Microsquirt as a piggyback, so close to perfection!

[yellow-fever]

As a learning and logging tool I instslled a Microsquirt, piggyback over the top of the factory ECU in a 2006 Skidoo 1000sdi 2 stroke Semi direct injection. It uses 4 conventional injectors located in the transfer ports that inject at or near bottom dead center on top of the piston with an alpha-n controll strategy. It has ERAVE electronically controlled exhaust port modifiers that I added a position sensor to. When the ERAVE valves open and close it has drastically different fueling requirments and I'm thinking of using table switching triggered off ERAVE valve position since the stock ECU uses some kind of map to open them anywhere between 6200 and 6800.

Right now it's all connected to the factory sensors and the stock ECU doesn't have a clue. I removed the bias resistors from the Microsquirt board with a quick and easy few snips with a pair of cuticle cutters. Was able to share the factory VR sensor and 36-2 wheel and just tapped into the signal and both the stock ECU and and the Microsquirt play nice together with no ill effects. I'm monitoring TPS, CLT, MAT, RPM, EGT and baro, then added a Wideband O2 and an ERAVE sensor I made from a 5V BMW ride height sensor that had a broken arm and was perfect for customization.

The stock ECU uses a knock sensor and pulls timing if knock is detected but I didn't want to touch that right now and left that stock. I have an aftermarket piggyback box installed that can only add and subtract fuel from 1 of the 2 sets of injectors. The factory ECU has a bunch of safety features built in like knock control and muffler pipe temp and can pull timing and add fuel to keep the engine alive in different hopefully rare situations. I would like to ditch the aftermarket fuel box and use microsquirt to add or subtract to a pulse width signal from a stock ecu like the simple aftermarket piggyback box does?

Can I intercept the stock coil signal and use that to trigger a coil at the same time as the stock ECU does? If I set up the tooth before TDC correct and zero out the spark map, could I then add or subtract over or under the factory curve in degrees.

I know these could be turned into the perfect piggyback computer to add or subtract fuel and ignition around stock curves. The engineers at skidoo are way more smart than I but the ability to use all that is built into the stock ECU and not have to completely recreate fuel and spark maps from scratch could be great for the Diy tuner. I could sell a ton of Microsquirt modules if we can get this to work. Zero out all the maps, zero out all the correction tables and then start tuning.

I'm getting more brave and may hook up a couple relays in line to the secondary injectors and a switch. The stock ECU does not appear to be very picky as far as signals go. Reconnect component and it just works again and the check light goes out so the momentary open circuit the stock ECU would see from the relay when switching from injectors to a resistor "to fool the ecu" may log a fault but it should operate just fine. I could run just the boost injectors and work on a map and if it's not right, flip the switch, adjust the map and swith back. A stock/mod switch?

If it's just not possible to make a squirt into a piggy back box, can I at least hook up my MS3X to the stock 36-2 wheel and the coil negative like it was a cam sensor and using VVT mode log factory ignition timing from the stock ECU still connected to make maps from?

Any tricks to logging a stock injector DC signal from a stock ECU to a spare input to create a fuel map?

Sorry for so many questions but I've run into so many dead ends and I think I'm pretty close to making this work for me and many others following my thread over at Dootalk.com
Any and all positive input is grearly appreciated and I just hope this is as easy to do as it sounds, but I'm probably way off

Thanks

[Matt Cramer]

I would like to ditch the aftermarket fuel box and use microsquirt to add or subtract to a pulse width signal from a stock ecu like the simple aftermarket piggyback box does?

The MicroSquirt can only generate a new pulse width signal from scratch. It is not able to modify signals to or from the stock ECU.

Can I intercept the stock coil signal and use that to trigger a coil at the same time as the stock ECU does? If I set up the tooth before TDC correct and zero out the spark map, could I then add or subtract over or under the factory curve in degrees.

Almost. There is a bit of a delay between the MicroSquirt getting a spark signal and the time it can fire the spark.

Any tricks to logging a stock injector DC signal from a stock ECU to a spare input to create a fuel map?

Sorry for so many questions but I've run into so many dead ends and I think I'm pretty close to making this work for me and many others following my thread over at Dootalk.com
Any and all positive input is grearly appreciated and I just hope this is as easy to do as it sounds, but I'm probably way off

Thanks

The MicroSquirt itself can't do this; there are some Innovate boxes that can do this sort of logging, or you could use an OBD2 logger if the ECU supports it.