[tanshi]

yeah i was reading, fiberglass reeds are better for low end power

[2stroker]

Some very switched on people have played with LJ50 engines in the past, anything you can think of has already been tried. All the 2 stoke theory has been explored, 20 years ago people were playing with bike carbies, expansion chamber design, electonic ignition, different pistons, different reeds etc, there was even an LJ50 running carbs, pistons, coilpacks etc from a Suzuki outboard motor.

In the end they were interesting projects but although some gains in performance may have been found it was always at the expense of something else like driveability, reliability or the torque curve. There is a lot to be said for a good standard LJ50 engine that is running well. Until you have had a good one you will not understand.

You can't improve on perfection.....

[tanshi]

I honestly think the best thing i can do is the EFI.

it will be fully tunable. i can pretty much tune it on the fly if i have a laptop in the car.

[JrZook]

tanshi wrote:

I honestly think the best thing i can do is the EFI.

it will be fully tunable. i can pretty much tune it on the fly if i have a laptop in the car.

\

EFI over the mods that 2-stroker has listed will be the greatest advantage. The tune will also be reliable and the overall efficiency of the engine will be increased.
Tashi: You got a spare engine to set up a mock up system?

[tanshi]

yep, i just need to get a gasket set and put it all back together.

might do rings while i have it apart.

[303zuke]

JrZook wrote:

tanshi wrote:

I honestly think the best thing i can do is the EFI.

it will be fully tunable. i can pretty much tune it on the fly if i have a laptop in the car.

EFI over the mods that 2-stroker has listed will be the greatest advantage. The tune will also be reliable and the overall efficiency of the engine will be increased.

How long will an O2 sensor survive on 2 stroke exhaust gases? Is 2 str oil Lead and Phosphorus free?

If you can't run an O2 sensor, you will only have an open loop EFI system, which is only marginally more efficient than a well set up and tuned carb.

Are there any factory 2 stroke set ups (ie bikes, outboards etc) that run EFI? I have only heard of CDI and pertronix-type ingitions, but no EFI.

[tanshi]

you can aparently get an O2 sensor from snow mobiles over in the states that run well with two stroke. heated ones also aparently last longer.

[2stroker]

Suzuki have been making efi 2 stoke outboards for 10-12 years now, not sure what set up they have, it may be worth having a look or speaking to some outboard mechanics.

[303zuke]

I think their EFI is only on 4 strokes, isn't it?. Their 2 strokes run electronic ignition only.

[JrZook]

2stroker wrote:

Suzuki have been making efi 2 stoke outboards for 10-12 years now, not sure what set up they have, it may be worth having a look or speaking to some outboard mechanics.

Well all EFI 2stroke outboards Im familiar with use direct injection systems such as orbital and the infamous ficht system. DI has its benefits although its wayyyy expensive and complicated.

Don't know how long the O2 sensor would last but it will be handy as a primary tuning tool.

The reasons why EFI will be more efficient than a well tuned carb is that it will enhance fuel atomization as well as reduce wall wetting from the fuel. What pressures are exhibited within the crankcase of these 2strokes? If you can mount the injectors within the crankcase (directed at the transfer ports) and leave the reeds to only transfer air there should be a descent increase in fuel atomization and efficiency.

Anyone got a pic of the barrels, ports and crankcase?

Dan

[JrZook]

303zuke wrote:

I think their EFI is only on 4 strokes. Their 2 strokes run electronic ignition only.

Refer to above post. OMC etec's are just another GDI 2stroke outboard and they run amazing compared to what they replace.

[tanshi]

i have a crank case pulled apart, i can try and get some pics at some point.

[Highway-Star]

tanshi wrote:

i have a crank case pulled apart, i can try and get some pics at some point.

I could probably launch a raid on your shed sometime this arvo, and get some pictures All I'm doing at the moment is triple checking I have all my camping gear and spares ready for this weekend...


Dan can you be more specific on what you want to gather from the photos? or just "pics of the barrel, ports and crankcase" ?

[tanshi]

yeah cool, it should be in a box in the corner near the grinder.

[JrZook]

Highway-Star wrote:

Dan can you be more specific on what you want to gather from the photos? or just "pics of the barrel, ports and crankcase" ?

Just would like to see a few angles of the bit to get familiar with the setup and look for possible injection positions. Never seen inside the guts of one b4.

Dan

[303zuke]

JrZook wrote:

What pressures are exhibited within the crankcase of these 2strokes? If you can mount the injectors within the crankcase (directed at the transfer ports) and leave the reeds to only transfer air there should be a descent increase in fuel atomization and efficiency.

Dan

I don't actually know any quoted figures, but I'd imagine fairly low. The combustion chamber compression is only 6:1 or 99psi. The crankcase volume would be much bigger. Pull the air pipe off the fuel pump and put on a vac/pressure gauge. You would get enough run time out of the fuel in the fuel bowl to get a reading on the gauge. My guess would be something like 20psi or less. Certainly nowhere near fuel rail pressures in an EFI system.

The difficulty in setting the fuel pressure with the injector within the crankcase would be timing it to coincide with the pressure/vacuum cycle of the crankcase.

[JrZook]

303zuke wrote:

JrZook wrote:

What pressures are exhibited within the crankcase of these 2strokes? If you can mount the injectors within the crankcase (directed at the transfer ports) and leave the reeds to only transfer air there should be a descent increase in fuel atomization and efficiency.

Dan

I don't actually know any quoted figures, but I'd imagine fairly low. The combustion chamber compression is only 6:1 or 99psi. The crankcase volume would be much bigger. Pull the air pipe off the fuel pump and put on a vac/pressure gauge. You would get enough run time out of the fuel in the fuel bowl to get a reading on the gauge. My guess would be something like 20psi or less. Certainly nowhere near fuel rail pressures in an EFI system.

