GRMiata

Hey guys,

I've just installed my freshly built MS2 into a 1995.5 Miata and I'm having an issue with getting a good cam signal. Here's the background (a bit long winded) but just to make it easier to diagnose.

I performed the tach input mods as described by DIYAutoTune's documentation. I.E.

1. Jumper Tachselect to VRIN & TSEL to VROUT
2. CMP (pin5) to JS10 with a 1k 1/4w resistor inline and a 5v pullup (470 ohm 1/4w from 5V proto)
3. CPK (pin24)
4. VRIN with a 5V pullup (470 ohm 1/4w from 5V proto)

I have the crank and cam signals both in shielded wires with the shields grounded to pin#2 on the DB37 and run completely separate from the rest of the harness. These wires run through an empty heater core hole to the MS (mounted on the firewall) while the rest of the wires route through the factory grommet all the way on the passenger side of the car.

TunerStudio ignition settings are as follows:

Spark Mode: 4G63
Ignition input capture: Falling edge
Spark output : Going low
# Coils : Wasted Spark
Spark A output Pin: D14
Cam input: Cam input

When using the composite logger the check the cam and crank signals I have a nice consistent squarewave from the crank sensor. However, the cam comes in as an impulse or spike. See screenshot below:



Has anyone seen this before? I've tried adjusting the pots (R52 and R56) with no success. Lowering R56 beyond 5 turns clock wise and the crank signal disappears. I started with R52 all the way counter clockwise. I kept turning up to 8 turns clockwise and no change. I'm getting to the end of my rope here and have no idea what I'm missing. I also tried rising edge with no change to the log. Any help from some of the MS experts or someone who has had this problem and fixed it would be greatly appreciated!

Matt Cramer

The spike is just a quirk of how it renders the cam as the code only uses one edge. Can you post a copy of your MSQ?

GRMiata

MSQ should be attached

GRMiata

So I've got a cam signal coming in now and by switching from falling edge to rising edge the peaks in the cam signal are now regularly spaced 360 crank degrees out from each other. Here is the composite log:


Ignition in "log crank & cam" mode:


Is it normal to still see sync errors at cranking speed? Is there some adjustment I need to do to the pots (R52 & R56) or in the software to fix this? Or do the sync errors disappear when the engine spins up to idle speeds?

GRMiata

Thanks to help from Matt Cramer I've gotten this fixed.

1. Removed TSEL/VROUT jumper
2. Jumped TSEL to VROUTINV
3. Switched back to falling edge ignition capture

That's all it took!

You will know to use VROUTINV or VROUT by looking at the crank signal. Each window in the CPK sensor wheel creates a short pulse which shows up as a square peak in the composite logger. The time between each square peak should be longer than the peak length. These pictures might help.

This one shows the correct signal coming from the crank. The crank peaks are shorter than the time between peaks.




If your crank signal looks like this:


The signal needs to be inverted from where it currently is and it will never sync properly unless you move your jumper. If TSEL is jumped to VROUT, jump it to VROUTINV, and vice versa. This may be very basic but it gave me loads of frustration and headaches until Matt helped me figure it out.

Hope this helps others avoid the same issues I ran into!