GM ESC modules and matched knock sensors.

[NomakeWan]

Just remember that the sensor and the module are two totally different things. I'm not suggesting you need to do anything with the sensor. But if you want the existing EFI to do knock retard like factory, then the knock module is what you have to adjust, and all it does is pull a line low to tell the ECM/PCM when it thinks knock is occurring. Sounds simple in theory, but when we don't know the pinouts for the module and have to account for how much knock to report and when, things get tricky.

There are absolutely other ways of doing it. It's ultimately only if you want to use factory hardware that you end up in the situation where you would need to create your own custom knock module.

[dfarr67]

There are absolutely other ways of doing it. It's ultimately only if you want to use factory hardware that you end up in the situation where you would need to create your own custom knock module.

And there is the rub- the engine is far from factory- and relatively noisy, so the knock system is not that useful.

As an aside, engine was intended to be 9.5:1 modeled after vortec with AFR head/FIRST TPI, have been trying to tune to 87 octane- I have a few avenues left to try but have audible ping in certain areas. Where do you give up and move up in octane?

[1project2many]

I have a few avenues left to try but have audible ping in certain areas. Where do you give up and move up in octane?

After failing to reduce knock by adding 1oz MEK per gallon to your 87 octane fuel. :-)

[dfarr67]

This is an EBL setup, and the ping has been an issue for some time. I dabble in tuning so don't really know it well. I was thinking last night that the learns is doing its thing, I've cut PE/SA to 0, I've taken 5 deg out universally and although it clears up most of the knock table it will still ping in a certain area even with 0 timing. I've filled up it up with better octane and the same thing. So I'm thinking it's going lean under heavy throttle and options are PE, AE, or VE adjustments. This is a 383 sbc with modern alum heads and a version of tpi- so I'm also thinking the tuned ram is really doing something.

[1project2many]

In order to stop kock the KS system will reduce spark advance when knock is detected then advance spark back to the ECM desired timing while knock is not occurring. If knock occurrs at any time then spark advance will again be reduced. In order to ensure effectiveness I would look at the kock and spark advance during knock to ensure the minimum allowed advance is not too high. If spark advance cannot be reduced enough then knocking will not stop. I would then look at the initial retard when knock occurrs and the rate at which the system returns advance.

And I wouldn't be afraid to add MEK. :)

[dfarr67]

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[Tom H]

I have been looking at the knock module from various LT1 and V6 applications in the late '90s. The circuit is housed in a plastic carrier with eight contacts. Inside there is a hybrid circuit (I believe it is thin film). On the circuit are a number of capacitors (one looks to be a larger polarized tantalum cap), LASER trimmed resistors and two ICs. One of the integrated circuits is a soic 8 pin manufactured by philips (marked NE532D dual op-amp [edit]) the other has a higher pin count (perhaps 16 pin) and is not packaged. The second chip has no markings because it is not packaged. I believe the part is made with solder bumps and is mounted directly on the substrate.

I find it interesting that when manufactured, the hybrid is mounted in the top of the plastic housing with some very low density elastomer. This material is very soft and I believe is used as a sound deadener to prevent flexing of the substrate from becoming microphonic. That is to say that the module could under some circumstance pick up vibrations and turn them into unwanted signal.

I plan to look at this module in the future & try to find it's operation, but for now this is all I have found.

One question for the group... knock is when the compression cycle heats the mixture to the point where it ignites before the spark (pre-ignition). How does retarding the spark seek to cure this? I can see how making the mixture richer might cool things. Overall retarding the timing would cool things when knock isn't present. Perhaps someone could explain?

-Tom