ESE's works engine tuner

[Frits Overmars]

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!

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?

This room was finally given with the design of the RSA. It was mainly used to sharpen the radial angle; the A-port's leading edges were angled more backwards,
away from the exhaust port. The picture shows how the RSA's exhaust-side studs are wider apart and further away from the A-ports than the RSW-studs.

[jamathi]

This room was finally given with the design of the RSA. It was mainly used to sharpen the radial angle; the A-port's leading edges were angled more backwards,
away from the exhaust port. The picture shows how the RSA's exhaust-side studs are wider apart and further away from the A-ports than the RSW-studs.

The transfer ducts were exactly the same.....Y-type....
Cooling was improved, which gave more power!

[Frits Overmars]

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.

You could use my tried and trusted 45°-bent feeler gauge Wob. It will handle any piston edge radius and any port edge radius as long as the port's roof angle is not steeper than 45°. Just pinch it between piston and port with its hand-held end vertical, measure from cylinder top deck to piston and subtract 1 mm from the measured value. This will give you an easily measurable dimension that can directly be compared to any other port height value. EDIT: picture updated following Wobbly's advice.

[Haufen]

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'd lower the cylinder by half the measure of the radius as a start. Then compare the curve shapes between that setup and no radius and then decide if it's okay or in which direction and by how much the cylinder is going to be moved next.

[wobbly]

I use the same setup Frits, just changing the feeler to 0.7mm gives 1mm port change - easyer for my brain to handle when measuring.
I have found a piston 0.5mm higher than stock and was planning on CNC cutting a 0.5mm rad on the timing edge, without moving the cylinder.
But i will now draw that feeler gauge scenario and see what numbers come up.

[wobbly]

OK - so did the CAD exercise and using the feeler method it seems that its easy.
If I have a 0.5mm rad then I need to drop the cylinder 0.25 ( rounded ).
I can do this without machining the cylinder base.
But with a piston that has a 0.5mm higher timing edge , I can do a 1mm rad and not change the cylinder at all.
An easy first test to see what happens, although I still have to do a special head insert to get the bore edge geometry and cc correct.

[TZ350]

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

Sure thing, here you go .....



Top half of a Honda NF4 RS125 cylinder.

[lodgernz]

Sure thing, here you go .....



Top half of a Honda NF4 RS125 cylinder.

Defo a bit of an issue with this one

[TZ350]

Defo a bit of an issue with this one

Yes looks like it. Probably not the only one. Like you say, a bit of work with the grinder may pay dividends.

[Muhr]

OK - so did the CAD exercise and using the feeler method it seems that its easy.
If I have a 0.5mm rad then I need to drop the cylinder 0.25 ( rounded ).
I can do this without machining the cylinder base.
But with a piston that has a 0.5mm higher timing edge , I can do a 1mm rad and not change the cylinder at all.
An easy first test to see what happens, although I still have to do a special head insert to get the bore edge geometry and cc correct.

Would be interesting to see a real test of rounded piston edge. Always have some doubts about VHM's tests and especially how they choose to zero.
with a feeler gauge pressed against the back of the cylinder. Assuming it's a 0.2mm, it might give more "duration" and still manage within the rules. but if it is better with the same duration, it does not tell.

[karter444]

Hi Wobbly
what lenght and ID do you recommend for a kz2 B/C stinger ,when using the size you recommend do you lose any power below peak ie from 10,000 to 13,500
cheers Richard

[wobbly]

Stingers on a KZ are a real can of worms, so much so that I use two different versions depending upon the track.
But in any case the shorter you make the U bend the better the power.

There is a rule for a MAX of 50mm of stinger sticking into the mufflers much bigger perforated inner.
Cut off the welded on washer, and move it back right to the very start of the bend.
Then cut off the tube at 25mm from the washer face - this is the same length as the slip on length inside the muffler.
On the other end that slips into the pipe spigot - again cut it off as short as you can to allow it to just slip in all the way.

As far as ID goes I use a genuine TM 28/28 OD tube with an insert pressed into the pipe slip fit end.This is 22.8 ID and 20mm long with 45* chamfers at each end.
The chamfer on the pipe side matches the 24.4 ID of the rear cone,and the other end simply matches the 26 ID of the tube.
This U bend is for tracks that favor higher rpm or in fact need a shit load of overev to allow deleting gearchanges between corners.
There is only a very small loss below peak , when run against a stock 26/28 TM tube.

For tracks needing more bottom end I use the TM 28/26 stepped stinger , just cut short as above , or if you can get them the 28/28 tubes made by ELTO with 1.5mm wall.
With this smaller ID tube I use a 24mm ID insert - this makes a little better top end,with the same bottom.

[TZ350]

Robs GP-NSR110 Mod.zip

So here is the pack file of Robs GP-NSR110 Mod by me, to generate the power curve as published previously.
Rob or anyone can ask for details on any input for explanation.
As I said the ports ( including the RV ) are all "stock " as set up originally.
First page to explain is the Engine. I went for 12 Bar at 12500 as this is what the STA say the ports are capable of.
Thus we have a fairly low bmep, and on AvGas this will happily take the 16.5:1 com input, used on short kart tracks where acceleration between corners is far more important than overev power..
This is proven by the TuBMax output with the stinger size optimized and a "normal " ignition curve that starts at 25* under the pipe then heads for 15* at peak power.
The Ex length input is 10mm, to look at the Mach in Pipe 2 = the stinger nozzle.

I have version EngMod 5.6.9e, the latest. Neels put out this update recently and was concerned other versions would not open packs if not up to date.

...........

[wobbly]

Hey Rob, last time I looked over 40 downloads of the GP-NSR110 file.
I am assuming that they must all have the new version of the code as no one has complained about not being able to open it ?

As far as the NF4 ports are concerned,I think the biggest gain would be to use a kit type piston with the ring pin at the middle and grind the rear wall
of the B ports to equalize and narrow the boost port dividers.
At the same time aim the ground walls to 1/3 of the bore radius from the boost port face.
Currently they are very steeply aimed at about 2/3 toward bore center line - very last century.

[koba]

Hey Rob, last time I looked over 40 downloads of the GP-NSR110 file.
I am assuming that they must all have the new version of the code as no one has complained about not being able to open it ?

I downloaded it and tried with an older version.
It does import some data but errors on heaps too.
I figured I'd worry about that later.

All of this is incredibly interesting btw, thanks!