Good to see this thread finally happened; I was going to start one myself, yet was postponing it until I have something worthwhile to share. My post will surely be long, please try to follow it, I will really appreciate any feedback.
For me that question first arose when I reached out to APR asking for a custom tune, as the ones available off the shelf matched the locally made race fuels poorly - for example, the cheap RON 102 blend did not see any improvement on APR 93 map, but was too risky to run on 100 map. Additionally, as far as I'm aware nobody has properly tuned for water injection yet (by properly adjusting ignition timing while carefully watching the EGT dynamics), instead resolving to very adhoc and risky stuff like running 93 octane with meth on 100 or even 104 tune.
Then comes the dual pulley. While being a rather trivial change hardware wise (many turbo guys would consider this a mere "boost up"), people use arcane stuff like ChipWerke piggybacks to prevent the ECU from bleeding excess boost. Additionally, boost in excess of 1.1 bar falls off the base map, which IMO is not a safe thing to do generally, and I mentioned this earlier (
here).
All in all, Continental ECU is very adaptable and many 3.0T guys were able to get away with all that stuff without major consequences, but in the most general sense the lack of custom tuning solution for this platform has handicapped this platform for a long time.
While SIMOS has some complexities with regard to tuning protection when compared to earlier ECUs, in my opinion the lack of custom tuning solution is mostly because large companies that were able to crack it are not interested in home flashing, and are much better off selling canned tunes to recoup their R&D costs.
That's enough for the introduction. From my interchange with APR i understood that no one among the big guys are really interested in giving you the tools of their trade, it's right against their profit model actually. So there is really no other choice other than develop a solution to this myself. This turned into a hobby project which at the beginning seemed insurmountable, but as time passes fewer unresolved issues remain. And here I will try to describe the grand scheme of things for people not familiar with chip tuning workabouts.
DOCUMENTATION
First and foremost, you can do little if you don't know where to see. There are internal documents in Audi which detail pretty much everything - from pin designations to every message sent on CAN bus. These are called Funktionsrahmens and are assumed to never be seen by anyone outside VAG, but we live in a world where everything can be stolen, so many of these can be purchased for a $200-300 fee on deep web or specialized closed forums. I currently have a copy of SIMOS 8.5 and DL501 Gen 2 funktionshrahmens, and gosh they are detailed - the one for the 3.0 TFSI is over 13k (yes, thirteen thousand) pages long, and it describes every memory location, every map and every operation algorithm there is.
These docs are used by Audi engineers to calibrate the engine, and having this info on hand thus allows you to tweak principally anything, provided you have the knowledge and tools. I'm really thinking of making a gratuity gift and sharing these documents for free, but I am not sure about legal consequences of that.
MAP PACKS
This is another component to a successful chip tuning - armed with the knowledge of what to tweak, you need to know where to tweak. The ECU file is a 2MB blob of binary data, and you need to know the exact locations. This information is available in A2L files, which are text files of special format which designate the binary location of all parameters described in funktionsrahmen, and are not purposed to be seen by anyone outside VAG too, but here we are. Sometimes they are converted to other formats like OLS (which is binary equivalent of A2L used by WinOls software) and are also available for trade. I have map packs for SIMOS 8.4 and DL501, which allows me to edit pretty much anything in my 2010 B8.
SOFTWARE & CABLES
Here things come cheesy - you need to download and upload your firmware, and there is no $20 cable for SIMOS flashing. You can try with professional chip tuning hardware like CMDFlash, MPPS, KESS etc. but this stuff costs thousands bucks when bought legitimately, and Chinese clones usually have issues. This is prohibitive for an enthusiast looking to tune his/her own car. Thus we B8 owners are simply unlucky to have an unpopular and complex ECU.
I'm a software engineer myself, so I took off to develop my own solution to flashing SIMOS and DL501. Having all the docs, this task is hard, but feasible. From hardware side all you need is a USB-CAN adapter like CAN hacker to talk to the ECU. But the flashing protocol, while described in functionsrahmen, is impeded with tuning protection, and I suppose that is the largest hurdle tuning companies have encountered on their way to OBD flashing without previous bench unlock.
Beating the tuning protection is a hard thing in itself, but luckily I don't have to - a friend chiptuner of mine has provided me with a full CAN bus sniffer log of a successful OBD flash. By reverse engineering it, I hope to get past this hurdle.
I also have purchased a salvage SIMOS 8.4 ECU off eBay to experiment on it - trying an unfinished software directly on my car sends chills down my spine, but I hope one day it wouldn't.
So, summing it up, having all the docs, map packs, custom written flashing software and a USB CAN adapter is basically all that is needed to provide a custom tuning solution for this platform. Given that you cheat a little (I mean peep into how the tuners have dealt with tuning protection instead of fighting it on your own) this is feasible for one software engineer to implement as a hobby project. I only imagine the possibilities that open when a whole community starts working on it in a typical open-source fashion - imagine custom tunes for basically anything, stuff like water injection, twinchargers, turbo conversions or Rotrex/Vortech instead of TVS1320, custom program switching or traction control, bigger throttle bodies, nitrous, etc. etc. etc. A whole world of possibilities which already exist in other car communities but have largely remained untapped on B8 S4 scene, with ridiculous stuff like piggybacks in their place.
So once I flash my experimentation ECU successfully I'm going to share my findings to the public, in hope that this platform will finally see something more diverse than a plethora of cloned 450 hp stage II cars. It's about time. The only thing I regret is that no one has accomplished that before me (that I'm aware of), so that I can just use an off-the-shelf solution.
So if anyone is willing to help make all of this happen sooner, let's work together. And to my understanding, OP, for now this is the only option for custom flashing we the B8 owners have.
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Originally Posted by bradsm87
DIY custom tuning
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