Cannot use VR2in with VR on cam b/c of transition offset

[bigbrotherjohn]

I am using a microsquirt with a 2002 GSXR600 engine. I am using stock sensors including an 8 tooth (no missing teeth) crank trigger with VR sensor and a single tooth cam trigger with VR sensor. The crank trigger is wired to VR1in+(Pin32) and VRin- (Pin33) and the cam trigger is wired to VR2in(Pin4) and VRin- (Pin33).

I have an oscilliscope trace taken from Pins 4,32, and 33 at the ampseal connector and both the cam and crank signals look good and are at approx 1v peak at cranking RPM. I used the Tooth Analyzer program to see what the microsquirt is reading and the cam signal is completely absent. I read that there is a pull-up resistor to make the triggering transition for VR2in to be around 1.8V. Because I am using a VR sensor and not a Hall effect sensor what can I do to make this transition at 0v?

I read that the microsquirt module has an ALT_CAM pin that can be used, is there something similar on the microsquirt or do I have to open the case and change something?

Thanks for any help.

-john

[bigbrotherjohn]

Here is the O-Scope trace of the VR signals

VR Signals.jpeg (67.58 KiB) Viewed 1362 times

[Matt Cramer]

You could use a 4 pin HEI module as a signal conditioner. Wire its coil output to VR2 with a 5 volt pull-up.

[bigbrotherjohn]

Matt, I agree that would probably work, but I would like to avoid adding extra pieces if necessary.

What i am trying to get at is to see if I can modify the existing VR circuit in the Microsquirt to lower the transition voltage offset. I just found the circuit diagram for the VR2in+ conditioning circuit, I didn't realize that was available. It looks like I can change either R48 or R55 to make the threshold trip point whatever I want it to be.

microsquirt mod.GIF

(13.91 KiB) Not downloaded yet

Changing R55 to 17K would make the threshold trip point close to 0V, would this work?

[bigbrotherjohn]

I changed R55 to an 18k resistor and put everything back together and ran the trigger analyzer, looks like it works now...

Trigger Analyzer2.JPG

(69.31 KiB) Not downloaded yet

[24c]

What i am trying to get at is to see if I can modify the existing VR circuit in the Microsquirt to lower the transition voltage offset.

Hi bbjohn, i have used twin VRs with an 8 tooth YZF and one tooth cam sensor with my cased Microsquirt...not got a module yet...I used a diode to sort out the cam VR circuit and it runs. I am in France at the mo, but if you PM me with some contact details..I'll be back Friday PM . If you search my posts you'll find similar traces to yours.

[bigbrotherjohn]

I think that the YZF and the GSXR set up would be very similiar, I have a good cank and cam signal now but I am not sure about how to configure the ignition options, what dual spak settings did you use? Rising Cam Sync with Tach or Wheel? or M-0 Wheel with Rising Crank Sync? I am having a hard time understanding which one to chose and the differences between them.

Also, do you use the Offset for Output #2 at all for an engine like this or should it be set to 0 ?

I've attached a timing diagram for the stock engine, everything is the same now except that coils 1 and 4 fire together and coils 2 and 3 fire together. Also the Vr signals that are sent to the microsquirt cross zero going positive whereas on the GSXR diagram they cross going negative (not sure where this comes into play) With this timing diagram and the trigger analyzer results I should be able to figure out all of the ignition configuration settings right? Maybe I can get a little help because what I have tried doesn't seem to work.

gsxr timing.JPG

(57.33 KiB) Not downloaded yet

[grippo]

Try this link and see if it helps: http://www.megamanual.com/seq/multichannel.htm It was written for the Sequencer, but the definitions and concepts are the same for microsquirt.

As far as the Offset for output #2 - leave it 0 unless you have an odd-fire engine.

[bigbrotherjohn]

thanks grippo,

I got the engine running, I think that i understand the terminology and the concepts a lot better now, the page for the sequencer was helpful. I am still having some perplexing problems, however, and started a new thread about it because I didn't want to go to off topic in this thread.
http://www.microsquirt.com/viewtopic.php?f=89&t=23474

[adamv61243]

Hi,

I've been tearing my hair out with John on the same GSXR600-K3 engine, and we're still having A LOT of trouble getting the ignition to work out... I'd really appreciate it if you could help me get this thing going, as my masters thesis due in the next month and I need this engine running to get some performance numbers for my intake design. After trying all the suggestions everyone listed, and not having any positive developments (beyond at least a RPM signal after changing the uS's transition voltage resistor setting), we took the head off last month and installed a tried and tested missing tooth wheel (from Performance Electronics for the GSXR600). And as my luck would have it, we're still having timing issues, despite it being the same configuration as on another GSXR600 engine we have working with the uS from last year!

We're using the most recent firmware, with these ignition settings:
Rising Edge
Trigger Rise
Teeth: 12
Missing Teeth: 1
Skip Teeth: 6
Delay Teeth: 2
Odd Fire: 0.0 deg
Single Crank Wheel Dual Spark
Trigger Offset: 0.0 deg
Spark advance table is set to all zeros
Alpha Beta Gamma are set to produce repeatable spark, though it usually takes a few tries to get the uS consistently sparking.

This engine is newly rebuilt, with a solid power supply, and cranks at around 320 RPM. It's in a wasted spark configuration. We've had it sort of idling, but running off 1&4 cylinders, and backfiring the rest into the intake as you'll see why in this diagram of the trigger wheel's configuration: http://notcooperedu.org/~vaugha/trigger ... n.12-1.png When the trigger wheel's magenta "TDC1" is aligned with the light blue "Engine TDC1", cylinder 1 is at TDC. The strobe scope shows sparks at the indicated light blue lines. SPK1 is spot on, SPK2 is off (this is an even fire engine). I've tried adjusting the trigger offset while cranking, but it doesn't seem to affect the spark timing at all, or it moves to some random location if I adjust it too far. I've also tried adjusting pretty much every other uS parameter, with no clear improvement. Additionally, I've tried just sparking the spark plugs in open air, just to be sure we have a solid spark for our dwell settings... and they spark just fine. Incidentally, we placed the missing tooth based off what we read on DIYAUTOTUNE's site... should it have been at TDC1? It seemed as if the uS's settings could handle any location, if we were wrong. I've been suspecting that this engine's VR sensor is at fault, after not seeing as strong a missing tooth signal out of it, compared to last year's working GSXR/uS setup and because it's the only thing left to play with. Also, the wiring harness is layed out identically to the other engine... with VR lines shielded and away from ignition/injection wires, although the signal is clearly better on the other setup. Additionally, I've tried three different uS's... and I get the same results from all of them.

This is the missing tooth VR signal we get from the current setup that DOESN'T WORK: http://notcooperedu.org/~vaugha/newEngi ... gTooth.png
This is the VR signal we get from the other engine, that DOES WORK: http://notcooperedu.org/~vaugha/oldEngi ... gTooth.png

What am I doing wrong? Is the VR signal too weak? Should I take the engine apart again to try moving the sensor closer than PE's documentation had recommend (0.023-0.030"), or is there another resistor that I can change? I really hope this is a simple fix.

Again, I really need this engine to work ASAP... I'd really appreciate any help you can offer so I can test my intake and graduate.

Warm regards,
Adam