[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 : 151 Localisation : usa Date d'inscription : 29/09/2013

hey guys is there any experts of con rods ? i see most rods have a oil hole in the small end but some rods dont. it seems the hole would be made at the final stage of manufacture but im not sure. if i have a rod with no oil hole can i drill it myself or will there be some problem ?

Hemeyla a écrit:: What about RSP ........... [Vous devez être inscrit et connecté pour voir ce lien]

we also try rapid solidification materials as amorphous AlCrFe alloy...they are more stabil (up tu 550°C) but they have bigger density as pure nano Al powders and price is about 2x higher and is very heavy to machining them on CNC

Nombre de messages : 20 Localisation : Allemagne Date d'inscription : 22/05/2013

brokedown a écrit:: hey guys is there any experts of con rods ? i see most rods have a oil hole in the small end but some rods dont. it seems the hole would be made at the final stage of manufacture but im not sure. if i have a rod with no oil hole can i drill it myself or will there be some problem ?

You can drill that hole on your own, for sure. Make sure that you have a Tungsten-drill, a hss drill will die very fast on the hardened needle running surface...
After you have drilled the hole, deburr it with a corund-tool

Nombre de messages : 151 Localisation : usa Date d'inscription : 29/09/2013

Tim Ey a écrit:: You can drill that hole on your own, for sure. Make sure that you have a Tungsten-drill, a hss drill will die very fast on the hardened needle running surface...
After you have drilled the hole, deburr it with a corund-tool

yes ill deburr the hole edges. what im thinking is 2 holes. one at 10'oclock position and one at 2 o'clock. or 11 oclock and 1 oclcock. what do you think about this ?

Nombre de messages : 20 Localisation : Allemagne Date d'inscription : 22/05/2013

brokedown a écrit:

Tim Ey a écrit:: You can drill that hole on your own, for sure. Make sure that you have a Tungsten-drill, a hss drill will die very fast on the hardened needle running surface...
After you have drilled the hole, deburr it with a corund-tool

yes ill deburr the hole edges. what im thinking is 2 holes. one at 10'oclock position and one at 2 o'clock. or 11 oclock and 1 oclcock. what do you think about this ?

I use to drill only one hole. 3mm, 12 o´clock. At the upper side is the lowest load.

Hi Jan!

I don't know if you have already talked about it, but I'd have a question:

At the area marked on the pic the piston's skirt will not influence the flow? I don't understand why is not at the same height as the bottom of the transfer duct?

Excause me if these questions have been already discussed!

Thanks in advance!

Forgi

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(köcsög gecsei jegyzetelj!)

Nombre de messages : 151 Localisation : usa Date d'inscription : 29/09/2013

forgi i dont know specific of the rsa125 but on other engines if the piston side is same as transfer opening then you get a shortcut to the exhaust from crankcase. see this page for a photo

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brokedown a écrit:: forgi i dont know specific of the rsa125 but on other engines if the piston side is same as transfer opening then you get a shortcut to the exhaust from crankcase. see this page for a photo

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Hi brokedown!

You are completely alright! In this case not the piston skirt needs to be cut, but I have to make a longer transfer duct. Take a look at the pic maybe this way it becomes clearer what I am talking about. What do you think?!

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Nombre de messages : 4 Localisation : USA Date d'inscription : 24/03/2012

Forgi,
Perhaps this is the page you are looking for?

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Forgi a écrit:: Hi Jan!

I don't know if you have already talked about it, but I'd have a question:

At the area marked on the pic the piston's skirt will not influence the flow? I don't understand why is not at the same height as the bottom of the transfer duct?

Excause me if these questions have been already discussed!

Thanks in advance!

Forgi

[Vous devez être inscrit et connecté pour voir cette image]

(köcsög gecsei jegyzetelj!)

We tried to modify the piston skirt, but it gave less power.
Also a radius was worse.
So we left it as it was!

Forgi a écrit:

brokedown a écrit:: forgi i dont know specific of the rsa125 but on other engines if the piston side is same as transfer opening then you get a shortcut to the exhaust from crankcase. see this page for a photo

[Vous devez être inscrit et connecté pour voir ce lien]

Hi brokedown!

You are completely alright! In this case not the piston skirt needs to be cut, but I have to make a longer transfer duct. Take a look at the pic maybe this way it becomes clearer what I am talking about. What do you think?!

[Vous devez être inscrit et connecté pour voir cette image]

This was also tried.
Less power, and it caused piston seizures!

