air passes through the filter, intake hose, throttle body and intake manifold. Reducing resistance along this route can make it easier for the engine to draw air in.
The exhaust side matters too.
After combustion, the piston pushes the burnt gases out during the exhaust stroke. They travel through the exhaust manifold, catalytic converter and exhaust system.
If resistance on that side is high, the engine must do more work to push the gases out.
Helping exhaust gases leave can reduce that workload and help create favourable conditions for the next charge of fresh air to enter.
Intake and exhaust therefore need to be considered together.
However, reducing exhaust resistance does not automatically increase intake airflow at every engine speed.
The valves open and close repeatedly. Flow varies, and pressure waves travel through the pipes. How those waves behave depends on pipe diameter, length, collector design and engine speed.
Simply fitting a larger pipe will not necessarily make the car more enjoyable than it was with the standard system.
Flow quantity and flow speed are different, too. For the same volume passing through each second, a larger pipe means a lower average flow speed. Creating capacity for more flow, while making useful use of gas velocity and pressure waves, is part of the design challenge.
Honda’s standard system brings these factors together to work across a wide range of engine speeds and driving conditions.
Before changing it, ask yourself: where would you like an improvement, and what would that improvement feel like?
3. What Would You Like to Change About the Standard Driving Experience?
Taking a healthy standard car as the starting point, the first question is what you would like to change.
Picture yourself driving your S2000.
Around town or on a country road, you press the accelerator a little further. Would you like the car to pull more strongly without changing down?
Or are you happy with its low- and mid-range behaviour, but interested in making more of the engine as the revs rise?
As we discussed above, intake and exhaust designs can favour particular engine speeds. Greater flow capacity at high revs may sound appealing, but if a change also alters the response where you normally drive, consider whether that suits you.
Look beyond the peak power figure. Think about how you want the car to respond in the rev range you use, and which qualities you would like to preserve.
There are also reasons to change intake and exhaust components beyond engine output.
Weight is one.
The exhaust includes the catalytic converter and substantial silencers. Depending on the components chosen, reducing weight can be part of the appeal.
Then there is sound.
For many owners, sound is an important part of enjoying an S2000. It certainly is for me.
Again, imagine when and how you would like to hear it.
Do you enjoy a higher-pitched note building as the revs climb? A deeper, fuller sound? Or something restrained in everyday driving that becomes more noticeable when you accelerate?
Volume and pitch are different qualities. An exhaust that sounds enjoyable under acceleration may also produce an intrusive drone at cruising speed, making longer journeys tiring.
Your preferred changes and your everyday use both matter when choosing a combination.
For our demonstrator, I value weight reduction and a higher-pitched exhaust note. On the exhaust side, I have built the specification around a 70 mm system.
That diameter is a choice within this particular specification. It is not a recommendation for every S2000.
Let us look at what we have chosen, and what we have retained, starting with the intake.
4. The Intake: Combining Aftermarket Parts with Original Honda Components
Our demonstrator uses the following arrangement:
SPOON air filter → modified original airbox → SAMCO elbow hose → original throttle body → original intake manifold
The air filter is the yellow SPOON element.
A filter needs to let air through while removing airborne contaminants. Filtration performance and maintenance requirements deserve consideration alongside airflow.
The K&N filter on the left alongside the yellow SPOON filter used on our demonstrator. Appearance alone cannot establish their airflow or filtration performance.
We retain the original airbox, with modifications to its internal layout.
Airbox modification could easily become an article of its own, so I will keep that discussion brief here.
From there, air passes through the SAMCO elbow hose, original throttle body and original intake manifold.
The original components remain part of the specification.
Honda designed the throttle body and manifold around airflow, response and the engine’s operating range. For this combination, we have chosen to retain them.
Deciding what to keep is part of developing the car, just as much as deciding what to replace.
5. Consider Intake Temperature Alongside Airflow
When looking at the air’s route into the engine, consider its temperature too.
At the same pressure, cooler air is denser, so a given volume contains a greater mass of air. Even with a freer-flowing intake, where that air comes from and how warm it becomes still matter.
Our demonstrator also uses CSO intake-manifold insulation.
Its purpose is to reduce heat transfer from the engine to the intake manifold.
