Anyone want to take a stab at this (electronics/relay guru's inside)

[dville_gt]

Of course, this has to do with my efi lsx in a coupe w/a th350 transmission.

In a modern car when you shift from park/neutral to a gear the motor adjust to the increased load accordingly by changing the idle airflow tables along with some timing increases as well. This gives your car a fairly seamless transition from no-load to now having the load of the transmission.

Since I am not running a modern transmission like the 4L80E that the PCM is used to operating, it has no idea what gear I am in at any time so it defaults to thinking the car is in Park/Neutral all the time.

With a very large cam (235/240 .648"/.609" 111lsa) the sudden load can sometimes overwhelm the short-term idle trims abilities and, although rare, sometimes the car will die.

So, I got to thinking about how I can solve this issue and looked through the wiring schematics to find that there are four wires (A, B, C, and P) that depending on the sequence of wires that are grounded or powered the PCM can tell exactly what gear the vehicle is in.

I am not concerned with the PCM knowing exactly what gear I am in, only that I am either in Park/Neutral or in a gear so that I can adjust the "In Gear" tables to tweak the idle airflow accordingly.

I am running a Hurst quarter stick that has a park/neutral safety switch (currently this is wired inline with my starter relay so that the car can only be started in park/neutral).

What I want to do is figure out the easiest way to design a relay setup that can provide ground to the proper switches when the neutral safety switch goes hot (+), indicating that the car is in Park/Neutral, and then with ground different switches when the safety switch is not energized.

The PCM provides power to each of the switches by default so currently all of the switches are positive (which it doesn't recongize and defaults to park nuetral), so all I need to do is provide ground to certain wires when the safety switch has power and provide ground to other wires when the safety switch is not powered (indicating I am now not in park/neutral).

Here is the combination of hi (+, or no ground since they are + by default) or low (-, grounded).

[dville_gt]

So for example:

I need a really that when provided +12v will ground PIN A and PIN P (Park), when the +12 is removed it needs to ground PIN B and PIN C (Drive)

[Beenfetchedlately]

Your making shit way more complicated then it needs to be. Flash a 6 speed VIN in the car and continue tuning..

[dville_gt]

Or if it is easier I could just permanently ground PIN P and have it alternate between grounding PIN A (PIN A+ PIN P = PARK) and Pin C (PIN C + PIN P = DRIVE (1).

[80coupe]

rustypnus it a guru with elect but dont know if he is doing it on the side with his job he has now!

[dville_gt]

Your making shit way more complicated then it needs to be. Flash a 6 speed VIN in the car and continue tuning..

Won't fix the issue of a sudden load being introduced on the motor.

[dville_gt]

Wouldn't a single pole double throw relay accomplish this?

[dville_gt]

When the coil of an SPDT relay is at rest (not energized), the common terminal (30), or ground in my case, and the normally closed terminal (87a) (PIN B and PIN C) have continuity. When the coil is energized, the common terminal (30), or ground in my case, and the normally open terminal (87) have continuity (PIN A and PIN P).

[Diabolic]

Perhaps you could get your tuner to allow for more timing to be added in the load range your car experiences when put in gear at idle rpm. THis would be the mbt or brake torque timing table. In Fords there is also spark bordeline temporary load increase table that could be utilized to increase the timing for a second or two while the transition is taking place. This is in the stratgy for my 95 Cobra and you most likely have something similar in your GM strategy.

[jw33]

So for example:

I need a really that when provided +12v will ground PIN A and PIN P (Park), when the +12 is removed it needs to ground PIN B and PIN C (Drive)

Hook up your switched 12V to 85, ground to 86, another ground to 30, PIN A and P to 87, PIN B and C to 87a.

[dville_gt]

Perhaps you could get your tuner to allow for more timing to be added in the load range your car experiences when put in gear at idle rpm. THis would be the mbt or brake torque timing table. In Fords there is also spark bordeline temporary load increase table that could be utilized to increase the timing for a second or two while the transition is taking place. This is in the stratgy for my 95 Cobra and you most likely have something similar in your GM strategy.

You are still going to miss out on a ton of idle strategy stuff this way, just at a quick glance there are more then 10 different idle tables that want to know if you are in P/N or in gear. Not to mention when looking at the log the cylinder airmass vs rpm table that you use to adjust timing doesn't change when it is shifted into gear.

[dville_gt]

Hook up your switched 12V to 85, ground to 86, another ground to 30, PIN A and P to 87, PIN B and C to 87a.

Ya, once I wrote it all out and posted it I started thinking, umm, wouldn't a SPDT relay work just fine here? Still interested to see if there are any other idea's but I am pretty sure this has to be the easiest.

[jw33]

As long as your 12v is strong enough to pull that coil closed and you give it a good clean ground, it will work.

[dville_gt]

As long as your 12v is strong enough to pull that coil closed and you give it a good clean ground, it will work.

It is already pulling the starter relay so I doubt it'll be a problem.

[Diabolic]

You are still going to miss out on a ton of idle strategy stuff this way, just at a quick glance there are more then 10 different idle tables that want to know if you are in P/N or in gear. Not to mention when looking at the log the cylinder airmass vs rpm table that you use to adjust timing doesn't change when it is shifted into gear.

.

No but the load vs rpm does change. I have a spark adder based off load vs rpm.