LT1 24x Conversion - No knock retard, ever.

[jahajazz]

Hello,

I have a 383 LT-1 which has been converted to run a 411 PCM with coil per cylinder ignition. The problem is, no matter what I do to the tune, I never see knock retard. This has me worried and thinking I've messed something up in the tune or knock sensor wiring.

For example, I tried the trick of hitting the block with a screw driver and still got zero knock retard.

I have tried pushing advance slowly up to 50 while idling, and no knock.

Can anyone provide some tests I can do? If I backprobe the knock sensor pins, is there a voltage or resistance I can look for?

[joecar]

Which knock sensors are you using...?

[jahajazz]

GM 10456287, which is the LT1 knock sensor. Its the same knock sensor used in the 2001 GMC 5.7 van, which is the factory SBC using the 411 PCM.

Are there sets of tables used to configure the pcm for the knock sensor?

[joecar]

You may have to use the calibration file from the 2001 GMC 5.7L van (i.e. the PCM may be tuned to the knock sensor type).

Edit: I meant copy all the knock sensor tables/parameters

[jahajazz]

Thats an interesting idea. However, since I've got coil per cylinder ignition, I think it wouldnt start as the van tune is expecting a distributor.

[5.7ute]

I think he meant to copy all the knock sensor tables from that calibration.

[Tom B.]

I know this is an old post. I had the same problem with a 411 swap on an LT4. After modifying the tables using the 2002 L31 parameters, I had to zero out the {B6244} Knock sensor multiplier "A" I then reduced the {B6245} multiplier "B" table 50%. {B6246} and {B6247} also set to zero. {B6250} and {B6255} reduced 75%. I hope this helps. (P.S. remember to set {B6201} value to 1)

[joecar]

I know this is an old post. I had the same problem with a 411 swap on an LT4. After modifying the tables using the 2002 L31 parameters, I had to zero out the {B6244} Knock sensor multiplier "A" I then reduced the {B6245} multiplier "B" table 50%. {B6246} and {B6247} also set to zero. {B6250} and {B6255} reduced 75%. I hope this helps. (P.S. remember to set {B6201} value to 1)Tom, Thanks,

[Highlander]

I am going to post something soon that should solve this issue.

[evilstuie]

I am going to post something soon that should solve this issue.

I'd be interested in this as well.

I have a SBC400 with x24 conversion that uses a COS 01290003 tune but using the old TPI knock sensor and I don't get any knocks logged at all.

[Tom B.]

I was able to restore the knock software tables back to within 90% of the stock settings. Using the Road Runner RTACS was a major help in getting the VE and timing maps sorted out. I don't think there is a proven solution for the 24X conversion due to all the variables in each engines components. I would start by increasing the Knock sensor sensitivity in 10% increments until you see some knock retard.

[evilstuie]

Any update on settings for this yet?

[evilstuie]

Any update on settings for this yet?

Guess not.

Well so far I've found that most people use the express van knock sensors:
2002 Express Van 5.7L knock sensor -- 10456288 and use the knock tables from one of them.
Either set to engine mode and it gets a lot of knock with the sensitivty set low, or cylinder mode, and doesn't seem to get any.

I've got one of these sensors and going to see if i get any knock once it's installed.

Otherwise the 2nd option and possibly the better one is that EFI-Connection now sell a bung that screws into the SBC/LT1 knock sensor location and allows you to use the smaller threader ls style knock sensors.
You'd still need to adjust the tables and sensitivty etc to account for the differences in location and block material. I think older ls1's were iron blocks so might be good to start with those types first.?

Anyone else got some insight into the knock sensor for SBC/LT1 setups and tables?

[Highlander]

The problem is that when you change the knock sensor location they are listening at the wrong time.

Knock sensor 1 listens to cyl 1-2 and knock sensor 2 listens to the rest. Not in a bank like location like the injextors or o2 sensors are.

[evilstuie]

The problem is that when you change the knock sensor location they are listening at the wrong time.

Knock sensor 1 listens to cyl 1-2 and knock sensor 2 listens to the rest. Not in a bank like location like the injextors or o2 sensors are.

Oh ok. How does it know when to listen though on a normal ls1?
Wouldn't it just be listening all the time and reference it to the CPS position?
If so it just means you'd get DTCs for wrong cylinders.

I'm more just worried about knock from timing issues from table errors for the motor as a whole rather than individual cylinder knock detection/diagnosing.

I've heard there's plenty of people running these setups, but no info on the knock sensor setup, it seems to be a big mystery non-one wants to share.