Infinity Design BMW S85 E60 M5 / E63 M6 100% Equal Length Headers

Infinity Design V4 Equal Length Headers – BMW E90 / E92 / E93 M3 S65

The Infinity Design V4 Equal Length Header represents the latest evolution of one of the most proven exhaust manifold designs available for the BMW E9X M3 S65 V8.

Building on the worldwide success of the V3, which has repeatedly demonstrated 30–40 hp gains on independently tested vehicles around the world, the V4 isn't about chasing a larger headline horsepower figure.

Instead, Infinity Design returned to the design and manufacturing process with a different objective:

To perfect every aspect of the S65 equal-length header.

The result is a completely refined design incorporating true equal-length 730 mm primary pipes, stepped primary diameters, significantly enlarged F1-style collectors, CNC-machined transition flanges and improved installation access.

Designed using detailed 3D scanning and CAD modelling before being manufactured entirely within Infinity Design's own facility, the V4 has been engineered for everything from standard 4.0-litre S65 engines through to extreme 5.5- and 5.8-litre builds.

Building on the Proven V3

The previous Infinity Design V3 header established an exceptional track record on the S65 platform.

Across numerous vehicles and independent dynamometers around the world, the V3 has consistently demonstrated gains in the region of:

+30–40 hp

Infinity Design doesn't expect the V4 to produce additional peak power over an optimised V3 installation.

That wasn't the objective.

Instead, the V4 focuses on refining primary length, internal volume, collector design, port transitions, exhaust tone, manufacturing quality, installation and future capacity for larger-displacement S65 builds.

It's an evolution based on engineering refinement rather than marketing a larger dyno number.

100% Equal-Length Primaries

One of the most significant developments is the move to true equal-length primary pipes.

The V3 was already extremely close – sufficiently so to be considered equal length by normal automotive engineering standards.

For the V4, Infinity Design took this one step further.

Every primary now has a 730 mm centre-radius length, creating a genuinely equal path from each cylinder head exhaust port to the collector.

This helps maintain consistency in exhaust pulse timing between cylinders and further refines the characteristics of the S65 exhaust system.

The change also has an effect on sound.

Compared with the previous design, the V4 produces a slightly smoother and more harmonised exhaust tone, complementing the S65's naturally aspirated V8 character.

Stepped Primary Design

Primary pipe dimensions have also been revised.

The V3 used a 41.7 mm primary, while the V4 begins at 42 mm before stepping to 45 mm approaching the collector.

This progressive increase in diameter provides additional internal volume as exhaust gases move downstream.

The objective is to maintain exhaust-gas velocity closer to the cylinder head while providing increased flow capacity as the gases approach the collector.

This becomes increasingly important as engine airflow and displacement increase.

Developed for 4.0L to 5.8L S65 Builds

The increased overall volume of the V4 isn't intended only for heavily modified engines.

The system remains suitable for standard-displacement S65s and vehicles fitted with conventional bolt-on performance upgrades.

However, the additional capacity also gives the header considerably more scope for the increasingly popular large-displacement S65 engine builds.

This includes applications from the standard 4.0-litre S65 through stroker configurations such as:

• 4.4L

• 4.6L

• 5.0L

• 5.5L

• Up to 5.8L applications

As displacement increases, so does the volume of exhaust gas the engine needs to move.

The V4's increased primary and collector volume has therefore been engineered with both current and future S65 engine development in mind.

Larger F1-Style Slip-On Collector

The V4 also introduces a substantially redesigned F1-style slip-on collector.

Both the overall length and internal volume have been increased, with the collector now constructed around the larger 45 mm pipework.

Collector design plays an important role in how individual exhaust pulses from each cylinder interact as they merge.

Combined with the true equal-length primaries, the larger collector creates a carefully controlled transition as exhaust gases leave the individual primary pipes and enter the remainder of the exhaust system.

CNC-Machined Cylinder Head Flanges

Attention to airflow begins directly at the S65 cylinder head.

The V4 uses CNC-machined exhaust flanges incorporating an internal transition from the engine's oval exhaust ports into the 42 mm outside diameter primary pipes.

