ESE's works engine tuner

[F5 Dave]

If a good rear angle (which I think I can do) on the A-port would fix the short cut to a low level, then no, why should I put in an extra divider. If not, my thought was that it would help the directional flow stability out from the A-port, particulary the section closest to the exhaust port, such that the flow would have more difficult to make a U-turn. A thin plate ending a mm into the port should not decrease the flow area. But maybe a good rear angle and enough material in the cylinder wall section in front of the A-port, towards the exhaust, eliminates the problem to a level where there is no real justification to try to do anything else.

So being that the transfers end up to some extent becoming exhaust ports breifly, resilience of that thin plate? It would be an unfortunate event if it dislodged.

[Norman]

So being that the transfers end up to some extent becoming exhaust ports breifly, resilience of that thin plate? It would be an unfortunate event if it dislodged.

I would first try to at least spot weld it in place, to secure. Yes, it would be hit by exhaust gas, but also cooled by fresh mix. Heat is also moving away through the welds to the transfer roof and bottom. I think that it should be ok.

[wobbly]

Beta, as I cant post a .jpg in a PM here is the answer to your question.
If you can drop the duct roof srarting from where the Aux ports enter the EX then you will get the huge power increase as I did.
I also dropped the side ducts back near the centerline of the lower exit area.
You have to be very careful with a stock casting not to make the side ducts too deep, or you get into water.

[tdc211]

Is this the angle you mean?

Attachment 338512

yes! yes yes

My 1st yes was to short to reply

[tdc211]

Thanks for the heads up, I wasn't sure what tdc211 meant before about "A port front hook angle" it looks like the Honda cylinders, MC21 and NF4 et all already have them.


Attachment 338530

Not sure if i ever said anything about a Honda.
I think one of best A ports for rear direction. Is a kx 85/100. Compete junk other than that. And those things make easy pwr. Spin like crazy with long piston to diffuser. Ktm 105 does not make easy pwr. It hate long piston to diffuser

the new 2018 ktm cylinder which looks like my epoxy cylinders
Only better as they tightened up bottom corner of ex port.
Finally have new 18 105 cylinder on my dyno now. Just released
Now that i know what i know. 1st thing i would do is weld up bottom corner of export and get good rear direction in A port


New cylinder in pic
Its a beast.
Pipe testing next few days. I have many pipes,also just built a new pipe.

I should add. There a bunch of guys on here. Some with ok cylinders.Some that are not. I know for sure. bad A direction is just terrible. But it can be fixed cheaply/ fast and is reliable if you prep well and use epoxy. Idk know why ,the hot gases dont seem to affect it .

[Muhr]

Has anyone tried to put a thin divider into the A-port as per the attached second picture? Let say out of 0,5 mm aluminium. I was thinking that it might help to decrease the short circuit of fresh mix into the exhaust by straightening and force more of the flow in the port angle direction? Could it make a performance difference? (More or less flow will also go straight at the section with the curved arrows).

Do not know if this was what you meant to do, but what I can see it seems to mostly create resistance.
(in compressible CFD)

[Norman]

Do not know if this was what you meant to do, but what I can see it seems to mostly create resistance.
(in compressible CFD)

Yes, in principle yes, maybe a little longer divider into the port. But, it seems not to give any positive effect..Perhaps it differs depending on what vertical layer and the dP/flow you are looking at. But no, I think the idea could be put aside for now. Thank you for taking the time to set the case up in the CFD!

[RomeuPT]

Not exacly a flat top...

[katinas]

Thanks to Wobbly, the 75% rule he does totally transformed an engine I was working on in 04. We took it from 3.25hp aprox, to 4.3 hp aprox with the exhaust insert and a new pipe. Without the insert with the 25% area reduction, it did not work very well at all, and could only run other pipes that limited the power output to the 3.25 hp range.
I learnt a lot from those tests. Thanks again Wobbly.

Another agree.

Honda CR 125 reed type cylinders , changed every year from 1981 to 1986. On first water cooled 81‘ CR 125, Honda made huge volume transfer ports with big transfer windows and these cylinders was used on early RS 125 model.
82‘ reduced transfers ports size, but trans windows left unchanged.
83‘ lowered transfer windows and this, together with exhaust windows size, remains almost unchanged until the last 86‘ reed cylinder type engine, even after stroke changed (from 50.6mm to 54mm) in 85‘
Exhaust windows area, from 81‘ to 86‘, very similar, but ex duct last dimension changed 3 times:
81‘-82‘- oval shape 35x39 mm,
83‘- oval 37x39mm
84‘-85‘ round 40mm,
86‘ -round 37mm.

One of the many tests this year was with CR 125 84‘ cylinder original 40mm ex duct and modified, with insert 34x38mm (add photo) on my NS engine. With insert, when engine is on the pipe, power feels sharper, especially at 10500 rpm. Can‘t show anything, because tested only on the road, but very nice to feel changes in good way with hands.

[husaberg]

Another agree.

