pcmhacking.net

8 track....now ya talking,quadraphonic stereo

I tried putting an original knock sensor in the Munro but the big starter
motors hit the sensor.
Then I decided to try the other side of the block but the dipstick
tube gets in the way
I know I have an efi small starter somewhere but bugger me if I can find it.

202t....you have been more than busy with all your projects.

When I had mine on the dyno the other week I just screwed it in to the bolt hole bellow the engine number. Don't know what type of knock sensor it was but biggvl would as it was his knock sensor

monaro308 wrote:For anyone that has an aux port in their stereo,just wire up an alloytec or ls knock
sensor and plug it in.
Work uses this method as a back up when using a towing dyno.

This definitely works, bought a knock sensor from trademe, some 2 core shielded cable and 3.5mm stereo plug to suit stereo aux input all for about $45, cut an injector plug off an old wiring loom and soldered it all up, plugged it in and bingo, working knock sensor

Awesome, hopefully get to test it out next weekend at the drags, just need to figure out a good spot to mount it on my mates 355.

What frequency range does knock normally occur? Hopefully we can tune out some of the excess noise using the stereo's equalizer.

depends on the bore size. somewhere around 6khz? for our engines.

It's a 355 Holden V8 so most likely 4.030" bore.

5.6Khz going by this.

http://www.phormula.com/KnockCalculator.aspx

i know in the ecotec Flash pcm Code for VX & VY Holden used 5.05khz Bandpass Filter Center Frequency with a 2DB Gain.

The1 wrote:i know in the ecotec Flash pcm Code for VX & VY Holden used 5.05khz Bandpass Filter Center Frequency with a 2DB Gain.

Isn't the knock sensor circuit(s) different on the ecotec flash pcm's compared with the earlier ecotec PCM in the VS-VT ?
I was told the earlier pcm's knock sensors were linked where as the flash pcm's two knock sensors were separated.

Did Holden use a different kHz for the two different PCM's ?

Cheers

This is what ive been able to workout so far, i have it on my long list to work it out some more and implement a better system for the enhanced code.

VS-VY Memcal models have the 2 sensors wired back to a standard A/D Single Input, the PCM just monitors it, if it see's a change for more than 2 code loops it then starts the ESC code, so essentially no frequency monitoring just a set of ignore times, attack and retard rates. Hence why VS-VY's are so aggressive when cam's are installed as the code gets tripped all the time by the valvetrain.

The Flash PCM uses the same setup but each knock sensor goes to it's own input, so one for each bank, it then works out which cylinder it's on via cam signal and then makes time windows from there to help calculate frequency and gain.

From testing so far on memcal code the ignore time is used during each 3x pulse, so you can change the ignore time to vary where in the 3x window you operate the knock.

guys, I think it maybe time we came up with our own circuit with adjustable band-pass, bandwidth and gain for an anoluge knock box.



The criteria I want to meet is.

1. adjustable gain with independent gain control per channel. Balance control a better term?
2. adjustable band-pass frequency to suit different bores.
3. dual channel input and stereo output for head phones. (ie, twin sensors) mono mode for single senors or twin (useful for people deaf in one ear)
4. adjustable bandwidth of the band-pass.


the professional knock box is only adjustable over all gain and thats it. has dual input and L/R head phones but its all mixed mono audio I have found using Biggvl's one. The worst part it costs quite a few 100 bucks and should be a whole lot more flexible for that price.

Plex do make a knock box like I describe plus DSP and digital interface and logging to boot. its around 850 EUR last I looked.

I found with knock, audio is by far the most valuable feedback, logging is all great but how do you prove what an ECU or digital knock filter is seeing is for real. Having tuned quite a few engine now using knock ears and comparing to what electronics thinks is knock, its very questionable at best, most of the time completely useless.

Its introducing that human oversight that gives real verification.

Ok, ready set...... discuss!