P01 PCM on SBC L31 Vortec Pros and Cons to running a 4x vs 24x Crank Reluctor OS

[ASX29]

I have a L31 Vortec that I was going to do a P01 PCM swap. I do have a spare 24x reluctor wheel sitting around that I could externally mount on the balancer as option 1 with the crank sensor mounted like a crank trigger. Or option 2 would be to buy the 24x reluctor to replace the 4x on the vortec behind the timing cover. Are there any benefits to running a 24x or should I just stay with the 4x OS to keep things simple? The cost of licensing the PCM and then an Express 5.7 tune wouldn't be worth keeping it simple if there are more enhancements on the 24x OS side of things. I was going to download a stock 5.7 L31 tune file to compare but wanted to ask first. I will be running a 4l80e with this setup so would the segment swaps still be the same for the L31 tune files?

Thank you in advance!

[5FDP]

The P01's only run on a 24/1x crank/cam trigger.

[ASX29]

The P01's only run on a 24/1x crank/cam trigger.

I thought I would be able to do a 'write entire' of a 2002 Express 5.7 tune file. No?

[ASX29]

Or is that only possible with a 411 PCM?

[5FDP]

My bad, I had LS engines on my mind, those are 24/1x on the P01's.

But yes, you could flash a P01 with a 5.7 Express Van file to run a L31 engine. That is usually the best route to go when doing a P01 computer swap.

[blindsquirrel]

The setting for 4x/24x is at System>General>System Options, 'Crank Low Res'. '1' is 4x, '0' is 24x.

[ASX29]

The setting for 4x/24x is at System>General>System Options, 'Crank Low Res'. '1' is 4x, '0' is 24x.

With that said do I even need to license a 4x tune file or can I just change the crank to low res on the stock tune on for the P01 PCM?

[blindsquirrel]

There is A LOT of stuff/code/data in a tune file that doesn't appear in the Editor's GUI. If you have an actual L31 I don't know why you wouldn't start with a real L31 OS, even if you might be able to get it to fire and/or run with the LS base OS. Assuming the PCM Service Numbers are compatible that is.

[ASX29]

Sounds like I have a couple options. I did notice when looking at an older 1999 5.3 tune file that I do not have the crank low res option in the system settings However, the 2002 L31 file did. I haven't read the file off the PCM I got yet to see what OS version it is running. The L31 file looks very similar to a licensed 2001 5.3 P01 file that I have. I will try my file first by changing the crank low res setting. The reason I didn't want to use a L31 file to start with because if I ever wanted to do an LS swap I didn't want to license another file when I can just change the crank setting back to 24x (and the firing or as well)

[Shnraines]

Would like to know how it drives if you just change to 4x crank. I have started a l31 engine as a test just changing to 4x, but didn't drive it. If I remember correctly it didn't rev well. Firing order would only matter for injectors

[blindsquirrel]

2002 Express 3500 5.7 4L80E 1GAHG39R621203269.hpt
2003 Express 3500 6.0 4L80E 1GCHG35U131147731.hpt

edit: maybe an oops, the '03 is P59

[Fast4.7]

Sounds like I have a couple options. I did notice when looking at an older 1999 5.3 tune file that I do not have the crank low res option in the system settings However, the 2002 L31 file did. I haven't read the file off the PCM I got yet to see what OS version it is running. The L31 file looks very similar to a licensed 2001 5.3 P01 file that I have. I will try my file first by changing the crank low res setting. The reason I didn't want to use a L31 file to start with because if I ever wanted to do an LS swap I didn't want to license another file when I can just change the crank setting back to 24x (and the firing or as well)

Just start with a 2002 operating system. If and when you LS swap, segment swap to a LS engine tune for the displacement you choose. Worked like a charm on my buddies 1997 6.0L swap and my 1999 Tahoe 8.1 swap.

[ASX29]

I appreciate the info and advise everyone! Good thing is I have options to try unlike other things I try to do.