BOOSTED C8's how is this done??

[Ghostnotes]

Kind of an off topic question but how are some of these shops boosting C8's with no access to the PCM/TCM? I understand that maybe at it's most basic level, It can possibly increase fuel for the extra incoming air to some degree. However what about spark/VT/VVT/PR/IAT/Transmission and a host of other things, if there is no access to the PCM/TCM?

Am I missing something?
Did GM finally bake enough range for the all this to be compensated for?

[Joshinator99]

Kind of an off topic question but how are some of these shops boosting C8's with no access to the PCM/TCM? I understand that maybe at it's most basic level, It can possibly increase fuel for the extra incoming air to some degree. However what about spark/VT/VVT/PR/IAT/Transmission and a host of other things, if there is no access to the PCM/TCM?

Am I missing something?
Did GM finally bake enough range for the all this to be compensated for?

Most of them are using a piggyback ECU.

[Ghostnotes]

Granted but that does not address a lot of the critical factors the PCM/TCM need to work properly?

[cadillactech]

Piggyback ECU controls port injection, boost control, ignition timing(creatively done here to keep the factory ECM happy).

Some components are left connected to keep the ECM happy but do not actually function as intended.

Its a beautiful hodge podge of factory stuff left working or connected to keep the factory ECM happy and a piggy back making sure fuel and timing are in line for the additional airflow, as most are getting turbos.

[tunerpro]

Its remarkable what they've been able to do without native tuning support, but you're not going to see strokers or cams working at all.

[tunerpro]

However what about spark/VT/VVT/PR/IAT/Transmission and a host of other things, if there is no access to the PCM/TCM?

There's limitations... As of about 6 months ago, one of the "turbo kits" out there hard wired into the upshift paddle on the C8 just to have a signal to yank timing during a shift to prevent smoking the transmission...

[Joshinator99]

There's limitations... As of about 6 months ago, one of the "turbo kits" out there hard wired into the upshift paddle on the C8 just to have a signal to yank timing during a shift to prevent smoking the transmission...

That and everyone of those cars are driving around with CELs on so forget driving it in a state with inspections. Not touching the C8 with a 10’ pole until the tuning is figured out for real.

[Ghostnotes]

I just don't see how they can run properly without dealing with PR/VT/VE.

However, I'm not a professional.

I mean if it sees more airflow at a given load it's going to add fuel which is more torque, which will close the throttle and or pull timing. Not being able to monitor or change knock sensitivity. And what about pressure ratio? Sure they can graft a new MAP, but what good is it if you can't scale it? This is all without even replacing the cam. Are they scaling down the signal with resistance?

[Ghostnotes]

There's limitations... As of about 6 months ago, one of the "turbo kits" out there hard wired into the upshift paddle on the C8 just to have a signal to yank timing during a shift to prevent smoking the transmission...

I get that but without making pressure adjustments, adding 200+ hp as some advertise will kill the clutches if left unmodified. Hold pressures have to be changed as well. Not arguing with you at all, I just don't see the upside to any of it yet. I guess to some degree if you have a bunch of disposable income, it doesn't matter.

[tunerpro]

At some point the holding pressures and physical characteristics of the clutches will certainly be an issue, but the gear to gear transition is (and always has been) the weakest point. I've watched some of the earlier videos of a well known YouTuber with a twin turbo C8, it appeared to hold the power fine - until it went to shift from 1st the 2nd at full boost. Consider the TCM requests an engine torque reduction during gear to gear transitions: if the ECM actually knew how much power the engine was making, how ever interruptive the power delivery might be, it would be capable of power limiting the engine to keep the transmission clutches from getting burned up in that situation.

Without tuning, their solution was to give the driver a choice: manually upshift at full boost, or smoke your transmission. It's not a great option but at least its AN option. But solutions like this are going to prevent modding C8s from ever becoming mainstream, I expect.

[tunerpro]

I just don't see how they can run properly without dealing with PR/VT/VE.

However, I'm not a professional.

I mean if it sees more airflow at a given load it's going to add fuel which is more torque, which will close the throttle and or pull timing. Not being able to monitor or change knock sensitivity. And what about pressure ratio? Sure they can graft a new MAP, but what good is it if you can't scale it? This is all without even replacing the cam. Are they scaling down the signal with resistance?

You're absolutely right about that. But, you can go a long way just spoofing a MAF signal. I haven't seen the system these builds are using but I believe they are capable of also modifying ignition timing curves. They can trigger off of all sorts of events, like pedal position, manifold pressure, the list goes on. I'm certain they're using some sort of non-integrated secondary fuel system, like an MPFI controller. Last I heard that TT C8 was over 1000HP, that's not possible without a complete DI system upgrade, which won't work without tuning. Maybe not possible even with a full DI system upgrade.

[cadillactech]

You're absolutely right about that. But, you can go a long way just spoofing a MAF signal. I haven't seen the system these builds are using but I believe they are capable of also modifying ignition timing curves. They can trigger off of all sorts of events, like pedal position, manifold pressure, the list goes on. I'm certain they're using some sort of non-integrated secondary fuel system, like an MPFI controller. Last I heard that TT C8 was over 1000HP, that's not possible without a complete DI system upgrade, which won't work without tuning. Maybe not possible even with a full DI system upgrade.

