EA82T knock sensor monitoring....

steptoe · Post by **steptoe** » Thu May 24, 2012 11:24 pm

started this a year ago by hooking up a multimeter to the diagnostic terminal near the coil, timing light on marks and tapped block to see multimeter go from normal 1.7V to 4.5V then timing adjusted back 10 degrees, then worked its way back to normal timing mark of about 18 for me.

On the road test with multimeter and fanging as much as dare - no Voltage change at all - a trailer may be changing that ....

Since mounted an analogue Volt meter in clock hole and never seen it budge off 1.7 V, may not be sensitive enough to register on the cheapy, so thinking old multimeter (now that Dick Smiths done generous close down deals ) in similar dash location and either hook up an IGN on relay to switch its own 9V battery or resistor or diode down twelve V to nine and feed it direct to see if any movment. Swear I can hear pinging with a 450kg trailer and its load .....

fredsub · Post by **fredsub** » Fri May 25, 2012 12:27 am

you will need something like a logic probe that can catch fast digital pulses
and give a LED indication of the pulses or an oscilloscope.
Not surprised a digital multimeter doesn't show any voltage change, they usually take nearly a second for a analog/digital conversion.
If your meter has a frequency or Hz setting, you might get some sporadic
numbers when its pinging pulses......
Likewise, an analog meter best shows an average voltage, no way would it
indicate fast pulses.

steptoe · Post by **steptoe** » Fri May 25, 2012 9:35 am

BUT, if you reread my as-yet unedited post, multimeter DID pick it up, it was the analogue panel meter that didn't, the change is not all that quick to go from retard to advance. What would be good would be a buzzer circuit that would buzz above the 1.7V , any suggestions other than a 4.5V buzzer , which is three 1.5 batteries, almost an old VW or motorcycle 6V horn !!

Gannon · Post by **Gannon** » Fri May 25, 2012 5:21 pm

Id say the output voltage would be of a high impedance source, so the analogue meter was drawing more power than the knock unit would supply, pulling the voltage down.

Something like this perhaps... http://www.ebay.com.au/itm/Mini-DC-0V-9 ... -Voltmeter

steptoe · Post by **steptoe** » Fri May 25, 2012 6:31 pm

Yup, ordered one from my local man in China with a zero to 50 V monitoring range

Gannon · Post by **Gannon** » Fri May 25, 2012 6:51 pm

Does it have 3 wires? A lot of chinese ones only have 2 wires and only measure the supply voltage. 3 wire ones can measure a voltage separate to the supply

steptoe · Post by **steptoe** » Fri May 25, 2012 8:02 pm

Uh OH....

how's about five wires

http://www.ebay.com.au/itm/DIGITAL-AMP- ... 3caf0b1f33

I got the last blue one , two bucks dearer

about right size for L Series clock hole too !

fredsub · Post by **fredsub** » Sat May 26, 2012 10:06 am

i'm thinking diverting eyes off the road, watching that meter, while your boot is putting the boost on and your going faster.....not a good idea:eek:

buzzer idea is good, but the implementation would require a comparator circuit, or maybe just a transistor switch, can't just connect a buzzer to such a digital/ECU signal output.

Gannon · Post by **Gannon** » Sat May 26, 2012 10:33 am

Nice find, this meter can measure current up to 200A too.

steptoe · Post by **steptoe** » Thu Dec 20, 2012 6:37 am

Hot weather update:

I switched voltage monitor to knock mode rather than battery

(BTW the unit I upgraded to, with LCD & switchable blue backlight , extra $2, instead of bright fluoro digits - the screen cover cannot handle our hot sun - bubbled up one end)

Engine metal temp 84C, outside air temp in shade 34C

As Fredsub says not good watching gauges etc while boost is shoving me a long so I missed the boost reading - likely about 10 psi in fourth and about 4200rpm , level road and about 110kph and noted readout shift for the first time , went from 1.7 to 2.2 and gradually to 3.3 V. Now, not sure if it needs to hit 4.5V before it activates full timing retardation but I suspect it does incrementally. It may have been 10 seconds betwen readout changes , up and down, I never saw it hit 4.5 , never felt any loss of perfortmance as I went along, so was keeping ignition in check. Another few runs saw similar result until I ran both fans and got engine temp down to 70C, then did not see more than 2.2V.

Now , curious to see if I reduce boost max to about 8 psi and see if still activating retard control.....