Advance signal?
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Any ways i saw a guy that put a voltmeter on the wire that sends the advance signal to the module and he said it was around 1.6 volts at idle. close to 3 volts at 3000 rpm. 195 engine temp on scanner half throttle in gear stopped is around 2 volts.
he said if he gave it more throttle the voltage drops and it backfires out the tb and almost dies. If he umplugs the temp sensor and plug in the extra one and just let it hang so the ecm sees 80-100 and do the same test half throttle is still around 2.0 volts but if I lean into it more the voltage goes up over 2.5 close to 3 and it starts spinning the tires(which says a lot in a truck with 265s 3.42s and 500 pounds of racing gear in the back.
he later found out that he did'nt have his timing set correctly because when he set his base timing he did disconnect a connector but not the right one and so his timing was off!
I was just thinking that by him measuring the voltage at that wire i assume he was able to monitor wether is advance was working
for example when the voltage went up to 3 volts mayby he was seeing 30degrees of advance
I'm not saying your wrong about the wire that you disconnect to set base timing being the one that you monitor but i was thinking that that wire that you disconnect would just disable the spark advance and mayby the top wire in the schematic would be the one you'd monitor.
In the schematic above C stands for Computer
he said if he gave it more throttle the voltage drops and it backfires out the tb and almost dies. If he umplugs the temp sensor and plug in the extra one and just let it hang so the ecm sees 80-100 and do the same test half throttle is still around 2.0 volts but if I lean into it more the voltage goes up over 2.5 close to 3 and it starts spinning the tires(which says a lot in a truck with 265s 3.42s and 500 pounds of racing gear in the back.
he later found out that he did'nt have his timing set correctly because when he set his base timing he did disconnect a connector but not the right one and so his timing was off!
I was just thinking that by him measuring the voltage at that wire i assume he was able to monitor wether is advance was working
for example when the voltage went up to 3 volts mayby he was seeing 30degrees of advance
I'm not saying your wrong about the wire that you disconnect to set base timing being the one that you monitor but i was thinking that that wire that you disconnect would just disable the spark advance and mayby the top wire in the schematic would be the one you'd monitor.
In the schematic above C stands for Computer
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It disables the spark advance to the distributor by removing the signal from the ecm to advance the spark. That's a neat idea of monitoring the voltage there but there is a lot more variables there that would affect the advance besides temperature sensor. What year vehicle does your friend have? Even if its an 80-90s truck/van, there are multiple spark tables involving temperature, rpm, load, and air/fuel to name a few. If its a newer vehicle, there are even more.
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I'm not sure what year truck he has but i know he put a 1996 vortec engine in it with a TBI intake that was made for Vortec heads , the guys a GM technician and i thought it was interesting that he was monitoring that voltage at the advance wire but i was'nt sure what exact information he would be getting from the voltage readings.
Since the TBI heads and cam and the Vortec head and cam require different fuel curves ,He took the yellow wire from the ecm temp sender and wired in a 0-5000 ohm adjustable resistor in line , This way its set now his ecm sees the engine as cold
when it is but only sees about 150 when its fully warmed at 200. The extra fuel
makes up for the improper fuel curve, for the most part. he did this as a temporary tune until he gets a proper chip burn .
Since the TBI heads and cam and the Vortec head and cam require different fuel curves ,He took the yellow wire from the ecm temp sender and wired in a 0-5000 ohm adjustable resistor in line , This way its set now his ecm sees the engine as cold
when it is but only sees about 150 when its fully warmed at 200. The extra fuel
makes up for the improper fuel curve, for the most part. he did this as a temporary tune until he gets a proper chip burn .
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