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

Piquer a écrit:: As aluminum has a higher dilation coefficient than iron cast, I would have left a less tolerance between the cylinder and the sleeve, it's correct?

Yes. But the best solution would be to use a conical fit, like Jan Thiel did on his last sleeved Jamathi cylinder.
Jan used a morse cone angle on both the sleeve and the cylinder. The tolerance was thus that only the last millimeter required a slight press fit. It was equally easy to remove the sleeve again.

Clever indeed! wanted - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 4) 241515

wanted - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 4) 1993206895

Invité

Frits Overmars a écrit:: Merci Emmanuel .

Your reaction makes me happy for more than one reason. Although I love this topic, it concerns me that it becomes more and more English (my own fault) and less and less French, and I feel somewhat guilty vis-à-vis my French hosts.

Dont feel guilty about frenck guys Frits. We are very proud to have you on Pit-Lane!
wanted - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 4) 199739

wanted - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 4) 199739

Hi Frits,Hi Jan;

Please check my picture.
You see this 2 points on the piston for sure.
Any idea to prevent or eliminate this?

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Thanks a lot for your advise.

Hi Frits,Hi Jan;

I hope you remember the 2 points on the piston crown.
Frits i hunt the bird out of my office wanted - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 4) 241515

Please find here more details concerning the port angles.
It belongs to a 125cc reed engine
Stroke 54,00
Bore 54,15
Conrod 102mm
1+2 128 °
3+4 125,5°
TT 125°
Exhaust 192,5° with 2 stage powervalve(176°_ 186°_ 192,5°)
Boosters 176°
Head volume 9,00 cc
Rev. limiter 15000 rpm

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Any idea trying to eliminate those scavenge defaults?

Thanks a lot.

Vortex a écrit:: Hi Frits,Hi Jan; Please check my picture. You see this 2 points on the piston for sure. Any idea to prevent or eliminate this?

If you had posted this picture yesterday, I would have been sure it was an April joke. No, I've never seen something like this before. Jan, what do you make of it? Ik looks like a bird dropped something just before Vortex closed the engine Rolling Eyes

.

Frits Overmars a écrit:

Piquer a écrit:: As aluminum has a higher dilation coefficient than iron cast, I would have left a less tolerance between the cylinder and the sleeve, it's correct?

Yes. But the best solution would be to use a conical fit, like Jan Thiel did on his last sleeved Jamathi cylinder.
Jan used a morse cone angle on both the sleeve and the cylinder. The tolerance was thus that only the last millimeter required a slight press fit. It was equally easy to remove the sleeve again.

Many thanks Mr. Frits, I'm very grateful.

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Frits Overmars a écrit:

Vortex a écrit:: Hi Frits,Hi Jan; Please check my picture. You see this 2 points on the piston for sure. Any idea to prevent or eliminate this?

If you had posted this picture yesterday, I would have been sure it was an April joke. No, I've never seen something like this before. Jan, what do you make of it? Ik looks like a bird dropped something just before Vortex closed the engine Rolling Eyes

.

Hahaha Frits,
No april joke and no bird in my office.

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

hi

what makes the damage on the piston if the engine detonates? it is because the piston gets to hot in this area or it comes from a other thing.
if it comes from to hot temperatur for the material, is it possible to take a material with higher melting temperatur? maybe make a piston with a dome for example of titanium.

has some one ever tried something in this way?

Manuel

Jan Thiel a écrit:

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.

Dear Jan!

You've written that you tried everything with 0,5 mm squish gap to make engine rev, but it didn't work. Have you tired a smaller squish band area ratio? If I'm right it was basically 50%.

Manuel Rainer a écrit:: what makes the damage on the piston if the engine detonates? it is because the piston gets to hot in this area or it comes from a other thing. if it comes from to hot temperatur for the material, is it possible to take a material with higher melting temperatur? maybe make a piston with a dome for example of titanium. has some one ever tried something in this way?

Yes the piston becomes too hot because the shock waves of the detonation blow away the boundary layer of gas that normally forms a heat insulation on the piston surface. Piston domes covered with ceramic or titanium have been tried but the problem is that the dome surface then stays much hotter which causes even more detonation.