IAT sensor relocation addresses another aspect: where intake air temperature is measured. Reducing the air’s actual temperature and reducing the influence of surrounding heat on the sensor are different tasks.
We discussed these subjects in our earlier articles on refresh and upgrade ideas alongside a coolant change and IAT sensor relocation.
For this article, the point is that airflow capacity is only one consideration when choosing intake components.
With the intake manifold removed. Heat transfer is another consideration when developing the intake specification.
6. The MUGEN Exhaust Manifold: Length and Collector Design Matter Too
Moving to the exhaust side, our demonstrator uses a MUGEN manifold designed for the F20C.
This provides a useful example of designing around a particular rev range.
MUGEN explains that it optimised the length from the exhaust ports to the collector and used an equal-length layout, prioritising torque improvement between 6,000 and 8,000 rpm.
Its 4-2-1 arrangement and collector design form part of that approach to mid- and high-rev performance.
That tells us more about the product’s intended character than simply describing it as “freer flowing”.
Compare the pipe routes, lengths and collector arrangement as well as the overall appearance.
Weight reduction is another attraction.
MUGEN’s published figures give the F20C manifold a weight of 6.4 kg, compared with 10.2 kg for the original: a difference of 3.8 kg. These are the manufacturer’s comparison figures.
The MUGEN manifold fitted to our demonstrator. From here, the exhaust continues through the catalyst and exhaust system.
7. From the SARD Catalyst to the CSO Exhaust
Behind the MUGEN manifold, we use a SARD sports catalytic converter.
The catalyst treats exhaust emissions. Choosing a sports catalyst involves considering flow resistance while retaining that emissions-treatment function.
The SARD catalyst above the Berk unit. Internal construction matters alongside external dimensions.
Next comes the CSO Silent Sports Exhaust.
CSO describes it as a 70 mm system without a deliberate narrowing in the flow path, using a silencing design that gives priority to engine output. Its internal construction, material selection and downward-facing tailpipe also form part of its noise-control approach.
I chose this combination with my preferences for weight and sound in mind.
However, “70 mm” does not describe every passage from the engine to the tailpipe.
The manifold has individual branches and collectors. The catalyst contains its own internal passages. Flange openings, gaskets and steps at the connections also deserve attention.
Consider the components individually, then look at how they join together.
Our demonstrator’s exhaust arrangement, viewed as a connected system.
Here is a short recording of the demonstrator’s exhaust.
Our demonstrator with its MUGEN manifold, SARD sports catalyst and CSO Silent Sports Exhaust. Recording conditions and playback equipment affect how it sounds.
Use it as a reference when thinking about your preferences. A short recording at the tailpipe cannot show you the full experience inside the car under load or at cruising speed.
The photographs and video illustrate the specification; they do not measure a power increase. The reasons for choosing components and their measured results are separate things.
8. Take an Interest in the People Making the Parts
My choices also reflect a personal preference.
Where comparable performance and quality are available, I like to choose Japanese-made products and Japanese brands.
Part of enjoying a Japanese sports car, for me, is taking an interest in the people who develop parts for it.
MUGEN, SARD, SPOON and CSO each bring their own objectives and design approaches.
Understanding why a component has a particular shape, or which driving conditions it was developed for, makes choosing parts more interesting.
Our demonstrator also uses British-made SAMCO components, chosen for their role and quality within the combination.
Alongside the parts themselves, we enjoy sharing something of the makers and thinking behind them.
9. Tell Us Your Current Specification—and What You Would Like to Change
What intake and exhaust components does your S2000 currently have?
Is it standard? Has a previous owner fitted parts? Have you changed the exhaust but retained the original intake?
Then consider what you would like to change about its response, weight or sound.
More useful pull at low and medium revs? More emphasis on the top end? Less weight? A particular exhaust note? Comfort on longer journeys?
Knowing your priorities makes it easier to consider suitable parts and decide which original components to retain.
You can also develop the specification in stages. Replacing a worn component can be an opportunity to consider the next step.
Tell us your current specification and the changes you have in mind.
From parts supply to installation, we can help you choose a combination around how you would like to enjoy your S2000.
See the Complete S2000 Restoration
Explore the complete restoration and development of our demonstration S2000—and the workshop experience behind it: