LS1b (411) PCM Swap - ZR-1 Net Registry Forums

VetteVet · 02-21-2012

I brought up the possibility of a 411 PCM swap in Jerry's "Ignition Impulse @ Balancer/Dampner" thread because it was somewhat relevant to the thread topic, but at this point I'd like to take the liberty to break it out into a new thread.

As has been discussed, there are several potential "show-stoppers" involved. The most serious ones are listed below:

1. Secondary system issues
2. 24x CKP and 1x CMP signals
3. CCM communication

Here are my proposals as to how these obstacles can be overcome:

1. In my opinion, this is by far the trickiest of the bunch. The 411 PCM software, as it is currently written, cannot handle our secondary injectors, nor the rest of the secondary hardware. This is, however, merely a software and not a hardware problem. Remember, our ECMs were not designed to handle dual mode operation either, but GM kludged together a solution by adding extra spark and fuel tables, solid state secondary injector relays, a secondary actuation solenoid, vacuum pump, differential vacuum sensor, the necessary code modifications, etc. Their are 2 possible routes to take toward resolution of this issue:

a.The easiest solution would be a one tailored toward engines that have had their secondaries removed. The 411 code would need to be modified so that it operates as designed at idle, but at off-idle it energizes unused outputs to bring the secondary injectors online while at the same time scales the pulse width by a factor of 0.5 (or 0.51 if we go by the ZR-1 ECM calibrations). I don't believe that we would need to implement separate fuel and spark tables as the engine would be operating on "primaries only" in such a narrow window and not at heavy load.

b. The preferred solution would be to implement full secondary system functionality. This would require more extensive code modifications, but the 411 PCM definitely has the necessary hardware and processing power.

2. The signals required to operate the 411 PCM are 24x CKP (24 pulses per crank shaft revolution or 48 pulses per camshaft revolution) and 1x CMP (1 pulse per camshaft revolution or 1/2 pulse per crankshaft revolution). Our CKP signal is 8 (or 9 if you count the odd synch pulse) VR (AC) pulses per revolution. This signal is processed by the Ignition Control Module (ICM) and the ICM generates a signal of 4 pulses per crankshaft revolution on the REF HI circuit, which is fed to the ECM. Installation of a 24x reluctor wheel combined with an L21 Hall Effect CKP sensor can provide the 24x signal to the 411 PCM. While our CMP signal is also 1x, it is not a 50% duty cycle, so a reluctor wheel with a 50% duty cycle (high for 180 degrees of camshaft rotation and low for the other 50%) combined with an appropriate Hall Effect sensor can provide the CMP signal. Assuming suitable mounting locations can be found, the appropriate reluctors can be fabricated and everything can be installed with the proper phasing, these signals should be suitable for running the engine.

3. Regarding communication with the CCM, I initially thought that this was going to require fabrication of an interface. The Gen III PCMs communicate via the Class II protocol and the ECM, CCM and other modules in our cars communicate via 8192 baud UART. The CCM acts as the master device in this arrangement and is the only device that the ECM communicates with directly. After lots of research, I recently found out that GM (Pontiac GTO) and Holden have produced cars with Gen III PCMs coupled with vehicle systems that utilized 8192 baud. They have a plug and play module called a Powertrain Interface Module (PIM) which translates between the PCM Class II and CCM (or BCM in later vehicles) 8192 baud protocols. While some code mods may be required so that the PCM can understand the CCM messages and respond aprropriately (speak the same dialect), the PIM will allow them to communicate at the hardware level (speak the same language).

Sorry for the long post, but I wanted to get my major ideas out on the table up front.

At this point, I'll open up the thread to comments (critical or not), questions, ideas and suggestions.

Thanks,
Jep

02-21-2012	#1
VetteVet Join Date: Jan 2009 Location: Mandeville, LA Posts: 340	LS1b (411) PCM Swap I brought up the possibility of a 411 PCM swap in Jerry's "Ignition Impulse @ Balancer/Dampner" thread because it was somewhat relevant to the thread topic, but at this point I'd like to take the liberty to break it out into a new thread. As has been discussed, there are several potential "show-stoppers" involved. The most serious ones are listed below: 1. Secondary system issues 2. 24x CKP and 1x CMP signals 3. CCM communication Here are my proposals as to how these obstacles can be overcome: 1. In my opinion, this is by far the trickiest of the bunch. The 411 PCM software, as it is currently written, cannot handle our secondary injectors, nor the rest of the secondary hardware. This is, however, merely a software and not a hardware problem. Remember, our ECMs were not designed to handle dual mode operation either, but GM kludged together a solution by adding extra spark and fuel tables, solid state secondary injector relays, a secondary actuation solenoid, vacuum pump, differential vacuum sensor, the necessary code modifications, etc. Their are 2 possible routes to take toward resolution of this issue: a.The easiest solution would be a one tailored toward engines that have had their secondaries removed. The 411 code would need to be modified so that it operates as designed at idle, but at off-idle it energizes unused outputs to bring the secondary injectors online while at the same time scales the pulse width by a factor of 0.5 (or 0.51 if we go by the ZR-1 ECM calibrations). I don't believe that we would need to implement separate fuel and spark tables as the engine would be operating on "primaries only" in such a narrow window and not at heavy load. b. The preferred solution would be to implement full secondary system functionality. This would require more extensive code modifications, but the 411 PCM definitely has the necessary hardware and processing power. 2. The signals required to operate the 411 PCM are 24x CKP (24 pulses per crank shaft revolution or 48 pulses per camshaft revolution) and 1x CMP (1 pulse per camshaft revolution or 1/2 pulse per crankshaft revolution). Our CKP signal is 8 (or 9 if you count the odd synch pulse) VR (AC) pulses per revolution. This signal is processed by the Ignition Control Module (ICM) and the ICM generates a signal of 4 pulses per crankshaft revolution on the REF HI circuit, which is fed to the ECM. Installation of a 24x reluctor wheel combined with an L21 Hall Effect CKP sensor can provide the 24x signal to the 411 PCM. While our CMP signal is also 1x, it is not a 50% duty cycle, so a reluctor wheel with a 50% duty cycle (high for 180 degrees of camshaft rotation and low for the other 50%) combined with an appropriate Hall Effect sensor can provide the CMP signal. Assuming suitable mounting locations can be found, the appropriate reluctors can be fabricated and everything can be installed with the proper phasing, these signals should be suitable for running the engine. 3. Regarding communication with the CCM, I initially thought that this was going to require fabrication of an interface. The Gen III PCMs communicate via the Class II protocol and the ECM, CCM and other modules in our cars communicate via 8192 baud UART. The CCM acts as the master device in this arrangement and is the only device that the ECM communicates with directly. After lots of research, I recently found out that GM (Pontiac GTO) and Holden have produced cars with Gen III PCMs coupled with vehicle systems that utilized 8192 baud. They have a plug and play module called a Powertrain Interface Module (PIM) which translates between the PCM Class II and CCM (or BCM in later vehicles) 8192 baud protocols. While some code mods may be required so that the PCM can understand the CCM messages and respond aprropriately (speak the same dialect), the PIM will allow them to communicate at the hardware level (speak the same language). Sorry for the long post, but I wanted to get my major ideas out on the table up front. At this point, I'll open up the thread to comments (critical or not), questions, ideas and suggestions. Thanks, Jep