Forgi a écrit:

Jan Thiel a écrit:

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.

Dear Jan!

You've written that you tried everything with 0,5 mm squish gap to make engine rev, but it didn't work. Have you tired a smaller squish band area ratio? If I'm right it was basically 50%.

Yes, less than 50% is what we started with.
But 50% gave a lot more power and less detonation.
This was when testing unleaded fuel, in 1998

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

Yes, less than 50% is what we started with.
But 50% gave a lot more power and less detonation.
This was when testing unleaded fuel, in 1998

Jan before the unleaded era what did you consider to be the best head form

Nombre de messages : 112 Localisation : Germany Date d'inscription : 07/02/2012

Manuel Rainer a écrit:: hi koenich

did your engine dont rev and detonate of the fact of too high compression or because it has a different shape?

first aid was only increased squish gap, so i think it was only due to too high compression. after doing my own inserts I could lower the squish while maintaining the overrev...

For the 50cc I simply did 3 different inserts - each 50% squish area, squish band following 100% piston crown and just changed the radius of the bowl resulting in 3 different compression ratios.

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

Frits Overmars a écrit:

Manuel Rainer a écrit:: what makes the damage on the piston if the engine detonates? it is because the piston gets to hot in this area or it comes from a other thing. if it comes from to hot temperatur for the material, is it possible to take a material with higher melting temperatur? maybe make a piston with a dome for example of titanium. has some one ever tried something in this way?

Yes the piston becomes too hot because the shock waves of the detonation blow away the boundary layer of gas that normally forms a heat insulation on the piston surface. Piston domes covered with ceramic or titanium have been tried but the problem is that the dome surface then stays much hotter which causes even more detonation.

hi

thanks Frits.

I thought that it is not the way to prevent detonations. only to prevent the damage on the piston. so also the head has to be of a higher temperatur resistant material.

i was thinking on this to make the engine to have a longer life.

but i think if the piston surface is hotter then with a normal piston it will cost HP. ?

thanks koenich i will try to make a new head with lower compression.

Manuel

Hello everyone.

Frits, I noticed your pipe concept get's the lenght of baffle cone the size of 0,236 of total lenght, meaning the baffle always start's at 76,4% of the total lenght.

Would this be somekind of best average?
Can you tell's us something, or some ideas about what's behind of this concept?

Thanks in advance

romeuh80 a écrit:: Frits, I noticed your pipe concept get's the lenght of baffle cone the size of 0,236 of total lenght, meaning the baffle always start's at 76,4% of the total lenght. Would this be somekind of best average? Can you tell's us something, or some ideas about what's behind of this concept?

Remember, it is called the FOS simple exhaust concept; I developed it for young people who are just starting to learn about two-stroke tuning, and who haven't yet got much theoretical knowledge.

Nombre de messages : 28 Localisation : Slovenia Date d'inscription : 19/03/2012

Frits, I have a rather unconventional question; is the thrust of the exhaust gasses exiting the exhaust system ever considered on a race bike? If so, what would be an raw estimate of the thrust produced, let's say on a GP 125 machine?

Thanks again! :)

roost a écrit:: Frits, I have a rather unconventional question; is the thrust of the exhaust gasses exiting the exhaust system ever considered on a race bike? If so, what would be an raw estimate of the thrust produced, let's say on a GP 125 machine?

On a race bike not really. Let's do a raw estimate: the average pipe pressure is about 1,3 bar. The restrictor area at the end cone is about 4,25 cm² so the thrust would be about 12N. Since the exit is pointing rearward anyway, that is some help, but nothing to write home about.

There is an other form of motorsport where thrust plays an important role: drag racing. Last year a drag racer said to me: "Our V-8 engines have more power than a Formula 1 car - per cylinder!" No wonder that these blown nitro-burning monsters produce 'some' thrust. The exhaust pipes are angled up in such a way that this thrust gives an optimal balance between forward thrust and downforce on the driving wheels.

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Calling RAW Rick you there?

Fast as a Top fueler accelerates a F1 car stops F1/Moto GP engine will last 2500km between rebuilds not 10 seconds. For sheer numbers and spectacle now much surpasses the Top Fuelers.

