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Yamaha Big Wheel EFI
Posted: Sun Aug 14, 2016 3:55 pm
by BW250
I have done hours and hours of reading and I think I have my plan mostly figured out, but I thought I would run it by the experts. I am using a Yamaha TTR 225 bottom end, which I currently only have the stator and pulse generator for (as far as electrical goes). I just can't seem to figure out ignition/injector timing. It sounds like I can run the spark off of the pulse generator (which would cause the spark plug to fire twice per cycle correct? This is referred to as wasted spark?) but the injectors need a crank position sensor as well as a cam position sensor (or just a cam sensor?) to fire only on the intake stroke and to fire at the proper time? Hopefully that question makes sense.
Here is my shopping list so far:
-Mircrosquirt with 30 inch harness
-Innovate MTX-L 3895
-Throttle body from 250cc Japanese bike (haven't settled on a brand, but it seems like any of them should provide the throttle position and MAP)
-Delphi T-11 fuel pump
I know I still need a pressure regulator, air intake temp sensor and engine temp sensor (air cooled) so if there are any suggestions on particulars of those I would appreciate it.
Thanks so much for the help, I don't know why this aspect is so difficult for me.
Re: Yamaha Big Wheel EFI
Posted: Mon Aug 15, 2016 7:17 pm
by BW250
Ok, so I think I may have got it figured out. I can run the ignition timing off of the pulse generator, and then install a trigger wheel on my camshaft to control the injection timing. Is this correct?
Re: Yamaha Big Wheel EFI
Posted: Tue Aug 16, 2016 8:54 am
by Matt Cramer
I'd probably source the regulator from the donor bike.
GM sensors shouldn't be too hard to adapt; their coolant temperature sensor can be used as a cylinder head temperature sensor as well.
Do you have any information on the ignition pulse generator's trigger pattern?
Re: Yamaha Big Wheel EFI
Posted: Tue Aug 16, 2016 12:32 pm
by BW250
I'm assuming you are just talking about the voltage regulator? Here is the ignition timing table, is that the same thing you were asking for?
I just scored a Microsquirt so it sounds like I'm going for it.

Re: Yamaha Big Wheel EFI
Posted: Thu Aug 18, 2016 4:53 am
by Matt Cramer
What sort of trigger wheel and sensor is currently triggering the ignition?
Re: Yamaha Big Wheel EFI
Posted: Thu Aug 18, 2016 5:11 am
by BW250
Right now the bike uses a pulse generator run off of the magnets on the rotor.
P.S. I checked out your site, its an awesome resource! Nice to see all of the components in one place.
Re: Yamaha Big Wheel EFI
Posted: Mon Aug 22, 2016 11:42 am
by Matt Cramer
How are the magnets arranged? How many pulses per revolution?
Re: Yamaha Big Wheel EFI
Posted: Mon Aug 22, 2016 3:59 pm
by BW250
Unfortunately, now that I get looking at it, it seems to have one magnet about an inch and a half long-- so I'm assuming one pulse per revolution. Is there a chance I can simply fit two sensors to trigger off of the same wheel on the camshaft and just use one to trigger the spark and the other to time injecting?
Re: Yamaha Big Wheel EFI
Posted: Wed Aug 24, 2016 6:29 am
by Matt Cramer
You can share one sensor between the MicroSquirt and the factory ignition in most cases.
Re: Yamaha Big Wheel EFI
Posted: Wed Aug 24, 2016 8:19 am
by BW250
My hope was to use Microsquirt to control both fuel and spark. Right now all I have is the stator and the pulse generator (which I am led to believe can provide a tach input for Microsquirt). My questions are as follows:
1.Can fuel be accurately controlled with only a camshaft trigger wheel?
2.Can spark be accurately controlled with only a camshaft trigger wheel?
3. If both of the above are a yes, than is it possible to simply fit two sensors to a single cam trigger wheel?
Thanks