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 Piston damage

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AuteurMessage
Frits Overmars

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Nombre de messages : 2131
Age : 70
Localisation : Raalte, Holland
Date d'inscription : 12/10/2010

MessageSujet: Re: Piston damage   Dim 23 Déc 2018 - 15:15

wos a écrit:
Döllinger a écrit:
ended the ignition curve on a 20° straight instead of curvature to 9° to get the heat out at high revs
I Think 20 degree is to much. ..that will produce a stay of more heat in the cylinder and cool down exhaust gas.
13- 15 degree at maximum revs would be better frits?  Wink  
Wolfgang, 20° ignition advance will indeed produce cooler exhaust gas, but it will also lead to less heat in the cylinder.
Heat transmission from the gas to the surrounding walls is strongly dependent on turbulence, and although the highest temperature is reached in the combustion chamber, most of the heat is transferred when the hot gases flow from the cylinder into the exhaust duct.
13°-15° ignition advance at maximum revs would probably be better for the efficiency of the expansion pipe, but if engine temperature is the biggest problem, pipe efficiency only comes second.
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wos



Nombre de messages : 9
Localisation : Germany
Date d'inscription : 05/04/2018

MessageSujet: Re: Piston damage   Dim 23 Déc 2018 - 15:51

Thank you frits!

That means in this case:
it is better to ignite earlier ..at lower turbulence...to avoid heat transition to the walls via high turbulence at later ignition time? Right?

Thanks frits...even when your answer corrects me...totally new aspekt for me! :) great to learn from you with every of your words!
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Frits Overmars

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Nombre de messages : 2131
Age : 70
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Date d'inscription : 12/10/2010

MessageSujet: Re: Piston damage   Dim 23 Déc 2018 - 16:03

Thanks for the flowers, Wolfgang. The turbulence in the combustion chamber is mainly caused by squish action.
Here, strong turbulence leads to fast combustion, which is desirable for two reasons. It means that you can ignite later, causing less pressure on the piston before TDC, and it means that the peak temperature is present during a shorter time.
Regarding the temperature input into the engine, it is not so much the rate of turbulence that you can influence; it's mainly a matter of managing the gas temperature at the moment of maximum turbulence, i.e. when the exhaust port opens.
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wos



Nombre de messages : 9
Localisation : Germany
Date d'inscription : 05/04/2018

MessageSujet: Re: Piston damage   Dim 23 Déc 2018 - 17:06

Have to think about a long time to understand frits!

In case of a thermal problematic engine that means you can poorly influence the gas temp. / speed of sound in the Exhaust via ignition! ?

in the last year we managed to widen powerband via variable ignition of a classic enduro tgm 125 1982 with a hiro engine :)

Original Ignition was a motoplat 24 degree static that caused heat problems even what we did Sad

We used then a hpi programmable and a curve like yours downscaled to 26 degree...falling with beginning resonance to power max to 17 degree...than a smaller decrease to rev max

no problems at three classic enduro races in south Germany :) had a wonderful powerband in opposite to the other oldies

maybe the hiro engine is less critical then maico even when its an ac too.

it has a curious intake system...reeds for the transfers. ..piston port for main inlet... Wink

Do you know the h.i.s.s System frits? ...it was also used in aprilia enduro with hiro engine in the early 1980 years...

have a nice day! :)

Grüße Wolfgang

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Frits Overmars

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Nombre de messages : 2131
Age : 70
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Date d'inscription : 12/10/2010

