VBOX HD2 RPM strange reading
07-12-2022 | 01:59 PM
#1
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VBOX HD2 RPM strange reading
Good afternoon all,
Just curious if anyone had run into this before. I'm running a VBOX HD2 on my air-cooled vintage racecar, with a micro-input module pulling the RPM signal from the "tach" wire on my MSD 6AL box. The signal is split between the MICIN and also feeds my autometer tach. The VBox records the signal perfectly until 6734 RPM, and then it drops to almost exactly half (3368 RPM) and continues reading linearly at half the actual RPM. Racelogic support advised that I need to purchase a separate isolator/filter to run in between the MSD signal and the MICIN. The module is designed for use on an ignition coil primary wire, and it seemed strange to me that I would need an isolator on what should already be a filtered signal coming out of the MSD box.
From the 6AL manual
TACHOMETERS
The MSD Ignition features a Gray Tach Output wire that provides a trigger signal for tachometers, a
shift light or other add-on rpm activated devices. The Tach Output wire produces a 12 volt square
wave signal with a 20% duty cycle.
Thanks for any ideas anyone has.
Just curious if anyone had run into this before. I'm running a VBOX HD2 on my air-cooled vintage racecar, with a micro-input module pulling the RPM signal from the "tach" wire on my MSD 6AL box. The signal is split between the MICIN and also feeds my autometer tach. The VBox records the signal perfectly until 6734 RPM, and then it drops to almost exactly half (3368 RPM) and continues reading linearly at half the actual RPM. Racelogic support advised that I need to purchase a separate isolator/filter to run in between the MSD signal and the MICIN. The module is designed for use on an ignition coil primary wire, and it seemed strange to me that I would need an isolator on what should already be a filtered signal coming out of the MSD box.
From the 6AL manual
TACHOMETERS
The MSD Ignition features a Gray Tach Output wire that provides a trigger signal for tachometers, a
shift light or other add-on rpm activated devices. The Tach Output wire produces a 12 volt square
wave signal with a 20% duty cycle.
Thanks for any ideas anyone has.
07-12-2022 | 02:14 PM
#2
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From: Durham, NC and Virginia International Raceway
Is the MicroInput Module part number for yours the MICIN01 or the MICIN01H (historic)? Additional filtering in that latter unit.
I have seen this with noise and EMI from the MSD in stock cars and others with HEI.
A good filter to use would be the AiM ARP-03 (unterminated wire connection) or AutoSport Labs CoilX (less expensive and just as good).
In all of the 550 HD2's I sold while a dealer, over eighty of which used the MICIN01 (mostly H versions), I only saw this three or four times.
Might want to route the wires differently and see if that helps, too. Never coil the excess wires, bunch them.
I have seen this with noise and EMI from the MSD in stock cars and others with HEI.
A good filter to use would be the AiM ARP-03 (unterminated wire connection) or AutoSport Labs CoilX (less expensive and just as good).
In all of the 550 HD2's I sold while a dealer, over eighty of which used the MICIN01 (mostly H versions), I only saw this three or four times.
Might want to route the wires differently and see if that helps, too. Never coil the excess wires, bunch them.
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www.peterkrause.net
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"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
Last edited by ProCoach; 07-12-2022 at 02:16 PM.
07-13-2022 | 08:42 AM
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From: NY Tri-State
Good afternoon all,
Just curious if anyone had run into this before. I'm running a VBOX HD2 on my air-cooled vintage racecar, with a micro-input module pulling the RPM signal from the "tach" wire on my MSD 6AL box. The signal is split between the MICIN and also feeds my autometer tach. The VBox records the signal perfectly until 6734 RPM, and then it drops to almost exactly half (3368 RPM) and continues reading linearly at half the actual RPM. Racelogic support advised that I need to purchase a separate isolator/filter to run in between the MSD signal and the MICIN. The module is designed for use on an ignition coil primary wire, and it seemed strange to me that I would need an isolator on what should already be a filtered signal coming out of the MSD box.
