S55 Upgraded Twin Turbos
We previously wrote a post about modding an S55 to make 600+whp on stock turbos. It’s pretty insane what the S55 accomplishes on stock turbos. However, it’s simply not enough for some. If you maxed your turbos and still want more then upgraded turbos may be for you. While the S55 is a strong engine, upgrading to larger turbos comes with serious risks. In this article, we’ll explore the various upgraded twin turbo options along with the power, risks, and cost of each.
*KRATOS Twin Turbo setup pictured above
A Little About the S55 Engine
We wrote a similar paragraph in our upgraded N54 twin turbo guide, and feel it’s important to state for the S55, too. First, the S55 is a beautiful engine. It really is a marvel of modern turbo engines. After all, how many mass production 6-cylinder engines make 600+whp with a tune and basic bolt-ons? Not many…maybe not any other than the S55. 600whp is already serious power. Additionally, the N54 shattered expectations in the tuning world. Of course, the S55 powering the flagship M3 had to be better. And it is – way better.
However, we’re going to bring things back to reality in this post. We may not say what readers want to hear, but we’re sure as heck going say what must be said. The S55 is far from indestructible. If you want to upgrade your turbos to run a more reliable 600whp – great. If you’re looking to push the S55 to 700+whp – we wish you the best of luck. Things aren’t going to be cheap. That kind of power is going to put some serious stress on OEM components. Depending on torque, the DCT will be past its limits. It may only take one knock to send a rod through the block. We ask that you please consider the implications prior to pushing the S55 to and beyond its limits. Can you afford and/or are you willing to drop a new motor into the car?
S55 Upgraded Twin Turbo Setups
Now that we got that out of the way, let’s dive into the exciting part. We’ll break down the twin turbo setups based on the following goals:
- “Modest” 600-700whp Twin Turbo Setup
- 700-850whp Twin Turbo Setup
- “Full Send” 850+whp Twin Turbo Setup
We’re big believers in keeping turbos within their efficiency range and not pushing them to the absolute limit. That said, if your initial goal is 600whp but you plan on eventually pushing things beyond 700whp then you may consider opting for larger, more capable turbos. Keeping turbos in their efficiency range helps with reliability and longevity. This is not only true for the turbos themselves, but also for the S55 engine. However, we also do not recommend going too overkill. Choosing S55 twin turbos capable of 900whp will introduce unnecessary lag if you’re planning on keeping them at 650whp.
It’s simply something to consider prior to pulling the trigger. Understand your goals and choose twin turbos that safely meet those goals. Consider turbos that allow breathing room for your goals, but don’t get too excessive.
“Modest” 600-700whp S55 Twin Turbos
We’re referring to this power range as modest since the S55 can eclipse 600whp on stock turbos. Though, even if your goal is low 600’s, there are still many benefits to running upgraded turbos. Some benefits to S55 upgraded turbos include:
- Top-end power improvements
- Flow more air at an equivalent PSI
- Turbo & Engine Longevity
We’ll give top-end power its own section just below and scan over the other two points quickly. PSI isn’t the only measure for turbochargers. The volume of air is also very important. All else constant, larger turbos will flow higher volumes of air at the same PSI when compared to smaller options. Turbo & Engine longevity tie into the previously mentioned benefits. Volume is easier on the engine as compared higher pressure (PSI). Additionally, larger turbos offer top-end improvements. You can make more power with less torque if you shift the curve right. We’ll touch on this again at the end of the below dyno comparison.
S55 Top-End Power
Larger, more efficient turbos often make more power on the top-end. Most S55 stock turbos making 600+whp are running the turbos outside their efficiency range. This is evidenced in the below dyno comparisons:
Stock Turbo S55
This Jordan Tuned stock turbo S55 is no doubt making some impressive numbers. However, the turbos simply cannot keep up on the top-end. They start dropping torque just after 4,000 RPM’s. Torque then falls off a cliff at 6,000+ RPM’s and brings power down with it. To note – you’ll see below that the bone stock S55 actually holds its power until redline. However, that’s not the case when the stock turbos are pushed towards their limit.
