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Thread: T56 has anyone ever got their speedometer to work?

  1. #1
    Join Date
    Dec 2015
    Location
    Connecticut
    Posts
    27

    Default T56 has anyone ever got their speedometer to work?

    I think Holley missed the boat on this one. I have read a lot of posts where people are having same issue, and sifted through the junk to find that setting up a T56 2-wire speed sensor to output correct speed and further to output speed to a speedometer is no small task. It seems like this is a frequently asked question and it's surrounded by a lot of mystery. One would think that this should be easy & straightforward, It's not! So far I can at least get the display on my tablet to show some speed when driving. When I'm doing 40 mph, it says about 10 mph, I've changed the PPM from 2 to 9999 in the Transmission ICF and it does not change the speed. How I got this far was by wiring both wires from the VSS to connector J4 (the transmission connector if you have an automatic) after creating a Transmission ICF & enabling speedometer output, per Danny Cabral. When I first tried to setup the speedometer, I tried to add a VSS input, selected IPU/Freq assigned it a pin and then grounded the other side, that seemed logical and obviously so have a lot of other people on here that didn't work. I like figuring things out as much as the next guy, but this is over-complicated. Please someone help me out here, show me the light. If I ask how to make toast please don't give me a rundown on how the toaster works, or how it was invented, or what type of bread tastes the best. Just simple instructions plug in toaster, place bread in slots set dial to desired color, push button, wait for toast. Example, once I have the Transmission IPU created and speedometer output enabled the J4 plug looks for VSS signal on 1 wire and ground on another. I have both of the wires going directly from the VSS to the J4 at their correct pin locations. Now I'm able to see a speed on the Holley gauges display on my tablet. It is the wrong speed though. Am I to understand that I would need to then piggyback a wire off of the VSS wire going into the J4 and create a separate "VSS Input" like I did in the first place assign it a freq pin-out and use that as my speedometer output?, or use the speedometer output that was created when I added the Transmission ICF? Either way because I have now created this VSS Input can I now go in and modify pulse to average or pulse per rotation to correct the Holley display on my tablet so it reads the correct speed? Sorry if I sound like a jerk with the toaster comparison, but I have devoted way too much time trying to get a speedometer to work, and just want to be done with this. Next step, I will remove my speedometer and place it in a vice, use a 4ft pipe on the vice to crush the life out of it then get a GPS speedometer. I'm at the end of my rope.

  2. #2
    Join Date
    Nov 2013
    Location
    Chicago IL
    Posts
    1,952

    Default

    The T56 uses a 17 tooth wheel. So using the standard VSS sensor, one wire goes to ground, and one wire goes to the Holley to a Speed Input (Type "S" Inductive pickup input since VSS sensors are a Variable Reluctance sensor).
    Then it's as simple as programming the I/O if you plan to use the Holley Digital Dash to display speed.
    Pulses to average = at least 1/4 of your total teeth, more if you need it smoother.
    Pulses = 17 (actual VSS Teeth on a T-56).
    Gear = Rear end gear.
    Tire Diameter = measured distance across tire or use math from tire size (275/60/15 = 27.99).

    Or if you use the Transmission ICF, you have to do some math. The Transmission ICF is looking for 40 pulses.
    So in the Speed Calculation section, you use your tire diameter (measure across the tire or use math to determine tire size).
    And then your rear gear gets changed to [Gear/(40/VSS Teeth)]
    40 ÷ 17 = 2.352941176.
    So as an example, if you had a 3.42 rear gear (common for many T-56 cars).
    3.42 ÷ 2.352941176 =1.4535. So you would enter your Gear as 1.45.

    Just change the rear gear in that equation to match your actual rear gear.
    This will make it report the correct amount in the Holley ECU.

    Then all you have to do is program the Speedo Output to match what your speedometer is looking for.
    Or do a custom calibration of the speedometer per the manufacturers instructions.
    (The Speedo Output is only available on the Dominator ECU. Must have the J4 Connector).

