- Thread starter
- #101
Ignore the mods that were displayed above, and if you do anything like this yourself - ignore the HEI upgrade kit. I don't understand (at all) how it's supposed to work - and for me, it didn't. Not even remotely.
Now.... on to what was actually done.
As I mentioned previously, the HEI upgrade kit from DIYAutotune was removed, and I followed this (and grounded the coil) to get signal/and the truck started enough to set base timing:
Removed C30, Removed D1 and installed a jumper, Jumper D2 (for now), remove C12, then jumper XG1 to XG2, OPTOIN to TachSelect, TSEL to OptoOut, and JS10 to IGN.
I attempted my SPR4 to 5V mod (with a 1k resistor) - which is then tired directly to the "B" pin on the HEI8 ignition control module.
The purpose of this - and how it works in a factory equipped vehicle - is when the car is cranking advanced timing is turned off. There is no 5 volt signal sent to pin "B", and as such no advancing of timing takes place. After cranking is done, or 5 seconds of cranking, 5 volts is sent to pin B and ignition advance is put into place.
Seems like no big deal - as long as the vehicle starts well, I can supply voltage full time.
For *whatever* reason, when I did this mod, I got no signal - no fuel. Unplug pin B (everything I've wired I use weather-resistant male/female crimps) and there's signal & fuel (and starts up). While running - plug that wire in, and it stays running.
So - I followed the suggestion in the MSExtra guidelines. Remove D16 (one of the 3 red LED's). Solder one side of a 1K resistor (I used a 1/4W, see below) to the resistor near it, then the other leg of that 1K resistor to the negative side of D16. After that is done, run a "jumper" wire from that same negative D16 over to your spare output pin (I used SPR4 since it's already wired). Set, in Tunerstudion, the GM HEI to "Bypass". Everything works - I can start/get signal, and timing advances after it starts.
The MSExtra guidelines indicate to use a 1/8W 1K resistor. I asked on the MSExtra forums if a 1/4W would be fine (I have lots of those, no 1/8W and nobody nearby carries 1/8W). The wattage of a resistor apparently doesn't have an impact on the circuit - generally the limitation of the wattage ends up being it's physical size. The wattage refers to it's capacity to withstand heat/power - most circuits are designed with 2-3x the necessary wattage, so bumping the wattage up is perfectly acceptable (even though I didn't get a response).
Following photo shows the mods...
(right now I have the driver-side muffler cut off trying to find a quieter option ironically, so I can't start it - once I get it filled back up with coolant I'll get some Tunerstudio screen captures).
This all means that now I can basically run ANY engine I want (as long as it has a distributor - the HEI8 allows for basically reading the inputs of any Hall/VR sensor and can be modified for use with other distributors) with little to no rewiring, just some pretty simple software changes and tuning. I know that sounds silly, but I have been seriously considering swapping engines....
Now.... on to what was actually done.
As I mentioned previously, the HEI upgrade kit from DIYAutotune was removed, and I followed this (and grounded the coil) to get signal/and the truck started enough to set base timing:
Removed C30, Removed D1 and installed a jumper, Jumper D2 (for now), remove C12, then jumper XG1 to XG2, OPTOIN to TachSelect, TSEL to OptoOut, and JS10 to IGN.
I attempted my SPR4 to 5V mod (with a 1k resistor) - which is then tired directly to the "B" pin on the HEI8 ignition control module.
The purpose of this - and how it works in a factory equipped vehicle - is when the car is cranking advanced timing is turned off. There is no 5 volt signal sent to pin "B", and as such no advancing of timing takes place. After cranking is done, or 5 seconds of cranking, 5 volts is sent to pin B and ignition advance is put into place.
Seems like no big deal - as long as the vehicle starts well, I can supply voltage full time.
For *whatever* reason, when I did this mod, I got no signal - no fuel. Unplug pin B (everything I've wired I use weather-resistant male/female crimps) and there's signal & fuel (and starts up). While running - plug that wire in, and it stays running.
So - I followed the suggestion in the MSExtra guidelines. Remove D16 (one of the 3 red LED's). Solder one side of a 1K resistor (I used a 1/4W, see below) to the resistor near it, then the other leg of that 1K resistor to the negative side of D16. After that is done, run a "jumper" wire from that same negative D16 over to your spare output pin (I used SPR4 since it's already wired). Set, in Tunerstudion, the GM HEI to "Bypass". Everything works - I can start/get signal, and timing advances after it starts.
The MSExtra guidelines indicate to use a 1/8W 1K resistor. I asked on the MSExtra forums if a 1/4W would be fine (I have lots of those, no 1/8W and nobody nearby carries 1/8W). The wattage of a resistor apparently doesn't have an impact on the circuit - generally the limitation of the wattage ends up being it's physical size. The wattage refers to it's capacity to withstand heat/power - most circuits are designed with 2-3x the necessary wattage, so bumping the wattage up is perfectly acceptable (even though I didn't get a response).
Following photo shows the mods...
(right now I have the driver-side muffler cut off trying to find a quieter option ironically, so I can't start it - once I get it filled back up with coolant I'll get some Tunerstudio screen captures).
This all means that now I can basically run ANY engine I want (as long as it has a distributor - the HEI8 allows for basically reading the inputs of any Hall/VR sensor and can be modified for use with other distributors) with little to no rewiring, just some pretty simple software changes and tuning. I know that sounds silly, but I have been seriously considering swapping engines....