Pure Turbo S55
This is a dyno from back in 2014 on Pure Turbos. As a side note, this was obviously in the early developments of the S55. Pure’s turbos have since been improved to make significantly more power. Nonetheless, this dyno paints a good comparison. Even on early developments the top-end power improvements are notable. Yes, torque still drops off fairly quickly. However, power remains much flatter. It also makes more peak power than the above example despite a lower peak torque number.
Circling back to previous comments – shifting the curve right is generally easier on the engine. The first dyno shows a stock turbo S55 making 600whp and 640wtq. Hypothetically, let’s assume bigger twin turbos could hold that same 640wtq all the way to redline:
WHP = WTQ x RPM / 5252
640WTQ x 7500 RPM / 5252 = 913.93whp
If upgraded turbos could hold that torque until the S55’s 7,500 redline then the engine would make a whopping 913.93whp. Compare that to the stock turbos 600whp and the benefits of shifting (or holding) the torque right are massive. Torque is a measure of force. That force is tied to the stress you’re subjecting the engine to. Horsepower is simply the ability to do work and is determined by the above equation. In summary, horsepower isn’t what dictates an engines limit…it’s torque. The hypothetical upgraded turbos boost horsepower by over 50% without subjecting the engine to additional peak force. More on this later, but of course there is a trade-off. You’re going to need large turbos to efficiently make that kind of torque on the top end. Of course, larger turbos come with a higher boost threshold and more lag.
Recommended S55 Supporting Mods for 600-700WHP:
- Downpipes & Intake
- Heat Exchanger & Intercooler
- Port Injection w/ E50+ fueling
- Clutch upgrade (for DCT S55’s)
- Crank Hub
If you’re running on the lower end of this power range then you can likely get away on stock fueling and stock DCT clutches. However, anything above 650whp is likely to push the fueling beyond its limits. The DCT also begins slipping around 650-675wtq.
600-700WHP S55 Twin Turbo Options
If you decided somewhere around 600-700whp is your goal then the following turbo options are great choices. For those who want to push closer to the 700whp mark may consider opting for the turbos in the next section. Additionally, the quoted horsepower will assume proper tuning and fuel. If you’re running 93 octane you’re going to need more turbo to make the same power. As such, if you’re looking to make 600+whp on 93 octane you may consider the more capable turbos later on in this post.
1. S55 Weistec W.3 Twin Turbos (600-650whp)
Weistec is well known in the Mercedes community, and recently began developing products for BMW, too. Their S55 W.3 turbos use the stock turbo frame which is machined to fit a larger CNC machined impeller wheel. Dyno testing shows these turbos making around 585whp on 93 octane with meth injection and 21psi. That was also done on a Mustang dyno, which are known to read a bit lower than dynojets. As a newer offering, we weren’t able to find too much other data. However, with better fueling and a bit more boost these turbos are surely capable of 600-650whp. We suspect they could be pushed beyond 650whp for occasional glory runs.
2. S55 Pure Stage 2 Turbos (650-700whp)
Pure Turbos offer upgraded turbos for most modern, turbo BMW engines. They’ve earned a good reputation by building quality turbos with proven results. Pure stage 2 and stage 2+ turbos are likely the most common upgraded turbos found on the S55. We’ll discuss the stage 2+ option in the next section. The standard stage 2 turbos will efficiently make 650-700whp with proper supporting mods and fueling. Some have even pushed these beyond 750whp, so they’ve definitely got some breathing room. The below link has tons of dynos and results for the Pure stage 2 S55 turbos.