Honda CR 125 reed type cylinders , changed every year from 1981 to 1986. On first water cooled 81‘ CR 125, Honda made huge volume transfer ports with big transfer windows and these cylinders was used on early RS 125 model.
82‘ reduced transfers ports size, but trans windows left unchanged.
83‘ lowered transfer windows and this, together with exhaust windows size, remains almost unchanged until the last 86‘ reed cylinder type engine, even after stroke changed (from 50.6mm to 54mm) in 85‘
Exhaust windows area, from 81‘ to 86‘, very similar, but ex duct last dimension changed 3 times:
81‘-82‘- oval shape 35x39 mm,
83‘- oval 37x39mm
84‘- round 40mm,
85‘-86‘ -round 37mm.

One of the many tests this year was with CR 125 84‘ cylinder original 40mm ex duct and modified, with insert 34x38mm (add photo) on my NS engine. With insert, when engine is on the pipe, power feels sharper, especially at 10500 rpm. Can‘t show anything, because tested only on the road, but very nice to feel changes in good way with hands.

Katinas do you have measurements for the cylinder widths and stud spacing for the 85-86 CR125 Cylinders.

[peewee]

Looks like more oil = more power.

Ok, not a test as such, but by using the Google "Site:" Search option. oil power site:https://www.kiwibiker.co.nz/forums/s...-engine-tuner?

I got these results.

Attachment 338411

well i dont know much more today that i didnt already know couple days ago, except to say that its amazing just how much qauntity of fuel you can put in the engine when theres nitro in the mix. for the hell of it i fully opened all four jets to see what would happen. it didnt flood the crankhouse like you would think. suprisingly it still ran pretty well but after reviewing the video it sounded like over fueling was just starting to creep in, mainly during gear changes when the engine load is breifly absent. still i was quit suprised considering with straight methanol the engine is a blubbering mess once you try to open the third jet

also it seems to run better and have more power if you can manage to get some heat into the engine. say about 130f and above. perhaps this is due to a high heat of vaporization needed for the mix to burn

[Muhr]

Yes, in principle yes, maybe a little longer divider into the port. But, it seems not to give any positive effect..Perhaps it differs depending on what vertical layer and the dP/flow you are looking at. But no, I think the idea could be put aside for now. Thank you for taking the time to set the case up in the CFD!

Here you have a "hook"

[wobbly]

The most powerful RS125 cylinder I did when experimenting with ports and pipes for a Belgian aftermarket supplier , had the duct exit at 41 wide ( the header size ) by 32 high oval.
This transitioned in the spigot to the 41 round , no steps anywhere.
And the 2002 cylinder used in SKUSA racing ( only 40 Hp ) has from memory a 40 by 34 oval exit, and again transitioning this within the spigot , into the SKUSA pipe header gives the best power.

[katinas]

Katinas do you have measurements for the cylinder widths and stud spacing for the 85-86 CR125 Cylinders.

From 83’to 86’ CR 125 cylinder studs spacing is the same (like NS250/400):

Along (between intake and exhaust sides - 79mm. (Yamaha TZ250 DP4 - 78mm)
Crosswise (from side to side) - 96mm. (81’-82’ right front stud is closer to left, so distance -85mm. Yamaha TZ250 DP4 -96mm.)
85’-86’ cylinder height - 98.5mm; 81’-84’ -93mm.
Widest 83’-86’ cylinder dimension crosswise - 116mm.

Widest place between transfer ports from side to side at lower cylinder plane:
81’- 107mm.
82’-86’ - 96-98mm.
All cylinders with iron liners cast in.

Husa, maybe you have some info about Yamaha TZ 250 prototype 82'-83' rotary tandem twin (08KO), looks like experimentation with half rotary OW60 500. Info from Racers magazine.

[husaberg]

From 83’to 86’ CR 125 cylinder studs spacing is the same (like NS250/400):

Along (between intake and exhaust sides - 79mm. (Yamaha TZ250 DP4 - 78mm)
Crosswise (from side to side) - 96mm. (81’-82’ right front stud is closer to left, so distance -85mm. Yamaha TZ250 DP4 -96mm.)
85’-86’ cylinder height - 98.5mm; 81’-84’ -93mm.
Widest 83’-86’ cylinder dimension crosswise - 116mm.

Widest place between transfer ports from side to side at lower cylinder plane:
81’- 107mm.
82’-86’ - 96-98mm.
All cylinders with iron liners cast in.

Husa, maybe you have some info about Yamaha TZ 250 prototype 82'-83' rotary tandem twin (08KO), looks like experimentation with half rotary OW60 500. Info from Racers magazine.

Cheers for that.
I remember there was a TZ that raced here in the 80's that had CR125 cylinders Grump will remember it I think it was Brent Jones?
Ifi t was Brent Jones that would be pretty Ironic as he used to Races a RG500 cylindered (race Bike RG Cylinder not road) on a Kawasaki 125 bottom end (Early KX i think) I think it was made at MClearly's
The forrunner to a lot of bucket racers.
No i have never seen a half a OW60, or heard of it.
I do know that Suzuki made up quarter a RGB racers for Asia.
I have a pic of an engine somewhere.
I put up some of a write up CW did of one of the Daytone overbored bikes big bored OW60 or similar last night.