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S50/M50 Turbo Tuning

Posted: Fri May 08, 2020 8:45 pm
by h82crash
Hello, I have collected most of the parts for a turbo build on my 95 M3. I will either use the S50 or build an M50b30. 506 DME. I have a 540i MAF and plan on using 42# injectors and pump gas. I believe that will get me to my goal of 350-400 whp. I have been researching the tuning and I think all of the info I have been reading is overwhelming. It is, of course, on tuning the factory DME I am referring to.

I have also looked into some stand-alone ECU options, and those have their own challenges. I have successfully DIY tuned a Megasquirt system so I am familiar with tuning but it has been 5 years since.

So, to help me decide, I have some questions.

Is your software more user friendly than TunerPro? I'm hoping I can just tune. I have read your papers on calibrating for MAFs and scaling injectors, but I think you already have files for my choices.

It seems like you offer great support. If I run into problems, will you help with issues and tuning?

Will my 540 MAF work on forced induction?

Data logging, what do you recommend?

Thank you.

Re: S50/M50 Turbo Tuning

Posted: Sat May 09, 2020 1:55 am
by Renovelo
We're glad to help answer any questions! Of course we think DTS is easier to use than TunerPro! TunerPro has a few shortcomings that we addressed. One of the big ones is the ability to edit axes within the table itself. Some people have figured out how to get TunerPro to do this by creating separate curves solely for the axes. However, this is not very intuitive during the tuning process. In our software, you can edit the axes directly in the table.

Another gap that TunerPro used to have (not sure if they've fixed it yet) was with very large tables like the MAF curve. When we were first developing DTS, we remember that when tracing the live MAF value using an emulator, it would stop advancing at some point later in the table. It was almost as if there was a maximum number of cells that it could handle.

Another aspect that is important to remember is that TunerPro is built as an open source tool for any platform. Don't get us wrong...this is a great tuning tool, but it requires huge amounts of input from the community. In other words, you have to rely on the community to develop XDF files. You also have to trust that whoever created those file knew what they were doing during the reverse engineering process. Back when we were heavily involved in OBD1 tuning, there were only a few trustworthy XDFs for OBD1 BMWs. There were still a few errors in those and they didn't have all of the tables identified that we do (like transient fuel tables and fuel timing advance tables). We spent countless hours reverse engineering these DMEs and thoroughly tested on a HIL (hardware-in-the-loop) bench setup where we could simulate all of the engine signals going in/out of the DME. Can you trust that the community has done this in as much detail as we have? And if you have a problem with an XDF file with TunerPro, who are you going to go to for support? The folks at TunerPro are not responsible for the content in any XDFs.

As you've seen, we stand behind our products and will provide indefinite support. If you have any issues, we are usually very quick to respond. If you find bugs with our tools, we can usually release new versions within the next day.

However, unless we have direct experience with tuning a specific platform, we usually don't advise customers on "how" to tune their vehicles. This is to protect ourselves as well as our customers. When we do have direct experience tuning a certain platform, we make that knowledge readily available on our forums. As you can see, we have a couple of OBD1 base tunes available for both larger injectors and MAFs.

You'll likely find that the 540i MAF will hit its flow limitations far before your turbo hardware will. We would recommend something better suited such as the HPX PMAS MAF. When we were tuning our E36 M3 shop car for a GT35R turbo, we bought a random MAF off of the forums and tuned for it. We're not 100% sure, but it looked very similar to this one:

As for data logging, this is the big problem. We actually tried developing a data logging tool for OBD1. Unfortunately BMW's diagnostic protocol in that era was barely capable of doing just diagnostics, let alone data logging. The refresh rates were incredible slow and impractical for the needs of a tuner. There are several aftermarket systems available that are more geared toward the racing community. We're not familiar enough with any of them to make a recommendation.

Re: S50/M50 Turbo Tuning

Posted: Sat May 09, 2020 11:41 am
by h82crash
Thank you! That was very informative. While I'm sure my trubo, gtx3584r, could eeasily exceed the limits of the 540 maf, is it adequate for my power goals? I mean, it could easily exceed the capability of of the transmission, driveshaft, differential, etc. and I'm not prepared to be swapping all that out so I'm keeping the power modest.
I understand and was not expecting you guys to tune it for me.
I'm leaning this direction, though. Thanks.

Re: S50/M50 Turbo Tuning

Posted: Sat May 09, 2020 2:08 pm
by Renovelo
It's difficult for us to say for certain if it will meet your power goals. We've never tried running that MAF at that power level. It may work in a draw-through setup but we highly doubt it will work in a blow-through setup. You can compare the differences in flow rates here: viewtopic.php?f=11&t=19

Re: S50/M50 Turbo Tuning

Posted: Sun May 10, 2020 9:21 am
by h82crash
After some research, I must agree with you regarding the MAF. Looks like I"ll be going with the HPX. Plenty of data on that one for MAF transfer function. How do you tune without data logging?