ESE's works engine tuner

[Michael Moore]

Has anyone tried putting a bearing bronze ring around the port opening in the case to try and deal with the wear issue?

With 3D modeling and CNC being relatively easy to come by I'd have thought lofting a surface between the circle profile at the slide and the trapezoid at the case to get a smooth transition would be commonplace.

cheers,
Michael

[Frits Overmars]

Has anyone tried putting a bearing bronze ring around the port opening in the case to try and deal with the wear issue?

Sure, and bronze, cast-iron and pertinax disc covers, ceramic coatings, inserted bronze guides like in the picture below, and so on. You name it; it has been tried.

With 3D modeling and CNC being relatively easy to come by I'd have thought lofting a surface between the circle profile at the slide and the trapezoid at the case to get a smooth transition would be commonplace.

No matter how smooth you make a transition, if you do it over too short a distance, the transition will become too steep.
For example, you can go from a circle to a trapezoid over a distance of ten times the circle diameter, or you can do it over a distance of one-tenth the diameter.
In both cases it can be smooth, but in the second case it will nevertheless cause a lot of turbulence.

[jamathi]

You can forget about wave action in the inlet tract. The inlet is open during more crank degrees than the exhaust port, so for a wave to travel up and down the tract once, that tract should be longer than the exhaust pipe (OK, the speed of sound in the inlet tract is lower because it's colder there, but anyway..)
A wave would travel up and down the usual inlet length so often between inlet opening and closure that it would have lost all of its energy by the time the port closes.

You want to open the inlet when there is no pressure difference over the disc. Opening it any earlier would cause pressure loss from the crankcase, and opening it any later would cost time.area and cause an unwelcome drop in crankcase pressure that would slow the transfer flow down.
The only benefit of a late opening is that the pressure difference will send a clearer signal to the carburetter.

That's it, Patrick. Any change in shape should be gradual, but you don't want a long inlet tract either, so you must compromise between a trapezoidal shape and a short tract.

Not necessarily, Husa. I'm curious about your view.

I can't; you'd have to ask the Great Leader; he insisted on that 'nose'.

Cutting off that 'nose' made no difference at all when we tried it....

[Jannem]

Calculated the scavenging angles of my cylinder based on information found here and got 22deg A and 10deg B.

However, my piston is old style dome, with approximately 15deg from top piston corner to top of the dome. Should this be taken into account with port angles or just ignored? If accounted for, how much should the port angles be increased?

[Frits Overmars]

Calculated the scavenging angles of my cylinder based on information found here and got 22deg A and 10deg B.
However, my piston is old style dome, with approximately 15deg from top piston corner to top of the dome. Should this be taken into account with port angles or just ignored? If accounted for, how much should the port angles be increased?

Hard to say Jannem. The mass flow would probably improve when you give the B-ports that same 15° axial angle, but then you may run the risk that the central scavenging column moves too fast.
Why use that old style piston? Has it anything going for it, or is it carrying a fistful of piston rings, in which case power might be found through reducing ring friction.

[katinas]

Return to Rygerised engine again, this time with almost isolated A, B transfers, just small parts left to do. But first decide to try this on std. engine, if this scheme works.

Today tested NS 250 engine with isolated A and B transfer channels, connected directly to carb through boyssens and isolated from crankcase (like in sketch) and special piston with pockets on sides (add pic), its like imitation Ryger on std. engine. Only C transfer work like normal.
First trying without reeds, but impossible to start from kick and impossible to push bike because winter outside.
With reeds, started easily and revs to 14200 rpm. and then na-na-na-na, feels like rev counter (honda rs 250 ignition 1986) I don't know.
And very interesting thing, when trying std. piston with very low transfers intake timing ( when piston is at TDC, transfers open just at they height) it revs to 12500 rpm. I cant believe. Before test I wish that engine with std. piston revs no more than 7000 rpm.
Can't say anything about power now, but want to try adjustable reed valve block, to understand if this scheme work without reeds at higher revs.

And one similarities with Rygerised engine is that it revs imeadeatly very cleanly without bubbling when engine is cold.

