Challenges of tuning for turbo (MS45 and MSS5x)

Get detailed info on tuning your DME
Post Reply
Site Admin
Posts: 180
Joined: Thu Aug 08, 2013 7:02 pm

Challenges of tuning for turbo (MS45 and MSS5x)

Post by Renovelo »

One of the most common questions we receive is "can I use ByteTuner to tune my car for a turbo setup?".

Tuning for a turbo setup is tricky for any DME which was originally naturally aspirated from factory. However, for almost all DMEs supported by ByteTuner, there are many examples in the market where people have successfully tuned for a turbo using the stock DME. The exception is MS45 and MSS5x. The two main reasons have been the lack of a MAF sensor range hack (for MS45) and the ability to manage the O2 sensors from two banks.

Regarding the MAF range, we are the first company in the world (that we know of) to publicly release a solution for this problem for MS45. With this hack, you can modify the MAF transfer curve to support any sensor up to 2048kg/hr! You can read more details here: ... =11&t=1717

Regarding O2 sensors from two banks, there is no solution to this yet. In almost all other DMEs supported by ByteTuner, this was accomplished with a parameter which was implemented in the logic by BMW/Siemens to allow for many different exhaust configurations. This was because BMW offered these vehicles in many different markets around the world which had different laws regarding emissions and different fuel qualities. This is why it has been so easy to change the engine to run with the O2 sensor(s) measuring a single bank. This parameter does not exist in MSS5x. Although MS45 has this same parameter, it's not designed to provide the same functionality as far as we can tell. You can read a little more insights about this parameter here: ... =11&t=1752

Now, for supercharged setups, this isn't a problem because you will still maintain two banks just like the OEM setup. ByteTuner will allow you to delete the rear O2 sensors for racing applications. However, if you combine the banks (like a log-style turbo manifold does) with two sensors, you'll quickly run into issues with fuel trims. The DME expects the responses from the O2 sensors to be slightly out of phase with one another. When putting both O2 sensors in the same bank, the fuel trim from each bank will fight the other one and you'll end up maxing the trims. This is pretty well documented on the forums in other applications like MSS5x. If you try to take a single O2 sensor and split the signal, you'll run into similar issues. The only way we know of to truly solve this in the DME logic is to hack the firmware to make the DME think there is only one engine bank. Another method would be to trick the DME into thinking there are two banks using external circuitry which would be almost as challenging. Unfortunately, we have not attempted either method yet.

All that being said, we have seen recent proof from a shop which uses our products and they were able to successfully tune a turbo application for MS45. They did it with some mechanical ingenuity in terms of keeping the exhaust banks "separate". We can't share any more details because we imagine they want to make this announcement public themselves as it is quite an accomplishment. This will be the largest hurdle to overcome for any MS45 or MSS5x turbo application.
Posts: 8
Joined: Sat Jan 11, 2020 12:58 am

Re: Challenges of tuning for turbo (MS45 and MSS5x)

Post by d_cleverzz »

I would like to provide insight on this. For others reading.

I, and some other tuners have attempted to make tune calibration configurations to manipulate the use of a single bank o2. All of us, as far as we can tell, have failed, it never works. Like Renovelo stated in their post, this would require hard code changes. MS45.1 utilizes dual channel widebands, which on its own is far more complicated than a dual channel narrow band.
Which even if we couldn't change the configuration like on MS43, you can somewhat still trick and split signal, which I and a customer of mine have had some success with, but still in testing.

As far as MS45.1. If you are in the market for turbocharging your ms45.1 car, please consult your tuner before hand.
To inform the community, log style manifolds seem by far the most difficult and hardest to trick with very little to no success, so please don't jump on chinese log style or SPA manifolds at this time. At the time of writing this post, I have some last trick up my sleeve to try and remedy this. There are some other solutions as Renovelo mentioned, but these "solutions" should be kept proprietary.

I guess the point of writing this is for the average reader. If this is something you are debating to do, please reach out to your desired tuner (like myself or some others found within this forum) before hand so you can build the correct setup. MS45.1 is a very capable ecu which should definitely get more love, when done right, it works and drives beautifully.
Post Reply