"In this Product Series, I document the development, unboxing and installation of the InfinityDesign Long Tube S85 V3 headers.

This entry covers backstory to the development of InfinityDesign's S85 headers, the V3 revisions to unequal length primaries and its effect on sound."
- Matt

The S85 and the S65: BMW M's N/A pinnacles. 

BMW M engineers managed to create equal length headers for the S85 and S65. Yet, like many street engines, it needed to meet emissions targets.

The V10 has primary cats right after the merge collectors and are built into the headers. The primary cats shortened the overall design of the OEM headers and forced BMW M designers to crimp and reduce the diameter of the primaries in sections of the design. 

The design immediately impacts exhaust flow and pressure - inhibiting potential performance from the S85B50. 

BMW M engineers still achieved an equal length design to obtain the signature exhaust note we love. 

The gains are here. 

It's been common knowledge in the M5 V10 communities that performance gains are mostly found by replacing the primary cats and improving upon the stock header design with a a lengthier runner design.

The V8 benefitted from the experiences learned with the V10 by placing the primary cats on the front pipes and created a full unobstructed equal length header design.

Primary cat delete. 

Tuners initially released primary cat delete pipes that were welded onto the OEM merge collectors. This retained the signature S85 sound, and enhanced performance, yet it wasn't optimal.

The primary cat is removed by cutting it out after the merge collector. A pipe is most often clamped or welded to connect with the section 1. 

The original V1s.

Many exhaust manufacturers released long tube headers in various runner and merge collector design. These were the better performing solution, extracting the most power from the V10. Unfortunately it sacrificed the tone of the V10 as it sounded quite harsh.

InfinityAutoDesign initially designed the optimal solution for S85 owners with their V1 headers. They were able to retain equal length primaries and along with it, the signature S85 exhaust note, while being the best performing header solution on the market.

They opted to to retain an even diameter across the runners, while achieving the required length through unique curvatures for max performance.

Unfortunately, the V1 design was problematic to install, and would come into contact with the steering column, amongst space related issues. 

The V3 same fundamental design changes that affect the signature sound. 

V3 Design Revisions. 

The design went through multiple design improvements as the primary hurdle was installation and engine bay space constraints. The V3 design changes were implemented to improve the jig's accuracy and precision in order to make installation easier. 

Revised, unequal primaries length.

Unfortunately, InfinityDesign chose to revise the primaries length and the primaries were now unequal length on 2x primaries, beyond the original deviations from BMW. 

Ultimately, this changes the signature sound from the original equal length headers, to a coarse, less high pitch tone most similar to an R8 V10 and Dodge Viper. 

Anderson Dick, a Brazilian Automotive Youtuber, measured and performed tests to compare OEM versus Infinity. You can watch it here. I have compiled his results in the table below. 

Below are pictures from the V3 design I received. 

The initial design had issues with 02 bungs placement and and made it time intensive to install. 

InfinityDesign tested various runner diameters to ultimately settle on 42mm for optimal performance on 5.0 displacement and strokers.

New merge collectors

The V3 also eliminated springs on the merge collectors in favour of a slip-on fit. They are sealed at the collector using high temp silicone to allow heat expansion.

As of June 2022, all V3 headers order are now shipped with bolts and nuts with holes on the primaries and merge collector to secure and seal them together. Using high temp silicone is still required. 

The headers are made in Pakistan from 304 stainless steel. They are TIG welded. The weld quality isn't the greatest, showing signs of excess heat.

.Each runner is individually tagged and aligned to slip into the merge collector.

Up next: I discuss the installation process and first impressions.