baronbob

I have a stock 7.4 MPI with a procharger M-1. I have installed two F.P. gages, a mech. on the regulator an elec. on the dash. I would like to know if the motor has sensed knock and have a big light and/or horn warning of same. Any ideas?

Scott

Great idea!
They do make a knock sensor gauge for the dash. The problem I see with trying to just hook up a Light or horn is that the knock sensor I'm guessing works off a pulse to the module. It never goes to complete ground and would require like it does now a module to "read" the pulse and then process it to a signal that would work with a gauge, light or buzzer. It would be nice to see an actual schematic for the existing systems that cut back the advance.

Remember this is a guess

Dave_N

Not sure about how you could rig a light or horn, but you could use a stardard knock sensor and knock sensor module connected to a volt gauge at the dash.

When the knock sensor sends a signal to the module that it has detected a knock, the module removes the voltage sent to the ECM (normal voltage with no knock is 8-10 volts), and the ECM retards the timing until no knock is detected. Instead of sending the voltage to the ECM, you have it send the voltage to a volt gauge on the dash.

You could watch the gauge and when the voltage drops below the normal 8-10volts, you have a knock present.

I have never done this, just throwing it out there for consideration.

Dave

Dave_N

After thinking about it a little, I think you could use the voltage to trigger a relay such that when the voltage is removed (knock detected) the relay closes and completes a circuit that would sound a horn / light a warning light.

Dave

Scott

Dave,
Thanks for the diagram. Now I understand

Just to add one thought I would use an electronic relay instead of a coil type. This way you won't pull down the voltage possibly causing problems or a false read at the ECM. I would have to guess the voltage out of the Knock sensor would be milliamps and not handle any load at all.

Dave_N

You know I missed the part about it being an MPI engine . I thought it was a carbed engine without an existing knock control system. I would not tap anything into the knock sensor output to the ECM, as Scott pointed out, it could affect the operation of the system with disasterous results.

Dave

US1 Fountain

iTrader: (1)

just a heads up, be very careful when tapping into the ECM wiring. I recently 'learned' this little tid bit while rewiring my relays for the dash warning lights.
12v sent the wrong way makes for a very expensive lesson. $350 for a used ECM, up to $350 to reprogram.

hillbilly24

I woudn't tap into the existing knock sensor but installing another one wouldn't be a big deal. Knock sensor's have a small piece of quartz in them wich is a strange rock, when you impact it with something or shake it violantly it actually releases minuscuel amounts of voltage and that is how it works, it does not produce near enough current to operate a relay or anything else like it. You could build a pretty simple circuit board with a $10 proscesor that could sense the tiny voltage spikes from the sensor though.