Thread: Megasquirt :)
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Old 08-10-2012, 04:23 PM   #3
naginalf
Handy Schtroumpf
 
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Joined: Jan 2010
Location: Madison, WI
Oddometer: 250
Ah. Now here I can be of some help. I was thinking of doing this as well, but thought I'd leave well enough alone, however, it would be nice to have a redundant setup using the carbs as throttle bodies, but there doesn't seem to be enough room for the injector behind the throttle plate. Thought about using this little guy:


DIY autotune is a very good resource btw. I had done most of the research I needed for this mod when planning to fuel inject my old honda, people had very good success with it. But is there anyone who's already done this to these bikes? You might do some research on the megasquirt forums and find all your maps already made .

To answer your question, yes that was a throttle position sensor, you'll be needing that trust me (although, you can get away without it, the pressure sensor can cover most if not all instances, the TPS just tells the pooter when you've got it hammered and is a little more precise when throttle is further open). In fact, you can do some super simple but very effective fuel maps with just the throttle position. You actually don't need the o2 sensor once you have your maps made up, but it's good to have some wiggle room for the o2 to adjust. The problem is that unless you go with a lamda sensor, it's not a very accurate affair, it basically bounces around between rich and lean and doesn't do much else. Wrangler is correct tho, you may want some sort of air flow/pressure sensor. Most 'squirters just use an air pressure sensor, usually the barometric correction type, that along with your throttle sensor is more than enough throttle/air input. Oh and you need an intake air temp sensor and it's preferable to have an engine temp sensor. With air cooled motors, you don't want to use an oil temp sensor because it heats up too quickly, usually people find a way to mount a cylinder head temp sensor to the back of the head between fins.

However, for a super simple FI, all you really need is a throttle position sensor, an intake and cylinder temp sensor, and some sort of RPM trigger. The rest is icing for smoothness (air sensors), power (the full gamut of sensors), and economy (o2 sensor).

You're also gonna want to install a trigger wheel somewhere, probably on the timing chain crank sprocket. It's not necessary per se, you can use the stock ignition trigger, but then it is much harder to play around with spark advance and whatnot (actually, I think you are forced to use the stock ignition). Plus you can replace the stock ignition all together, while leaving it in place for a backup.

I wouldn't do a megasquirt tho, it's not sealed. Get a microsquirt, it's all sealed up waterproof, made for bikes, small, and has everything you need built in.

As for the O2 sensor, I was considering adding one simply for tuning the carbs, but I got to thinking about it this morning and was wondering where to put the sensor and wire up the heater, then I realized that there is the perfect bung already installed on the bike where the secondary air system went. I wonder if there's any o2 sensor that will fit there? Plus, then you don't need the heater (2 wire type as opposed to 3/4 wire type).
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naginalf screwed with this post 08-10-2012 at 04:46 PM
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