LS1b (411) PCM Swap

[VetteVet]

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

[RHanselman]

Jep,

I've looked into using the LSx type PCM in an effort to solve some issues with my turbo car. I was specifically looking into the Big Stuff 3 system which has an option for 16 injectors. I would think this would solve most my issues especially if I could get it to talk with the CCM. This PIM sounds like it may be the answer...

Cheers,
RH

[VetteVet]

Ron,

If you were looking into the 411 PCMs then I'm sure you're aware that EFILive anf HPTuners offer 2 and 3 bar custom operating systems. I haven't looked into them enough to know if they support wastegate control, but do know that even the stock code has a table for mapping out fuel pressure so any type of FMU or VFPR can be accomodated very easily to take care of the increased fuel demand.

Jep

[RHanselman]

Jep,

411's were not in my crosscheck when I was doing the initial research. Do you have a website you like best?

[VetteVet]

Ron,

You can go to the EFILive and HPTuners websites:

http://www.efilive.com/
http://www.hptuners.com/

Both sites have user forums and offer custom operating systems that support boosted applications. I'm sure if you poke around on the forums, you should get a feel for the capabilities.

Also, both sites offer free demo versions of their software for download. I have installed both and they have been invaluable for getting a feel of the 411's capabilities. GM really made quantum leap advances over our ECMs.

The whole code segment thing took a while to get my head wrapped around. For example, if the binary file for a 2001 Corvette is closest to meeting my needs, but the transmission that I want to use was never offered in the Corvette, then all I have to do is swap the transmission segment from another vehicle into the Corvette binary and the PCM can now control that transmission and all of the tuning parameters that apply to that transmission are now valid.

You can also look at these forums as well:

http://www.ls1tech.com/forums/
http://www.ls1.com/


There are many others, but these should get you started.

In other news, I have brainstormed the crank and cam position signal issue and think that I have a bolt-on solution. More news to follow as I get the details worked out.

I have a PCM and PIM on the way. $59.00 for the PCM and $99.00 for the PIM. I can't believe how cheap these PCMs are.

I had a good conversation today with Jon at F.I.C. I think the injector situation can be handled. I've got several ideas and am not sure which, if any, will end up being the final solution.

Once I have the PIM and PCM in hand and my test bench is finished, I'm going to try to see if the PCM can be made to talk to my CCM. By the way, most of the dash functionality is not tied to the CCM. All gauges should work fine even if the PCM can't talk to the CCM. I think the only things that wouldn't work would be the fuel economy stuff and the engine diagnostic display via the LCD (don't quote me on this because I haven't looked into this extensively yet). If we can get the PCM and CCM talking via the PIM, then everything should work normally. The PCM has two independently scalable outputs for speed signal, so it will accomodate the signals needed by the speedo and cruise control.

Thats it for now. If you think of anything else, feel free to post in this thread or PM me. You can also contact me via the methods below.

Thanks,
Jep

vettevet(at)charter(dot)net
Cell: 985-789-5118

[-=Jeff=-]

Anything on the LCD is controlled by the CCM.. just a FYI

[VetteVet]

I got my LS1 crankshaft reluctor today. $30.00 for a brand new part!!





Note the 24x pattern that the LS1 uses:





Coincidentally, it is the same O.D. as the LT5 harmonic balancer pulley.

[RHanselman]

How are you going to mount it? Also, would you need to run 16 injectors or could you use 8 large in the primary location and just keep the secondary inj's in as inactive hole plugs?

[VetteVet]

Ron,

I don't plan on using that wheel. I purchased it to get the measurements to design a one piece solution that would attach to the balancer.

I'm about 50% done with the CAD design for the CKP reluctor wheel assembly. I still need to design the sensor mount.

I've been concentrating on the CMP sensor housing design, as that is the more challenging one. I'm about 95% done with that.

As far as injectors, I've made phone calls to some gurus and am pretty confident that it can be run on 16 injectors full time. I'm still working out the details on that. More information to follow.

Within the next week or so, I should have some 3D CAD images to post up.

Jep

[RHanselman]

What do you think of the wheel that Jerry has?