I don't know about Ryger real working principle, but if its in this way, maybe very short con rod on Ryger engine, generated stronger suction signal and faster accelerate fresh mix from carb, through transfer channels when piston close up to TDC.

[Muhr]

So here is the result of doing the opposite to having a hot exhaust duct.
I drilled thru the holes from the watercooled case, up underneath the Exhaust duct,and moved the main water inlet to the cylinder
from over the Exhaust port, around to the inlet, allowing cold water to flow directly over the transfers.
Simple mod - 1 Hp, and no sign of deto as the datalogger showed under 1.5V
Thankyou Mr Dyno.

Good test again!

If we play with the idea that it would only be due to the lower temperature of the mixture, it would mean about 3-4 kw less heat energy transmitted. (If I did not mess up my calc)
Intessant thought

[breezy]

Return to Rygerised engine again, this time with almost isolated A, B transfers, just small parts left to do. But first decide to try this on std. engine, if this scheme works.

Today tested NS 250 engine with isolated A and B transfer channels, connected directly to carb through boyssens and isolated from crankcase (like in sketch) and special piston with pockets on sides (add pic), its like imitation Ryger on std. engine. Only C transfer work like normal.
First trying without reeds, but impossible to start from kick and impossible to push bike because winter outside.
With reeds, started easily and revs to 14200 rpm. and then na-na-na-na, feels like rev counter (honda rs 250 ignition 1986) I don't know.
And very interesting thing, when trying std. piston with very low transfers intake timing ( when piston is at TDC, transfers open just at they height) it revs to 12500 rpm. I cant believe. Before test I wish that engine with std. piston revs no more than 7000 rpm.
Can't say anything about power now, but want to try adjustable reed valve block, to understand if this scheme work without reeds at higher revs.

And one similarities with Rygerised engine is that it revs imeadeatly very cleanly without bubbling when engine is cold.

I don't know about Ryger real working principle, but if its in this way, maybe very short con rod on Ryger engine, generated stronger suction signal and faster accelerate fresh mix from carb, through transfer channels when piston close up to TDC.

So Katinas, your transfer ports a+b are open for almost 360 degrees?

[katinas]

So Katinas, your transfer ports a+b are open for almost 360 degrees?

Transfers and exhaust timing is std. ( aprox Ex 198 trans 132), but suction timing from transfers to crakcase its aprox 220, it depends on how high is cut on piston ( transfers controlled like piston port engine intake window). A B C are open 132 and A B open to crankcase aprox 220.
With std piston suction timing from transfers to crakcase its around 120, I don't measure

[lodgernz]

Calculated the scavenging angles of my cylinder based on information found here and got 22deg A and 10deg B.
However, my piston is old style dome, with approximately 15deg from top piston corner to top of the dome. Should this be taken into account with port angles or just ignored? If accounted for, how much should the port angles be increased?

Hard to say Jannem. The mass flow would probably improve when you give the B-ports that same 15° axial angle, but then you may run the risk that the central scavenging column moves too fast.
Why use that old style piston? Has it anything going for it, or is it carrying a fistful of piston rings, in which case power might be found through reducing ring friction.

I have a related question concerning the "Edge Angle" of the piston dome. I define this as the instantaneous angle at which the dome rises from the notional flat-top measured at the edge of the piston, that is, the angle of the tangent to the dome, at the outer edge of the piston. While this Edge Angle is not the same as the angle discussed above, I wonder how it might affect scavenging patterns.


In my collection of piston "possibles" for my engines, most of which are modern domed racing pistons, every one has an edge angle of 15º or greater. Even a 53mm piston with a mere 3.7mm dome has an edge angle of 15.8º.
Since my B-transfer axial angles will always be considerably less than 15º, I wonder if these pistons will be less than optimal in performance. As the port opens, the designed axial angle of its upper edge will be usurped by the piston edge angle, deflecting the flow upwards at an angle greater than the port axial angle. This will only last a few degrees until the piston moves down far enough for the axial angle to reassert itself, but I wonder if that initial deflection affects scavenging.
Presumably, at least the flow will attach well to cool the piston in the B-port area.

