2020 C8 Corvette Stringray

[aaronatstate]

[quote=""tabasco122""]I haven’t been keeping up with the thread, I would say a running twin turbo setup is a far cry from no kidding period. I’m sure it’s not optimal, but it’s running lol.[/quote]

She is running 2-3 lbs. of boost, which the fuel trims can account for. Though it won't let her transmission shift some times due to too much torque. If you watch the videos about it, they literally did nothing except make a turbo kit that bolts up. Zero tuning, except watching data logs with HP Tuners.

StreetSpeed717's they actually are tricking some of the sensors, and running more boost, and actually making close to 600whp if I remember right. But I'm not sure how good of a solution that is either.

[Jeff V.]

You can hear the LMR / SS717 car slipping really bad at several points in the video.

Couple relevant things I learned from GMs service info yesterday.

The transmission solenoid assemblies (there are two) and the clutch assembly have unique performance characteristics. When you replace those parts, you enter a serial number unique to that specific piece. The programming system goes out to a database and retrieves the parameters for that piece and loads them into the TCM.

It'll be interesting to see how the aftermarket adapts to that. I wonder if Porsche and Nissan have similar procedures for their DCTs?

I also stumbled on something really weird about the MAF sensor. It communicates with the PCM over a LIN bus. It looks like it also has a standard 0-5v airflow signal, so I don't know what that LIN bus is for. It also doesn't have air temp, baro and humidity signals in that sensor like my car does. Or maybe it does, and that's what's on the LIN bus? I might dig a little deeper into that before my pass expires.

[aaronatstate]

How much does a pass cost?

[Jeff V.]

$20 for 3 days.

[aaronatstate]

[quote=""Jeff V.""]$20 for 3 days.[/quote]

I'll get you another 3 days, call it payment for the rheostat switch and the double din bezel

[Jeff V.]

The three days I have now is plenty. Thanks though.

[aaronatstate]

[quote=""Jeff V.""]The three days I have now is plenty. Thanks though.[/quote]

Well if you need more time, the option is there!

[Jeff V.]

Here's what I've learned about the onboard networks. There are 26 major control modules on a C8. That's roughly the same as a C7.

The serial data gateway is basically a firewall for the whole car. Everyone is talking about hacking the engine and trans modules. I think the bigger concern is going to be this gateway. I suspect it's not going to let you even start a conversation with those other modules until you authenticate with the gatekeeper first. You could potentially pull those modules out and bench program them, but that would get old fast. It'll be interesting to see if someone comes up with a programming tap to splice in somewhere behind the gateway.

Also, the gateway is buried deep in the dash. Half the interior has to come out to get to it.

There are 5 Ethernet networks. One goes between the OBD port and serial gateway and is used for diagnostics and programming. The other 4 are used for communication between modules.

There are 11 CAN buses. 5 are used for communication between the serial gateway and other sub-systems. 1 is used for diagnostics and programming, but only goes between the gateway and the OBD port. There's another dedicated CAN bus for programming at the assembly plant. That one is also exposed on the OBD port. There are 2 private CAN networks. One between the PCM and fuel pump controls, and another one between the 2 blind spot monitoring modules.

But the really interesting ones are the 2 'private presentation CAN buses'. Those are for engineering use only. They're used to observe communications on CAN buses that aren't exposed to the OBD port, and require special security codes to access. This would likely let you see the uncensored communication between modules, as well as send modified data.

There are 2 other CAN buses specified for the new platform. They're for automated driving and hybrid/EV systems. Those aren't used on the C8.

There's least 10 LIN buses. Those are for really basic communications for things like power window motors and apparently the MAF sensor.

The old single-wire CAN / GMLAN is no longer used. Neither is MOST (media oriented systems transport). That was used on previous cars for moving infotainment data between things like the radio, amp and cluster.

I've found absolutely nothing that talks about security on these buses. I'm not all that surprised. There was precious little info available on the old Global A security system. It makes sense that this is locked up even tighter.

[mjannusch]

Yeah, I don't think we're going to see much other than simple piggybacks on this platform for a while, if ever. LMR is doing about all you can to trick it into letting the turbos do some actual boosting, but the DCT control is going to be the sticking point as far as a limit to how far you can push it. I thought I saw that someone was making a new DTC clutch pack, but without being able to program the DCT for it I doubt that will help much, and will probably make the DCT software freak out.

If you need to have more power, probably best to wait for the Z06 or ZR-1.

[Jeff V.]

Cicio Performance and Dodson Motorsports are working on clutch assemblies. Dodson has made parts for the GTR and Porsche PDK cars. There's a good read here, along with some excellent transmission pictures in posts #1 and #60.

https://www.corvetteforum.com/forums/c8 ... mance.html

[DCIV]

Jeff, is this like the 3/s, maybe one day they will just make and ecu that they can swap in?


Coop

[Jeff V.]

Doubt it. This is WAY to complex for that.

Look at it this way. The ZR1 ECUs were a couple thousand dollars. And those were just altered, stock ECUs. Doing one from scratch would cost a fortune.

[mjannusch]

The bus encryption and the data gateway are going to have this thing locked down tight. Unless GM wants to let people in there, they probably aren't getting in there for a long time. Someone would need to determine or "obtain" the encryption keys to break into it, and then you'd still have to decode and understand it all.

I'm wondering if Chevy is going to announce the Z06 for 2021 or hang onto it for 2022. I'm thinking probably 2022, which I'm not sure I'd want to wait that long. The base car with Z51 is probably enough for me, and put some mild upgrades on it over time.

[Jeff V.]

My biggest unanswered question is if they're going to have modules authenticate each other. Like if someone does hack or physically modify the PCM, will the gateway and other modules reject it like a bad organ transplant?

They're going to have to do something with the Z06 soon. I don't know how long IMSA and the FIA are going to give them a waiver on the engine they have in the race car. It's required to have a version for sale to the public.

[mjannusch]

I'd guess that if the messages on the bus aren't signed by a valid key, the gateway will block them from getting to any other modules.

[Jeff V.]

I was thinking that, or at least some kind of initial authentication when the module starts up.

There are some standards that provide encryption for CAN messages, but as I understand it they're pretty CPU intensive.

[mjannusch]

Sounds like they have some beefy CPUs in these devices, so they likely can run everything fully encrypted/signed. If they didn't, it would seem fairly easy to intercept and inject your own CAN data.

[aaronatstate]

Didn't they do this with the new GM diesel trucks too? Has there been anything on that front regarding tuning?

[Jeff V.]

They used an encrypted PCM in the trucks, but not the new digital vehicle architecture. That's only on the Cadillac CT4, CT5, and the Corvette for now.

[aaronatstate]

There gonna have to let tuning happen at some point. The big thing about the C8 was to appeal to a younger crowd, and I feel the younger crowd wants that ability, and will look at other vehicles potentially. Time will tell though I guess.