If you have been researching the 4N Motorsport single turbo kit for the BMW F82 M4 or F80 M3 S55 engine, you have found the right page.
We installed the 4N Motorsport bottom mount single turbo kit on a customer's F82 M4 at Tysautoworks Performance and documented the entire build from the moment the stock twin turbos came out to the final dyno pull. The results were 710 wheel horsepower. Here is everything you need to know about the 4N Motorsport kit, the installation process, the critical tips that the instructions do not cover, and what this conversion actually does to the character of the S55 engine.
What Is the 4N Motorsport Single Turbo Kit
The 4N Motorsport single turbo kit is a bottom mount single turbocharger conversion for the BMW S55 engine found in the F80 M3 and F82 M4. It replaces the stock twin scroll twin turbocharger setup that BMW installs from the factory with a single large turbocharger mounted at the bottom of the engine using a new custom exhaust manifold and supporting hardware.
The kit includes the single scroll exhaust manifold, the turbocharger itself, oil feed and return lines, coolant lines, a wastegate actuator, and the supporting hardware required to complete the conversion. The 4N Motorsport manifold is specifically engineered with runners designed to be as close to equal length as possible, which is a significant factor in both the power output and the distinctive sound character that the 4N Motorsport kit is known for in the S55 community.
The quality of the 4N Motorsport kit is immediately apparent when you take it out of the packaging. The welds on the manifold are clean and consistent. The hardware is properly specified for the application. This is not a budget single turbo kit that cuts corners on the components that see the most heat and stress. It is a purpose-built system designed for the specific demands of the S55 engine under serious boost levels.
Why BMW M4 and M3 Owners Choose the 4N Motorsport Kit Over the Stock Twin Turbo Setup
This is the core question that every S55 owner asks before committing to a single turbo conversion of any kind, and the 4N Motorsport kit specifically.
The stock S55 twin scroll twin turbo setup is genuinely excellent for what BMW designed it to do. It provides fast spool, immediate power delivery from low RPM, and a linear, predictable power curve that makes the F80 M3 and F82 M4 so easy to drive quickly in a wide range of conditions. The twin turbo character is instant and accessible.
The 4N Motorsport single turbo conversion trades that instant hit for something different. As we described it during our build, it trades the instant twin-turbo response character for the classic pull-to-redline thrill of a big single. The power arrives differently, building progressively and then continuing to climb well past where the stock twin setup runs out of breath. The single turbo pulls through the RPM range in a way that a twin turbo setup simply cannot match at the top end.
This is either exactly what an S55 owner wants or exactly what they do not want. The 4N Motorsport single turbo kit is for the enthusiast who wants a different kind of S55 experience, one that prioritizes the drama of a big single's power delivery and the sound character that comes with it over the immediate accessibility of the stock twin setup.
The 4N Motorsport Kit Installation, What the Process Actually Involves
The single turbo conversion on an S55-powered F82 M4 using the 4N Motorsport kit is a serious job. It is not a weekend shade tree project and it requires genuine familiarity with the S55 engine and its supporting systems to execute correctly. Here is the real process including the critical tips that you will not find anywhere in the kit instructions.
Pre-installation bench work
Before the car is touched, do as much preparation as possible on the bench. The 4N Motorsport manifold should be inspected and the turbo should be prepared separately before either goes near the car. Removing the cold side of the turbo housing before installation and keeping it somewhere safe prevents accidental damage to the turbine fins during the installation process. These fins are the most vulnerable part of the entire assembly during installation and damaging them means buying another turbo.
Removing the stock twin turbo setup
The stock twin turbos come out first. This is the most time-consuming part of the build. The exhaust studs on the S55 should be removed before the new 4N Motorsport manifold goes in. This is not covered in most installation guides and it makes fitting the new manifold significantly easier than attempting to work around studs that are in the way of getting the manifold into position correctly.
Installing the 4N Motorsport manifold
The 4N Motorsport single scroll manifold goes in once the stock components are cleared. The manifold fits tightly in the S55 engine bay and needs to be worked into position carefully. Rushing this step risks scratching or damaging the manifold or surrounding components.
Mounting the turbocharger
The 4N Motorsport turbocharger is large. Seriously large. Getting it into position requires careful maneuvering and the help of someone who can manage the weight of the turbo while you guide it into the correct orientation on the manifold.