The difficulty in setting the fuel pressure with the injector within the crankcase would be timing it to coincide with the pressure/vacuum cycle of the crankcase.

That is a good argument Sir. With mega squirt and alike, fully programmable ECU's it is possibly to play with injector timings and either advance it with rpm or keep it constant. With the fuel pressure issue obviously it wont be ideal and again highly dependent on the vacuum/pressure signal strength from within the crankcase but you can work around it if you say set it as a constant ie measure 20psi crank pressure, set the rail pressure 3bar above this. The pressure differential variation between this assumption can be sorted by modifying your VE or fuel tables accordingly. Well these are my thoughts about possibly rectifying the situation

Dan

[royce]

hook the pressure regulator up to teh crankcase and not the inlet manifold?

[303zuke]

Each crankcase for each cylinder is sealed from each other to provide suction from the manifold and injection into the combustion chamber at pressures (or vacuum) specific to the cycle of that cylinder. At any one time you will have different pressures in each crankcase.

You would need to have 3 fuel pressure regulators for each crankcase and injector. Or just have TBI and one regulator.

[Highway-Star]

OK Darren, pretty sure I found the "crappy engine", as its a bit rusty and had the oil injection in the barrel. And appologies about the crapness of one or 2 of the pictures...


Pictures:

Crank:


Crankcase, looking at the intake side, where the reeds bolt onto:


Crankcase, looking "top down", where the barrell bolts onto:


Crank in crankcase. Looking "up":


Crank in crankcase. Looking at the intake side again, case ready to split apart:


Barrell, bottom side up:


Close up of cylinder number 3:



If anyone wants pictures of something specific, let me know and I'll see what I can do.

[waimser]

I just thought id come throw my 2c into the mix.
My understanding of the 2 stroke engine is that its pointless to do anything to the engine without making the expansion chamber to match.
If you change the reads, porting,exhaust size or anything else, you need the corrasponding expansion chamber change. Do all of these things at once and you need an entirely different chamber again.

On top of this you have the power band issue. An expansion chamber works through a specific rev range. So if you want to max out top end power on a 2 stroke you absolutely sacrifice low down torque. As well as throwing a bunch of fuel out the exhaust.
Its not me that knows what im talking about btw, this all comes from a guy running 70 hp out of a 350cc bike engine.

Now a bit more on the topic, and im surprised the old man hasnt seen this thread and piped up. He used to tell me of his lj with 3 expansion chambers. One chamber came off each cylinder and was tuned for a different rev range that overlapped. With one cylinder giving low down torque, one midrange, and one high end power. The exhaust was designed and built by someone who really knew what they were doing with 2 strokes though.
This lj was aparently a monster, having no trouble breaking the speed limit or overtaking.

[tanshi]

yeah, interestingly i dont run any expansion chamber at the moment and have no power or torque issues at all.

[royce]

I always thought an expansion chamber was to provide exhaust scavenging on a single cylinder engine that wasnt able to use the vacuum created by the other cylinders exhaust port

Wheres Ball, finally he has a chance to post more than boobs

[tanshi]

i thought the same thing. i have a set of LJ50 extractors which im going to try at some point to see if they have any effect.

[JrZook]

303zuke wrote:

Each crankcase for each cylinder is sealed from each other to provide suction from the manifold and injection into the combustion chamber at pressures (or vacuum) specific to the cycle of that cylinder. At any one time you will have different pressures in each crankcase.

You would need to have 3 fuel pressure regulators for each crankcase and injector. Or just have TBI and one regulator.

Like i said before you could overcome this by setting the fuel reg up to a constant pressure above atmosphere. The only drawback it that you will have a differential pressure drop across the injector, thus the flowrate per injector opening time will vary but this can be compensated by altering the fueling table.

[tanshi]

JrZook wrote:

303zuke wrote:

Each crankcase for each cylinder is sealed from each other to provide suction from the manifold and injection into the combustion chamber at pressures (or vacuum) specific to the cycle of that cylinder. At any one time you will have different pressures in each crankcase.

You would need to have 3 fuel pressure regulators for each crankcase and injector. Or just have TBI and one regulator.

Like i said before you could overcome this by setting the fuel reg up to a constant pressure above atmosphere. The only drawback it that you will have a differential pressure drop across the injector, thus the flowrate per injector opening time will vary but this can be compensated by altering the fueling table.

glad you know what your talking about dan

[Highway-Star]

tanshi wrote:

JrZook wrote:

303zuke wrote:

Each crankcase for each cylinder is sealed from each other to provide suction from the manifold and injection into the combustion chamber at pressures (or vacuum) specific to the cycle of that cylinder. At any one time you will have different pressures in each crankcase.

You would need to have 3 fuel pressure regulators for each crankcase and injector. Or just have TBI and one regulator.

Like i said before you could overcome this by setting the fuel reg up to a constant pressure above atmosphere. The only drawback it that you will have a differential pressure drop across the injector, thus the flowrate per injector opening time will vary but this can be compensated by altering the fueling table.

glad you know what your talking about dan

Took me a couple of times reading it, but I think I get what he is saying.

Think he is suggesting using a solution of "estimate" a value for fuel pressure. Then to compensate for the fact that you'll get different amounts of fuel sprayed by the injector due to the difference in pressure between the fuel and the crankcase, adjust the "fuelling table" when tuning the ECU. I'm guessing the fuelling table will allow you to make the injector stay open for longer or shorter periods of time at certain conditions?

Feel free to tell me I got it all wrong if I did...

[tanshi]

ahh ok, that makes more sense.

[JrZook]

[3cyl]

Man I thought TBI would be hard enough!