Cytherea

Cytherea
Participants
Skills	Mechanics, Electronics, Soldering, megasquirt
Status	Active
Niche	Electronics
Purpose	Fun
Tool	No
Location	Nurdspace
Cost	Priceless
Tool category

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{{#if:No | [[Tool Owner::{{{ProjectParticipants}}} | }} {{#if:No | [[Tool Cost::Priceless | }}

Challenges

To the readers that are still with me after this introduction, I salute you. In order to make everything work, I had quite some obstacles to overcome. Both mechanical and electrical in nature. In the past, I tried to build the ECU myself, but having not enough skills or education, I gave up on that path. However, for people like me, some guys with the proper skills and education developed a kit called MegaSquirt. When I jumped in in 2009 we were at Rev II, so that's the one I got. The cool thing is that I had to solder it myself, and it came with at least 100 components, so I had a lot of fun assembling it. The build guide was complete and very thorough and allowed for different hardware features depending on your requirements. (more about this later.)

• Assembling the ECU
• Fitting the fuel tank with a fuel pump
• Building the cable loom that ties the whole thing together
• Aquiring, calibrating and fitting various sensors
• Aquiring and mounting the trigger wheel
• Machining a custom fuel rail out of aluminium extrusion
• Removing the carburettors
• Mountin throttlebodies from a different bike
• 3D print a prototype of a simple mountpoint for the trottle cables
• Having said design machined by a friend
• Having said design laser cut by profzon (y)
• And probably some more

Assembling the ECU

Assembling the ECU wasn't that hard. I ordered a kit off of https://www.diyautotune.com/ which included the PCB, all the components and the casing. I also orderd to stimboard, used to simulate different sensors, and actuators. Assembly was pretty straight-forward, as the instructions were very clear (steps) and it would have you test the board at different stages of assembly. I took particular care in soldering everything, as it's supposed to last and I dread the idea of having to find a cold joint on the ECU.

One cool feature of the ECU is that it comes with a proto area in which you can hack your own cool features. In my case I used it to build support for a second ignition coil, the ECU comes with support for just one by default. I also added a transistor to drive the tachometer from the ECU.

Another cool feature is that is comes with support for Hall sensors, VR sensor and a thingamagic sensor to let the ECU know about the engine speed and position. The type of sensor determines how to assemble the board, so it comes with different "pathways" which you can enable/disable by bridging PCB traces or not.

Throttle bodies

Throttle bodies are the place where the fuel meets the air for the first time, setting themselves up for an explosive relationship. We'll need some way of controlling them, therefore throttle valves have been invented. Throttlebodies therefore allow for passage of air, come with a mounting hole for the fuel injector and have a throttle valve fitted. In my case, I didn't have holes for injectors, so rather than drilling them myself, I want to look for a bike which had them already. My bike is a Suzuki Bandit 600, so I deemed it natural to look for a Suzuki 600cc injected bike. Enter the GSX-r 600 SRAD.

The throttlebodies are separate units fitted next to eachother on two rails. They are mounted with rubber rings to the engineblock. This was very fortunate for me, because the spacing between the cilinders of the GSX-r is not the same as on a bandit. So, no hacksaw needed in this case :)

One sucky thing which turned out to be a pain in the ass was finding the right rings. The rings that came with the TB's didn't fit my bike and the rings that came with my bike didn't fit the TB's. Fortunately, with some careful measuring, it turned out that the rings of 1989 1200 cc GSF Katana would suit my needs, and they did!

So, now we have an engine block with mounted throttle bodies

Fitting the fuel pump

In order to get the fuel through the injectors one needs to have some pressure. Unfortunately, my bike didn't have a pump. Rather, fuel would just drip into the carburattors when the valve was engaged, and that's about it. So, I had to get a pump inside somehow. First I had to figure out what pressure I needed, turns out it's pretty much all the same, (3bar) so I got an pump from a Yamaha R1 from the salvage yard and did some guestimation about the size and wether or not it would fit. So, got the pump, but now how to fit it? Luckily I have a friend working in a metal shop, and he was kind enough to machine a flange on which to mount the pump. Now, the flange had to be welded onto the tank. For this I contacted a welder, as I don't have the required skill to pull this off. Unfortunateley, the welder didn't have it as well, as shown by the fuel dripping from the seams, so I had to have another welder redo the job. It took some effort, but I ended up with a fuel pump in the tank! (and no leaks)

Machining a custom fuel rail out of aluminium extrusion

Now that we have the tank + pump, how do we get the fuel to the engine? This is done by means of a fuel rail. A fuel rail is a hollow piece of metal with holes drilled into them that house the injectors. The injectors are put into their sockets and clamped onto the the throttle bodies by the fuel rail. The fuel rail is then connected to the fuel pump.

As I said earlier, the spacing between the cilinders of the GSX-r and the Bandit aren't the same. The GSX-r uses 100mm spacing between all cilinders, whereas the Bandit uses 100mm between the outermost cilinders, but 110 mm between the innermost. The reason for this is that the chain that drives the cams in located in the middle in the case of the Bandit, and on the side in the case of the GSX-r. So I had to bridge a gap. Mounting the TB's wasn't a big deal, I just had to cut a small bus in two, and using them as spacers. However, this also meant I couldn't use the fuel rail of the GSX-r. Which was a bit of a bitch, as now I had to create my own.

Machining a fuel rail isn't a big deal as it turned out. I drew up some plans in autocad, got myself a column drill, orded the extrusion, thread cutters, the right drills and off I went. I used special half inch bolts as end caps, and used the fuel hose mount of the GSX-r. Luckily I did it right the first time, using a slow speed setting on the drill, using machine oil to cool the drill and let it do its work. This is in order to reduce play, which could form a problem when inserting the injectors.