[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked)

Nombre de messages : 11 Localisation : Slovenia Date d'inscription : 27/03/2013

Frits Overmars a écrit:: 0,7 * (33,3 mm / 47,6 mm ) ^4,57 * 47,6 mm = 6,5 mm

Thank You Frits. I was drawing port shapes almost the entire evening but i still need to ask you another question. Which drawing is the correct way to measure ? I know it says half-axis but the radius seems a bit big. (also compared to the rsw drawings)

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The drawing on the left shows the correct way. Remember that in addition to the half-ellipse the Aprilia main exhaust port has a radiused upper port edge (look at the dotted line). The true half-axis is larger than it appears in the drawing below.

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Nombre de messages : 8 Localisation : Watertown Date d'inscription : 06/03/2014

What was the direction of coolant flow through the rsa? Our engines flow from the head down to base. Head is vented back to reservoir to avoid air pushing back into the engine. I thought of making it flow reverse of that so the base would get the coolest water. Frits do you have an opinion? Thanks

Hi Frits,

This is from a fixed gear 125cc kartengine with 2 step powervalve.

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What do you think about this shape?

thx

jasonsmithrealtor a écrit:: What was the direction of coolant flow through the rsa? Our engines flow from the head down to base. Head is vented back to reservoir to avoid air pushing back into the engine. I thought of making it flow reverse of that so the base would get the coolest water. Frits do you have an opinion? Thanks

The water from the pump enters the top of the cases between the gearbox and the crankshaft. It then flows downward, forming a heat shield between the hot gearbox oil and the crankcase, circles around the crankshaft and comes up at the front of the engine where it enters the cylinder below the exhaust duct, and finally exits from the head cover.
You can also see the small vent nipples at the highest point of the head cover and in the connection between pump and cases. Everything is just as you were suggesting Jason Wink

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Vortex a écrit:: Hi Frits, This is from a fixed gear 125cc kartengine with 2 step powervalve. What do you think about this shape?

I don't see anything wrong, Vortex, but it's difficult to judge from just a couple of pictures.

Frits Overmars a écrit:: forming a heat shield between the hot gearbox oil and the crankcase,

Frits, did you ever happen to measure a typical temperature in vs out difference ?

I would have supposed that a high flow rate would increase the total heat transfer but would tend to reduce the max vs min temp difference, so you'd get a lower head temp but warmer crankcases. Is my intuition faulty here?

Incoming and outgoing coolant temperatures were of course measured. I have no data at hand but I seem to remember something like 4°C difference. Maybe Jan can be more precise.
A higher flow rate will certainly lower the head temp. But warmer crankcases? The incoming coolant will be warmer, but since there will be more of it per unit time, and since a higher flow velocity will improve heat transfer, the cases might as well be cooler Wink

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Dear Frits,
Is a higher flow velocity always push down the work temperature?
Because it seems to me than if lowering the speed of the pump when it is very hot outside, the water better cool down with the same radiator, or is that totaly wrong?
Thx.

Nombre de messages : 11 Localisation : Slovenia Date d'inscription : 27/03/2013

Frits Overmars a écrit:: The drawing on the left shows the correct way. Remember that in addition to the half-ellipse the Aprilia main exhaust port has a radiused upper port edge (look at the dotted line). The true half-axis is larger than it appears in the drawing below.

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Thank you again Frits. I did some measuring today and realized i can't make such a big radius like the left drawing because the timings would be to big. What do you say for the right drawing with the black line for corner radiuses and a nice chamfer radius on the upper port edge ? Excuse me that i am asking so many questions but the best way to learn and get some extra HP is a chance to talk with experienced like you [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) - Page 38 771973

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) - Page 38 771973

Frits Overmars a écrit:: The incoming coolant will be warmer, but since there will be more of it per unit time, and since a higher flow velocity will improve heat transfer, the cases might as well be cooler .

I guess then it would depend on the direction of the temperature difference between head and cases: it seems to me that the limiting case of very high water flow is that everything on the cooling circuit converges to the same temperature... and if the same total heat is to be shed, that has to be the average of the radiator inlet & outlet temps. In which case it would become interesting to have a separate cooling system for the cases...?

Vortex a écrit:: Dear Frits, Is a higher flow velocity always push down the work temperature? Because it seems to me than if lowering the speed of the pump when it is very hot outside, the water better cool down with the same radiator, or is that totaly wrong?

When in doubt, exaggerate, Vortex. Let us assume that we reduce the flow velocity through the radiator down to zero. Then the water in the radiator will assume the ambient air temperature. But that won't do the engine much good....

ice t a écrit:: I did some measuring today and realized i can't make such a big radius like the left drawing because the timings would be to big. What do you say for the right drawing with the black line for corner radiuses and a nice chamfer radius on the upper port edge.

Define 'a nice chamfer radius', ice t. If you make the radius large enough, you don't need an elliptical port roof at all.
But 'nice' won't work in a formula.

GrahamB a écrit:: .. it seems to me that the limiting case of very high water flow is that everything on the cooling circuit converges to the same temperature.