Rather than forcing exhaust gases through an abrupt change in shape, the internal taper creates a smooth transition between the cylinder-head port and tubular primary.

This attention to the beginning of the exhaust path is just as important as increasing pipe diameter further downstream.

Designed Using 3D Scanning & CAD

Packaging eight long, genuinely equal-length primary pipes into the confined E9X M3 engine bay requires considerably more than conventional fabrication.

Infinity Design began development using detailed 3D scans of the S65 engine and surrounding engine bay.

These scans were brought into CAD, allowing the position and routing of each primary to be developed accurately within the available space.

This digital development process makes it possible to optimise:

• Primary length

• Primary routing

• Collector positioning

• Engine-bay clearance

• Cylinder-head access

• Installation requirements

• Overall exhaust volume

The final geometry could therefore be established digitally before progressing into physical manufacture.

Designed & Manufactured In-House

The V4 isn't an outsourced product carrying an Infinity Design badge.

The headers are designed and manufactured by Infinity Design within its own facility, giving direct control over development, fabrication and final quality.

Fabrication uses high-end argon gas-purged welding with full penetration, helping produce strong, clean and consistent welds throughout the system.

For a component subjected to extreme exhaust temperatures, vibration and repeated thermal cycling, manufacturing quality is every bit as important as the underlying geometry.

Improved Installation & Serviceability

Performance wasn't the only consideration during the V4 redesign.

One of the major practical improvements is better access to the cylinder-head studs and retaining nuts.

The primary routing has been revised so that, when the correct fitting sequence is followed, all retaining nuts can be accessed using normal workshop tools.

This makes installation considerably more straightforward and reduces the need for specialist or modified tools simply to access the manifold hardware.

It's a small detail from a performance perspective, but an important one for the technicians actually installing and maintaining the system.

Performance

The V4 builds upon a header design already proven to produce substantial gains.

Independent testing of the previous V3 system across numerous S65 applications demonstrated consistent gains of approximately:

+30–40 hp

Infinity Design does not claim that the V4 will make additional peak horsepower simply because it is the newer product.

Instead, the V4 provides a more refined solution with:

• True equal-length primaries

• Greater overall exhaust volume

• Larger collectors

• Improved port transitions

• Increased capacity for large-displacement engines

• Improved installation

• Refined exhaust tone

For us, this is a far more credible approach than redesigning an already successful product and automatically attaching a larger horsepower claim to it.

Key Features

• Developed specifically for the BMW E9X M3 S65 V8

• Latest evolution of the proven V3 header

• V3 independently demonstrated approximately 30–40 hp gains

• 100% equal-length primary design

• 730 mm centre-radius length for every primary

• 42 mm primary pipe diameter

• Stepped to 45 mm approaching the collector

• Larger F1-style slip-on collectors

• Increased collector length and internal volume

• CNC-machined cylinder-head flanges

• Internal transition from oval exhaust port to round primary

• Designed using 3D engine and engine-bay scans

• CAD-developed primary routing

• Designed and manufactured in-house

• Argon gas-purged welding

• Full-penetration welds

• Improved cylinder-head stud access

• Installation possible using conventional workshop tools

• Suitable for standard and modified S65 engines

• Designed to support large-displacement builds up to 5.8 litres

• Smoother, more refined exhaust tone

Manufacturing Lead Time

Each V4 header system is manufactured at Infinity Design's own facility.

As of April 2026, customers should allow approximately a six-week manufacturing lead time.

Lead times can vary depending on production demand, so please contact PERON before ordering if you require the system for a specific build date or workshop booking.

Infinity Design x PERON

At PERON, we work closely with Infinity Design, supporting development through technical feedback, testing, datalogging and access to the PERON Technology Centre and our Dynojet 424x linked dyno facility.

The V4 Equal Length Header is exactly the type of product this relationship is built around.

It doesn't replace a successful V3 simply to claim a bigger horsepower number. Instead, it takes an already proven concept and improves the areas that matter from an engineering perspective – exhaust pulse consistency, flow capacity, collector design, manufacturing, installation and support for the next generation of high-capacity S65 engine builds.

For customers looking to extract the full naturally aspirated character and performance potential from the S65, the V4 represents Infinity Design's most developed equal-length header package to date.