ESE's works engine tuner

[philou]

unfortunately when there is an image, people don't read the text.

it is a file found on the internet. I insist on checking on a real cylinder that the data is correct.


http://adardaine.free.fr/file/Aprilia_RS125.zip

[HenkS]

unfortunately when there is an image, people don't read the text.

it is a file found on the internet. I insist on checking on a real cylinder that the data is correct.


http://adardaine.free.fr/file/Aprilia_RS125.zip

Ok, I understand.
But the warning about these wrong numbers was right, so be carefull.
It seems they come from a program which didnot work right.
You call it an Engmod2t file, but I can't imagine that's right ?

[Javier Ruda]

Total Port Transfer area sum = 834.91 (not 940.14).
Eff. dia area 852.13 = 32.94 (not 34.85).
Eff. dia area 1019 = 36.02 (not 37.78).
Eff. dia area 132.62 = 12.99 (not 17.16).

Thank you HenkS and philou, in my opinion the file could be a modified Rotax.

My measurements, with 0.5 mm cylinder gasket would give this sta numbers:
Blowdown: 0.00116 s/m
Transfer: 0.00860 s/m
Exhaust: 0.01448 s/m

[Javier Ruda]

You want to have as much area as possible. If the rings are to stay in the same location, naturally there is a potential benefit from widening the c an b port respectively.

Thank you for noticing that. I will not move the ring pegs.

Now the pegs pass exactly in the middle between B and C and they are separated 8 mm in circumference. If I reduce the gap for pegs from 8 to 4 mm, then there is potential to enlarge 2 mm B and 2 mm C each side.

[Javier Ruda]

to choose in my opinion, it is better to work on the efficiency of scavening even if it means losing a bit of surface.

enlarge the C even more, will decrease its effectiveness

Merci Philou, I think you are right. As Janbros pointed out, because of the axial angle the flow from C is much weaker than from B.

So there is small potential benefit and danger of decreasing scavenging quality as you mentioned.

[Javier Ruda]

the greater the angle of a port, the smaller it's effective flow area.
so widening the C-port (for example 4mm) by the same amount as widening the sum of the B-ports (for example eacht B-port 2mm) generates less extra TA than widening the B's,
and keep an eye an the angle of the scavenging column while changing the ports so that you do not end up with a crzay angle.
and don't mkae the angle of the A's to big, as the higher if flow's , the easier it can flow straight out the exhaust.

Thank you Janbros for noticing that. I did the check using you wonderful spreadsheet (thank you again!) and +1 mm on B width generates +0.00018 s/m while only 0.00007 s/m on C. That is more than double.

The original column is 80º and the new one could be 83º-84º, keeping the same roof angles (I measured around 20º on both A/B and 50º on C).

[philou]

I never touch C port. just clean and sometimes touch up the angle of the roof.

it would be nice if you post some data of your cylinder. not all of them know him. and what they find can be misleading.

for Axial angles I have this, rotax 123 Aprilia RS.
but again it was not me who measured

My measurements, with 0.5 mm cylinder gasket would give this sta numbers:
Blowdown: 0.00116 s/m
Transfer: 0.00860 s/m
Exhaust: 0.01448 s/m

your results are not very far from those of the file

Blowdown : 0,001440
Transfert : 0,008637

[wobbly]

Its way more important how you generate the STA numbers , than just looking at the result.
You say the Rotax axials are 12-5-50 , but later you say the A,B are both 20*.
Either way those numbers are so far wrong it wouldnt matter what the calculated STA is , the scavenging regime is seriously wrong and thus would never work correctly to produce the predicted STA power.
Yes , the C port is way too wide already ( RSA/PVP is 15mm , its easy to narrow this with epoxy ) and to get anything like the RSA scavenging the B,C need to be around 0.4mm higher than A , with the axials up around 28,7,52.

With its shallow axial and its high timing , any extra width on the B is always going to achieve the greatest return.
I would narrow the C , put the ring pin over the boost and widen the B fully - but as to what timings to use , this depends on how much Blowdown STA can be generated.
The final Exhaust STA is irrelevant , but dont try lifting the floor above BDC , as this only works if the full Aux Blowdown capability is used.

There are plenty of single ring , center pinned pistons you can use in this engine - so you dont have to suffer brain damage moving the pin.

[Javier Ruda]

it would be nice if you post some data of your cylinder. not all of them know him. and what they find can be misleading

Bien sure philou, I did some measurements for using the spreadsheet, but the accuracy on angles was very poor. Now the cylinder is on the motorbike though. I will think on how to get a better measurement.

[Javier Ruda]

... to get anything like the RSA scavenging the B,C need to be around 0.4mm higher than A , with the axials up around 28,7,52.

With its shallow axial and its high timing , any extra width on the B is always going to achieve the greatest return.

Thank you wobbly. I measured the axials very poorly. I extended the roof to the opposite wall and did some trigonometry. I got 19° for both A and B but I do not dare to use 2 significant digits so let’s say they are 20°ish.

I think I could leave A port as it is, raise B and C 0.4 mm, widen B 2 mm, and flatten B roof. Of course making that transfer and blowdown have matching bmep numbers. And in a 2nd step, a center pinned piston with maximum B width.

[wobbly]

You could drop the cylinder to get enough material above the A port for more axial angle , but then all the ports BDC edges will be low - and alot of extra grinding needed to restore the other ports.
Better to epoxy the A roof with increasing thickness of fill as it goes around the outer radius - this will keep the timing as needed but give you a proven axial scavenging pattern.
You dont need to go to Italy to see the Leaning Tower , we can all have one in our workshop.

[HenkS]

unfortunately when there is an image, people don't read the text.

it is a file found on the internet. I insist on checking on a real cylinder that the data is correct.


http://adardaine.free.fr/file/Aprilia_RS125.zip

Thank you HenkS and philou, in my opinion the file could be a modified Rotax.

For me it was not about which engine the data is for, but about the errors and in which program.
Philou wrote Engmod2t, was that correct?

[Vannik]

For me it was not about which engine the data is for, but about the errors and in which program.
Philou wrote Engmod2t, was that correct?

That is from a very old version of the EngMod2T preprocessor, Dat2T and is probably about 15 years old.

[philou]

Philou wrote Engmod2t, was that correct?

No.

I did not design the engmod2t software, Vannik designed and developed it.

I didn't make the file either.

as no information was communicated by the applicant.
I looked for data on the internet to be able to reflect and help him in his request.

[Javier Ruda]

Better to epoxy the A roof with increasing thickness of fill as it goes around the outer radius - this will keep the timing as needed but give you a proven axial scavenging pattern.
You dont need to go to Italy to see the Leaning Tower , we can all have one in our workshop.

😂 thank you wobbly, I will try to keep the tower on the right side!