ESE's works engine tuner

[SwePatrick]

MZ once used them, but they cracked....

Thanks for the answer, i guess it´s no problem for me then, i´m just racing 201m at the time
Is the function still nearly as good as a round one?

[SwePatrick]

http://www.pit-lane.biz/t6246p550-gp...vermars-part-5

Go to the bottom of page 23. You'll have to login to see the images

I have no login on that site
any chance of posting the pics here?

However, i read what Frits wrote, my pipe is almost 100% straight at the point where i need to make it a little bit oval.
No curve at that point of the pipe.

[lodgernz]

I have no login on that site
any chance of posting the pics here?

However, i read what Frits wrote, my pipe is almost 100% straight at the point where i need to make it a little bit oval.
No curve at that point of the pipe.

Frits, would you be happy to post those pics here? I can do it if you're busy.

[philou]

The header seem to be in aluminum. What is the interest?

[teriks]

Iam wondering why exhaust pipes are round or sligthly oval.
The exhust jet during blowdown is some kind of rectangular and it will not be more difficult to edge weld four funny looking strips(methinks)?

Mecanical strength for one, round is simply the strongest cross section available (when pressurized).

Look at what happen when hydroforming a pipe for example.

Now, the exhasust pulses are of lower magnitude, but a pipe with "squarish" walls will behave lot more like a speaker membrane than a round pipe with the same wall thickness would.

[cotswold]

Pinky has been given a new heart and it's not too far off ready to make a blue haze. Wiring and ignition is next on the list.

[F5 Dave]

That will be great.

So, white bodywork and flowers?

[Frits Overmars]

Frits, here in your FOS data it says the squish angle in the RSA head is 8.17°. if I draw that in solidworks, that's the angle of the tangent line to the piston radius. but wasn't the squish paralel to the piston crown radius ?

Yes, they are; both the piston dome and the squish band have a 190 mm radius.

shouldn't the squish radius be 190.7 mm ?

If you want parallelity at 0,7 mm gap, then yes. But when the engine is running, that 0,7 mm gap has vanished .

[Frits Overmars]

Jan Theil, Frits Overmars, Wobbly.
A question, as i got spaceproblems, is it a big loss shaping a pipe somewhat oval? I need clearance so i can have some suspensiontravel left.

MZ once used them, but they cracked....

Yamaha did that with their first version of the TZ750. Those pipes were not just oval, they really had flat-sided bellies (don't we wish we had too?)
Those TZ750-pipes cracked like mad. One temporary cure was to drill a small hole through the middle of each flat, poke a bicycle spoke through the holes and butt-weld it to the flat sheet areas, so these could no longer vibrate in- and outward quite so much.

Changing the pipe from round to oval can be done in several ways. If you keep the circumference constant, the cross flow area will decrease. Just imagine pushing the pipe flat: the circumference will still be the same but the cross flow area and the pipe volume will become zero.
You'll want to keep the cross flow area and the pipe volume equal to that of the round pipe, so initially you will have to give it a bigger circumference at the place where you are going to flatten it afterwards. And then the power loss should be minimal.

[JanBros]

Yes, they are; both the piston dome and the squish band have a 190 mm radius.If you want parallelity at 0,7 mm gap, then yes. But when the engine is running, that 0,7 mm gap has vanished .

Once again, Im outsmarted by you, but I have absolutly no problem with that

But I still don’t understand the squish angle of 8,17

[Frits Overmars]

Once again, Im outsmarted by you, but I have absolutly no problem with that
But I still don’t understand the squish angle of 8,17

That's not the squish angle; it's the squish edge angle; the squish angle is variable because of the spheric squish band.
Imagine the vertical line through the center of the piston dome radius. Then imagine a line through the center of the piston dome radius and the upper timing edge of the piston. The angle between those two lines is 8,17° for a piston with a 54 mm bore and a 190 mm dome radius.

[Frits Overmars]

I have no login on that site . any chance of posting the pics here?

Frits, would you be happy to post those pics here? I can do it if you're busy.

Thank you for the offer Lodgernz. But I think those two pictures are not relevant here; they deal with the cross flow area shape of a curved pipe, not with a straight pipe that is pushed out of round.
Besides, those pictures are available for all to see; there is no need to register here or anywhere else. You'll find them at https://drive.google.com/drive/folde...rNTk89_KgwgWof in the folder FOS Tips & Concepts

[yatasaki]

The header seem to be in aluminum. What is the interest?

That's casting but of iron or steel, no way that could be aluminium as exh. temp. on that bike is around Al melting point.
Only if double walled water cooled

[JanBros]

[QUOTE=senso;1130750329]

That's not the squish angle; it's the squish edge angle; the squish angle is variable because of the spheric squish band.
Imagine the vertical line through the center of the piston dome radius. Then imagine a line through the center of the piston dome radius and the upper timing edge of the piston. The angle between those two lines is 8,17° for a piston with a 54 mm bore and a 190 mm dome radius.

yes, that I know. that's what I draw in Solidworks. I just didn't understand why you used that angle. but I think I get it now. I use a "parralel angle" which corresponds with the straight line from the outer edge to the inner edge of the squish band, and also cut my squish in the head straight which off course gives a small deviation, but in my world my tolerances are a lot bigger than in Aprillia's GP-world .

I was entering all the RSA data into my spreadsheet to test it but that angle didn't work and now I know why.
So you use the tangent angle because it is the only angle you can mathematicaly true define,

[husaberg]

That's casting but of iron or steel, no way that could be aluminium as exh. temp. on that bike is around Al melting point.
Only if double walled water cooled

You mean like the piston or the Exhaust port does?



not to mention hundreds of thousands of CR125's