What do YOU know about fuel injection?

[philwecksr]

So, I'm going to undertake a couple projects over the next year or two and need some information on fuel injection. Well, I guess its one question at this point that may spawn more...

Lets say you are converting a carb bike to a fuel injected bike. If not trying to gain performance or substantially modify the feel of the bike, how would you size the throttle bodies?

For instance. A 1998+ Kat 750 uses 36mm carbs. If you wanted to fuel inject that bike, would you want 36mm throttle bodies? I would think you would, but whenever the GSXR's stepped from carbs to throttle bodies the sizes always increased. This could be due to tech advancements over the years and just searching for more power, or there could be a reason I'm not aware of...

Anybody know?

[arsenic]

[philwecksr]

Thanks I guess....

[arsenic]

that covers what I know about FI

[ctandc]

Normally yes...BUT.. (a big but at that)..

EFI is simply more efficient than a carb. So if the tuning and fuel mapping is done correctly, you can actually add larger throttle bodies, that are CAPABLE of delivering more fuel, but they only deliver it on demand. So again, IF the tuning is correct, and the ECM / PCM sees the demand for that extra fuel, it can be used to increase power.

Go here

http://www.diy-efi.org/

READ.....research.........READ some more. Everything you want to know about tuning / converting / and even putting together your own EFI controller setup is in there. I'm sure it can be adopted to a motorcycle (more than likely someone already has).

Here is a stand along EFI controller setup

http://www.megasquirt.info/

EFI is a wonderful thing. I've done more than a few EFI swaps into project cars and trucks.

Personally I wouldn't try to reinvent the wheel. I'd score a factory service manual for say a EFI equipped GSXR and READ.

[TheSteve]

Not too sure if this will help you, but I'm also attempting to convert my Kat to EFI. I'm trying to do this on the cheap so it might not be the "nicest" install. Basically the story is I bought a bike in pieces, and the carbs are completely trashed and gummed shut. Not sure I even want to mess with them.

I have 2 other vehicles running on Megasquirts, so I figured I'd see what I could do for the kat. The easiest way I've found so far is to adapt a TBI setup to a custom intake manifold. The TBI (if you aren't familiar) is an all in one unit consisting of the injector, throttle body, pressure regulator, sensors, etc all in one compact package. I went to a junkyard and found the smallest TBI I could, and bought it for $25. It came off a 95 Geo Metro with the 1.3L 4cyl engine. Quick calculation showed that at full throttle at redline the Geo still takes more fuel than the 600cc kat, so the unit is plenty big. Airflow is another story, this TBI has a single throttle body. Havent measured it yet but it appears to be about an inch in diameter. So I'm probably going to lose power at the top end until I switch out for a bigger unit. These TBIs also come with dual 1.5" butterflies on the larger Chevy motors. Those should flow plenty, but are a bit larger physically.

The next step is to fab up an intake manifold. This is the part I'm a little worried about, as I'm not very good with a welder yet. My current plan is to make it out of a combination of 1 1/2" OD pipe and 2" OD pipe for the plenum. Basically the smaller pipe would be the intake runners which would connect into the 2" pipe serving as a plenum. This would be just slightly longer than the carbs. Then where the airbox would normally go I would have the TBI connected to the plenum by another section of 2" pipe. Alternatively I could try using box steel, which would probably be easier to weld the runners to.

In my head, this all seems easy enough. Simple megasquirt install running fuel only on top of the stock ignition system, new intake manifold to adapt the TBI to the engine, TBI unit handling injection and offering a throttle plate. Theres plenty of space where the airbox is to mount even the larger TBI units.

Now this might not be the best way to do things. Say you have a set of old carb housings. You could drill bosses to mount standard fuel injectors to, remove the guts of the carb, and retain the stock look and powerband. But then you have to make a fuel rail. Or maybe theres an EFI bike engine whos intake manifold matches the ports on the Kat? Thatd be nice. Hell, maybe the TBI unit could be bolted to/in the stock airbox, and then gut the carbs except for the throttle plates. Not sure if that would flow right, or if the airbox is even airtight.

The possibilities are endless, and only limited by skill and unfortunately money..

[philwecksr]

I think I'm gonna try and fit up a 2001-2005 gsxr600 throttle bodies in place of the carbs. They are 38mm vs the 32mm the kat's carbs are, but we'll see what happens....

[TheSteve]

Wait, are you saying theyre spaced identically? If so they should pretty much bolt up. If thats the case then to hell with my plan, I'll run the GSXR stuff with the megasquirt and not have to deal with the custom parts. Let me know how that works out though, I hate carbs and really want an easy EFI conversion.

Steve

[crazyboy68]

i am in the process of changing one of my buddies gsxr's from carbs to fi. if u are changing you will need the wiring harness, throttle bodies, coil sticks, computer, sub harness for the coil sticks and throttle bodies. its not a hard change at all just have to find the correct throttle bodies to fit the intake

[philwecksr]

i am in the process of changing one of my buddies gsxr's from carbs to fi. if u are changing you will need the wiring harness, throttle bodies, coil sticks, computer, sub harness for the coil sticks and throttle bodies. its not a hard change at all just have to find the correct throttle bodies to fit the intake

I shouldn't need all that if I'm using the Megasquirt (although I'm kinda leaning toward the Microsquirt at this point, doesn't change anything though). The Megasquirt system is a standalone ECU type deal. If I sub in the throttle bodies I should be able to use the stock Kat parts elsewhere...

Wait, are you saying theyre spaced identically?

No, I'm not saying that at all. In fact I doubt it seriously, but I'm gonna give it a whirl anyway... I'll let you know how it turns out...

[Sin]

no there not the same spacing at all the cams on a new F.I motor the gears are on the end not in the center like a kat so there about 2 inches diff

[TheSteve]

Hmm. Ok, I just went outside and measured the intake port spacing on my spare 600 motor. The intake boots have an ID of about 40mm, and the port spacing is about *80*90*80* with the asterisks being the center of the intake ports. NOTE: These are very rough measurements. I merely eyeballed the port centers.

In comparison, the 01 GSXR TBs have even 80mm spacing all around. With a simple spacer in between the two center bodies this should be easy. The butterfly diameter is 42mm, apparently the runner then tapers to 45mm so I read. Unfortunately the site doesnt mention which motor these came from. Looks like the 750 and the 1000 are identical, but I'm not sure of the size of the 600.

I think it would fit pretty well, though itd be a tight fit into the boots without trimming.

Am I right? Or completely off base? I might be a little too excited about this idea to be thinking about it clearly, as this is much easier than my original plan.

[thetable]

Here is a great resource for FI with the mega/micro squirt: http://www.msruns.com/viewforum.php?...b8db4573fc46da

[TheSteve]

Well, I just ordered a set of throttle bodies with injectors from an 03 GSXR 600. I'll let you guys know how it works out. Hopefully itll fit with little modification and I'll have a 3rd megasquirted vehicle in the garage soon

[philwecksr]

Well, I just ordered a set of throttle bodies with injectors from an 03 GSXR 600. I'll let you guys know how it works out. Hopefully itll fit with little modification and I'll have a 3rd megasquirted vehicle in the garage soon

You too?? My throttle bodies came yesterday...

As a note, the 2001 750 and 1000's had 42mm throttle bodies. The 600's had 38mm... Assuming the taper is a fixed size and not a ratio that means the runners will taper to 43mm. 3mm is something that can be overcome I think...

The big question I'm interested to see is how they fit into the intake boots, cuz 10mm is significant. What are intake boots made out of? Are they just rubber? I've had my hands on them so many times but never really paid attention...