YZ 250 EFI

[2T Institute]

Injectors aimed back at mid way between bore centre and the C port would do nicely

[scottydog]

Awesome work uniflow! Think I seen your other bike out Maddix park a while back.
I started a EFI project for my YZ 144 but put that in the too hard basket for now.

Are you working out of a machine shop in Tauranga somewhere?
I ask as I need some bike(non motor type) parts CNCed up,

Scott

Yes probably, you don't see too many Bighorn Kawasaki's around these days. The day you would have seen  the Kawasaki the fuel pump split, it only ran for a short while.
I live in Hamilton, machine shop in the yard out the back of the house. Walk to work every morning. We already do a bit of work for Wobbly. Certainly I'm interested but we are very busy at the moment, your job might have to sit in line.

Sweet as, what I need is small scale production run of parts I have been using a guy up Waipu ways and just looking at other options.
PM me your email and I'll be in touch

Scott

[TMKIWI]

Another "new" injection engine.
Thought you might find it interesting uniflow.

http://www.arcticinsider.com/Article/Tech-Insight-Inside-the-new-Arctic-Cat-600-C-TEC2-Engine

[factoryX]

Yum

[Uniflow]

There you go, they copied me   Not. This system is what I've been on about, transfer port injection. Sort of what my Kawasaki Bighorn is like. The new YZ360 will have a very similar system, but different. See how good EFI can be!! And easy as well, all standard car parts.

[Jeram]

There you go, they copied me   Not. This system is what I've been on about, transfer port injection. Sort of what my Kawasaki Bighorn is like. The new YZ360 will have a very similar system, but different. See how good EFI can be!! And easy as well, all standard car parts.

Hey uniflow, how much you want to merge these arctic cat crankcases with an 600 supersport clutch and gearbox? I'd happy pay a couple thousand

didnt wobbly try this or do this some time ago? was it through you?

Would be bloody awesome to be able to mount this directly into an R6 or triumph 675 and have a 6 speed gearbox.

[citabjockey]

This slot in the piston -- I hope its strong enough at the bottom of the skirt. My SC500 motor had failed for the prior owner from cracks that form from  slots in the piston to the bottom of the skirt. This was very common on these motors from what I understand:



That said I am very gratified to see Arctic Cat put out this motor. And to be doing the manufacture in house? Very Cool. Go USA (for once).

[SachsGS]

The Arctic Cat functions as a DFI engine at low speeds, correct? I wonder how the Orbital patents are affecting all of this?

The old aircooled open class mx's ran a lot of piston clearance and you could hear the piston knock until things warmed up. I've got an old Yamaha 400 in the shop right now and it's pretty noisy when it first fires up. I'm pretty sure piston metallurgy has improved quite a bit since those old SC500's.

[neilie]

i love the 2 strokes , shame on those who killed them in mx , big applause for those who still work on them like YOU!, 2 small problems , maintaining a 4 amp power at idle:  have a small battery/capacitor to store peak charge for release at idle? nowadays this may not add much weight.
 Since you are setting up efi, why not use a big tuning advantage over carbs, that is,Inputting the e.g.t. into the efi and tuning  to match the pipe will  broaden the peak rpm of the pipe. e.g. colder egt after peak , hotter egt before peak.   there could possibly be a point where it can ,as rpm decreases, change from hot to colder but this would require almost instant egt change (maybe this is possible as it does change very quickly). tuning older 2 strokes with an optak was very effective. cheers and all the best

[neilie]

for the throttle body, since you have the ability to cast and machine, id like to see a rotating arrangement ,like a old  the old ypvs .... think snail cams!, it might take up too much space but there will be a way........very aerodynamic, enought for an exhaust port! so there will be a huge flow increase!

[Uniflow]

Like this?
Or like this

[HCE]

The Arctic Cat functions as a DFI engine at low speeds, correct? I wonder how the Orbital patents are affecting all of this?

Technically it is direct injection at idle, but traditional direct injection refers fuel being injected just before ignition with all ports closed.   Also traditional direct injection systems operate at much higher fuel pressures to over come the pressure of the compressed air in the cylinder. 

[2T Institute]

What about a D or oval shaped hole in a sliding plate? That could be made 20mm thick, but lengthwise would be long with a 40odd mm of travel.

[evo550]

....is every Kiwi an offspring of Burt Munroe???

[Jeram]

Since you are setting up efi, why not use a big tuning advantage over carbs, that is,Inputting the e.g.t. into the efi and tuning  to match the pipe will  broaden the peak rpm of the pipe. e.g. colder egt after peak , hotter egt before peak.

Thats what ignition advance if for almost all twos stroke ignition curves do this to some degree.
If you want to play with it yourself all you need is a programmable ignition unit, you dont have to have EFI to do that.

you wouldnt adjust the EGTs with fueling as it'd be a good way to sieze the motor, however you could simply have a function in the programing which alters fueling based on EGTs to keep her right on the money.

Ie: IF TPS>17mA AND EGT>1200F, increase injection pulse duration