ESE's works engine tuner

[andreas]

Maybe it's the story of a wasted spark setup.

[SwePatrick]

SwePatrick:
I just measured a 2004 YZ125 clutch plate and it has the same dimensions as one you posted.

Nice,, thank you.
this will make things easy, i can fit two or three more plates with the rekluse ones, dunno thickness of them yet, but from what i can see on pictures.

[SwePatrick]

Maybe it's the story of a wasted spark setup.

Might be, but i´ll test everything else first as i know many many twostrokes run the same setup.

[SwePatrick]

For sure sounds rich if it gets worse as it warms up.
The overly rich mixture is burning so slowly , as the piston is descending , that its still happening when the Exhaust port opens.
One way to see if its very rich oround idle ( closed throttle ) would be to start it with no choke at all.
If it runs fine with no choke , then thats the story right there.
If its lean down low then it wil take ages to settle down to an idle , that also can have a mixture so lean it burns slowly and pops when backing off.
But again , that can be tested by leaving the choke on , if the pops go away , even if idle is OK , then that is the other story being told.

Yes, the first symptom sound accurate, i´ll make some test this evening.
It´s mind distubing that the plugs says go the other way, but i guess i can't read the plugs as the pulls in dyno is so short, just a couple of seconds as the clutch slips.
I actually think it´s the powerjets that are messing with me.(i´ll block them off first)

I need to fix the clutch, and might have a solution with the yz250f discs.

[F5 Dave]

Might be, but i´ll test everything else first as i know many many twostrokes run the same setup.

Methanol with wasted spark will ignite. Petrol unlikely

[Frits Overmars]

It´s mind distubing that the plugs says go the other way...

You are using methanol fuel, aren't you Patrick? My limited experience with methanol taught me that you must not try to get the plugs dry. The engine will perish before the plugs dry up.

[adegnes]

So.
After half a year of brain cooling axe-work I'm back at it.
If you've watched the videos you know that I've managed to start the engine on the primary intake, and that's about it.

Short description of the specimen in question:

Attachment 347170

- 50cc
- Primary reed intake, secondary valveless intake
- Primary = carb on gas, secondary = continous nitromethanol injection
- 100% bore width exhaust port
- special piston(thanks makr) with retained ring
- CVT transmission, electronically controlled belt tension.

So far(admittedly not very far) the ring has not snagged, not with it's original full "T" profile, nor after grinding away everything but two short tabs opposite of the ring gap.

Ring with full "T".



Two small tabs left.


With the full "T" I struggled with getting it to seal properly, uneven pressure, tight in some areas, not even touching the bore in some. No quite sure what made it behave like this. Twisting force?
With tabs the ring seems to be sealing fine, and in the middle of the exhaust port is really the only place it needs to be retained.
A better solution, provided it stays in one piece...
Mark has a thinner (0.5mm) ring and corresponding piston planned/in the making, the current ring (1mm) is too soft, and probably to heavy for higher rpm.


Attachment 347167
Attachment 347168
Attachment 347169

Massive case volume(390cc), hard to say exactly where the intake ends and the case begins - effective case volume might be smaller.

Hard starting, probably due to primary compression being far from reed friendly. Last test was with 50cc of crank stuffing, but prior to that a backfire cracked my reeds(sanded from 0.4 to 0.2mm),and the test was performed with a different reed cage. Ran much better.
Next test without the stuffer, hoping it was the reeds that helped.

Must admit I didn't give the primary much thought while designing the engine, should have...

As long as it's possible to start, warm up, and pull into the powerband I'm happy, after that the secondary intake takes over.

That PVC plumbing valve is a placeholder for a more refined thing, will be run fully open/closed.



In retrospect I regret not designing in a slide valve much closer to the crank, would've served as a combined intake opener and case expander.
If I can't get it working with softer, more, or different size reeds I'll probably put in a valve like that, but it won't be as slick.


Not as slick.
Attachment 347171
Attachment 347172


50% of the youtube comments say I need a pipe for backpressure, here it is, not primarily for backpressure though...

[wobbly]

I would say that the 50% saying you need a pipe for back pressure are a solid part of the 90% on FB that talk complete rubbish about Twostrokes.
What does an expansion chamber do to facilitate startup ." Backpressure " is completely irrelevant at that point , though I am very willing to be completely wrong.
But as Jan sucessfully dynoed an Aprillia with no pipe at all ( needed rejetting obviously ) I think I am pretty safe.

