12200411 PCM swap for 1996 to 2000 GMT400 trucks

[Mildphil]

Base tune was retarded easy for me. Swiped VE table from a black box, guessed on a spark table, kept existing MAF table, mish mashed 5.7 and 8.1 idle ****, told it it was a 454, and the truck worked well from the get go. I didn't swipe the 8.1 knock sensor info and I should have and plan to. I first want to log observed knock and the spark trims before they're lost by simply flashing new knock sensor values into the PCM.

Good, that's reassuring. I was very confused about how the tuning works. How much does it cost for all the equipment to tune it?

 

[AK49BWL]

I'm not so sure you can just throw an unmodified 8.1 PCM onto a 7.4, due to the differences not only in spark firing order, but injection order (which cannot be changed in the tune the same way firing order is), and the fact that the 8.1 likely has the 24x reluctor with CoP ignition, where the 7.4 likely only has a 4x reluctor - tunes between the two are not interchangeable. The tune table values might work, but the OS itself wouldn't, at least from my understanding, and if I'm wrong, (anyone) please let me know... But I do believe the PCM would need to be full-write retuned with base values from a 4x reluctor tune before trying to install it.

 

[Christian Steffen]

I'm not so sure you can just throw an unmodified 8.1 PCM onto a 7.4, due to the differences not only in spark firing order, but injection order (which cannot be changed in the tune the same way firing order is), and the fact that the 8.1 likely has the 24x reluctor with CoP ignition, where the 7.4 likely only has a 4x reluctor - tunes between the two are not interchangeable. The tune table values might work, but the OS itself wouldn't, at least from my understanding, and if I'm wrong, (anyone) please let me know... But I do believe the PCM would need to be full-write retuned with base values from a 4x reluctor tune before trying to install it.

Definitely need to do a full write with the correct OS, 12212156.

Good, that's reassuring. I was very confused about how the tuning works. How much does it cost for all the equipment to tune it?

There is a bit of a learning curve to the tuning but its not awful. The cost depends on the system used, i believe efi live is $800 or so? Hp tuners standard is cheaper, like $300 plus credits, but if you're going to tune a lot of vehicles EFI live probably pans out as more cost effective. Also if you're considering tuning a diesel efi live is better, it can be done with hp tuners but the support isn't as good.

 

[Supercharged111]

I'm not so sure you can just throw an unmodified 8.1 PCM onto a 7.4, due to the differences not only in spark firing order, but injection order (which cannot be changed in the tune the same way firing order is), and the fact that the 8.1 likely has the 24x reluctor with CoP ignition, where the 7.4 likely only has a 4x reluctor - tunes between the two are not interchangeable. The tune table values might work, but the OS itself wouldn't, at least from my understanding, and if I'm wrong, (anyone) please let me know... But I do believe the PCM would need to be full-write retuned with base values from a 4x reluctor tune before trying to install it.

I don't know if you can full flash a 350 tune onto an 8.1 PCM. I know the transient fuel tables are 3D vs 2D because I wanted to steal the 8.1 transient values for my dually but it was apples and oranges. On the other hand, you could just tell the 24X tune that it has a low res reluctor and it would look for the 4x wheel. Now you've got me thinking of trying this on mine assuming it's compatible with a custom operating system. . .

 

[AK49BWL]

I've often wondered myself if it's possible to just "tell" the computer to use Crank Low-Res and it would automatically switch to distributor mode rather than CoP. But I do know that you can't use a CoP output on a distributed engine because the output for the ICM on distributor engines, is Cyl 1 ONLY on CoP engines (PCM has 8 outputs, one for each coil, rather than an ICM)... Meaning you would be missing 7 spark triggers to the coil per 2 revs.

 

[Mildphil]

Definitely need to do a full write with the correct OS, 12212156.


There is a bit of a learning curve to the tuning but its not awful. The cost depends on the system used, i believe efi live is $800 or so? Hp tuners standard is cheaper, like $300 plus credits, but if you're going to tune a lot of vehicles EFI live probably pans out as more cost effective. Also if you're considering tuning a diesel efi live is better, it can be done with hp tuners but the support isn't as good.

I'd probably only ever tune my truck with it. I do have a WS6 Trans am which has a factory 411 PCM, but It is bone stock so I don't think tuning would do anything, besides maybe killing off the VATs system directly from the pcm? Is there any special hardware required to do the tuning?

 

[Christian Steffen]

I'd probably only ever tune my truck with it. I do have a WS6 Trans am which has a factory 411 PCM, but It is bone stock so I don't think tuning would do anything, besides maybe killing off the VATs system directly from the pcm? Is there any special hardware required to do the tuning?

Just a cable to connect to the laptop..

And its possible there would be gains from tuning the ws6. Timing is usually conservative and dialing in the AFR can help a little. Eliminate burst knock and reduce TM. Etc.

 

[Mildphil]

Just a cable to connect to the laptop..

And its possible there would be gains from tuning the ws6. Timing is usually conservative and dialing in the AFR can help a little. Eliminate burst knock and reduce TM. Etc.

So just cable +software+computer? Not bad. What Is TM? Haven't had any knock issues with my car before, I'm always far more hesitant to modify anything on the trans am as it's so nice, only 50k miles.

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[Christian Steffen]

So just cable +software+computer? Not bad. What Is TM? Haven't had any knock issues with my car before, I'm always far more hesitant to modify anything on the trans am as it's so nice, only 50k miles.

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Pretty much yeah, you pay for the interface and that gets you the hardware.

I'm Doubting you have any issues with knock now, I should have clarified. Burst knock is a predictive knock retard based off of rapid airflow increases. So it pulls timing without there actually being knock. The stock knock sensors do a good job so this can be disabled.

Tm is torque management. It limits torque during shifts. If you do have an auto it might be worth leaving mostly intact. 4l80e's don't need it but 4l60s do.

Looks like a very clean ws6.

 

[Mildphil]

So just cable +software+computer? Not bad. What Is TM?

Pretty much yeah, you pay for the interface and that gets you the hardware.

I'm Doubting you have any issues with knock now, I should have clarified. Burst knock is a predictive knock retard based off of rapid airflow increases. So it pulls timing without there actually being knock. The stock knock sensors do a good job so this can be disabled.

Tm is torque management. It limits torque during shifts. If you do have an auto it might be worth leaving mostly intact. 4l80e's don't need it but 4l60s do.

Looks like a very clean ws6.

Ah ok, I understand the while k lock thing now, it's pretty much redundant due to the sensors. And my car is a 6 speed so would the torque management actually do anything? Is it even applicable to a manual car? Thanks for the wealth of knowledge BTW, this whole 411 swap/tune is very intriguing.