The opposite question arises for the A-transfers: Since the axial angles of these ports will always be greater than 15º, the scavenging flow will not be deflected by the edge angle, but may not have the same attachment to cool the piston.

Clearly it's not a trivial matter to ameliorate these perceived issues, but are they really important? Am I tilting at windmills?

[lodgernz]

In all the photos I have seen of disc valve setups, I've only seen one with a trapezoidal shaped inlet port.
Such a shape would seem to offer the least radial angle for a given port area, thereby maximising the fully-open period of the valve.
People who know stuff, like Jan with Aprilia, didn't use this shape so clearly there are issues with it.
Perhaps because the valve would open instantaneously rather than progressively. Closing would still be progressive but rather sudden at the end.
Attachment 335120

Anyone care to comment?

Thanks for your contributions guys. A very useful discussion.

[lodgernz]

Return to Rygerised engine again, this time with almost isolated A, B transfers, just small parts left to do. But first decide to try this on std. engine, if this scheme works.

Today tested NS 250 engine with isolated A and B transfer channels, connected directly to carb through boyssens and isolated from crankcase (like in sketch) and special piston with pockets on sides (add pic), its like imitation Ryger on std. engine. Only C transfer work like normal.
First trying without reeds, but impossible to start from kick and impossible to push bike because winter outside.
With reeds, started easily and revs to 14200 rpm. and then na-na-na-na, feels like rev counter (honda rs 250 ignition 1986) I don't know.
And very interesting thing, when trying std. piston with very low transfers intake timing ( when piston is at TDC, transfers open just at they height) it revs to 12500 rpm. I cant believe. Before test I wish that engine with std. piston revs no more than 7000 rpm.
Can't say anything about power now, but want to try adjustable reed valve block, to understand if this scheme work without reeds at higher revs.

And one similarities with Rygerised engine is that it revs imeadeatly very cleanly without bubbling when engine is cold.

I don't know about Ryger real working principle, but if its in this way, maybe very short con rod on Ryger engine, generated stronger suction signal and faster accelerate fresh mix from carb, through transfer channels when piston close up to TDC.

Where do you place the reed valve?

[crbbt]

Big question.

will NX5 cylinders bolt on to later NX4 cases without modification?

[Frits Overmars]

... my piston is old style dome, with approximately 15deg from top piston corner to top of the dome.

I have a related question concerning the "Edge Angle" of the piston dome. I define this as the instantaneous angle at which the dome rises from the notional flat-top measured at the edge of the piston, that is, the angle of the tangent to the dome, at the outer edge of the piston. While this Edge Angle is not the same as the angle discussed above...

My definition of the edge angle is the same as yours, Lodgernz. I assumed that Jannem meant the same with his "15deg from top piston corner to top of the dome".
I can't see what else he could have meant.

In my collection of piston "possibles" for my engines, most of which are modern domed racing pistons, every one has an edge angle of 15º or greater. Even a 53mm piston with a mere 3.7mm dome has an edge angle of 15.8º.

No engine I worked on in the past three decades had a 15° edge angle. Most pistons were between 7° and 12°; the highest value I found was 13° (in a Suzuki T500).
To ascertain that we both use the same approach, I took your 53 mm bore, 3,7 mm dome height, 15,8° edge radius and it checked out OK (with a 97 mm dome radius).

Since my B-transfer axial angles will always be considerably less than 15º, I wonder if these pistons will be less than optimal in performance.

As I wrote in my answer #28610 to Jannem, the optimum performance of the B-ports does not soleley depend on mass flow: http://www.kiwibiker.co.nz/forums/sh...post1130452977

As the port opens, the designed axial angle of its upper edge will be usurped by the piston edge angle, deflecting the flow upwards at an angle greater than the port axial angle. This will only last a few degrees until the piston moves down far enough for the axial angle to reassert itself, but I wonder if that initial deflection affects scavenging.

It's not just that initial reflection; a high piston dome limits the cross flow area much like the axial angle of a transfer roof does.

[jasonu]

Big question.

will NX5 cylinders bolt on to later NX4 cases with modification?

You can bolt anything to anything. Depends on the amount of faffing around you want to do.