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

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 39 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 39 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 39 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 39 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 39 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!

Hi,
Dear Jan;
I made some test with the squish band always with the same combustion volume (9 cc) and it seems that narrower the squish that more the squish angle has to open, otherwise the rev. ability go worst passing 13000 rpm to maximum 15000 rpm.
Do you agree to this?
A parallel squish band needs more distance.
The best result for me was 0,70mm squish with 1,5 degree upgoing with a 4 degree domed piston.

Thanks again Jan and Frits sharing your knowlege with us.

Vortex a écrit:: Hi,
Dear Jan;
I made some test with the squish band always with the same combustion volume (9 cc) and it seems that narrower the squish that more the squish angle has to open, otherwise the rev. ability go worst passing 13000 rpm to maximum 15000 rpm.
Do you agree to this?
A parallel squish band needs more distance.
The best result for me was 0,70mm squish with 1,5 degree upgoing with a 4 degree domed piston.

Thanks again Jan and Frits sharing your knowlege with us.

Our best results were with 0,7 parallel squish.
But we never tried to reach 15000 rpm.
Gear shifting was done at 13250.
The engines were tested until 14500.

Vortex a écrit:
Hi,
Dear Jan;
I made some test with the squish band always with the same combustion volume (9 cc) and it seems that narrower the squish that more the squish angle has to open, otherwise the rev. ability go worst passing 13000 rpm to maximum 15000 rpm.
Do you agree to this?
A parallel squish band needs more distance.
The best result for me was 0,70mm squish with 1,5 degree upgoing with a 4 degree domed piston.

Thanks again Jan and Frits sharing your knowlege with us.

Our best results were with 0,7 parallel squish.
But we never tried to reach 15000 rpm.
Gear shifting was done at 13250.
The engines were tested until 14500.

Ok, thank you.
In kart, gear shifting is done near 14300, i suppose it is due to the 30mm carb the minimum volume of 11cc and the homologated
fix ignition curve that we have to rev higher.

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

Frits Overmars a écrit:

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.

I was thinking of a 1-1,2 mm radius above the port edge ,almost geting the shape of the desired elliptical port . Would a straighter port roof with a radius give a higher power output than a eliptical one ? It sure has more port area. I also don't have auxiliary exhaust ports so every port area i can get is good.

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

Jan Thiel a écrit:

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!

hi

I thought so, you always has tested the things the right way.

my question was only because i have seen that in my 125 Kart engine if i rise the compression up to 16:1 or more the engine dont want to rev over 13800. also if the squish was 0,8.

so i thought compression near 16:1 with 95er pump petrol dont let the engine rev, dont matter what squis gab.

thanks

Manuel

by changing your squish gap you'll change the amount of heat in your pipe, so you can also change your over rev by this way

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

mr Thiel

do you mean , with small squish gap(less than0.65mm on the rsa), it can stop the firing of the spark plug ?

pagi a écrit:: 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

mr Thiel

do you mean , with small squish gap(less than0.65mm on the rsa), it can stop the firing of the spark plug ?

Stopping the firing would have broken the ignition coil I think.
That is what happened when we once tried a spark plug without mass electrode.
This gave more HP, until the coil broke!
But maybe the spark did not ignite the mixture anymore.
Or the fresh mixture did not reach the spark plug anymore.
Maybe too much turbulence?
That is what I think!
You can also reach a point where the blowdown becomes insufficient.
Then the engine stops firing through lack of fresh mixture.

Manuel Rainer a écrit:

Jan Thiel a écrit:

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!

hi

I thought so, you always has tested the things the right way.

my question was only because i have seen that in my 125 Kart engine if i rise the compression up to 16:1 or more the engine dont want to rev over 13800. also if the squish was 0,8.

so i thought compression near 16:1 with 95er pump petrol dont let the engine rev, dont matter what squis gab.

thanks

Manuel

Sorry Manuel,
But how can you reach a compression ratio of 16:1 with a kartengine with a min. volume of 11cc with a in this engine normaly used mainexhaust diagramm of something between 195 and mabe 197 degree?
The corrected one is for sure under 10:1!
For me Mr. Thiel is right when he wrote; The fresh mixture did not reach the spark plug anymore.
Maybe too much turbulences?

Jan or Frits, do you think a 120mm con rod would yield similar benefits on a piston ported engine. Having optimised ignition, Carburation, etc. And the same for reed engine ???
Jan mentioned earlier on the forum about 50cc engines with long rod ratio, were they piston port, disc valve, or reed.
Thanks in advance [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 39 809262

Paul Gane a écrit:: Jan or Frits, do you think a 120mm con rod would yield similar benefits on a piston ported engine. Having optimised ignition, Carburation, etc. And the same for reed engine ???
Jan mentioned earlier on the forum about 50cc engines with long rod ratio, were they piston port, disc valve, or reed.

Paul, you mention a 120 mm rod and you mention 50 cc engines. Am I to understand that you want to try a 120 mm rod in a 50 cc engine? It certainly won't be too short then Wink

.
When I see a 120 mm rod length I think of a 125 cc engine, so let's assume that is what you are talking about. And then I agree with Jan that this rod length will work irrespective of the type of induction system.

Frits, thanks. I was referring to a 175x2 (TZ350). I remembered Jan saying about rod ratios on 50cc, I should have made myself clear.

Nombre de messages : 44 Localisation : Portugal Date d'inscription : 08/11/2011

If I'm not mistaken the derbi 50cc engines had a 90mm rod from factory, and I read here and in some other sites that when you kept the 50cc the engine gained a bit more "breath" when using a 84-85mm rod.

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

Vortex a écrit:: Sorry Manuel,
But how can you reach a compression ratio of 16:1 with a kartengine with a min. volume of 11cc with a in this engine normaly used mainexhaust diagramm of something between 195 and mabe 197 degree?
The corrected one is for sure under 10:1!
For me Mr. Thiel is right when he wrote; The fresh mixture did not reach the spark plug anymore.
Maybe too much turbulences?

hi

i am not driving official races. there is no limitation of head volume.

i got to 16:1 in my 125 TM KV95 rotary valve engine, with a head volume of 8,3 cc. ex on 197° squis gab 0,8. in this case the engine not want to rev over 13800.

Manuel Rainer a écrit:

Vortex a écrit:: Sorry Manuel,
But how can you reach a compression ratio of 16:1 with a kartengine with a min. volume of 11cc with a in this engine normaly used mainexhaust diagramm of something between 195 and mabe 197 degree?
The corrected one is for sure under 10:1!
For me Mr. Thiel is right when he wrote; The fresh mixture did not reach the spark plug anymore.
Maybe too much turbulences?

hi

i am not driving official races. there is no limitation of head volume.

i got to 16:1 in my 125 TM KV95 rotary valve engine, with a head volume of 8,3 cc. ex on 197° squis gab 0,8. in this case the engine not want to rev over 13800.

Hi,
Ok that changes everything.
How much advance do you use?
Did you try more squish?
Which exhaust temp. do you reach?

» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked)
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