GM LS3 crank wheel gap/TDC relationship
12-09-2014, 05:09 PM
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GM LS3 crank wheel gap/TDC relationship Hello,
I am working on an ignition design for a carbureted LS3 (I am an EE), and I'm trying to find the timing relationship between the gap in the crank sensor wheel (the 58x wheel) and the crank position. I saw in a couple of places the statement that the GM 58x wheel gap "starts at 30 deg ATDC of cyl 1", but in looking at the LS3 I have on the stand, that does not seem to be correct. If I turn the crank by hand, the start of the gap as seen through the sensor hole by the starter motor is actually about 5 BTDC of cyl #3 (the last cylinder in the sequence), OR 95 deg BTDC of #1. The gap ends at 80 deg BTDC #1, so it is about 15 deg wide. I can't seem to reconcile this discrepancy. Does anyone know what the gap AT THE SENSOR relationship to TDC #1 is? Where does the "30 degree" figure come from?
Thanks,
Dave T.
I am working on an ignition design for a carbureted LS3 (I am an EE), and I'm trying to find the timing relationship between the gap in the crank sensor wheel (the 58x wheel) and the crank position. I saw in a couple of places the statement that the GM 58x wheel gap "starts at 30 deg ATDC of cyl 1", but in looking at the LS3 I have on the stand, that does not seem to be correct. If I turn the crank by hand, the start of the gap as seen through the sensor hole by the starter motor is actually about 5 BTDC of cyl #3 (the last cylinder in the sequence), OR 95 deg BTDC of #1. The gap ends at 80 deg BTDC #1, so it is about 15 deg wide. I can't seem to reconcile this discrepancy. Does anyone know what the gap AT THE SENSOR relationship to TDC #1 is? Where does the "30 degree" figure come from?
Thanks,
Dave T.
08-20-2017, 01:48 AM
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Don't know if this specificly answeres your questions but, from my understanding you need the gap in the 58x reluctant wheel for the ECU to start/restart its count so the first tooth after the gap is number one count. on my LY6 cylinder #1 TDC starts at the falling edge of tooth 15. that would be 1 tooth equals 6 degrees so 15•6= 90 degrees. the biggest reason the gap is befor cylinder one is it looses resolution or looses 12 degrees of resolution when passing over the gap. also just FYI at TDC the cam sprocket is in the middle of the half moon gap on the falling edge (keeping in mind the engine spins clockwise)
hope this helps you and anyone who needs these specs for setting up a 58X (60-2) crank and gm 4x style cam sprocket ��
i know this info would have really helped me on my VEMS install on my LY6 in my 280z.
hope this helps you and anyone who needs these specs for setting up a 58X (60-2) crank and gm 4x style cam sprocket ��
i know this info would have really helped me on my VEMS install on my LY6 in my 280z.
Last edited by 91Camaro man; 03-21-2018 at 11:38 PM.
08-20-2017, 06:01 PM
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GM 58x (60-2) Hi Dave, As a member of the inventor team 60-2 in 1984 (US patent 1986) I have some tech.
The Allegro Hall sensor goes LOW when it "sees" a tooth, the 13 tooth, in the direction of engine rotation (+1.75* trim as an average) AFTER the Missing Tooth Section is TDC.
Gap = Wheel Diameter/Sensor Distance
Missing Tooth Section Location IS what you ask.
This sensor is an adaptive dual element, there are Data sheets (167,164, etc.)
THUS your answer = 78 degrees.
MY ECU, YOUR ECU, will see a 59 tooth WD-Bug.
The MOST FUNNY ITEM is WHY GM called the TW a "58x"
The MORE CORRECT NAME should have been the 59.
I use a 12x Tooth Timer @ 160 Mhz.
Would you state YOUR processor AND speed ?
TODAY I use the 60-2 TW on my Star Motor for the Field Orientation Correction method.
Lance
The Allegro Hall sensor goes LOW when it "sees" a tooth, the 13 tooth, in the direction of engine rotation (+1.75* trim as an average) AFTER the Missing Tooth Section is TDC.
Gap = Wheel Diameter/Sensor Distance
Missing Tooth Section Location IS what you ask.
This sensor is an adaptive dual element, there are Data sheets (167,164, etc.)
THUS your answer = 78 degrees.
MY ECU, YOUR ECU, will see a 59 tooth WD-Bug.
The MOST FUNNY ITEM is WHY GM called the TW a "58x"
The MORE CORRECT NAME should have been the 59.
I use a 12x Tooth Timer @ 160 Mhz.
Would you state YOUR processor AND speed ?
TODAY I use the 60-2 TW on my Star Motor for the Field Orientation Correction method.
Lance