[Flettner]

Thankyou Adegnes, good to see real development work happening, not copying or just talk. I am excited about this trapped ring development. Look forward to you showing up all the doubters. Pitty we all have to do this kind of work on a shoestring isn't it.

[adegnes]

I would say that the 50% saying you need a pipe for back pressure are a solid part of the 90% on FB that talk complete rubbish about Twostrokes.
What does an expansion chamber do to facilitate startup ." Backpressure " is completely irrelevant at that point , though I am very willing to be completely wrong.
But as Jan sucessfully dynoed an Aprillia with no pipe at all ( needed rejetting obviously ) I think I am pretty safe.

They're a strange crowd....

Thankyou Adegnes, good to see real development work happening, not copying or just talk. I am excited about this trapped ring development. Look forward to you showing up all the doubters. Pitty we all have to do this kind of work on a shoestring isn't it.

Thanks!
All I need is unlimited money and time, is that too much to ask for!?

Can't get anything done until Sunday night now, social obligations have me pinned down.

[SwePatrick]

You are using methanol fuel, aren't you Patrick? My limited experience with methanol taught me that you must not try to get the plugs dry. The engine will perish before the plugs dry up.

Not in this engine yes, ordinary pumpfuel(in Sweden 98octane, research?)

I tested a thing yesterday to quickly lean the engine, i bought some e85, ofcourse it went really lean directly with 100% 85 and 4% oil.
So i splashed in some 98octane, roughly about 30% petrol, so 70% e85 mixed with 30% petrol.
This started to work actually, just had to pull out the chokes, then it was roughly correct, it idled and responded really good.
The pops ang bangs got less, now it was only above 12000rpm, on 100% petrol it started at ~10000rpm.
So it tells me it was rich on petrol.

It is really hard to get into the ballpark with jetting with hard tuned twostrokes, i got many years experiance, they are really really sensitive, and i use to read the plugs.
Now that tuning tool was diffuse as the pulls were so short.

The engines often sounds really crisp when freerevving, so in comparing to tune a 20hp 125cc it is hard, those 20hp tells me direct what they want.
But high tuning grade makes all diffuse

[SwePatrick]

Not in this engine yes, ordinary pumpfuel(in Sweden 98octane, research?)

I tested a thing yesterday to quickly lean the engine, i bought some e85, ofcourse it went really lean directly with 100% 85 and 4% oil.
So i splashed in some 98octane, roughly about 30% petrol, so 70% e85 mixed with 30% petrol.
This started to work actually, just had to pull out the chokes, then it was roughly correct, it idled and responded really good.
The pops ang bangs got less, now it was only above 12000rpm, on 100% petrol it started at ~10000rpm.
So it tells me it was rich on petrol.

It is really hard to get into the ballpark with jetting with hard tuned twostrokes, i got many years experiance, they are really really sensitive, and i use to read the plugs.
Now that tuning tool was diffuse as the pulls were so short.

The engines often sounds really crisp when freerevving, so in comparing to tune a 20hp 125cc it is hard, those 20hp tells me direct what they want.
But high tuning grade makes all diffuse

Kind of forget what o wrote about it was better,,,,
I feel like a rookie,, nothing works.
i need to start over.

[adegnes]

Regarding my 100% of bore single exhaust port.
It provides more STA than bridged ports, no doubt, but what about velocity?
Even though there's a slight curve to the top edge + a bevel, it opens the whole duct volume at once, not like a 3-port where the aux's should stay closed a few degrees.
The floor is just slightly below transfer roofs, and duct exit is 75% of effective port area(if I remember correctly).

[wobbly]

A T port at 100% bore as was used in A kit Honda 125/250 GP cylinders had a dead straight timing edge.
This obviously worked very well.
Your 100% port with no bridge , but a much higher floor than the old Honda's had , should have greater duct velocity and work even better.
More so using the reduced duct exit concept as well.

[andreas]

I read it like the effective port area is the whole ex-area, not just the blowdown-which is then reduced to 75%. But what happens when the whole area is more or less the same as the blowdow area?