3. S55 Full Race Turbos (625-675whp)
These turbos may not be available much longer. We’re not familiar with Full Race but it sounds like they’re working on liquidating their inventory as they have not sold well. However, they’re worth a mention since they’re as close to OEM as you can get. None of the turbo components are custom or remanufactured. They are all 100% brand new components from the OEM supplier, Mitsubishi Turbos. However, they use a 47mm turbine and 56mm compressor wheel (as compared to 43 and 51 for the stock S55 turbos).
700-850WHP S55 Twin Turbos
Breaking the 700whp barrier is beginning to near the upper limits of the S55 engine. Again, torque is really the determining factor and that’s where things get interesting. These turbos are going to make their peak power well north of 6,000 RPM’s. However, they’re still capable of making massive peak torque in the mid-range. Ultimately, you have a couple of options. One, limit boost in the mid-range as to keep torque under 700 to the wheels. They will still make big top-end power with the right tuning (as we touched on previously). Two, build your engine and unleash the turbos full potential.
Of course, there are still considerable risks to pushing 650-700+ wheel torque through a stock S55. The engine may let go at that torque. However, 650 torque should be a relatively safe limit for the S55 with proper tuning, fueling, and supporting mods. 700 torque is starting to push the upper limits. That’s kind of the grey area where you have to accept the higher risk or choose to build your engine up-front. And that’s not the only consideration.
Recommended S55 Supporting Mods for 700-850WHP:
- Full bolt-ons (DP’s, intake, intercooler, heat exchanger, etc)
- Crank Hub
- Port injection w/ 100% E85
- Upgraded clutch packs
- Built engine
- Lots of tuning work*
The turbos themselves may not be much more expensive. However, the list of supporting mods adds up quickly. Port injection is required to support 700+whp, which starts around $1,200 and can run up to $2,000+. Upgraded clutch packs for DCT’s run in excess of $4,000 – not including install. Axles are also over $1,000. Then, you need the proper wheel and tire setup to make the power usable. Again, a built motor should be something to seriously consider. That alone can run $5,000-10,000+ depending how far you decide to build it out. Finally, extensive tuning is recommended for these setups. It’s going to take time and effort to dial in a quality, safe tune.
700-850WHP S55 Twin Turbo Options
1. S55 Pure Stage 2+ Turbos (750-850whp)
Pure Turbos makes the list once again with their quality, highly proven stage 2+ S55 upgraded turbos. Expect to trade-off a little bit of spool with these turbos in favor of the top-end power. One of Maximum PSI’s M3’s managed a staggering 899whp and 800wtq with these turbos on a built engine. An M4 made 682whp on pump gas. Impressive numbers no doubt, but we recommend keeping these turbos in the 750-850whp ballpark. This is also an excellent turbo option for anyone looking to make low 700whp. All around – it’s tough to go wrong with these turbos.
2. S55 Doc Race Turbo Kit (800-900whp)
Price: $7,495.00 to $8,995.00
Doc Race will make another appearance in the higher horsepower section. Their turbo kits actually use Garrett turbos rather than custom S55 turbos. For those not familiar with Garrett Turbos – they’re very popular on many platforms. Many N54 single turbo conversions run a Garrett turbo. Additionally, Doc Race builds some awesome kits. The quality of this kit is absolutely there.
We’re focusing on the Gen2 GTX2867R and Gen2 GTX2871R turbo options in the Doc Race kit. These turbos are capable of making 800-900whp with Doc Race’s turbo kit. The price point is definitely high, but these are quality turbo kits with awesome, highly proven turbos. Additionally, the turbos can be swapped down the road. You don’t have to get the full kit again and the turbos themselves are much less expensive.
“Full Send” 850+WHP S55 Twin Turbos
These setups are quite literally full send. Not many of these S55’s are out there. You’re now entering unknown territory where often times information is limited or non-existent. This is especially true if you’re shooting for 1000+whp. The S55 supporting mods are more or less the same as we discussed for the 700-850whp setups. However, things like built engines and clutch packs become a necessity rather than a means of engine safety. A built cylinder head is also an important piece to the puzzle.
