domes head

Sujet: domes head Jeu 20 Oct 2016 - 20:44

Mr Overmars
since i saw your toroidal shape for the combustion chamber, im going to make one for my engine(jetski)
it s a 2 stroke ( off course),twin cylinder, 82x74 (bore/stoke)780cc,390cc per cylinder,max power at 7350 rpm...
do you think it s could be a good idea or not..?could this shape work well with a engine have not hight rpm?
(for now I can not download a pdf files, i m going to see if i can convert this pdf files) i have a drawing, but it s not complete

thank you

Sujet: Re: domes head Jeu 20 Oct 2016 - 21:33

pagi a écrit:: Mr Overmars since i saw your toroidal shape for the combustion chamber, im going to make one for my engine(jetski). it s a 2 stroke ( off course),twin cylinder, 82x74 (bore/stoke)780cc,390cc per cylinder,max power at 7350 rpm... do you think it s could be a good idea or not..?could this shape work well with a engine have not hight rpm? (for now I can not download a pdf files, i m going to see if i can convert this pdf files) i have a drawing, but it s not complete.

I think that the toroidal shape can work well for your engine, Pagi. It does not specifically need a high rpm.

Sujet: Re: domes head Jeu 20 Oct 2016 - 22:42

well,next week i m going to put some drawing with my original shape and what i want to go.
the domes (x2) i have to machine, need more capacity,they are too small (24.9cc) and i need around 30cc with 1.09 squish gap to have a little bit less compression ratio( i have before with 27.3cc and 1.45 squish gap on my engine,but i want to keep this domes(27.3cc) like this for a another engine))
1.45mm-0.365=1.085mm by a new base gasket (the rules in my class does not allow to machine the top off the cylinder) that s give around 2cc i have to put in the chamber so 27.2+2cc=29.2 and i want 30cc for my new compression ratio,but this domes(like the 27.2cc) have squish band with 56-57 per cent area...!!! i find that a little bit too much isn t it??????
i specify, my ignition have variable timming (26°max at 4000 rpm) , then the advance decreases

sorry for my bad english !!!

best regards

Sujet: Re: domes head Ven 21 Oct 2016 - 10:11

Your english is fine, Pagi, much better than my french.
56-57 % squish area is much but not necessarily too much. 1,45 mm squish gap is definitely too much. You still haven't mentioned your desired compression ratio. But never mind, I'd like to make it clear that I do not intend to perform individual calculations here.

Sujet: Re: domes head Ven 21 Oct 2016 - 13:18

i have dont measure exactly my compression ratio , i m going to make that this week end
if i could keep my squish band like this or a little less wide that help me for my new shape....
i have make a thirst design, but it s make too much cc... i need to add 4.6cc and the result it s 8.70cc

here my original shape [Vous devez être inscrit et connecté pour voir cette image]
the width of the squish band is not correct, it s a error, it s make 15mm
another (the same domes[Vous devez être inscrit et connecté pour voir cette image]

and my first dome change [Vous devez être inscrit et connecté pour voir cette image]

and the result off my dome change[Vous devez être inscrit et connecté pour voir cette image]
on the result, theres not the squish band, only the change area

next week , i m going too put another drawing

for my new capacity, i include that i m going to machine the "intrusion or bump" (around 0.423cc), to make a true offset (i have question about this!!!) is there a rule off thumb, or the result off the external radius, total volume ?

Sujet: compression ratio Lun 24 Oct 2016 - 20:11

well, my compression ratio is 13.62/1......do you think it s too hight or could work? i have very little detonation on a dome , could be due to the squish gap too tall like i think ?if you think it could work, i keep this ratio for my new domes.....
have you a rules of thumb to define the width of the offset or does it s the result off the outside radius, chamber volume ?

Sujet: Re: domes head Lun 24 Oct 2016 - 22:56

pagi a écrit:: well, my compression ratio is 13.62/1......do you think it s too hight or could work? i have very little detonation on a dome , could be due to the squish gap too tall like i think ?if you think it could work, i keep this ratio for my new domes.....
have you a rules of thumb to define the width of the offset or does it s the result off the outside radius, chamber volume ?

Pagi, I know nothing about your engine, how much power it makes, not even if it's aircooled or watercooled, so how should I know what compression ratio it will tolerate?
I have no rule of thumb for the offset; it will have to be calculated. But like I wrote in my previous post, I do not intend to perform individual calculations here.

Sujet: Re: domes head Lun 24 Oct 2016 - 23:37

my engine is near 105cv (my engine is not run on a dyno), this is an estimate with the manufacturer data exhaust , is watercooled..

do you see something wrong on my drawing ? (domes change)

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