ESE's works engine tuner

[Flettner]

I fly on cylinders plated by NZ Cylinders, totaly trust them.

[vro46i]

NZ Cylinders plating is a licenced setup from Langcourt in UK , so the coating is well proven.
The issue is getting detail finishing - to the point I have told them not to touch anything , I will do it all myself.
You grind the ports and put on any required chamfers ( not needed at all on transfers anyway ) before the replating is done.
In fact the best way is to get them to take off the chrome and return it to you before plating.

Hi Wobbly,

Yes, there will be detailed work required along with a repair to the exhaust bridge. I would like to copy the port shape and timing from an NX4 cylinder. Langcourts! that was the name of the UK firm that I had forgotten.

Thanks for the advice, I will proceed as recommended.

[Tim Ey]

Langcourt Coating is superb. Also while honing, they do a proper job.
But I would recommend to engrave "DO NOT GRIND THE PORTS" on the cylinder. Otherwise it might be that they chamfer your cylinder anyway.

[TZ350]

I would like to copy the port shape and timing from an NX4 cylinder.

Just copying the port shape, it is not as simple as that. A NSR and NX4 are both 54mm stroke x 54mm bore.

A short stroke NSR cylinders exhaust port with a 48,3mm stroke will be able to have the same timing in crankshaft degrees as a NX4 cylinder but the shape of the exhaust will have a lower top edge and appear to be smaller. But when you calculate out the crankshaft Angle (degrees) and Area you can have the same STA (specific time area) as an NX4. STA is everything.

A short stroke NSR and normal stroke NX4 cylinders exhaust ports, although they may have the same STA, they wont look the same. The shapes will be different.

Something we did with our best short stroke NSR cylinder but we have not totally confirmed it by back to back tests. Posted as, just something to think about. The wider NSR exhaust bridge can have the sides rounded so that it flows much better while retaining its original strength with the narrower NX4 like ring support. The top edges and sides in the exhaust ports blow down area may also be rounded to improve flow out of the cylinder during the blow down period.

With the short stroke 110cc NSR's. We found we had to trim something off the top of the cylinders to get the squish right. Then we found if it was taken from the bottom of the cylinder we could re angle the top of the transfers for a more up swept angle on the transfer ports. See the leaning tower of Pizza principle and transfer port theory:- https://www.kiwibiker.co.nz/forums/s...tuner/page2000

[TZ350]

.

2Stroke Stuffing. God HATES Two Strokes? If not, then why!? Was so close to getting that dyno ready, then... https://youtu.be/ZwsWTBnDyRU

[philou]

nikasil at Monardi in Italy. hardness and quality of finish

http://www.monardiromanosnc.com/

[wobbly]

This is what I am saying about having the plater do the finishing.Those transfer chamfers are huge ,absolutely no point as they loose power , and why do you need them .
Its impossible for the ring to bulge out into a transfer port . Only the boost port top and bottom ,needs a small chamfer to help guide the ring ends into the groove.

[vro46i]

This is what I am saying about having the plater do the finishing.Those transfer chamfers are huge ,absolutely no point as they loose power , and why do you need them .
Its impossible for the ring to bulge out into a transfer port . Only the boost port top and bottom ,needs a small chamfer to help guide the ring ends into the groove.

Wobbly, further question regarding your comment regarding the large radius in the pictures provided by Philou. By maintaining a sharp (ish) edge, is the aim of the passing piston ring(s) acting as a guillotine and positively cut the mixture and creates and linear and positive port seal?

Apologies if this is a silly question, I am wanting to understand the concept from a first-principles perspective.

Thanks

[Vannik]

Wobbly, further question regarding your comment regarding the large radius in the pictures provided by Philou.

I am not Wobbly but my understanding is that the radius causes attachment of the flow and diverts it from the direction it is meant to go. Scavenging is not working as designed with the flow on the edge of the scavenging streams sort of fanning out and mixing with the burnt gas and there a bigger chance of short circuiting.

[philou]

the wide chamfers are not good as they function as a funnel allowing the burnt gas to enter the transfers.

for road engines, the nikasyl professionals do not take any risks and make large chamfers to guarantee a certain reliability

[wobbly]

Neels is right, with a chamfer on a transfer port roof or floor the flow stays attached to the surface and tries to " go around the corner ".Thus the exiting column of mixture looses its coherent shape
and fans out with lots of turbulent eddies , thus ruining the scavenging pattern , with random flow in the wrong places.
The sharp edge corner only needs to be broken with a cotton mop , and this has no effect on ring life at all.

The worst case of this is effect shown when putting a radius on the piston edge.
At the boost port , that is angled up sharply , the flow attaches to the piston radius , and pulls down the boost flow directly at the Exhaust on the opposite side.
I had a flash of inspiration the other day when I saw a picture on here of a boost port with the floor up away from BDC - keeping the flow away from that piston radius..
This is probably easyer than making a piston radius start and stop before the boost port , and then having to grind the port timing correction as well.

[lodgernz]

The sharp edge corner only needs to be broken with a cotton mop , and this has no effect on ring life at all.

Wobbly, I've not encountered a cotton mop before. Can you explain what it is please?

[wobbly]

Impregnated cotton fibre rotary deburring wheels for die grinder use.Most famous brand is RexCut.
Mounted on 3mm or 1/8 shaft.
Perfect for use on plated cylinders.

[vro46i]

Impregnated cotton fibre rotary deburring wheels for die grinder use.Most famous brand is RexCut.
Mounted on 3mm or 1/8 shaft.
Perfect for use on plated cylinders.

Hi Wobbly, I just looked up the product you mentioned. In my previous life, I was an airframe structures repairer, I have encountered many deburring tools but I can't say I have come across this one.
Great! another tool to add to the arsenal. Thanks for the tips.

[Frits Overmars]

I had a flash of inspiration the other day when I saw a picture on here of a boost port with the floor up away from BDC - keeping the flow away from that piston radius.
This is probably easier than making a piston radius start and stop before the boost port , and then having to grind the port timing correction as well.

Forget probably. Damn sure it's easier! Why didn't I think of that? Thanks, Wob and whoever posted that picture.