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Thread: How split crank/cam sensors, piggybacking LS.

  1. #1

    Default How split crank/cam sensors, piggybacking LS.

    I want to piggy back a Holley Terminator on my 2000 Trans Am. I want to keep the cluster and the rest of the car functioning, but have the Holley control the fueling/spark. I know this has been done. Heck I've seen it done on the newer E38 and E40 PCMs. I'm guessing the guys who have figured it out don't talk about how they did it, which I completely understand. The biggest question I have is how you split the crank/cam sensors, so the stock PCM and the Holley see them. I'm not so much worried about splitting the cam sensor because I don't see why the stock PCM needs to see it. It just needs to see RPM. I've listened to several podcasts from people way smarter than me who talk about needing a resistor to get the crank sensor to work correctly, but don't understand why this is needed.
    Last edited by Jay@HAP; 06-03-2019 at 09:52 AM.

  2. #2
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    Start by informing us if the crank & cam sensors are Hall-Effect or VR/Magnetic type sensors.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3

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    That information would probably help. It's a 3-wire Hall-Effect sensor. I believe on that year it's +12V, but I'd have to look at a wiring diagram to be 100%. GM went to a 5V sensor later on.

    I probably should've posted this is the Terminator/LS section. I didn't think about that earlier when I posted this.

  4. #4
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    Quote Originally Posted by Jay@HAP View Post
    That information would probably help. It's a 3-wire Hall-Effect sensor. I believe on that year it's +12V, but I'd have to look at a wiring diagram to be 100%. GM went to a 5V sensor later on.
    If they're Hall-Effect sensors (3-wire, 0-12V), the signal wire can be split to two devices. I'm not aware that resistors are required.

    I probably should've posted this is the Terminator/LS section. I didn't think about that earlier when I posted this.
    I moved this thread for you.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  5. #5

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    Thank you for the response and thank you for moving the thread. If I split the signal wire, does it matter where the supply voltage and ground come from? For example, if I use the stock PCM connector to the crank sensor, so I just split the signal wire and run it to the Holley and not worry about the supply voltage and ground from the Holley?

  6. #6

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    I looked at a wiring diagram when I got home and according to GM, it's a magnetic pickup sensor and the cam sensor is a Hall-Effect sensor. IIRC looking at the CKP with a scope, it was a square wave. Maybe I'm confusing myself here.
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  7. #7

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    I'm pretty sure that whether you have Gen 3 +12V cam/crank sensors or whether you have the Gen 4 +5V crank/cam sensors, they are all Hall-Effect. Andrew

  8. #8
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    Quote Originally Posted by Jay@HAP View Post
    For example, if I use the stock PCM connector to the crank sensor, so I just split the signal wire and run it to the Holley and not worry about the supply voltage and ground from the Holley?
    Correct, Holley EFI only need the crank/cam signal wires.

    I looked at a wiring diagram when I got home and according to GM, it's a magnetic pickup sensor...
    If that's true, that explains the need for resistors and such. Because that signal type can't be split to two devices without modifying the circuitry.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  9. #9

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    I did this exact thing on my '02 C5Z. First with my HP EFI and now with my Terminator X Max for full DBW control as well. The cam & crank signal wires can be split to both the factory PCM and the Holley ECU just fine.

  10. #10
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    Quote Originally Posted by TraviZ28 View Post
    The cam & crank signal wires can be split to both the factory PCM and the Holley ECU just fine.
    Yes, but are they Hall-Effect sensors?
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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