From the 6AL manual
TACHOMETERS
The MSD Ignition features a Gray Tach Output wire that provides a trigger signal for tachometers, a
shift light or other add-on rpm activated devices. The Tach Output wire produces a 12 volt square
wave signal with a 20% duty cycle.
.
Just curious if anyone had run into this before. I'm running a VBOX HD2 on my air-cooled vintage racecar, with a micro-input module pulling the RPM signal from the "tach" wire on my MSD 6AL box. The signal is split between the MICIN and also feeds my autometer tach. The VBox records the signal perfectly until 6734 RPM, and then it drops to almost exactly half (3368 RPM) and continues reading linearly at half the actual RPM. Racelogic support advised that I need to purchase a separate isolator/filter to run in between the MSD signal and the MICIN. The module is designed for use on an ignition coil primary wire, and it seemed strange to me that I would need an isolator on what should already be a filtered signal coming out of the MSD box.
From the 6AL manual
TACHOMETERS
The MSD Ignition features a Gray Tach Output wire that provides a trigger signal for tachometers, a
shift light or other add-on rpm activated devices. The Tach Output wire produces a 12 volt square
wave signal with a 20% duty cycle.
.
Not sure whether this will make you feel any better but I have the exact same problem with my VBOX on my aircooled car (MSD ignition also) and have never been able to resolve it, whether with additional filters or otherwise. I do not have that problem with the AIM system I installed.
07-13-2022 | 11:47 AM
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Thanks Peter,
I looked up the label on my input unit, it's MICIN01CH. I got the whole setup from you back in 2017, and as you promised it has proven to be some of the best money I've spent on either the car or the driver. I was hoping the issue would be resolved after I completely re-wired the car this winter. I routed signal wires separate from power wires and and bonded the negatives together and to the battery with dedicated ground wires to avoid any strange ground loops, however the issue persists. Anyway, it looks like the CoilX piece is only about $40 so at this point I'll just hit that easy button.
Frank, thanks for sharing your experience, send me a PM in about a month and I'll let you know if the module resolves it.
I looked up the label on my input unit, it's MICIN01CH. I got the whole setup from you back in 2017, and as you promised it has proven to be some of the best money I've spent on either the car or the driver. I was hoping the issue would be resolved after I completely re-wired the car this winter. I routed signal wires separate from power wires and and bonded the negatives together and to the battery with dedicated ground wires to avoid any strange ground loops, however the issue persists. Anyway, it looks like the CoilX piece is only about $40 so at this point I'll just hit that easy button.
Frank, thanks for sharing your experience, send me a PM in about a month and I'll let you know if the module resolves it.
07-13-2022 | 11:55 AM
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From: Durham, NC and Virginia International Raceway
Thanks Peter,
I looked up the label on my input unit, it's MICIN01CH. I got the whole setup from you back in 2017, and as you promised it has proven to be some of the best money I've spent on either the car or the driver. I was hoping the issue would be resolved after I completely re-wired the car this winter. I routed signal wires separate from power wires and and bonded the negatives together and to the battery with dedicated ground wires to avoid any strange ground loops, however the issue persists. Anyway, it looks like the CoilX piece is only about $40 so at this point I'll just hit that easy button.
Frank, thanks for sharing your experience, send me a PM in about a month and I'll let you know if the module resolves it.
I looked up the label on my input unit, it's MICIN01CH. I got the whole setup from you back in 2017, and as you promised it has proven to be some of the best money I've spent on either the car or the driver. I was hoping the issue would be resolved after I completely re-wired the car this winter. I routed signal wires separate from power wires and and bonded the negatives together and to the battery with dedicated ground wires to avoid any strange ground loops, however the issue persists. Anyway, it looks like the CoilX piece is only about $40 so at this point I'll just hit that easy button.
Frank, thanks for sharing your experience, send me a PM in about a month and I'll let you know if the module resolves it.
Please reach out to Scott, Dave or others at Racelogic USA (Farmington Hills, MI) for more support (support <at> racelogic.com) and include a .vbo so they can see it. They'll stand behind it, for sure.