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

Jan Thiel a écrit:: You should always prepare your cylinders yourself before and after plating.
NEVER permit the plating shop to do this!

Yes, of course Frits!
I really did not think anybody would be stupid enough to do this!
But you never know....

Remember Albert Einstein's words:
"Only two things are infinite: the universe and human stupidity. And I'm not yet sure about the universe...."

Albert Einstein also said'
“We can't solve problems by using the same kind of thinking we used when we created them.”

“Any fool can make things bigger, more complex, and more violent. It takes a touch of genius-and a lot of courage-to move in the opposite direction.”

Howard Gifford a écrit:: Albert Einstein also said “We can't solve problems by using the same kind of thinking we used when we created them. Any fool can make things bigger, more complex, and more violent. It takes a touch of genius-and a lot of courage-to move in the opposite direction.”

A simple design is not something you will achieve through sloppy thinking; on the contrary. I tell my pupils: "When you think you have finished a design, think a bit more and try to eliminate as many parts as possible. Each part that you can leave out, doesn't cost anything, doesn't weigh anything and never breaks down.

Nombre de messages : 2 Localisation : Sweden Date d'inscription : 25/09/2012

Frits Overmars a écrit:

Blommen a écrit:: HI, are you able to send me that Cad file?

Hey Dennis, I think you just proved that the Swedish have a great sense of humour [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 809516

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 809516

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I guess couldn´t agree more [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 921866

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 921866

I was expecting that kind of answer, but i figured it was worth a try. With some luck i could have been a "public" sketch that houndreds of people had but i hade missed it troughout the thread.

I find it very useful that you and Jan ar able two answer our questions about 2-stroke tuning and on such famous engine.

No need for a presentation on me, im just a happy amatuer and im only 17 yrs old. Very Happy

Frits Overmars a écrit:

Blommen a écrit:: HI, are you able to send me that Cad file?

Hey Dennis, I think you just proved that the Swedish have a great sense of humour [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 809516

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[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 998726

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 2878

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 980796

Frits Overmars a écrit:: "When you think you have finished a design, think a bit more and try to eliminate as many parts as possible. Each part that you can leave out, doesn't cost anything, doesn't weigh anything and never breaks down.

Lean thinking [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 771973

Nombre de messages : 37 Localisation : Hellas Date d'inscription : 08/02/2012

What can be done after the plating without damaging it?
Is there a compromise between chamfering the transfer ports and longevity of the rings?

Is it possible to reveal the ignition timing of the RSA?

Nombre de messages : 6 Localisation : usa Date d'inscription : 14/09/2012

XpTpSMTT a écrit:: What can be done after the plating without damaging it?
Is there a compromise between chamfering the transfer ports and longevity of the rings?

Is it possible to reveal the ignition timing of the RSA?

A lot can be done. I have used 3 plating companys and get 3 different results. All require more touch up work.

Thanks for the transfer port clarification Jan.
I am with Howard. I already made some gains from this great thread.

XpTpSMTT a écrit:: What can be done after the plating without damaging it?
Is there a compromise between chamfering the transfer ports and longevity of the rings?

Is it possible to reveal the ignition timing of the RSA?

The best way to work on plated cylinders is by using dental diamond burs.
There were never any problems with the piston rings with unchamfered transfer ports.

Frits should have the ignition curve of the Aprila RSA.
No problem to show it I think.

Jan Thiel a écrit:: The best way to work on plated cylinders is by using dental diamond burs.
There were never any problems with the piston rings with unchamfered transfer ports.

Clear and very usefull!

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 1993206895

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 1993206895

Nombre de messages : 37 Localisation : Hellas Date d'inscription : 08/02/2012

mxer a écrit:: ......touch up work.

ok,i thought maybe there was more i was missing.

But why do most production cylinders(at least the ones i have seen)
have some sort of chamfering,some more others less?
So my problems are coming from somewhere else and unchamfered ports were not the cause.
Does this also aplly for cast iron cylinders or iron sleeved?

The only way to break a piston ring at Aprilia was through insufficient ring gap clearance.
It had to be 0,30, less would cause the ends to touch!
Then the ring would become very hot, expand even more, and the only place to go was into the exhaust port.
Result: a broken ring and a ruined cylinder.
0,25 clearance was insufficient!

About the chamfers, of course it makes no difference if the cylinder is plated, cast iron, or has a liner.
But you must have good quality piston rings!

Sujet: Port finishing Lun Oct 01 2012, 10:40

Hi Jan,
Thank you for the comments about port chamfers - could you describe how you finish the cylinder ports after the cylinder is plated please? [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 809262

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 12 809262

Best regards
Allan.

Jan Thiel a écrit:

XpTpSMTT a écrit:: Is it possible to reveal the ignition timing of the RSA?

Frits should have the ignition curve of the Aprila RSA. No problem to show it I think.

