Crank Signal Problems

[Dan G]

Hello all, I'm new to the forums. Our team is eagerly preparing for the upcoming competition and is running into a snag with the crank signal.

We are running a 2001 GSX-R with a Megasquirt controlling fuel and an MSD MC4 controlling spark. The megasquirt should work fine running off the tach signal output from the MSD, so that isn't the problem. The problem is feeding the MSD an acceptable crank position sensor input.

We've hooked the stock GSX-R sensor up to a o-scope and found it to put out a spike to 12V, then it immediately spikes down to -12V, then goes back to 0. This event happens every 45 degrees, or 8 times per engine rotation.

A little digging tells us the MC4 is looking for a square wave signal. I am unsure of the duty cycle of this square wave, and I am also unsure of how many times the signal is high per rotation. From what i've heard, the MSD requires the signal to be high for "20 degress of rotation." It is not clear to me what this means. I'm curious at what crank angles the signal is high (verses #1 at TDC), and what angles it is low for an entire rotation.

Regardless, we will either need to modify our existing signal, or custom-fit a different crank position sensor with the desired output.

I've drawn up a crude paint diagram I can email to anyone if they feel they might be able to help.

MSD's tech support has been less than stellar. They won't let us talk directly to real engineers, and have been very slow to respond at all. If anyone has a good contact that I could use for my questions, I'd appreciate it greatly.

Thanks everyone,

Dan G
Carnegie Mellon University
Engine Team Leader

[Dan G]

Hello all, I'm new to the forums. Our team is eagerly preparing for the upcoming competition and is running into a snag with the crank signal.

We are running a 2001 GSX-R with a Megasquirt controlling fuel and an MSD MC4 controlling spark. The megasquirt should work fine running off the tach signal output from the MSD, so that isn't the problem. The problem is feeding the MSD an acceptable crank position sensor input.

We've hooked the stock GSX-R sensor up to a o-scope and found it to put out a spike to 12V, then it immediately spikes down to -12V, then goes back to 0. This event happens every 45 degrees, or 8 times per engine rotation.

A little digging tells us the MC4 is looking for a square wave signal. I am unsure of the duty cycle of this square wave, and I am also unsure of how many times the signal is high per rotation. From what i've heard, the MSD requires the signal to be high for "20 degress of rotation." It is not clear to me what this means. I'm curious at what crank angles the signal is high (verses #1 at TDC), and what angles it is low for an entire rotation.

Regardless, we will either need to modify our existing signal, or custom-fit a different crank position sensor with the desired output.

I've drawn up a crude paint diagram I can email to anyone if they feel they might be able to help.

MSD's tech support has been less than stellar. They won't let us talk directly to real engineers, and have been very slow to respond at all. If anyone has a good contact that I could use for my questions, I'd appreciate it greatly.

Thanks everyone,

Dan G
Carnegie Mellon University
Engine Team Leader

[Dan Deussen @ Weber Motor]

If you need to convert the signal from your sensor into a square wave, try the LM1815 IC from National Semiconductor. I'm not a EE but I know that's what our ECU's use to convert an inductive signal into a square wave output. Make sure to get an EE to help you wire it correctly.

Hope this helps!!!

Dan

[Ben Beacock]

http://www.diy-efi.org/efi332/hardware/4layer/input.pdf

This has a schematic for converting a variable reluctance sensor signal (GSXR) to a square wave and uses the LM1815.

Ben Beacock
Chassis Design and Technical Coordinator
Gryphon Racing - University of Guelph

[Dan G]

Thanks for the quick responses.

Now how about the questions on the MSD MC4? Does anyone here know specifically what the required input signal is? Like is it just a single pulse square wave with 20 degrees duration that triggers when #1 is at TDC? Or could it be 8 pulses per rotation and each pulse has a duration of 2.5 degrees? I guess once we get the signal converted to a square wave, it won't hurt to just connect the wires and give it a shot.

Thanks,

Dan G
Carnegie Mellon University
Engine Team Leader