Hello from the other side

Hi guys (and girls),

First off, my name is Bop Westerduin, I'm currently 24 years old and I live in Rotterdam, The Netherlands. I've been part of the local drift scene (if you could call it that) since my early teens which sparked my interest in Japanese cars. I've been the owner of a Japanese import Miata/Roadster/MX-5 for the last 6 years, and a few years ago after interning at a company that specialises in rotary engines I decided to swap a 13B in it :)

My initial setup was very basic, dizzy and carb setup, because I was a broke ass student and I wanted to get it running on a budget. After I graduated uni and started working I was finally in a position to give the entire car some well deserved TLC so I tore the entire thing down to a nearly empty shell. Some endless struggles, months abroad and general underestimation of the time and money needed later the car is now fully back together and ready to go. Except for the fact that I can't get it to start. Which is why I came here!

Enginewise I decided to go EFI and try to build a setup with individual throttle bodies. The ECU I chose is a Megasquirt MS3-X, because at that time it was the only ECU I could find that would do staged injection etc. whilst fitting in my budget. There is a fairly comprehensive article online devoted to Megasquirting a 13b, which is where I got most of my info from. The trickiest bit hardware wise has to do with the Crank Angle input; the trigger I'm using (FC3S stock CAS) is a vr sensor that draws a very weak signal that forces you to turn down the trigger pullup potentiometers and hysterisi adjustment in order for the ECU to actually get signal.

The problem I'm facing now is that it doesn't read anything whilst cranking. It will get (a very hysterical) signal when you spin the CAS quickly by hand but at low RPM it doesn't pickup anything. I've been playing with the 4 potentiometers on the MS3 board that adjust the different impedance values for the trigger input but so far no luck. I'm now at a point where I'm thinking about throwing the weak ass CAS in the bin and just build a triggerwheel setup which would give me a strong signal.

Which leaves me to ask you guys: 1) does anyone happen to have experience with Megasquirt (or similar) ECU's that can shed some light on my situation, and 2) if I end up going with a triggerwheel, what kind of sensor would you advise me + any pointers on the trigger wheel itself (no. of teeth, what to use for the reset etc).

Thanks in advance!

Bop

Hi there bop. I'm also from the Netherlands.

I can see that you're engine bay is resprayed. And you have diificulties with a weak signal of the cas. Did you remove all the paint on the mass/ground connections? This could be an issue. Did you measure the voltage off the cas sensor. If the voltage is to low, than youre signal will be weak.

First thing is to check if you have the correct Voltage.

Maybe you did this already, but you never know.

"The other side" Looks like The Netherlands is heaven. (or Hell) :)

Hi RJ,

Nice to see a fellow Dutchman on here :) RE the earthing, I cleaned up all the earth points in the bay and on the engine so thats not an issue. The CAS sensor gets a dedicated shielded earth wire straight from the ECU so this shouldn't effect the functionality. The CAS sensor creates it's own voltage (which triggers the ECU) so it doesn't get a +12v or 5v input. Thanks for het meedenken ;)

And since we are on the opposing side of the globe from HPA I figured hello from the other side to be a good pun ;p

I've looked up how the wiring is on my CAS sensor on my skyline. The CAS gets power from the battery and the ground is through the chassis.

I don't know how youre CAS is working (lack of knowledge) but it sounds very strange for me that a CAS is creating it's own Voltage. Than it should have a kind of alternator inside. When youre car is @ idle it will make less Voltage then when it's on high rpm. Or is this exactly how the CAS is working. What i mean is, that the ECU is looking @ how high the Voltage is and then the ECU knows @ what rpm it is running.

Just interested. Knowledge is power :)

By chance I found out what the issue was last weekend when I attended our local version of 7's day (rotary galore). Apparently there is a very specific combination of settings that are neccesary to get an FC CAS to work T-T. Has to do with the trigger settings, rising edge/falling edge etc. Applied my newfound knowledge when I got home and guess what, there was a trigger during cranking! After my inlet manifold comes back from the machineshop I'll try and get it started :) :)

RJ; there are different types of CAS sensors. Hall effect sensors will need 12v to operate, the one on an FC engine is a variable reluctor (VR) meaning that it creates its own current (that functions as the trigger signal) using magnets and shit. Like you said, the higher the rpm the higher the voltage will be (from 1,5v during cranking to 80+v at 9000rpm).

Anyway, found the problem, now onto starting the car for the first time and seeing if I can get a somewhat decent map in it :)

Good that you found the problem. And i have learned something.