    And just for reference, the Tire Math is:
    Numbers on side of the tire are Tread Width in Millimeters / Sidewall Ratio in percent / Rim Size in inches
    So we convert Width to Inches (Tire width / 25.4).
    Then multiply by the sidewall expressed as a decimal 60 = .60.
    Then multiply that by 2 (2 sidewalls across the tire diameter), and add the rim size.
    So a 275/60/15 becomes:
    275/25.4 = 10.82677165
    10.82677165 * .60 = 6.496062992
    6.496062992 * 2 = 12.99212598
    12.99 + 15 = 27.99

    And to reply to the title of your post, yes. LOTS of people have gotten the speedometer to work just fine. I've done a few of them myself with zero issues.
    Last edited by S2H; 07-03-2016 at 02:16 PM.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  3. #3
    Join Date
    Dec 2015
    Location
    Connecticut
    Posts
    27

    Default

    OK now I have a speedometer reading that is accurate in my tablet. Just had to change the ratio in the Transmission ICF to around 1. Because the speedometer output is PWM+ and my speedometer looks for a frequency, how do I make my speedometer work? From what I understand, there is two different ways to setup a speedometer. One is taking raw IPU Freq data from the sensor and setting up a Custom I/O for that, assigning a pin configuring the pulses etc. The other is capturing the VSS data with a signal & ground wire on the J4 connector and setting up a Transmission ICF and enable speed output. Is there a way to see correct data on my tablet, and have pulses going to my speedometer?

  4. #4
    Join Date
    Dec 2015
    Location
    Connecticut
    Posts
    27

    Default

    OK, so for anyone who searches how to get their speedometer to work and get the correct speed output in their tablet laptop, here it is in the simplest terms possible.

    1. Make sure you have a J4 connector, take the two wires from your magnetic VSS run one wire to pin B18 of the J4 connector, take the other wire and run that to a ground pin on the J4 connector.
    2. Select toolbox, add individual config, transmission, base config.
    3. In the transmission config that is now at the top of your screen check the box speedometer output enable, then follow S2H instructions: "The T56 uses a 17 tooth wheel. So using the standard VSS sensor, one wire goes to ground, and one wire goes to the Holley to a speed input (type "S" Inductive pickup input since VSS sensors are a Variable Reluctance sensor).

    Then it's as simple as programming the I/O if you plan to use the Holley Dash to display speed.
    Pulses to average = at least 1/4 of your total teeth, more if you need it smoother.
    Pulses = 17 (actual VSS Teeth on a T-56).
    Gear = Rear end Gear.
    Tire Diameter = measured distance across tire or use math from tire size (275/60/15 = 27.99).

    Or if you use the Transmission ICF, you have to do some math. The Transmission ICF is looking for 40 pulses.

    So in the speedo section, you use your tire diameter (measure across the tire or use math to determine tire size).
    And then your rear gear gets changed to [Gear/(40/VSS Teeth)]
    40 ÷ 17 = 2.352941176
    So as an example, if you had a 3.42 rear gear (common for many T-56 cars).
    3.42 ÷ 2.352941176 =1.4535, so you would enter your Gear as 1.45.

    Just change the rear gear in that equation to match your actual rear gear.
    This will make it report the correct amount in the Holley ECU."
    4. To get your speedometer to work if it's a programmable unit simply piggyback the signal wire that is going into J4 B18.
    Thank you for putting me on the right track S2H. I appreciate the help, as I've been on & off trying to get this to work for quite some time.

  5. #5
    Join Date
    Nov 2013
    Location
    Chicago IL
    Posts
    1,952

    Default

    Quote Originally Posted by TheBuMan78 View Post
    OK so for anyone who searches how to get their speedometer to work and get the correct speed output in their tablet laptop, here it is in the simplest terms possible.

    1. Make sure you have a J4 connector, take the two wires from your magnetic VSS run one wire to pin B18 of the J4 connector, take the other wire and run that to a ground pin on the J4 connector.
    A VSS sensor is NOT Magnetic, it's Variable Reluctance. It's an inductive pickup type.

    2. Select toolbox, add individual config, transmission, base config.
    3. In the transmission config that is now at the top of your screen check the box speedometer output enable, then follow S2H instructions

    Quote Originally Posted by S2H
    "The T56 uses a 17 tooth wheel. So using the standard VSS sensor, one wire goes to ground, and one wire goes to the Holley to a speed input (type "S" Inductive pickup input since VSS sensors are a Variable Reluctance sensor).

    Then it's as simple as programming the I/O if you plan to use the Holley Dash to display speed.
    Pulses to average = at least 1/4 of your total teeth, more if you need it smoother.
    Pulses = 17 (actual VSS Teeth on a T-56).
    Gear = Rear end Gear.
    Tire Diameter = measured distance across tire or use math from tire size (275/60/15 = 27.99).

    Or if you use the Transmission ICF, you have to do some math. The Transmission ICF is looking for 40 pulses.