MessageSujet: Re: Piston damage   Dim 23 Déc 2018 - 18:03

wos a écrit:
In case of a thermal problematic engine that means you can poorly influence the gas temp. / speed of sound in the Exhaust via ignition?
You can very well influence the gas temp via the ignition for any engine. But it's a question of priorities: if the engine has temperature problems, do not give too much advance, or you will provoke detonation, and do not give too little advance, or you will heat up the cylinder. Reliability is always more important than the working of the exhaust pipe. In such cases 20° advance should be a reasonable starting point for the ignition timing.
Citation :
in the last year we managed to widen powerband via variable ignition of a classic enduro tgm 125 1982  with a hiro engine. Original Ignition was a motoplat 24 degree static that caused heat problems even what we did. We used  then a hpi programmable and a curve like yours downscaled to 26 degree...falling with beginning resonance to power max to 17 degree...than a smaller decrease to rev max.
24° ignition advance over the complete rev range can be too much when the engine is nearing its maximum torque rpm. Beginning detonation is not always clearly visible, but it can blow the boundary layer of stationary gas off the cylinder, head and piston surfaces, severely aggravating heat transfer. And of course there is always the possibility that an ignition does not do what it is supposed to do. Ignitions that drastically change their timing when they get hot, are notorious. In such cases changing the brand of ignition system can make far more difference than changing the timing.
Citation :
maybe the hiro engine is less critical then maico even when its an ac too. it has a curious intake system...reeds for the transfers. ..piston port for main inlet... Do you know the h.i.s.s System frits? ...it was also used in aprilia enduro with hiro engine in the early 1980 years.
Yes, I remember the Hiro very well. If I'm not mistaken it was being used in a Garellli street model when I was assisting Jan Thiel in the Garelli racing department.
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wos



Nombre de messages : 9
Localisation : Germany
Date d'inscription : 05/04/2018

MessageSujet: Re: Piston damage   Dim 23 Déc 2018 - 19:28

Frits Overmars a écrit:
wos a écrit:
In case of a thermal problematic engine that means you can poorly influence the gas temp. / speed of sound in the Exhaust via ignition?
You can very well influence the gas temp via the ignition for any engine. But it's a question of priorities: if the engine has temperature problems, do not give too much advance, or you will provoke detonation, and do not give too little advance, or you will heat up the cylinder. Reliability is always more important than the working of the exhaust pipe. In such cases 20° advance should be a reasonable starting point for the ignition timing.
Citation :
in the last year we managed to widen powerband via variable ignition of a classic enduro tgm 125 1982  with a hiro engine. Original Ignition was a motoplat 24 degree static that caused heat problems even what we did. We used  then a hpi programmable and a curve like yours downscaled to 26 degree...falling with beginning resonance to power max to 17 degree...than a smaller decrease to rev max.
24° ignition advance over the complete rev range can be too much when the engine is nearing its maximum torque rpm. Beginning detonation is not always clearly visible, but it can blow the boundary layer of stationary gas off the cylinder, head and piston surfaces, severely aggravating heat transfer. And of course there is always the possibility that an ignition does not do what it is supposed to do. Ignitions that drastically change their timing when they get hot, are notorious. In such cases changing the brand of ignition system can make far more difference than changing the timing.
Citation :
maybe the hiro engine is less critical then maico even when its an ac too. it has a curious intake system...reeds for the transfers. ..piston port for main inlet... Do you know the h.i.s.s System frits? ...it was also used in aprilia enduro with hiro engine in the early 1980 years.
Yes, I remember the Hiro very well. If I'm not mistaken it was being used in a Garellli street model when I was assisting Jan Thiel in the Garelli racing department.

Thanks frits for this christmas gift!!! :)

We tried other values down to 17 degree but as you told...maybe the ignition had a malefunktion...kind of missfireing...we dont know.

For sure 24 degree is too much for well filled combuston chamber... was wondering about these high value in the tecnical data too Wink

there were two versions of the hiro zylinder. ..one piston ported...the other with the combined intake system...

The combined one has ha terrible layout...very narrow round exhaust port but 205 degree timing... while the transfers work on 130 degree...if i remember correctly Wink ...c ports direction is directly in exhaust...rolleye :)

We like to change this in next months Wink

Welding exhaust to 190...give hin a modern shape from about 70 percent...maybe drill boost ports.

question to you frits... has the combined intake system oft the hiro engine any benefits?