Nombre de messages : 151 Localisation : usa Date d'inscription : 29/09/2013

hi jan thnx for a response. for a long time i had the same question as forgi. all the engines i seen had the piston side well below the transfer opening at BDC causing the transfer opening to be smaller. on the rsa125 was the duct volume very large and thats why its ok for the transfer opening to become smaller as the piston descends ?

assuming the rsa125 had large transfer ducts, then as the piston goes down maybe most of the intake volume gets pushed to these large ducts, so when the piston finally gets lower and decreases the transfer opening, most of the intake fuel has already been pushed to the large ducts so a small transfer opening wont matter much because most of the volume is now in the ducts ready to enter the cylinder ? does this sound possible ?

perhaps with small transfer ducts most of the intake charge will still occupy the crankcase (directly under the piston) as the piston descends because theres not as much volume in the transfer ducts, so the transfer opening size becomes more important ?

brokedown a écrit:: hi jan thnx for a response. for a long time i had the same question as forgi. all the engines i seen had the piston side well below the transfer opening at BDC causing the transfer opening to be smaller. on the rsa125 was the duct volume very large and thats why its ok for the transfer opening to become smaller as the piston descends ?

assuming the rsa125 had large transfer ducts, then as the piston goes down maybe most of the intake volume gets pushed to these large ducts, so when the piston finally gets lower and decreases the transfer opening, most of the intake fuel has already been pushed to the large ducts so a small transfer opening wont matter much because most of the volume is now in the ducts ready to enter the cylinder ? does this sound possible ?

perhaps with small transfer ducts most of the intake charge will still occupy the crankcase (directly under the piston) as the piston descends because theres not as much volume in the transfer ducts, so the transfer opening size becomes more important ?

Yes, the transfer ducts were quite large.
In the beginning I thought they were too large, but making them smaller cost power.
They were made this way because rotax made 125 and 250cc engines using the same
crankcase castings, as you see: no brilliancy at all!
I think al the fresh charge going into the cylinder is that what is already contained in the transfer ducts!
Of course also including the crankcase ducts.
When you think of it: would there be time for the charge under the piston, or between the crankwebs
to reach the transfer ports?
And also there is a too large distance!

Thanks Jan and for all!

Jan Thiel a écrit:: When you think of it: would there be time for the charge under the piston, or between the crankwebs
to reach the transfer ports?
And also there is a too large distance!

@Jan: what do you think the expansion chamber isn't able to suck the fresh charge under the piston and from the crankcase?

Jan Thiel a écrit:: [Vous devez être inscrit et connecté pour voir cette image]

This was also tried.
Less power, and it caused piston seizures!

Maybe it worth for trying a "shorter" duct as you can see on the pic. What's your opinion?

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Forgi a écrit:: do you think the expansion chamber isn't able to suck the fresh charge under the piston and from the crankcase?

The exhaust pipe can work miracles, but the time is simply too short: at 13000 rpm there is only 0,0017 second between the beginning of the transfer opening and the moment that they are completely shut again.
It takes an average of five crankshaft revolutions for the mixture to travel from the crankcase entry to the cylinder.

Citation :: Maybe it worth for trying a "shorter" duct as you can see on the pic. What's your opinion?
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The transfer ducts have one smooth internal radius. If you shorten the ducts, this radius will become tighter at some point, hindering the flow.

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

Hello

can anyone tell me why in the PVP Superkart engine there is a 115mm connecting rods used and not a 120mm? because the cylinder is like that of the RSA. has it a specific reason in the kart sport?
I think that also the FPE engine has a shorter connecting rod.

thanks

Manuel

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

Manuel Rainer a écrit:: Hello

can anyone tell me why in the PVP Superkart engine there is a 115mm connecting rods used and not a 120mm? because the cylinder is like that of the RSA. has it a specific reason in the kart sport?
I think that also the FPE engine has a shorter connecting rod.

thanks

Manuel

The DEA also has a 115 rod & BRC , you can fit 120 if you wish / rules allow,
But yes is there a reason why this perceived advantage is not used more,
I've been told tuning is different, don't know why or by how much as I have no experience with them

Nombre de messages : 151 Localisation : usa Date d'inscription : 29/09/2013

Frits Overmars a écrit:: It takes an average of five crankshaft revolutions for the mixture to travel from the crankcase entry to the cylinder.
.

interesting frits. i would of thought the crankcase would of been emptied to the cylinder at every cycle, atleast when the engine is on the pipe but ive never put much thought into this.

is there such a thing as a crankcase that varies it volume some how, maybe based on rpm ? perhaps this could make the engine run better at all rpm ranges ?