Interesting Eccelstone was bemoaning the lack of noise from the lastest F1 cars, Bernie thinks he can change the exhaust for more noise. I wonder if he realises that the turbo uses energy from the exhaust and that's where the noise has gone lol!

Institute of TwoStrokes a écrit:: Eccelstone was bemoaning the lack of noise from the lastest F1 cars, Bernie thinks he can change the exhaust for more noise. I wonder if he realises that the turbo uses energy from the exhaust and that's where the noise has gone.

Eckie had been warned about the noise reduction over a year ago. He didn't react then. Maybe he thought he could bend the laws of physics by just telling them loud enough how he wanted things to be.

Nombre de messages : 28 Localisation : Slovenia Date d'inscription : 19/03/2012

Frits, thanks for the clarification! wanted - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 4) 771973

wanted - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 4) 771973

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

Some top Fuel Dragster numbers, from a standing start
0.87 seconds = 60 feet of travel & already reached 100Mph
A good run you will cary the front wheels for the first 330 feet
The fuel pump requires around 120 hp to run it
Fuel pressure 650 psi @ 85 gallons p/min
32 fuel injectors for 8 cylinders
Clutch doesn't lock up 1:1 until approximay 3.4 seconds into the run
Supercharger 60 psi & requires 800 hp to run it @ 8400 crank rpm
Power, above 8,000 hp, nearer to 9,500 hp nowdays
Crank turns approximately 750 times for a pass then a full rebuild
10 passes then rods are no longer used, 20 on a crank
Tyres 4.5 psi
At the 1,000 ft mark pistons are reaching there melting temperature, the next 440 ft of the run is so quick that the pistons are finished being used USUALLY before the crowns sink
Several valves that are hanging open after the engine is stopped usually bend along the stems as they are so hot they deform

Frits Overmars a écrit:

Institute of TwoStrokes a écrit:: Eccelstone was bemoaning the lack of noise from the lastest F1 cars, Bernie thinks he can change the exhaust for more noise. I wonder if he realises that the turbo uses energy from the exhaust and that's where the noise has gone.

Eckie had been warned about the noise reduction over a year ago. He didn't react then. Maybe he thought he could bend the laws of physics by just telling them loud enough how he wanted things to be.

Bernie has bent many things in the past(rules and laws) I suppose he thought he might try physics. lol!

RAW a écrit:: Some top Fuel Dragster numbers, from a standing start
0.87 seconds = 60 feet of travel & already reached 100Mph
A good run you will cary the front wheels for the first 330 feet
The fuel pump requires around 120 hp to run it
Fuel pressure 650 psi @ 85 gallons p/min
32 fuel injectors for 8 cylinders
Clutch doesn't lock up 1:1 until approximay 3.4 seconds into the run
Supercharger 60 psi & requires 800 hp to run it @ 8400 crank rpm
Power, above 8,000 hp, nearer to 9,500 hp nowdays
Crank turns approximately 750 times for a pass then a full rebuild
10 passes then rods are no longer used, 20 on a crank
Tyres 4.5 psi
At the 1,000 ft mark pistons are reaching there melting temperature, the next 440 ft of the run is so quick that the pistons are finished being used USUALLY before the crowns sink
Several valves that are hanging open after the engine is stopped usually bend along the stems as they are so hot they deform

Thanks RAW for that intersting information, but do you also know the total weight of a topfuel dragster with pilot?

Jan Thiel a écrit:

Forgi a écrit:: Dear Jan!

You've written that you tried everything with 0,5 mm squish gap to make engine rev, but it didn't work. Have you tired a smaller squish band area ratio? If I'm right it was basically 50%.

Yes, less than 50% is what we started with.
But 50% gave a lot more power and less detonation.
This was when testing unleaded fuel, in 1998

Thanks Jan!

I thought that because of the squish gap which was smaller than 0, 7 mm, the squish velocity became too high and because of it the rev. was also lower. If the squish band ratio is smaller then the squish velocity will be lower. But according to the abovementioned I suppose I was wrong.

» [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 5)
» [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 1) (Locked)
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