We thougt about removing it and to fix a complete and ordinary reed valve...

any benefits for changing to only reed valve? we hope so...Wink

Vielen Dank :)

Grüße Wolfgang



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wos



Nombre de messages : 9
Localisation : Germany
Date d'inscription : 05/04/2018

MessageSujet: Re: Piston damage   Dim 23 Déc 2018 - 19:53

Frits Overmars a écrit:
wos a écrit:
In case of a thermal problematic engine that means you can poorly influence the gas temp. / speed of sound in the Exhaust via ignition?
You can very well influence the gas temp via the ignition for any engine. But it's a question of priorities: if the engine has temperature problems, do not give too much advance, or you will provoke detonation, and do not give too little advance, or you will heat up the cylinder. Reliability is always more important than the working of the exhaust pipe. In such cases 20° advance should be a reasonable starting point for the ignition timing.
Citation :
in the last year we managed to widen powerband via variable ignition of a classic enduro tgm 125 1982  with a hiro engine. Original Ignition was a motoplat 24 degree static that caused heat problems even what we did. We used  then a hpi programmable and a curve like yours downscaled to 26 degree...falling with beginning resonance to power max to 17 degree...than a smaller decrease to rev max.
24° ignition advance over the complete rev range can be too much when the engine is nearing its maximum torque rpm. Beginning detonation is not always clearly visible, but it can blow the boundary layer of stationary gas off the cylinder, head and piston surfaces, severely aggravating heat transfer. And of course there is always the possibility that an ignition does not do what it is supposed to do. Ignitions that drastically change their timing when they get hot, are notorious. In such cases changing the brand of ignition system can make far more difference than changing the timing.
Citation :
maybe the hiro engine is less critical then maico even when its an ac too. it has a curious intake system...reeds for the transfers. ..piston port for main inlet... Do you know the h.i.s.s System frits? ...it was also used in aprilia enduro with hiro engine in the early 1980 years.
Yes, I remember the Hiro very well. If I'm not mistaken it was being used in a Garellli street model when I was assisting Jan Thiel in the Garelli racing department.

Thanks frits for this christmas gift!!! :)

We tried other values down to 17 degree but as you told...maybe the ignition had a malefunktion...kind of missfireing...we dont know.

For  sure 24 degree is too much for well filled combuston chamber... was wondering about these high value in the tecnical data too Wink

there were two versions of the hiro zylinder. ..one piston ported...the other with the combined intake system...

The combined one has ha terrible layout...very narrow round exhaust port but 205 degree timing... while the transfers work on 130 degree...if i remember correctly Wink ...c ports direction is directly in exhaust...rolleye :)  

We like to change this in next months Wink

Welding exhaust to 190...give hin a modern shape from about 70 percent...maybe drill boost ports.

question to you frits... has the combined intake system oft the hiro engine  any benefits?

We thougt about removing it and to fix a complete and ordinary reed valve...

any benefits for changing to only reed valve? we hope so...Wink

Vielen Dank  :)

Grüße Wolfgang
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Frits Overmars

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Nombre de messages : 2131
Age : 70
Localisation : Raalte, Holland
Date d'inscription : 12/10/2010

MessageSujet: Re: Piston damage   Dim 23 Déc 2018 - 20:30

With a 190° main exhaust port you will definitely need auxiliary exhaust ports.

I liked the principle of the Hiro inlet with a central piston-controlledd port, that has little flow resistance when it is open, and auxiliary reed valves that feed the transfer ducts when the crankcase pressure goes below atmospheric.
It is more or less the same principle that Suzuki and Aspes tried with a piston port and a reedvalve beneath it.

