ESE's works engine tuner

[tdc211]

Hello. Haven't been on here for a while.
Been playing with cars and working.

As some of you may know. I played with the old model ktm 105
Alot. Changed the transfer port tunnel shapes,timings and Area's, pipe dimensions ,export, even tried exhaust extension, All the basic things and some of the other things that's been talked about on here . Leaned how bad the A ports can short circuit cause of this engine . Learned some things on B port volume/shape cause of this engine. Tried alot of pipes I made.
took 3 years to make 34 hp,up from 27.5hp. With the old style cylinder n epoxy. My new more modern cylinder 105 1hp less.. Couldn't of done it with this forum or Frits Jan and Wob or engine mod 2t and alot of head scratching. Wob even helped me with a yz85 flat track eng. Thank you all very much.


I had a guy give me a new yz 85 that was bored and stroked.
To see what i can do with it.
he wasn't to happy with it as is. I see some very obvious things I can make quick work of. Yamaha tightened up the transfer port volumes. These are much longer ports than I am use to. Different roof angles than I am used to . Completely different shape ports than I am use to. So I am sure different results than I am use to. Here are 2 inner radius transfer shapes.
I know how the shorter shape works . (For now)
Dis regard the tails on right side. Bottom of bore ends on right side bend. Any input how thess longer ,different shape will work? I have a idea/maybe. I do own a flow bench. But where talking 2 strokes. So I am sure, I am in for some surprises when I dyno this thing. I need make port molds yet.

[TZ350]

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Ok, it did not work as expected so what is going on here.

I imagined that the depression behind the slide would draw fuel up the purple tube attached the power jet pickup. Fuel flow being moderated by the solenoid valve.

The Ignitec ignition has an option for PWM of a power jet and I am using this to control the solenoid valve. With the frequency set at 2Hz ( the solenoid should handle that) and PWM at 100%. I was expecting the engine to run way over rich but nothing happened. No extra fuel?

The solenoid works, I tested it by sucking on the tube when the solenoid was activated, so all good there. And I was expecting that at WOT fuel would be sucked from the tube just like it is with the main jet. And at closed throttle it would gush out like a fountain.

But nothing, could it be that the pressure recovery on the engine side of the slide is such that there is no real depression there ????. Any suggestions would be welcome.

[Tim Ey]

Hi Teezee,

I think it is certainly not helping, that you force the fuel to participate in a exhausting long rollercoaster ride before joining the game

I would use the valve the other way around: connect the 90° bent to the vaporizing tube and make a short and straight hose down in the chamber. No bends, no long paths to go.

Also I would point the vaporizing tube in the center of the bore. (Idea stolen from wobbly)

If that does not help at all, mount a brass plug in the hose with a 0.2mm hole in it. That will act like a check valve and no fuel will flow back into the chamber (Idea stolen from Suzuki RGV powerjet hose)

Cheers
Tim

[F5 Dave]

It is pretty hose.

Pretty big hose. Usually very small bore.

[wobbly]

Its normal to operate the valve at something like 12Hz and vary the % to vary the flow rate.
Try using the solenoid to operate the std powerjet , just to see if that well provrn system actually works.
Then stick a piece of clear tube on the jet behind the slide down into a small container of fuel next to the bowl and see if fuel is drawn up on the overrun.

[TZ350]

Hi Teezee, I think it is certainly not helping, that you force the fuel to participate in a exhausting long rollercoaster ride before joining the game I would use the valve the other way around: connect the 90° bent to the vaporizing tube and make a short and straight hose down in the chamber. No bends, no long paths to go. Cheers Tim

Pretty big hose. Usually very small bore.

Its normal to operate the valve at something like 12Hz and vary the % to vary the flow rate. Try using the solenoid to operate the std powerjet , just to see if that well provrn system actually works. Then stick a piece of clear tube on the jet behind the slide down into a small container of fuel next to the bowl and see if fuel is drawn up on the overrun.

Thanks for the tips.

Now, I have become really interested in what the actual pressure is behind the slide. At closed throttle the small amount of airflow across the pilot jet orifice causes a venture effect but the actual pressure behind the slide might be quite high. There may not be that much differential between the front and back of the slide. When I get a chance I am going to measure it.

[speedpro]

Your previous measurement of crankcase pressure at various times should be a clue I'd have thought.

[TZ350]

Your previous measurement of crankcase pressure at various times should be a clue I'd have thought.

Yes. True, ...... where was my head at. Looks like I trapped myself with four stroke thinking again. Where the pressure behind the slide of a 4S is really low.

And if the average two stroke's crankcase pressure is close to atmospheric at closed throttle then of course the pressure behind the slide must be close to atmospheric too. So little suction there. And when it is on WOT the average crankcase pressure is only a little lower, but not by all that much. The air moves through the 2S motor in a series of short pulses. Unlike a 4S which is more pumping action than pulse action.

[Muhr]

The pressure drop in the carburetor veturi has a lot to do with speed.
You should have dynamic pressure drop for close to 200 mm at peak power. It does not happen to be checked that it should be invert polarity (do not know what it looks like on ignitec but have made the mistake myself)

[TZ350]

.

The pressure drop in the carburetor venturi has a lot to do with speed. You should have dynamic pressure drop for close to 200 mm at peak power.

Yes that makes sense, the average crankcase pressure does not change much but at WOT the max and min crank case pressures are much greater than at lesser or closed throttle. And with large swings in crankcase pressure there will be larger gas speeds through the inlet venturi.

[ceci]

I was wrong, he talks about the rsw 2 which is indeed the 500.

he maintains that there is only one injector. I do not believe it. one cannot be enough to feed properly

Francesco didn't lie

[andreas]

Sorry TZ, I don't have a solution to this predicament, out of curiosity I wonder; You change the original PJ outlet to what must have been an oil pump inlet- for some reason, and since he jet sits in the original over-venturi nozzle, how does it meter the fuel? But there shouldn't be less depression in this new location compared to where it was, I don't think.

[wobbly]

There must be a depression on the engine side of the slide when closed, as that is where the pilot circuit is activated from.

[TZ350]

There must be a depression on the engine side of the slide when closed, as that is where the pilot circuit is activated from.

Yes there is sufficient to draw minimal air under the slide and across the pilot jet but not sufficient to lift fuel from the fuel bowl all the way up to where I have placed my nozzle behind the slide apparently. The depression behind the slide on a two stroke at closed throttle is much much much less than it is on a four stroke.

[Muhr]

Even when releasing the throttle with gear, the flow should be the volume after clost transfers minus the crankcase low pressure times rpm on each individual occasion?