That seems to me too.

Citation :: and if the same total heat is to be shed, that has to be the average of the radiator inlet & outlet temps.

But we just agreed that inlet and outlet temps have become identical [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) - Page 38 349660

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) - Page 38 349660

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Citation :: In which case it would become interesting to have a separate cooling system for the cases...?

Not counting the complications of multiple pumps and radiators and the accompanying increase in friction losses and air resistance: yes. But that's too complicated for me, Graham. I like KISS.

Hi Vortex,
What brand of motor were the photos of?

Hi Frits or Jan,
Can you remember what was the temperature the gearbox oil run at before water cooling cases were introduced and how much improvement did it make?

Thanks in advance for your answers. [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) - Page 38 809262

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) - Page 38 809262

GtG001 a écrit:: Hi Frits or Jan,
Can you remember what was the temperature the gearbox oil run at before water cooling cases were introduced and how much improvement did it make?

I can't. Maybe Jan can. Be I suspect it is an unanswerable question. The oil temperature will fluctuate with the amount of oil, the viscosity of the oil, the power passing through the gearbox, the external heat dissipation of the gearbox, and the duration of a power measurement.

Frits, when it was decided to use a engine driven water pump , instead of a electricly powered pump mentioned earlier in the forum. Did Jan and yourself design a water pump specifically for the RSA, or did you use parts from a current model from the Aprilia foul stroke range, for instance.
Would you or Jan have any details or photos of impeller diameter, pipe id, etc.
Many thanks to you and Jan for sharing all your knowledge [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) - Page 38 241515

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) - Page 38 241515

I did not have anything to do with the design of the pump. Jan may be able to tell you more.
I don't think any Aprilia foul-stroke had a pump with anything like this capacity.
By the way, the RSA was not built by Aprilia but by Derbi.

Nombre de messages : 86 Localisation : Australia Date d'inscription : 05/05/2012

Jan you wrote if a pipe is to long it will respond positively to a poor adjustment,
What do you mean- lean / rich / ignition or all of these

RAW a écrit:: Jan you wrote if a pipe is to long it will respond positively to a poor adjustment,
What do you mean- lean / rich / ignition or all of these

Did you traduce that from Dutch?
It means leaner and/or retarded, to raise the temperature.

Paul Gane a écrit:: Frits, when it was decided to use a engine driven water pump , instead of a electricly powered pump mentioned earlier in the forum. Did Jan and yourself design a water pump specifically for the RSA, or did you use parts from a current model from the Aprilia foul stroke range, for instance.
Would you or Jan have any details or photos of impeller diameter, pipe id, etc.
Many thanks to you and Jan for sharing all your knowledge

The engine was designed and made at Derbi.
And we assumed that the electrical pump used there would be sufficient.
When Piaggio bought Aprilia the engine went there, and Derbi was closed.
At Aprilia some very serious testing was done, with a big waterpump with variable speed.
The result of this test was: the faster the circulation the better!
For cooling as well as against detonation.
So the insufficient electric pump was abandoned.
And a mechanical pump with the same impeller as the Aprilia RSW was fitted.
It was not too beautiful, on the outside of the primary cover.
But we could not do anything else, as the crancases were already finished.
Making the pump inside, as on the RSW, would have meant a whole new design of the crankcase!
And there was no more time to do that.
The outside pump never gave any problems, not even when the bike was crashed!

Thanks, Jan!

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) - Page 38 1993206895

Nombre de messages : 98 Localisation : Italy Date d'inscription : 30/10/2012

hi

Jan in part 2 page 12 you talking about the squish in the RSA:

Jan Thiel a écrit:: The 0,7mm squish was the minimum we could use with good power at high pm.
Less squish gave more power at low rpm, until 12000 rpm, but the engine would not rev.
It would just stop firing at about 13500
We tried everything we could to make the engine rev with a 0,55 squish.
Impossible! Even 0,65 was negative!
The piston would touch with 0,45.
So the 'real' squish at high rpm was 0,25

did this test where made always with the same combustion chamber? if yes, do you increase the compression ratio by reducing the squish gap.

did the engine dont want to rev of the fact of to high compression ratio?

thanks Manuel

Thanks for the water pump info Jan [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) - Page 38 809262

bravo

Manuel Rainer a écrit:

hi

Jan in part 2 page 12 you talking about the squish in the RSA:

Jan Thiel a écrit:: The 0,7mm squish was the minimum we could use with good power at high pm.
Less squish gave more power at low rpm, until 12000 rpm, but the engine would not rev.
It would just stop firing at about 13500
We tried everything we could to make the engine rev with a 0,55 squish.
Impossible! Even 0,65 was negative!
The piston would touch with 0,45.
So the 'real' squish at high rpm was 0,25

did this test where made always with the same combustion chamber? if yes, do you increase the compression ratio by reducing the squish gap.

did the engine dont want to rev of the fact of to high compression ratio?

thanks Manuel

No Manuel, the squish was varied maintaining the same compression ratio!
Doing it otherwise would not be serious!

» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked)
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