    So in the speedo section, you use your tire diameter (measure across the tire or use math to determine tire size).
    And then your rear gear gets changed to [ Gear/(40/VSS Teeth) ]
    40/17 = 2.352941176
    So as an example, if you had a 3.42 rear gear (common for many T-56 cars).
    3.42 / 2.352941176 =1.4535, so you would enter your Gear as 1.45.

    Just change the rear gear in that equation to match your actual rear gear.
    This will make it report the correct amount in the Holley ECU."
    4. To get your speedometer to work if it's a programmable unit simply piggyback the signal wire that is going into J4 B18.
    Thank you for putting me on the right track S2H. I appreciate the help, as I've been on and off trying to get this to work for quite some time.
    Most speedometers are looking for a +12V square wave signal. Your VSS does not output that signal, it outputs a sine wave AC voltage signal. To get your speedometer to work, you *usually* have to convert that signal to the +12V square wave output. Some can be made to work using a +12V pull-up resistor if you have the Dominator with the J4 connector. You can use a PWM output for the speedo. I told you how to do it, it's NOT a piggyback wire. And using the speedo output works perfectly when you set it up correctly.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  6. #6
    Join Date
    Dec 2015
    Location
    Connecticut
    Posts
    27

    Default

    Quote Originally Posted by S2H View Post
    A VSS sensor is NOT Magnetic, it's Variable Reluctance. It's an inductive pickup type.
    Most speedometers are looking for a +12V square wave signal. Your VSS does not output that signal, it outputs a sine wave AC voltage signal. To get your speedometer to work, you *usually* have to convert that signal to the +12V square wave output. Some can be made to work using a +12V pull-up resistor if you have the Dominator with the J4 connector. You can use a PWM output for the speedo. I told you how to do it, it's NOT a piggyback wire. And using the speedo output works perfectly when you set it up correctly.
    I know my speedometer works, and it reads the speed correctly. I got there by tapping into the signal wire directly off the sensor. I'm not saying your way is wrong, just saying my way works flawlessly and is simple, with no ill effects. Probably because it's an aftermarket Auto Meter not an OEM. A variable reluctance (VR) speed sensor, aka inductive pickup, uses a magnet to generate a signal, speed sensor, crank sensor, ABS sensor; all have magnets from my experience.

  7. #7

    Default Tremec Magnum and Holley VSS Success

    Quote Originally Posted by S2H View Post
    The T56 uses a 17 tooth wheel. So using the standard VSS sensor, one wire goes to ground, and one wire goes to the Holley to a Speed Input (Type "S" Inductive pickup input since VSS sensors are a Variable Reluctance sensor).
    Then it's as simple as programming the I/O if you plan to use the Holley Digital Dash to display speed.
    Pulses to average = at least 1/4 of your total teeth, more if you need it smoother.
    Pulses = 17 (actual VSS Teeth on a T-56).
    Gear = Rear end gear.
    Tire Diameter = measured distance across tire or use math from tire size (275/60/15 = 27.99).

    Or if you use the Transmission ICF, you have to do some math. The Transmission ICF is looking for 40 pulses.
    So in the Speed Calculation section, you use your tire diameter (measure across the tire or use math to determine tire size).
    And then your rear gear gets changed to [Gear/(40/VSS Teeth)]
    40 ÷ 17 = 2.352941176.
    So as an example, if you had a 3.42 rear gear (common for many T-56 cars).
    3.42 ÷ 2.352941176 =1.4535. So you would enter your Gear as 1.45.

    Just change the rear gear in that equation to match your actual rear gear.
    This will make it report the correct amount in the Holley ECU.

    Then all you have to do is program the Speedo Output to match what your speedometer is looking for.
    Or do a custom calibration of the speedometer per the manufacturers instructions.
    (The Speedo Output is only available on the Dominator ECU. Must have the J4 Connector).

    And just for reference, the Tire Math is:
    Numbers on side of the tire are Tread Width in Millimeters / Sidewall Ratio in percent / Rim Size in inches
    So we convert Width to Inches (Tire width / 25.4).
    Then multiply by the sidewall expressed as a decimal 60 = .60.
    Then multiply that by 2 (2 sidewalls across the tire diameter), and add the rim size.
    So a 275/60/15 becomes:
    275/25.4 = 10.82677165
    10.82677165 * .60 = 6.496062992
    6.496062992 * 2 = 12.99212598
    12.99 + 15 = 27.99

    And to reply to the title of your post, yes. LOTS of people have gotten the speedometer to work just fine. I've done a few of them myself with zero issues.
    I was able to get this working, but I have to do a TPS Autoset each time I get in the car. Does anyone know why that would be? Thanks.

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