Logging ignition pulses with microsquirt

[motthomas]

Hi there. I recently bought a Microsquirt V3 module for my EFI CBR250RR project. Initially this was going to be a fuel only conversion but I like the idea of having only one module to control both fuel and spark to tidy things up. The problem is though that I have no idea what the stock ignition map is like and being such a small, high-revving engine Im very wary of messing with the ignition settings in case I do damage.

One possibility I have thought about is trying to use the microsquirt to log ignition pulses and draw the map myself from that but Im not sure if it is capable of doing this... The bike runs with a 2D ignition map as standard and I would like to try and use this map as a starting point for developing a 3D map. The stock CDI unit takes an input from a 7-1 crank rotor and outputs to 2 coils (wasted spark).

My idea is that I could wire up the microsquirt with 2 ignition inputs. One from the stock VR sensor (VRIN1+ & VRIN1-) at the crank and the second tapped into the wires to one of the coils (VRIN2+ & VRIN2-). Run the bike on carburettors for a few runs while logging all inputs. Hopefully I will be able to get a graph of crank sensor output (CDI input) and coil input (CDI output). By comparing both graphs I would hope to calculate spark advance timing across the entire rev range.

Im just not sure if its possible to log the VRIN inputs to microsquirt? Is the module capable of doing this? Has anyone ever done something like this before?

[mfro]

Interesting idea indeed, but I think it would be overkill for your problem. In my opinion it should be enough to just pick up a few RPM/advance pairs from the OEM ignition with a timing light for an initial map. You won't get the complete map from this obviously, but I don't think using this as a guide would do any harm to the engine as long as you don't give more ignition advance than the OEM ignition. The OEM ignition maps I've seen on small engines are usually pretty straightforward: initial advance for ease of start, full advance from - say - 3000 rpm onwards, possibly an RPM limiter at max rev.

If it's more sophisticated, it would probably have additional advance when coasting. Not having this initially would most likely only increase fuel consumption and not do any harm.

Regards,
Markus

[motthomas]

Im not sure actually if it would be much more work than a normal install. I will only be hooking up 2 extra connections over what I would anyway. I would basically be half installing the system, going for a ride, logging and then completing the install.

Plus I dont have a timing light so for me this is the easier option!

[mfro]

Im not sure actually if it would be much more work than a normal install. I will only be hooking up 2 extra connections over what I would anyway. I would basically be half installing the system, going for a ride, logging and then completing the install.

Plus I dont have a timing light so for me this is the easier option!

Regardless of what you end up doing, you should really think about purchasing one anyway. Essential tool to do ignition work with a Microsquirt IMHO.

Back to your idea: not sure if it will work, honestly. You'll probably need to tweak the stock sensor's VR signal to the needs of the µS by adding resistors and/or diodes. If that's the case, I'm not sure if what's left is enough to fire the stock CDI.

Regards,
Markus

[motthomas]

Interesting point alright. Thats something I hadnt thought about. Though If that is the case I should be able to modify the signal after the stock CDI. If I tap into the CDI input wires and add any resistors needed only just before the MS unit, I should be able to keep the signal to the stock unit as before. I will try this approach at the weekend anyway I think and see how I go. It wont be too far off the ultimate goal anyway.

[EWflyer]

I know (from your post on Tubular's MSruns thread) that you're still looking for a fuel pump. If your CBR fuel tank can't easily accept an in-tank pump setup, you should look at the Suzuki LT-R450 Quadracer pump, which is an external type fuel pump. It is a very small pump housed within a fuel-flooded aluminum case, so it actually functions like an in-tank pump. It is probably the best solution for an external fuel pump on a motorcycle DIY fuel injection setup because of its low electrical draw. I've never measured its draw but this guy http://www.madhu.com/content/Main/FuelPumpController says it draws just under 2 amps max. His pulse-width-modulation fuel pump controller might even help with your CBR project because it can adjust the pump's output pressure (which might come in handy for a project like yours, trying to get a fuel pulse into a cylinder in the very brief time available at 19,000 RPM) and it also saves on electrical draw. Anyway, the LT-R450 fuel pump works great in my Kawasaki EX-250 microsquirt setup.

Looking forward to seeing you make progress with your CBR250RR.