So, not quite sure where to put this as it's not a full on car build like I have posted on the vette, but a sort of side, fun project I am doing during this lock down.
So, this idea has always floated around in the back of my mind for the past 2-3 years. I know people have mentioned (can't find any documented proof) that before HP Tuners was HP Tuners some of the guys mentioned about getting 2 step, boost by gear/speed/rpm to work on the stock 24X PCMs and the project never came to fruition.
Here were are with a random guy in his basement and a work bench and many P01's at his disposal. I am building my entire gauge cluster for my C4 corvette using an arduino and running aftermarket and stock sensors to it. After being semi successful with it I decided why can't I use an arduino to possibly change how the stock PCM functions a little bit? What is the first thing that most people complain the stock PCM can't do that say a holley system can do....2 step. So I started there. Yea you could buy an aftermarket MSD system or something but that is $250 and yes...you get the idea.
I decided to figure out how to cut ignition based on a value, the value being RPM signal. Both the P01 and P59 have an output for RPM and it's PWM. The arduino can read PWM through it's many input/output digital ports. Ok, so we know that's an option so we can deal with the programming later (I HATE that part). Might as well tie in the 4K speed signal too as we may need that (boost by gear/speed/rpm).
So I started tearing down a P01 and looking at what each pin does like I have a few times now. I do know there are many unused pins on the PCM. Also inside the case there are leads right in front of you that go from the board to the outside pinouts. P01 and p59 are almost identical on all the unused pins. From this point on I am only going to be talking about the P01 as I am now realizing this could get confusing, but just so people know this is going to almost 100% work for P59 as well.
I begin to start pulling what wire leads from the board I can phisically clip to connect to an arduino to be used as say sensor info or anything. Blue connector 49, 50, 52, 62, 64, 67, and 78 can be cut. So I cut them. IF you have ever looked inside these the leads sit behind one another. So trying to get to the leads behind are almost impossible, but not completely. So with those pins cut I look hind those cut ones to see if others can be to be used. Yup! Now we have Blue pins 9, 10, 22, 24, and 27. These are also unused. So that gives us a very easy 12 pinouts to the harness we can use as outgoing or ingoing to/from the engine harness.
So now time to get hardware and start on the first focus of 2 step. We know we have to interrupt the ignition side of it on a value (RPM). So first thing was to just cut the power to coils. Well since the arduino runs on 0-5v and the ignition system is 12V there needs to be a relay or transistor/mosfet to do the switching. Looked online for a day or two and was hard to find anything small enough and cheap enough. So someone (RYAN) on Sloppy Discord server found the coil pinout for me. The PCM sends a 5v signal to each ignition coil and then has a low reference back (ground). Thing is it has 8 signal wires out and 2 reference back. The reference are tied by the banks, bank 1 and 2. So the easy way since the arduino is 0-5v is to use a either a transistor/mosfet or a relay that can switch fast enough. Well the best choice would be either a good transistor or Solid state relay so there was not issues on latency time. I have a few of these high/low relays on hand that can do open or close circuit. Since the circuit is Normally Closed (NC) I have 2 wired per bank to do it. Now these can switch on/off within roughly 5-10 ms. Which is about perfect to what I need. So I set everything up and know I need to cut continuity to red connector 60 and 61 when I want the 2 step to happen. Well I decided to wire the relays load side to the bottom of the PCM board to those pins and then used two unused pins (blue 49,50) to be used as the new locations for the low reference back. This way the harness can still look good and its just a simple pin swap.
I added a super tiny voltage regulator to turn the arduino on with the ignition-on for the PCM and that powers the entire arduino setup and relays. I would like to make a switch on the dashboard that is the kill switch to kill arduino and that would make the PCM function 100% stock without any issue.
And this is where we are currently at. Sorry for the book. I just wanted to get everyone on board with my thought process to know where and why I have currently have the setup I do. I have a few videos on my YT that go over each idea and change. But as of right now I have all the system wired as I want. I ordered some Arduino Nanos to supply a virtual crank signal as the engine would. Someone supplied me with it (Pete, he is smart and is the creator of the great LS Droid and GM to Dodge CAN-BUS stuffs) and will use that to test it. I need to figure out the programming to do it but once we do it will be easy as pie to implement Boost control to a MAC valve based on RPM/speed. Eventually I would like to introduce gear as well based on the PCM commanded gear.
So here we are. Hopefully I did not bore you or am giving you false hope. I'm, in my mind, I full on novice and noob but trying to make something work for the peoples and myself. Here is the latest updates and you can go back and look at the others a well.
