Fuel injected two stroke Husky sm 125

[2T Institute]

But you talking about a 4T engine, 4T engine is easy to apply EFI to as each phase of the cycle is distinct and you have 720 deg of crank rotation to play with.
A 2T engine has at LEAST 2 phases of the cycle happening at any 1 time, which does not give much time and needs a lot of computing power to go from say 3000 up to 9000 and back to 3000 in the blink of an eye. EFI is 'dumb' ie you have to tell it what to do, a carb is smart it will work off engine demand and throttle position. Will will have 2 distinct progams for off and on pipe, and high rpm/low throttle situations etc etc etc.
Then there is the decision to DI or replace the carb with an injector. Putting a throttle body in place of a carb is relatively easy  the DI is much more complicated and expensive. Japanese factory's lost billions of YEN in the GFC they are just not prepared to spend the money.A contact in Japan went to Hammamatsu and was talking to a few Suzuki engineers at the new gixxer 1000 launch a few of them would love the opportunity to build another RG500 street bike, they were confident they could meet emissions targets etc etc but management crushed the idea.

[Chokey]

But you talking about a 4T engine, 4T engine is easy to apply EFI to as each phase of the cycle is distinct and you have 720 deg of crank rotation to play with.
A 2T engine has at LEAST 2 phases of the cycle happening at any 1 time, which does not give much time and needs a lot of computing power to go from say 3000 up to 9000 and back to 3000 in the blink of an eye. EFI is 'dumb' ie you have to tell it what to do, a carb is smart it will work off engine demand and throttle position. Will will have 2 distinct progams for off and on pipe, and high rpm/low throttle situations etc etc etc.
Then there is the decision to DI or replace the carb with an injector. Putting a throttle body in place of a carb is relatively easy  the DI is much more complicated and expensive. Japanese factory's lost billions of YEN in the GFC they are just not prepared to spend the money.A contact in Japan went to Hammamatsu and was talking to a few Suzuki engineers at the new gixxer 1000 launch a few of them would love the opportunity to build another RG500 street bike, they were confident they could meet emissions targets etc etc but management crushed the idea.

If fuel injection systems are fast enough to keep up with 15,000 rpm 4 cylinder sport bikes or 20,000 rpm 4 cylinder F1 engines I see no reason why they can't handle my single cylinder 9000 rpm 250 two-stroke.

I understand that the Japanese companies aren't going to invest R&D funds for bikes they don't even sell in their largest market anymore, but that's strictly economics. I just don't think I believe that their are any valid engineering reasons why FI is excessively difficult for our two-stroke MX bikes. The Bimoto V-Due was Direct Injected, and aside from some minor mapping issues it was nearly ready to go when Bimota ran out of money. They were a much smaller company than any of the OEMs and yet they made it work. They solved the fuel atomization issues and the piston cooling issues associated with DI on a high-rpm two-stroke. They simply bit off more than they could chew by also simultaneoulsy designing and building their own engine from scratch, which ultimately bankrupted them. A major manufacturer would have had the developmental resources to see that project through to fruition. I have read from more than one source that at the time of it's pre-pro debut, even though it still needed a little more low-speed mapping fine tuning, the V-Due engine had the highest specific output of any production motorcycle ever made at that time.

[TMKIWI]

The currant DI injector (ETEC) is able to inject the fuel needed in 0.0025 seconds at 5000rpm and is capable of 10000 rpm's. 0.00250sec is about 90 deg crank rotation at 5000rpm.
The old injector took 0.0050 seconds to do the same.
So in only 4 years they halved the injector time.
The new injectors have been out for 5 years now so i dont think it would be hard to make them quicker still.
I understand what you are saying 2T , but i dont think the designers are that far away from getting a system working.
I service a locals 250hp race boat (DI) and that has no problem going from 1000-6000 and back again without problems.
I know 9000rpm is alot higher but as i said i think they are getting close.
The problem has always been to get the fuel in quick enough between the exhaust ports closeing and TDC.
They actually inject before the exhaust port closes because the return exhaust pulse effectivly closes of the port.

[2T Institute]

Here we go again.
 For starters a outboard has a water cooled pipe and that makes a massive difference.An outboard can also use the water to choke the 'stinger ' size down or up if they want to. Yes the outboard can go up or down the rev range no problems but the vast majority of the throttle position is constant ,off or on. Which makes calculations easy. Look at the port arrangement on an outboard and if you replicated that in a motorcycle engine it would simply not work very well at all. Next we have torque loadings, when you back off on a boat the prop will not continue to drive the engine under zero throttle, like a wheel will. There is nothing/very little in an outboard that can cross over to a motorcycle engine and vice versa.
Also what sort of bore/stroke are outboards? As 90deg of a long stroke is much longer than 90 deg in a 54.5mm 125.
Chokey they are 4 stroke engines. Funny you mention Bimota as there injection system is let down by the ECU, a contact in Finland has a latest Motec on there and enlisted a MotoGP engineer(who lucky come from his home town) makes 106HP on the dyno, the same engine on a  set of VHSB Delorto's 125HP Go figure.
They were a LONG way from 'working' in fact the V-due sent Bimota broke with many many reliabilty issues/waranty claims and the fact that they were no good to ride. In fact the factory sent out a refit Delorto carb set, hey presto no more problems.
There are only really 2 people who have successfully made EFI 2T engines (Steve Murphy aka SMURPH and Martin Keiltsch aka MKRD) who have adapted the Microsquirt system to their RZ350's. Both those blokes Smurph is an EFI engineer and Martin is a Mechanical/Electrical engineer. With lots of time money and pistons they they have it working fine, what is basicaly a throttle body replacing the carb. Is the juice worth the squeeze, ask them
Maybe I'm wrong and EFI is just around the corner, maybe with a big pile of cash and pistons you can have a DI/EFI 2T engine that is rideable and reliable. I can show you plenty of cheap aftermaket EFI ECU's if it's so easy then why not have a go yourself?
 

