Knock Sensor Output?

[turbo_bu]

I read in a recent post on how to hook up a factory knock sensor to a FAST system.

http://www.turbobuick.com/forums/showthread.php?threadid=91413

I have a sequential FAST system so I am unable to utilize this feature, but I would still like to have some form of knock reading. Does anybody know what type of signal is outputed by the factory knock sensor box? PWM, 0 to 5 volts, ???

I am thinking of doing a DYI knock sensor readout so I have a little warning about what is going on. I know that they make extrnal stand alone boxes, but the ones I have seen only flash a light / sound an alarm. I would like to know that the ECM would be trying to pull out 2 degrees of timing, or 20 degrees of timing.

 

[Glen]

The trouble tree says under 6 volts on wire "C". Over 6 volts and replace ESC module. This is based on '86-89 V-8 TPI

 

[TurboTR]

Several people have done DIY knock beepers. The GN ESC module provides the analog interface to the actual sensor. The module output to the ecu is just an active low digital out basically. The module makes the hardware decision that knock is occurring. The ecu knock processing code may then make some additional judements as to what exactly to do when the ESC signals in. I think our own board member ijames has posted some of that routine before. Anyway, when there is no knock the ESC signal stays high, around 10v or so. When the ESC module decides that knock is occurring the signal pulls low, near 0v. Some in the know have hinted that the duration spent low is proportional to the knock intensity, but good luck trying to decide on that. Most boxes just beep when the signal goes low basically.

TurboTR

 

[turbo_bu]

Originally posted by TurboTR
.....The ecu knock processing code may then make some additional judements as to what exactly to do when the ESC signals in. I think our own board member ijames has posted some of that routine before. Anyway, when there is no knock the ESC signal stays high, around 10v or so. When the ESC module decides that knock is occurring the signal pulls low, near 0v. Some in the know have hinted that the duration spent low is proportional to the knock intensity, but good luck trying to decide on that. Most boxes just beep when the signal goes low basically.

TurboTR

Do you have a link to the post where ijames talked about the routine? If it is a duration thing, a counter / timer could be used to "correlate" so many degrees of knock to the signal. ????? Not sure if it would work, just trying to see if it is possible

 

[John at J&S]

Don't remember where I read it, but the software varies the amount of retard per knock with RPM.

 

[ijames]

I've posted some stuff here and on gnttype.org. Dennis Leek has just finished a writeup on the esc stuff that puts it all in a nice package. Go to http://www.turbotweak.com/Knock.pdf for his paper. There's some other stuff he's written also at turbotweak.com that's good reading.