So, this idea has always floated around in the back of my mind for the past 2-3 years. I know people have mentioned (can't find any documented proof) that before HP Tuners was HP Tuners some of the guys mentioned about getting 2 step, boost by gear/speed/rpm to work on the stock 24X PCMs and the project never came to fruition.
Here were are with a random guy in his basement and a work bench and many P01's at his disposal. I am building my entire gauge cluster for my C4 corvette using an arduino and running aftermarket and stock sensors to it. After being semi successful with it I decided why can't I use an arduino to possibly change how the stock PCM functions a little bit? What is the first thing that most people complain the stock PCM can't do that say a holley system can do....2 step. So I started there. Yea you could buy an aftermarket MSD system or something but that is $250 and yes...you get the idea.
I decided to figure out how to cut ignition based on a value, the value being RPM signal. Both the P01 and P59 have an output for RPM and it's PWM. The arduino can read PWM through it's many input/output digital ports. Ok, so we know that's an option so we can deal with the programming later (I HATE that part). Might as well tie in the 4K speed signal too as we may need that (boost by gear/speed/rpm).
So I started tearing down a P01 and looking at what each pin does like I have a few times now. I do know there are many unused pins on the PCM. Also inside the case there are leads right in front of you that go from the board to the outside pinouts. P01 and p59 are almost identical on all the unused pins. From this point on I am only going to be talking about the P01 as I am now realizing this could get confusing, but just so people know this is going to almost 100% work for P59 as well.
I begin to start pulling what wire leads from the board I can phisically clip to connect to an arduino to be used as say sensor info or anything. Blue connector 49, 50, 52, 62, 64, 67, and 78 can be cut. So I cut them. IF you have ever looked inside these the leads sit behind one another. So trying to get to the leads behind are almost impossible, but not completely. So with those pins cut I look hind those cut ones to see if others can be to be used. Yup! Now we have Blue pins 9, 10, 22, 24, and 27. These are also unused. So that gives us a very easy 12 pinouts to the harness we can use as outgoing or ingoing to/from the engine harness.
So now time to get hardware and start on the first focus of 2 step. We know we have to interrupt the ignition side of it on a value (RPM). So first thing was to just cut the power to coils. Well since the arduino runs on 0-5v and the ignition system is 12V there needs to be a relay or transistor/mosfet to do the switching. Looked online for a day or two and was hard to find anything small enough and cheap enough. So someone (RYAN) on Sloppy Discord server found the coil pinout for me. The PCM sends a 5v signal to each ignition coil and then has a low reference back (ground). Thing is it has 8 signal wires out and 2 reference back. The reference are tied by the banks, bank 1 and 2. So the easy way since the arduino is 0-5v is to use a either a transistor/mosfet or a relay that can switch fast enough. Well the best choice would be either a good transistor or Solid state relay so there was not issues on latency time. I have a few of these high/low relays on hand that can do open or close circuit. Since the circuit is Normally Closed (NC) I have 2 wired per bank to do it. Now these can switch on/off within roughly 5-10 ms. Which is about perfect to what I need. So I set everything up and know I need to cut continuity to red connector 60 and 61 when I want the 2 step to happen. Well I decided to wire the relays load side to the bottom of the PCM board to those pins and then used two unused pins (blue 49,50) to be used as the new locations for the low reference back. This way the harness can still look good and its just a simple pin swap.
I added a super tiny voltage regulator to turn the arduino on with the ignition-on for the PCM and that powers the entire arduino setup and relays. I would like to make a switch on the dashboard that is the kill switch to kill arduino and that would make the PCM function 100% stock without any issue.
And this is where we are currently at. Sorry for the book. I just wanted to get everyone on board with my thought process to know where and why I have currently have the setup I do. I have a few videos on my YT that go over each idea and change. But as of right now I have all the system wired as I want. I ordered some Arduino Nanos to supply a virtual crank signal as the engine would. Someone supplied me with it (Pete, he is smart and is the creator of the great LS Droid and GM to Dodge CAN-BUS stuffs) and will use that to test it. I need to figure out the programming to do it but once we do it will be easy as pie to implement Boost control to a MAC valve based on RPM/speed. Eventually I would like to introduce gear as well based on the PCM commanded gear.
So here we are. Hopefully I did not bore you or am giving you false hope. I'm, in my mind, I full on novice and noob but trying to make something work for the peoples and myself. Here is the latest updates and you can go back and look at the others a well.