Custom EFI for the XS - Megasquirt of course
Sensors
The megasquirt manual is a bit much to take in very quickly. However, there's a nice summary writeup here.
The Megasquirt controller is so flexible that we can literally pick and choose from various availabe parts, so it's a bit of a shopping and planning exercise to get everything together.
throttle bodies/injectors
The first thing to solve for the EFI conversion is the question of throttle bodies. Some people have machined old carbs, but there are so many fuel injected bikes being parted out on ebay that it's just a matter of searching for some suitable donor parts.
Initially I picked up a set of four cylinder bodies thinking that I'd pull one body off and cut down the set. Unfortunately, there was a smaller offset in the center bodies making alignment a pain. So I set out again, and simply searched for 'throttle bodies' on ebay. I found these:
They're from a 2006 Triumph 675 triple. They feature 9 hole injectors, light weight and simple construction. Perfect. The Yamaha set I'd picked up provided a handy set of mounting rubbers. I'll probably have to machine some mounts to fit pod filters to the bodies, but that'll be a fun weekend milling project later on.
Ignition
The original ignition was actually electronic on the 1980 XS, but it was very early technology - it works but I'm after modern reliability here.
The cylinders fire at 120 degrees from each other, so wasted spark isn't an option - we need direct firing coils.
The answer is a Ford EDIS ignition system made for a 6 cylinder car. It has three coils that were set up to do wasted spark on every other cylinder. We simply use one coil per cylinder. The EDIS requires a crank pickup, but we need one for the Megasquirt controller anyway, so it doesn't require any extra work.
I'll document the EDIS conversion on my ignition page if you want more information.