No problem at all, Jan, especially beause I already posted it once in Pit-Lane Wink

. I cannot find where that was (I can never find anything with the search funtions of forums), so here it is once more.
[Vous devez être inscrit et connecté pour voir cette image]

Dank u Frits...
If I could then ask 2 supplementary questions:
- was the curve modified at partial throttle to try to reduce detonation?
- did the timing evolve at all with different versions of Elf mits-xx ?

GrahamB a écrit:: ...was the curve modified at partial throttle to try to reduce detonation?

The part-throttle detonation was caused by the scavenging pressure dropping soo low that burnt gases entered the transfer ducts, notwithstanding a blowdown time.area that was sufficient for full throttle at high revs. It was not a situation that could have been cured by altering the ignition timing.

Citation :: did the timing evolve at all with different versions of Elf mits-xx ?

Aprilia did not use Elf products....

Nombre de messages : 37 Localisation : Hellas Date d'inscription : 08/02/2012

yes,I have found the importance of ring gap the hard (and expensive)way!
But still 0,3mm seems large
(???),does it have to do with the breaking in of the new piston and cylinder
or lack of?How was it done(braking in)
What should the correct gap be then for 67mm bore?steel rings.

Thank you for the advance curve,it says 100% throtlle
Was it corrected from the TPS reading or other factors?

(edit:eg for smooth acceleration inside corners)

Nombre de messages : 19 Localisation : England Date d'inscription : 07/09/2012

I've pulled this from Part 1

Jan Thiel a écrit:: Very little computer simulation was used, as far as I remember only for the cilinder and head cooling.
We once had an exhaust design software on loan from a very well known company, the results were useless! It was mostly cut and try!
Cilinder development was done without any computing, just logical thinking.
The exhaust ducts were CNC machined.
All improvements were fully understood..

Could you divulge the name of the exhaust design software?

Jan, When you modified the B port duct with epoxy to direct the flow more centrally (before you modified your casting moulds), did the epoxy stay put during a race situation or did you just test the epoxy on the dyno? I want to try this modification but I am afraid the epoxy will detach and cause grief. Was there a certain type of epoxy that worked best? I have used Devcon aluminum putty and liquid aluminum with limited success. I have also tried JB weld. It seems all eventually work loose despite my best etching and roughening of the aluminum.. Welding in the port would be next to impossible.

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

Howard, if I may add my experience with epoxies;
I also found that the usual aluminium-filled epoxies stick relatively poorly to the surfaces.
One very important thing about epoxies is post-curing. Room temperature cured epoxy softens at relatively low temperatures (glass transition temperature; Tg, around 40-60°C, depending on type). So they require post curing, that means keeping the epoxy heated at higher temperatures for a certain time. Keeping the epoxy at 100°C for about 3-5 hours will rise substantialy the Tg.
The best working epoxy for me is Loctite 9492. I even repaired the exhaust duct (I cut a hole into the water jacket). With filling the transfers I had no problems at all trough the whole race season.

Regards.

Howard Gifford a écrit:: Jan, When you modified the B port duct with epoxy to direct the flow more centrally (before you modified your casting moulds), did the epoxy stay put during a race situation or did you just test the epoxy on the dyno? I want to try this modification but I am afraid the epoxy will detach and cause grief. Was there a certain type of epoxy that worked best? I have used Devcon aluminum putty and liquid aluminum with limited success. I have also tried JB weld. It seems all eventually work loose despite my best etching and roughening of the aluminum.. Welding in the port would be next to impossible.

At Aprilia we had a very good epoxy, called 'stucco verde' in Italian.
Never worked loose and even withstood replating!
Sorry I do not know were it was made!

XpTpSMTT a écrit:: yes,I have found the importance of ring gap the hard (and expensive)way!
But still 0,3mm seems large
(???),does it have to do with the breaking in of the new piston and cylinder
or lack of?How was it done(braking in)
What should the correct gap be then for 67mm bore?steel rings.

Thank you for the advance curve,it says 100% throtlle
Was it corrected from the TPS reading or other factors?

(edit:eg for smooth acceleration inside corners)

Braking in was done on the dyno, 3 minutes full throttle at 10000 rpm. followed by 30 seconds at 12000

Less than 0,3 mm gap would break the ring.

There were different ignition settings for part throttle.
I think more advance was used.
There was no way of avoiding part-throttle detonation through the ignition setting.
As it was 'auto-ignition'

Jan Thiel a écrit:: [There was no way of avoiding part-throttle detonation through the ignition setting.
As it was 'auto-ignition'

Hi Jan

I have never thought of it like that before. I had always assumed detonation (either part or full-throttle) was initiated by the sudden rise in pressure once the sparkplug had fired and ignition commenced and that retarding the ignition would tend to reduce that detonation.

Of course I have always noted that changes in piston (flat or dome), transfer port design, squish band design and clearance, compression and fuel quality also have major effects on onset of detonation.

This way of thinking might explain some problems I had been puzzling over.

Many thanks for provoking my thoughts . . . . again!!

Best Regards

Ian

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