Project X

[madforitkev]

Managed to get some knackered barrels......Cheers Ian D!!

Looks like my injectors will drop right it the gaps. I am aiming for base of transfer injection.

Just need some fancy ports cut and a fuel rail now!!

[Alan H]

Will you use 1 injector per cylinder or 1 in each port? Using one might give a decent swirl, but would it affect fuel air mixing if you only squirted fuel up one port with 'half' the air going up the other?
Not being critical, just curious and very interested in the project.
I keep wondering why the injector isn't in the main inlet to get better fuel/air mix?
I must admit here, I went back and re read the thinking of air inlet control as I couldn't remember that bit.
I really do appreciate what you're doing with this, I couldn't stand the angst to start doing a project like this one.

[madforitkev]

Al,

One each port. I have got good help from a Kiwi group who have been playing with high revving 2 strokes.

One should do it and mixing should be OK as injection will start earlier and earlier dependent on revs to try to make all injection finish around BDC if at all possible.

Apparently if I inject on the inlets ' I might as well be running carbs' for the power gain it gives on a 2 stroke. makes sense all modern dirt bikes are port injection and mine climbs walls!!

Its a balance though. Big injector lots of fuel, short inject time but then at low revs it 'dribbles' and may not run smooth.

So I need to get my injectors to supply just enough at peak power and play with the injection timing.

I may have to also run a crank MAP sensor which doesn't really work on a 2 stroke (but maybe not as revs are low really), but if I do, it will have to have averaging software to allow for pressure waves. Thats my last thing to try.

So I am starting with 200cc injectors and ending squirt around BDC then play with injection volume (opening time) to get best power. Oh and mess with the timing but at least that's fully programmable now.....

What can possibly go wrong.

[Alan H]

I suspect that injecting as you say might benefit from increasing injector pressure for better fuel atomisation as revs increase? Doubtless such as Ferrari already thought of that, but I think your budget may be somewhat less.
Wonder what modern bike injector pump pressures are and if they increase with revs?
Regarding injecting into the (main) inlet, wouldn't a higher injection pressure give better fuel air atomising and mixing? Just thinking as I type here.
I remember the relatively low pressure (125psi?) lucas injection on my 2.5pi Triumph was nowhere as good (or reliable) as the bosch jetronic (200 psi?) at the time, but hey ho that was BMC in those days.
Cheap beats better, or not........

[madforitkev]

AL,

As far as I know most ported injection works around 3 bar. Which seems to be more than enough.

Injector squirt patterns can be important but I think mixing is mostly about getting a good end/start injection time.

Still lots to learn.

Ignition first, just waiting for the trigger back from machining then get that running with carbs. Will keep you posted......

[teazer]

Nice looking transfer ports. Someone has spent some time cleaning those up. What are the port dimensions compared to stock? Just asking for a friend....

[madforitkev]

Teazer

As far as I know they are stock. The pics are an old knackered set of barrels I am using for prototypes.

My modified transfer dimensions, I sent you a while ago. Do you need them again?

[madforitkev]

Thought I would post a summary of where my ports are and a comparison to stock and what I can find out about the TR750 porting.

Caveats are;

Std and my tune are port traces so reflect the total length round the barrel area of the port. The TR reference is from a document so could be cross dimension (straight line).

My next step is upping the CR a bit by fitting new squish heads then I may raise the transfers slightly but we will see.

Exhaust port is a bit more rounded at the bottom. These are CAD drawings from the original tracings so corner radius's aren't accurate.

If anyone has more clarity on TR porting that would be nice.....

[Kettletimes3]

I have a genuine late TR barrel here.
When I get a Minuit I will measure it up.
You won’t get a fancy drawing like your’s tho.

[madforitkev]

This week I 'ave mostly been making an ignition!

Based on the Speeduino EFi which is really a car unit,which makes programming a bit of a challenge.

Anyway long story short, you have to kid it to get a 3 cylinder 2 stroke going on 120 degree fire timing. Mine thinks its a 6 cylinder, 4 stroke using wasted spark ignition now. Any road up, timing looks good on the scope.

The Speeduino then fires an ignition trigger to make the low current into a high current and basically provide a switch to short the coil at the timing point (having previously energized it). Bit of a drama until I realised I hadn't translated the German correctly and I had the inputs and outputs swapped (need more tea). Upside is it made me make an ignition module tester (fancy word for resistor and LED).

So all good and my custom crank wheel and pickup from an HPI ignition works a treat.

Clearly I need to ruggedise it a bit but here is the first step in the motor with the clutch slave and the pickup nicely fitted inside my shortened cover. I attached the crank trigger wheel to the clutch slave and basically threw the other bits I didnt need away which gave me a nice 3 bolt mount that I can adjust.

I've designed a proper case for the ECU and should get that back next week then I can fit the newer high compression heads and run it again with programmable ignition!!