Nombre de messages : 15 Localisation : usa Date d'inscription : 24/12/2012

Jan Thiel a écrit:

Forgi a écrit:: Hi Jan!

I don't know if you have already talked about it, but I'd have a question:

At the area marked on the pic the piston's skirt will not influence the flow? I don't understand why is not at the same height as the bottom of the transfer duct?

Excause me if these questions have been already discussed!

Thanks in advance!

Forgi

[Vous devez être inscrit et connecté pour voir cette image]

(köcsög gecsei jegyzetelj!)

We tried to modify the piston skirt, but it gave less power.
Also a radius was worse.
So we left it as it was!

You say a radius was worse? On the piston skirting you tried a radius and it was worse?

Isn't a big radius from the bore continuing into transfer ducts the best? (instead of just the common chamfer in bore)

Nombre de messages : 151 Localisation : usa Date d'inscription : 29/09/2013

williams i think your getting confused. jan is refering to the piston skirt, a radius was worse

it was said some pages back a radius on the bore edge leading to the transfers gave more power

brokedown a écrit:

Frits Overmars a écrit:: It takes an average of five crankshaft revolutions for the mixture to travel from the crankcase entry to the cylinder..

i would of thought the crankcase would of been emptied to the cylinder at every cycle, atleast when the engine is on the pipe but ive never put much thought into this.

That would be nice: getting 675 cc of mixture into a 125 cc cylinder at every revolution.
Then a 125 cc engine would easily produce over one hundred horsepower [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 30 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 30 809262

.

Citation :: is there such a thing as a crankcase that varies it volume some how, maybe based on rpm ? perhaps this could make the engine run better at all rpm ranges ?

Ajustable crankcase volumes have been tried a couple of times, mainly for test bench purposes.
But I have not yet seen a crankcase volume that varies with rpm. I doubt whether the result would justify the complication.

Frits Overmars a écrit:: The exhaust pipe can work miracles, but the time is simply too short: at 13000 rpm there is only 0,0017 second between the beginning of the transfer opening and the moment that they are completely shut again.
It takes an average of five crankshaft revolutions for the mixture to travel from the crankcase entry to the cylinder.

Hello Frits :)

Really? It is very interesting, I thought that the exhaust pipe sucks the fresh charge from the crankcase.
Of course NOT! all of the 675cc! [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 30 809262

According to my calculation the volume of the aprilia transfer and crankcase ducts is about 85-90cc. Am I right?

Now it is clear to me what Jan keep telling me about the fresh charge which goes to the cylinder and which is the same what was contained by the transfer and the crankcase ducts.

Jan Thiel a écrit:: I think al the fresh charge going into the cylinder is that what is already contained in the transfer ducts!
Of course also including the crankcase ducts.

I also can understand why isn't so important the piston skirt from that point of view as I thought at first.

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

RAW a écrit:

Manuel Rainer a écrit:: Hello

can anyone tell me why in the PVP Superkart engine there is a 115mm connecting rods used and not a 120mm? because the cylinder is like that of the RSA. has it a specific reason in the kart sport?
I think that also the FPE engine has a shorter connecting rod.

thanks

Manuel

The DEA also has a 115 rod & BRC , you can fit 120 if you wish / rules allow,
But yes is there a reason why this perceived advantage is not used more,
I've been told tuning is different, don't know why or by how much as I have no experience with them

thank RAW

Frits did you know why there is only used a 115mm connecting rods in these engines?

thanks Manuel

Nombre de messages : 62 Localisation : Denmark Date d'inscription : 12/02/2012

PVP is using 115mm. conrods and so are DEA and FPE. VM ( DEA copy ) is using 116mm. rods, perhaps to make sure to get the after sales.

Change from 115mm. to 120mm. will require dyno time to remap/adjust ignition because of the longer dwell at TDC.

For the European superkarts running under CIK regulations conrod length is one of the very few dimensions stated in the homologation paper so this can't be changed.

Nombre de messages : 151 Localisation : usa Date d'inscription : 29/09/2013

frits just today i took apart my honda because i have new ideas to try. its T exh port with A/B/C transfers and reeds in the cylinder. but im stumped at the B port. with 15* upward angle it matches the piston dome very well.

i dont know the correct term but if the port enter the cylinder flatter then i guess it would let more mixture pass to the cylinder. so if i made B less than 15* (lets say 10*) then perhaps alittle more mixture can make it to the cylinder but it still has no choice except to follow the contour of the piston top. so i dont know what to do here. did rsa125 B port angle match piston top ? thnx

» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked)
» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked)
» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5)
» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 4)
» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5)