Whether the Hiro system will function satisfactorily, depends on its reed valves: are they favourable to the flow?
I don't remember the details; it is 40 years ago since I saw that cylinder and I never did any work on it myself.
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wos



Nombre de messages : 9
Localisation : Germany
Date d'inscription : 05/04/2018

MessageSujet: Re: Piston damage   Dim 23 Déc 2018 - 21:12

Thanks a lot frits! :)

Tried to upload a picture. ..but didnt managed it... sorry frits

What i found is a patent Script :)

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Cause of the flow of the reeds...dont know if the reeds work propperly...direction of them, seems ok to me

hope we manage to drill , grind or elctro erosion Wink auxillary ports...not much space to the stud bolts ...we never did this job before...

michael...an old fellow of mine and the owner and driver of the tgm bike...recogniced that the h.i.s version has a bit more torque :)

If i remember right... reed flaps are made of steel ...maybe changing into carbon bring us an advatage Wink
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lvs



Nombre de messages : 9
Age : 59
Localisation : nederland
Date d'inscription : 08/01/2011

MessageSujet: Re: Piston damage   Mer 2 Jan 2019 - 21:07

.Tried to upload a picture. ..but didnt managed it... sorry frits
-----------------------------------------------------------------

cilinder 1 = hiro 1980 - bore 54
cilinder 2 = hiro 1982 - bore = ??

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wos



Nombre de messages : 9
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Date d'inscription : 05/04/2018

MessageSujet: Re: Piston damage   Ven 4 Jan 2019 - 12:43

Thank you ivs Wink

Yes...the first pic shows the Layout of the his intake...and its an aircooled one too...but our s has larger cooling rips


The side intake ports are connected with the transfers and contolled by reeds...the mid intake is controlled by piston. ..port c is connected to the transfers

Our bore is also 54 mm

Dont know the second watercooled  cylinder ...nice! :)
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lvs



Nombre de messages : 9
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MessageSujet: Re: Piston damage   Dim 13 Jan 2019 - 20:09

cilinder  hiro  -ac .

-in 1981 there were probrems with the reed housing .
………..the rubber part, was higher than the aluminum part
…….the plate did not close properly anymore .

…..last picture its me in 1981 ,, tgm 125 wc



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wos



Nombre de messages : 9
Localisation : Germany
Date d'inscription : 05/04/2018

MessageSujet: Re: Piston damage   Lun 14 Jan 2019 - 10:02

Hey ivs :)

thanks a lot!! We will pay the Rubber extra attention!

This friday we had a closer look at our reed  ac cilinder. .. timings are lower than at the pure piston ported one
193/130/160 inlet piston

So we do not have to weld the roof of exhaust duct :)

So far...so good :)

The piston is not complete radiused one at the dome...There is a plaine angle from 15 degrees in the area of the squish gap...

frits! ?

What do you think! ? Wink

Is this effektiv?
Or better to dome piston completely ?

or is the plaine angled dome an Advantage. ..if the transfers directioned nearly horizontal. ..the c transfers are horizontal too Sad
...and not easy to change this Sad
Nearly no space to the mid inlets...Without welding no chance too do something to angle them more upwards...



Thanks too all :)

Wolfgang
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Frits Overmars

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MessageSujet: Re: Piston damage   Lun 14 Jan 2019 - 13:21

A squish area angled 15° upward is more or less acceptable in view of the nearly horizontally angled transfers, and it is easier to adapt the head to those 15° than to radius both the piston and the head.
The nearly horizontally angled transfers themselves are not ideal. But can't you correct this by adding epoxy instead of welding?
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wos



Nombre de messages : 9
Localisation : Germany
Date d'inscription : 05/04/2018

MessageSujet: Re: Piston damage   Lun 14 Jan 2019 - 18:14

Thanks for your support frits! :) great!

Radius piston and head ist not the problem...there is space to weld or do metal work Wink

Thougt about epoxy too...but in the moment the cylinder is uncoated and welding is more sympatic to a toolmaker Wink

but to weld is difficult. ..there is not much space for ther wig/ tig welding head ...difficult for me in english to express Wink...thr part with the tungsten neadle! :)

We have a look this evening...drink a beer and discuss the possibilitys frits!! :)

cheers! Wink

And thanks a lot frits !

Wolfgang

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