[TMKIWI]

2T Institute, I never said it would be easy, just that there is always new developments that can supprise people.
I understand the problems associated with getting DI to work on a bike but i dont see it as a dead end.
There are clever people in this world. It just might take awhile.
BTW the smallest DI motor has a 63mm stroke .
I think the system needs to be developed on larger engines first.

In regard to your mate who talked to the Suzuki engineers wanting to build a RG500, what sort of fueling system were they thinking about to meet emission standards ?

[TotalNZ]

What you seem to overlook is sleds and outboards have one thing in common. Constant throttle opening. This makes open loop EFI a doddle.Sleds have a CVT which allows a narrow band of rpm but a wide range of operating speeds. Outboards are off or on, like the 50cc Aprilia Orbital scooter.
The ECU will have trouble coping with, off/on part throttle applications not to mention the hot/cold pipe. Not unless there is a massive jump in affordable computing power.

totally agree. from what i can see ( which isn't much really lol ) you'd have trouble getting fast accurate info to the cpu, what would you use for sensors? oxy sensor? not on a 2t, MAP sensor? don't think that would work either what then some sort of airflow meter na we're not in the 90's lol
A dirt bike is totally different to an outboard or a sled in the way we ask it to deliver it's power.
When you can make a carb or variant of it work so well then i can't see efi or dfi anytime in the near future.
just my 2 cents

So, FI works just fine with the constant throttle transitions of a four-stroke MX biked (without an O2 sensor), but it for some reason will be completely flummoxed by the constant throttle transitions of a two-stroke MX bike? Please explain why?

I'm not so much thinking of computing power but how you would configure the necassary sensors to give the right info to the ECU

[ford832]

There are clever people in this world.

Aww,shucks,stop TMKIWI,you're making me blush :-[But thanks anyway

[SachsGS]

TMKIWI,does that 250 hp DI racing outboard have expansion chambers? As well,the Ficht/E-tec system advances injection timing relative to a positive change in engine rpm to the point where,given CPU and fuel pressure constraints (and the "lag" associated) the exhaust port is exposed and expansion chamber exhaust wave resonance comes into play? If that outboard has expansion chambers,do you feel a surge in power at that point or is it linear?

The achilles heal of a modern schnurle loop inducted expansion chamber equipped two stroke is that exhaust port timing varies as a function of change in RPM whereas expansion chamber, and hence exhaust resonance,timing is fixed and as a result,when these two overlap the engine comes "on the pipe"(I'm thinking out loud here).At other times the intake charge is lost out the exhaust port and the engine makes no power.

At lower RPM,a DI engine would have fuel introduced into the combustion chamber after the ports were closed,hence no losses. In my mind this would mean a DI 2S would be a "torque monster" - just what the 4S guys don't want to hear. While different technology was used (but the objective was the same), wasn't that experimental Honda 400 2S a "torque monster" as well?

While I am being made aware of the current technological constraints of FI/DI technology as they relate to two cycle gasoline engines, I sense even more so now that a DI 2S engine is THE future. As they say "where there is a will there is a way".

[TMKIWI]

 Outboards do have expansion chambers as such. As with all 2 strokes you need a tuned exhaust system that will work for your application.They is no "lag" as the bottom end of the power range has been increased and there is no delay in either the injectors or timing of the computing system.
The problem has always been to make the system work over a large rpm range. Hence we have power valves.
Its not possible on a bike to have different length pipes at the same time. Some model etecs have an exhaust valve in the expansion chamber which changes the length of the return pulse and you definitley feel the "hit" on those models.
The "coming on the pipe" feel is a combination of the exhaust pulse and the resulting incomplete combustion of fuel not working together. As you said.
With DI you will definitley have more low end power because the engine will have a complete combustion burn even though the exhaust pulses are out of "sink" with the rpm's.
You will always have a "hit" because the rpm range we want will still mean a exhaust will be "tuned" to a certain rpm.
I don't think you will ever have a perfectly linear power curve unless someone can come up with a constantly varible expansion chamber.
Here's a quick video.
 E-TEC Voice Coil Fuel Injector System
Everthing you have said Sachs is pretty spot on.
The sensors required are TPS,CPS, Cylinder temp,Barometric & air temp sensor, power valve postion.
I dont understand the fuss about exhaust temp when a carb has no idea what it is.?
I also dont take much stock that 2 guys have managed it with their RZ's after having alot of problems (regardless of how cleaver they may be), they can not be compared to a multinational company.