2011 AMG G55 Build

[FINOCJ]

speedkills previously posted:

[speedkills]

It was the portals. I think they tried to keep them as narrow as possible, and they were able to make the front narrower than the rears due to the brake configuration, but I prefer them the same track width, fixed now.

[speedkills]

Doing some reversing of the protocol on canbus C today. I want more information than I can get on the ODBC or chassis can-b so finally found a good point to access can-c and got to work. First up, where can I find CAN-C (powertrain canbus)? On my G55 it is near where your left calf would be if you were in the passenger seat, lower part of the center console.


TLDR, if you aren't interested in can bus you might just want to skip this post.





I rarely have an excuse to twist a pair of wires but when I do and use my drill to do it I always get a silly satisfaction out of it. There were two spare ports available in the can bridge so I went ahead and put two wires in, one to my AIM Sports PDM32 dash/power distribution unit, and one to my laptop so I could sniff the bus and see what messages were being broadcast on it.





For sniffing the can bus I am using a TouCan device, I don't know anything about these but it does everything I need at the moment.





I used some connectors I happened to have laying around the house that fit, but don't lock in like the correct connectors Mercedes uses do. I'll swap out to the correct connectors before I button everything back up.





This got me to a point where I could see the messages streaming over the bus in real time while fiddling with controls. I was most interested in initially just doing a proof of concept, making sure I understood how everything worked and could decode trivial messages so today I decided to just try to figure out how to decode the shift lever position. Once I was seeing the can data stream by I started moving the shift lever around and kept noticing message id 230 popping up, and luckily it was one of the smaller messages, only one byte. Smaller is better for me since I have no idea what I am doing, I figured that would make it easier to figure out how Mercedes is encoding the data. I saw the number 8 while sitting in park, and while I moved the shifter around it changed from 5-13 so this encouraged me to see if I could get it displayed on the AIM unit.





Unfortunately AIM only supports ODBC data for my G out of the box but they also have the capability to do custom can bus protocols, you just have to supply them. Well crap, here goes nothing.


Documentation is slim but I was able to stumble through adding a new message to the custom can protocol, I set it up to read message id 0x0230 and just convert the full byte to an integer then display it on the dash. To make it easy to see what was going on I setup a simple dash display and set the center-top section to display the data read from the can bus.








At this point I was pretty excited, it actually worked, I was able to move the shifter around and see the cell update on my PDM in real time. Only click the youtube link if you have 7 seconds to spare watching me move a shifter around.





As I did this I wrote down the values shown in the different positions and realized that I was only seeing values 5-13, which for anyone familiar with binary means you only need 4 bits, not the full 8 to transmit that information. Time for round 2 of PDM configuration changes, this time I told the PDM to only read the first 4 bits and then to map each value to a text string, so instead of 5 show D for drive for example.


I updated the decoder, added some friendly output mappings and gave it another go. If I do much more of this I will likely try to just make a DBC file by hand and import it into the program so I can store the code on github or something, it was pretty tedious doing this all in a GUI.





And now I can display the gear selector position on my PDM. It's not much, but even this I think I can use to hook up paddle shifters once I swap my steering wheel, I'm hoping I can just intercept the paddle presses and then drop a message onto the can bus identical to what is generated when pressing left or right on the shifter to make the paddles work. I also want to dig in further in the coming months and pull out some data I would like displayed that I don't currently have access to, trans fluid temp, stuff like that.


Here is a 7s video of my final result, I move the shifter around and you can see N, D, -, +, etc on the display as I move the shifter.





I likely won't do too many updates like this unless someone expresses interest as I realize I'm getting further into things interesting to programmers than your average car enthusiast.

[Jim]

COOL - I'd be curious for updates.

[Java]

Paddle shifters! This is the most unpredictable build thread ever.

[Jim]

Paul previously posted:

[speedkills]

I first had paddle shifters in my old Range Rover and unexpectedly fell in love with them. They are super fun in the canyons and faster off-road sections. I need to swap my steering wheel anyway to get rid of the wood on this one which I really dislike, and the one I found on ebay from a Mercedes car had paddle shifters so I figured I might as well try to hook them up. I have various useless buttons in the cabin too that I could hookup to other functions if I can figure out what messages they send on the canbus network, which seems fairly straightforward now if a little time consuming.

[speedkills]

I'm taking off for a trip to California to see family in a few days and dropped my truck off at Hoover Mercedes to have the headers installed as I have had my fill of exhaust work for the year. While they were at it I had them weld on my exhaust sliders which came with a u-bolt to attach to the frame that didn't look nearly strong enough to my eyes and install some wider fender flares.

I asked them to do an articulation test to make sure there was no rubbing with the new flares and they sent me this hilarious video in response.

[FINOCJ]

Your tire was definitely contacting some sheet metal when flexing....

[open_circuit]

Typical Mercedes driver

[speedkills]

They put the headers on for me which I didn't want to touch.

[speedkills]

I took off the old footsteps, and installed the brackets for the rock sliders, then let Hoover weld the slider frame mount on as I didn't think the u-bolt that came with it was going to be strong enough of a mount. They had to swap back to my smaller/louder exhaust at the same time as the sliders wouldn't clear the stock mufflers.

[speedkills]

Then test fit the new fenders for me. I didn't like the way they hung down so low below the bumper so I asked them to cut them off at the same angle.

[TDash]

omg that articulation video is hilarious


fender looks good too, i need to have some similar last minute shaving tomorrow to eliminate some rub

[jayson44]

nice!

J.

[Rocrawlr]

No RTI ramp? No problem!

[speedkills]

That actually is a Saab RTI ramp. Swedes are just odd I guess.

[speedkills]

I had some rubbing when I got my rig back from the shop, Scott helped me identify the contact points and 30 minutes with a cutting wheel and some flat black paint and no more rubbing.

Another funny thing I realized only after getting my truck back, the stock exhaust manifold is crap. I know they are not wonderful on many cars, but in this case I think it might be the same manifold used on the non-supercharged model. I had never inspected it closely and now I see why I am feeling such a bump in power, the stock units are doing a little false advertising and downsize the exhaust pipe right before joining the manifold which I hadn't noticed before. I'm going to keep my foot out of it until I get a tune on the truck for the headers as this looks like enough of a back-pressure change between cylinders that I worry I could run the end cylinders lean under boost.

[TDash]

Any news on the heat from the floor?

[speedkills]

I had all of the floor insulation pulled back to get to some wiring under the carpet. I think that stuff just does a really good job and I hadn't realized how warm it can get without it.