ESE's works engine tuner

[trevor amos]

Could it be possible that the port casting is perfectly ok, but the bore is off-set and/or miss-aligned from initial manufacture, does happen?

Trevor

[TZ350]

Anything is possible, away at the moment, give me a day or three to get back and I will look at it a bit closer.

[Vannik]

I will have another look at the original piece, maybe face it back a bit in the lathe so the cut is definitely square.

When you have faced it and taken a new pic - would there be a chance to use it in Dat2T Help files?

[TZ350]

Yes of course...

[Muhr]

Would have been interesting if the japs had a vortex theory, or any other exciting thing going on. but feels like something in the manufacturing gone wrong as the wall thicknesses of C trans indicate and uncentrated borr as a result.
As Trevor suggested

[jfn2]

Here is possibly another way to look at the angles. Done with molds sitting on top of the case with piston propped up at port height.

[philou]

Cylinder Metrakit 50 cc for Derbi engine (lathes machining)

[Muhr]

Cylinder Metrakit 50 cc for Derbi engine (lathes machining)

May have been inspired ...

[husaberg]

May have been inspired ...

If you ask Jan or Frits the hooked B ports might be more to do with the stud position that was forced on them by managements insistence that it still bolt on every 125 made back for 20 years or so.

[jamathi]

If you ask Jan or Frits the hooked B ports might be more to do with the stud position that was forced on them by managements insistence that it still bolt on every 125 made back for 20 years or so.

I was perfectly happy with the Aprilia's B-ports and ducts.
They were unchanged from 1997 until I retired!
Also on the RSA!

[Frits Overmars]

I was perfectly happy with the Aprilia's B-ports and ducts.
They were unchanged from 1997 until I retired!
Also on the RSA!

It was mainly the leading edge of the A-ports that was hampered by the stud positions and the coolant ducting.

[Muhr]

It was mainly the leading edge of the A-ports that was hampered by the stud positions and the coolant ducting.

What would you or Jan have liked to do if the room had been given? More angle or area?

[wobbly]

I want to try a piston timing edge radius.

Anyone got any ideas on the need to move the cylinder by what amount if say I use R1.5.

This in effect means the ports start to open 1.5mm sooner, but instead of a sharp transition from " closed " to "open" we now have a very gradual

uncovering ( or covering for that matter ) of the flow area.

Am I overthinking this and should simply move the cylinder 1.5mm and see what happens.

[husaberg]

It was mainly the leading edge of the A-ports that was hampered by the stud positions and the coolant ducting.

Can you point to it?
Because I was thinking of the hook at the bottom of the picture that seems to be pushed around the Stud position?

[Matt@TYGA]

I want to try a piston timing edge radius.

Anyone got any ideas on the need to move the cylinder by what amount if say I use R1.5.

This in effect means the ports start to open 1.5mm sooner, but instead of a sharp transition from " closed " to "open" we now have a very gradual

uncovering ( or covering for that matter ) of the flow area.

Am I overthinking this and should simply move the cylinder 1.5mm and see what happens.

I think on this question, both options need testing and a full report written

But it's an interesting thing to look at.

Did a quick sketch and lets say that a sharp edged piston has just closed/opened the port, there would still be an opening (depending on piston size, dome radius etc). The dimensions I chose are just some numbers, so meaningless at this point, but let's just say that the flow is parallel to the port roof (for measurements sake) then the opening available is not 1.5mm, so I don't think I'd make the 1.5mm move of the cylinder.

Maybe changing the cylinder height 1mm would work, as this seems to give a similar open area at first opening.

I'd just give it a go first and then have a play.

Matt.