One critical step that catches people out during the 4N Motorsport installation is the wastegate actuator rod. The kit uses a different wastegate setup than the stock twin turbo system and comes with a replacement actuator rod. This rod must be correctly positioned before the cold side housing goes on. When putting the front housing on the turbo, the rod must be lined up with the hole on the hot side of the wastegate. If you miss this step and fully install the cold side housing before checking the rod alignment, you will have to take the housing back off to correct it. Check the rod alignment every time before the housing goes on. This is the single most important installation tip for the 4N Motorsport kit that is not clearly covered in the instructions.
Oil and coolant connections
The 4N Motorsport kit includes an oil feed line to the top of the turbo and all necessary coolant connections. The oil feed line takes a 14mm wrench to properly tighten. The blockoff ports for the old twin turbo drain locations need to be addressed correctly to prevent oil management issues after installation.
Upgraded injectors and valve cover
A single turbo conversion at serious power levels requires upgraded injectors to support the fuel demands of the new setup. On this build we addressed the valve cover and valve cover gasket at the same time, which is straightforward on the S55 if you have done the job before.
Spark plug gapping
This is a step that many people underestimate. For stock configuration, BMW gaps S55 spark plugs at 0.024 inches. For an off-the-shelf tune, that gap closes to 0.022 inches. As power output and boost pressure increase, the gap needs to be closed further to ensure consistent ignition at the higher cylinder pressures involved. The 4N Motorsport build on this car was started at 0.022 per the tuner's recommendation. Getting this wrong affects how reliably the engine fires under boost.
Wastegate linkage adjustment
Before the downpipe goes on, the wastegate linkage needs to be adjusted using a laptop connected to the appropriate software for your specific tuner's requirements. This adjustment is critical for proper boost control with the 4N Motorsport kit and skipping it causes boost management issues that affect both power output and reliability.
The 4N Motorsport Kit Dyno Results on Our F82 M4 Build
Here are the real numbers from our build.
The car went to the dyno on day four of the build after the 4N Motorsport kit installation and initial tuning work by Steve from Wedge Performance.
First pull of the day produced 667 wheel horsepower. That number alone should tell you the capability of the 4N Motorsport kit. Starting at 667 on the first pull before serious tuning work had been done is a strong baseline.
Through the session, working the tune progressively while monitoring data, the car climbed to 676, then continued working toward the team's goal. The final result of the day was 710 wheel horsepower.
The tuner also demonstrated the improvement between the first and final pulls. At 5,500 RPM, the car went from 564 horsepower on the first pull to 682 horsepower by the final pull. That mid-range improvement illustrates exactly what proper tuning does for a 4N Motorsport equipped S55 and why the tuning component is as important as the hardware itself.
710 wheel horsepower on the 4N Motorsport single turbo kit. The goal was 700. The car cleared it with room remaining.
What the 4N Motorsport Kit Does to the Sound of the S55
The sound change from the stock S55 twin turbo setup to the 4N Motorsport single turbo is significant and immediate. The equal-length runner design of the 4N Motorsport manifold is specifically engineered to produce a sound character that is distinctly different from the stock twin turbo setup and from other single turbo kits that do not prioritize manifold runner design.
The S55 with the 4N Motorsport kit sounds like a different engine. The twin-turbo character that BMW engineered into the stock system is replaced by the deeper, more mechanical sound of a large single spool building boost through the RPM range. It is one of the most noticeable transformations available for the F82 M4 or F80 M3 in terms of pure driving soundtrack.
Who the 4N Motorsport Single Turbo Kit Is For
The 4N Motorsport kit is for the S55 owner who has identified exactly what they want from their M4 or M3 and that thing is a different power delivery character, a higher power ceiling than the stock twin setup can provide, and a sound that sets the car apart from every other S55 on the road.
It is not for every owner. The stock twin turbo S55 is genuinely excellent and the 4N Motorsport conversion is a significant modification that changes the fundamental character of the car. But for the owner who has done the research, driven behind the decision, and decided that a large single turbo on their S55 is what they want, the 4N Motorsport kit is one of the most complete and well-engineered options available for this application.
Watch the Complete 4N Motorsport S55 Single Turbo Build
The complete build is documented across multiple videos on the Tysautoworks Performance YouTube channel, covering every step from day one through the dyno session.
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