M400 Crank Signal on BMW G450X

[sebtoombs]

Hi,
I have an M400 operating a BMW G450X engine (Formula SAE Car). I'm trying to set up the M400 to run the engine, however I'm concerned that the M400 may not be seeing the crank signal as I wish. The crank signal comes from the factory crank sensor which is a magnetic sensor detecting 18 evenly spaced teeth on the stator housing. There is one tooth that is physically slightly longer, but appears on the signal capture as can be seen in the attached image.

I have set up the M400 to mode 5 (one missing twice) and falling edge. Looking at the signal capture, I assumed that the motec would be able to see the falling edges, but would ignore the falling edge with the 'kink' that occurs every 18 pulses (this is the longer tooth).

https://www.dropbox.com/s/o3htktkl446mah0/CrankCam%20Capture.PNG?dl=0

Ignore the dark blue and the orange trace in this picture. The light blue square wave is my custom cam sensor signal (hall). It picks up the cam lobe as it passes its upmost point (i.e. 180degrees after full open valve).

It can be seen that the longer tooth occurs 7 teeth after the rising edge of the cam signal (working from the left of the image).

I cannot get the cam and crank signals to synchronise. Is it possible that the motec is seeing the falling edge (with the kink in it) as a falling edge and thus does not see a missing tooth? Should I instead configure the M400 to look for 18 teeth per crank revolution? Sorry if this entire post is somewhat confusing and convoluted.

ADDITIONAL INFO: The error I am getting from the ECU Manager Software is; -Error Sync Signal
I have no spark. I have tested using the ignition test and my wiring is fine, however when cranking there is no spark.

However it should be noted that the M400 can see the raw sync signal as I have performed a ref/sync capture and the trace is there (same as above figure).

Cheers,
Seb

[AdamW]

That trace looks nothing like a missing tooth form so no surprises that it doesn't work.
Best option would be to stick with mode 5 but grind off that longer tooth (provided it isn't too close to TDC).
Another option would be to change to mode 2 (multitooth) and choose whichever edge has the even spacing. 18 teeth on multitooth mode however can be a little fussy to get it to work if the sync position drifts any. Missing tooth mode will be the most robust option.

[sebtoombs]

Ok, cheers for that. Yeah the longer tooth is exactly at TDC so i guess that rules that out. So will the motec see that falling edge (of the longer tooth) with the kink in it as a legitimate edge?

[Scott@FP]

http://www.vermontel.net/~dcma/Max/G450 ... ggers..jpg

Looks like what you can do is grind/mill the long tooth to match all the others, then remove a tooth where the crank is approx. mid-stroke. Then its golden.

This is something you'd want to do with some precision, like on a rotary indexing table.

[sebtoombs]

Roger that, that may be what we will have to to. For now, I seem to have it synced using multi tooth mode, but I'm getting injector open circuit error. I did previously have injector peak error, but I set the current to a small negative value and that cleared all errors. The open error popped up shortly after. I have manually tested the wires, and performed injector test, both of which confirmed that an open circuit is not present.

Any ideas what else would cause injector open error? All other injector settings are default, injector resistance is roughly 10.7 ohms. (Keihin motorcycle injector)


Additionally, can anybody advise how I would be able to use a timing light on this engine to confirm/adjust timing? Being a bike engine I don't have a crank pulley & timing marks...

[Scott@FP]

I'd ignore the injector errors for the time being.

For high RPM engines your best bet for a single cylinder synced mode is a twice per cycle missing tooth mode with the sync edge in the middle of the two missing teeth per cycle.

Another option would be to run it with no sync sensor as a waste spark/waste inj setup (fires inj and ign every revolution).

Reason for getting the missing or additional tooth away from TDC/BDC is the RPM variance at cranking speeds occurs there, once its fired up its OK, but 150-300 RPM it can vary too much and not want to sync.

[Jonny Rochester]

Hi, I am working with sebtoombs on this same engine.

We have modified the crank signal as suggested. The long tooth was shortened back, and another tooth about 90 degrees from this was removed. (Is this called 18 -1 ? I'm wanting to get the correct notation). Was 18 tooth, now only 17.

I'm having trouble downloading the Manager software on my personal computer so I don't have that in front of me.

I am thinking wasted spark of some type is the easiest way to get this running. Which mode/settings do we need to choose. We would have no sync, just a ref signal (18 -1?)

I have also read some people select "2-stroke" to get this happening? Do we enter the no. of cylinders with a minus, or is there another 2-stroke option if that is needed?

[sebtoombs]

Further to Jons post, the modified trigger wheel allowed the REF/Sync to properly synchronise, however we ran into an issue regarding the use of the cam lobe as the sync trigger (as various people advised). Additionally, this was due to a misinterpretation (by me) of the CRIP. I thought it was the number of degrees up to TDC for the beginning of the cycle, however it is apparently the number of degrees to TDC at the end of the compression stroke. Hence my SYNC trigger was 360 degrees too early. We will work on figuring out a different cam sensor. In the meantime I'm trying to get it to run using wasted spark (as it did from factory).

On this topic:
I assume mode 6 is the correct mode (one missing once).
Is the CRIP still the number of degrees from the first active edge after the missing tooth, to the active edge at TDC compression?
Do I need to set the number of cylinders to -1 (e.g. two stroke operation)?

Cheers for all the help

[Scott@FP]

ref/sync mode 6 and -1 cylinders should make inj and ign operate once per rev.

For visual help on ref/sync and crip setup download the utilities pkg, there is a graphical ref/sync setup applet-

http://www.motec.com.au/filedownload.php/utils_103.exe?docid=3739