I believe Fueltech's C8 has a full port injection system controlled by their piggy back ECU along with timing control from that ECU while still letting the factory ECM think its controlling the timing.
They also swapped their own TB on to take control of that and left the factory one plugged in off to the side so it can close all it wants but not limit power.

Raybestos already has upgraded steels and frictions for the transmission clutches as well to help with the additional power.

If the CAN bus can be decoded for this system then putting a full M1 Motec system into this car while keeping everything happy isn't out of the question.

[tunerpro]

If the CAN bus can be decoded for this system then putting a full M1 Motec system into this car while keeping everything happy isn't out of the question.

At the bus level, Global B uses CAN-FD at higher speeds on an isolated powertrain bus. So, you'd have to tap into the powertrain CAN bus directly with hardware that can properly decode CAN-FD messages...

Not sure what you mean by keeping everything happy, but if you're talking about taking the factory ECM out and replacing it with an aftermarket unit, you can forget about that. The ECM is just one of about 20 different ECUs that is required to transmit authenticated messages to other ECUs in the vehicle. If the message isn't trusted by other ECUs, it's ignored, so there goes your transmission control, brake control, steering, just about everything.

[cadillactech]

At the bus level, Global B uses CAN-FD at higher speeds on an isolated powertrain bus. So, you'd have to tap into the powertrain CAN bus directly with hardware that can properly decode CAN-FD messages...

Not sure what you mean by keeping everything happy, but if you're talking about taking the factory ECM out and replacing it with an aftermarket unit, you can forget about that. The ECM is just one of about 20 different ECUs that is required to transmit authenticated messages to other ECUs in the vehicle. If the message isn't trusted by other ECUs, it's ignored, so there goes your transmission control, brake control, steering, just about everything.

Yes the serial data gateway module would have to be dealt with or hardwire into the powertrain bus but I suspect even if you did that you would have issues.

Many other car platforms have been removing factory ECU's and plugging in Motec M1 ECUs which replicate factory CAN messages to allow the car to keep full TCM control, ABS, Traction control, electric steering, etc. It allows full direct injection control as well along with auxiliary port fuel system control when you start to need more fuel. It is a pretty impressive ECU and if you are going to try and build a reliable 4 digit horsepower car, this is how most are getting it done.

Obviously this takes thousands of man hours to decode factory CAN messaging and then replicate them on another ECU but the Motec M1 series ECU was designed just for this. The Global B cars may take even more labor hours to figure out but the C8 platform is too tempting I think for the aftermarket to ignore.

[tunerpro]

Obviously this takes thousands of man hours to decode factory CAN messaging and then replicate them on another ECU but the Motec M1 series ECU was designed just for this. The Global B cars may take even more labor hours to figure out but the C8 platform is too tempting I think for the aftermarket to ignore.

More, or less, GM didn't change the CAN messages from Global A to Global B. There's a few new ones but most of the existing messages carried over.

The problem is with message authentication. As you know, the ECM broadcasts various messages about the engine's state. Everything from engine coolant temperature to calculated torque output to which driver mode has been selected. In addition to that, with Global B, are message authentication codes - it's the hash of the message being broadcasted, encrypted by keys in the ECM - keys that are unique to that ECM, and unique to the collection of other modules the ECM communicates with.

The other ECUs listening to these messages will validate the authenticity of the ECM's messages based on their keys by calculating the code from message and comparing it to the one the ECM sent with it. If they don't match, the message is ignored and a U1962 sets on that ECU.

An aftermarket ECM will never be able to generate these authentication codes correctly, and as such, no other ECU in the vehicle will trust or accept any message from the ECM. Even if you were able to start the engine (which you wouldn't be able to, since the BCM doesn't trust the ECM, and it sends engine crank command), the gear shift module wouldn't let you put it in Drive. Or the parking brake module wouldn't let you release the brake. Or the TCM wouldn't engage any of the gears. 

Without authenticated messages from the ECM, virtually nothing will work in the vehicle.

[Ghostnotes]

More, or less, GM didn't change the CAN messages from Global A to Global B. There's a few new ones but most of the existing messages carried over.

The problem is with message authentication. As you know, the ECM broadcasts various messages about the engine's state. Everything from engine coolant temperature to calculated torque output to which driver mode has been selected. In addition to that, with Global B, are message authentication codes - it's the hash of the message being broadcasted, encrypted by keys in the ECM - keys that are unique to that ECM, and unique to the collection of other modules the ECM communicates with.

The other ECUs listening to these messages will validate the authenticity of the ECM's messages based on their keys by calculating the code from message and comparing it to the one the ECM sent with it. If they don't match, the message is ignored and a U1962 sets on that ECU.

An aftermarket ECM will never be able to generate these authentication codes correctly, and as such, no other ECU in the vehicle will trust or accept any message from the ECM. Even if you were able to start the engine (which you wouldn't be able to, since the BCM doesn't trust the ECM, and it sends engine crank command), the gear shift module wouldn't let you put it in Drive. Or the parking brake module wouldn't let you release the brake. Or the TCM wouldn't engage any of the gears.

Without authenticated messages from the ECM, virtually nothing will work in the vehicle.

Which to me severely limits what can actually be spoofed and will limit how much power you can safely output. Unless I'm missing something, you can produce all the power you want, but if your tables are not updated you are going to hit a wall.