We’ll keep things short here. Ultimately, expect these setups and supporting mods to run into the territory of $25,000+. It will take serious dedication and lots of time. You’ll need a deep wallet, patience, and a lot of knowledge and/or assistance from others.
1. S55 KRATOS Competition Turbos (800-1100+whp)
First off, these things look beautiful (from the first image in the article). Not that it matters much once they’re bolt onto the car. However, it shows the level of detail and quality which is a must at this price point. We also love the dynos and data they provide.
This dyno was done on a stock S55 engine with midrange torque limited for engine safety. We appreciate KRATOS posting this dyno with their insights added. No marketing BS by turning up the turbos to 100%. Anyways, this is a great example of what to target if you’re sticking with a stock motor. These turbos can be turned up even further to unleash the true potential in the mid-range and more power up top. Though, that’s territory that should only be explored on a built engine. Speaking of exploring the limits of these turbos…they made 1150whp and 985wtq on a built S55. As far as we’re aware – that’s still the S55 twin turbo record. Check it out here.
There’s more, too. KRATOS turbos are in use on a Strom Motorsports endurance M4 race car. Apparently this M4 took first place in a GT4 class 12 hour race. Pretty impressive. The price may be tough to swallow, but this is an exciting development. We really like these turbos.
2. S55 Doc Race Turbo Kit (1000-1200+whp)
As mentioned, Doc Race is making their second appearance on the list since they utilize Garrett Turbos with a plethora of options. Choose from these turbos to meet your 1000+whp goals:
GTX3076R (1000hp), GTX3576R (1100hp), GTX3582R (1200hp)
Gen2 GTX3071R (1050hp), Gen2 GTX3076R (1150hp), Gen2 GTX3576R (1300hp), Gen2 GTX3582R (1400hp), Gen2 GTX3584RS (1600hp)
Again, this is a high quality kit with awesome turbos. The Garrett turbos can make the power, but the previously mentioned KRATOS turbos made the S55 world record 1150whp for twin turbos. It’s going to take a lot of work to get the platform to fully realize the potential of these larger Garrett turbos. For context, some N54’s run the Garrett Gen 2 GTX3584RS turbo as a SINGLE turbo setup. Here is an N54 making 800+whp with the single turbo.
Point is – that’s a massive turbo to be used in twin turbo configuration on a 3.0L engine. Imagine having to spool two of those. It would probably take 5,000+ RPM’s to even get these large Garrett turbos to peak boost, and that’s a conservative guess. It doesn’t make for a whole lot of usable power. You’d need a very strong built engine that could handle at least 8,000 RPM’s and ideally more. With time the S55 will experience further developments and improvements that may allow twin turbos to achieve 1,200+whp. There are turbo options that will meet those goals. However, there is still a lot of testing, development, and improvements that need to occur before the S55 is going to reach the full potential of these turbos.
BMW S55 Upgraded Turbos Summary
The S55 is one hell of an engine. However, it’s also far from indestructible. Upgraded turbo setups have the ability to easily push the S55 to and beyond its limits. We ask that you understand your goals, the risks, and costs prior to opting for upgraded turbos. There are modest setups that can make a reliable 600-700whp with minimal supporting mods. The list of supporting mods grows drastically when you look to push 700+whp. We highly recommend building your S55 prior to pushing this power OR run a conservative tune with midrange torque limited.
Finally, those looking to push 850+whp are entering relatively unknown territory. These setups require extensive tuning and a deep wallet. A built engine becomes a necessity. You may find yourself taking additional risks and experimenting because the answers or data do not exist. You’ll be one of the few truly pushing the platform towards the next level.
All that said, the most important aspect is understanding your goals and what it takes to get there. Nonetheless, the S55 is a beautiful engine and upgraded turbos will boost it to the next level. It’s tough to go wrong with any of the turbos mentioned throughout this post.