Twingo rs pistons same as Clio k4m??
- Thread starter benmc
- Start date
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Fact is the Clio GT has the same, lower compression ratio (9.8) like the normal 112hp K4M engine...
In the Twingo RS press release from 2008 there is written:
"The design of the combustion chamber and piston enables a high compression ratio of 11.0:1, leading to enhanced combustion and efficiency and reduced harmful emissions."
So I think the conrods are the same, but the pistons are specific.
In the Twingo RS press release from 2008 there is written:
"The design of the combustion chamber and piston enables a high compression ratio of 11.0:1, leading to enhanced combustion and efficiency and reduced harmful emissions."
So I think the conrods are the same, but the pistons are specific.
singlespeed
Well-known member
I'll ask if theres any pics of my engine with the head off, to see the piston crown and any valve cut-outs.
From what I heard long ago, I think its a flat crown with a couple of small cut-outs but can't confirm as I've not seen it
From what I heard long ago, I think its a flat crown with a couple of small cut-outs but can't confirm as I've not seen it
frediiii
Well-known member
12,7 is brave... Good luck 
singlespeed
Well-known member
The 12.7:1 Woosners have an intruder top to the piston crown -^- bit sticking up in the middle of the combustion chamber to reduce the volume. Because the combustion chamber is essentialy square shaped with the valves giving rounded corners>>
The bit sticking up, must be in the middle of the combustion chamber and also have cut-outs to clear the valves. So, the hill becomes relatively tall and probably jagged for the gain in CR.
I'm prety sure the 11:1 pistons are flat topped, so there isn't a big hill in the middle to interfere with the gas flow across the chamber when you have inlet/exhaust valve overlap and the piston is near TDC. Being flat, theres also less corners to become hot and, an you get an undivided volume of gas which should allow it to burn well.
Higher CR is good for both power and efficiency, but any gain from increasing CR with an intruder piston could be given back by building in a less efficient piston crown design. I'm not completely sold if intruders are realy the best way...
1. Skimming the head face will reduce the chamber volume as a whole(not just a bit in the middle). But it will also move the valves closer to the pistons by the same amount skimmed off. So, slightly deeper valve cut-outs may be needed so the inlet valves clear the piston around TDC.
2. If the pistons are still recessed in the cylinder bore at TBC. Then getting them flush or slightly proud (don't forget theres a head gasket to still give some piston/head clearance) would also increase the CR. Skim the top face of the block or changing the piston/conrod to bring the face up. Again, deeper cut-outs may be needed
The bit sticking up, must be in the middle of the combustion chamber and also have cut-outs to clear the valves. So, the hill becomes relatively tall and probably jagged for the gain in CR.
I'm prety sure the 11:1 pistons are flat topped, so there isn't a big hill in the middle to interfere with the gas flow across the chamber when you have inlet/exhaust valve overlap and the piston is near TDC. Being flat, theres also less corners to become hot and, an you get an undivided volume of gas which should allow it to burn well.
Higher CR is good for both power and efficiency, but any gain from increasing CR with an intruder piston could be given back by building in a less efficient piston crown design. I'm not completely sold if intruders are realy the best way...
1. Skimming the head face will reduce the chamber volume as a whole(not just a bit in the middle). But it will also move the valves closer to the pistons by the same amount skimmed off. So, slightly deeper valve cut-outs may be needed so the inlet valves clear the piston around TDC.
2. If the pistons are still recessed in the cylinder bore at TBC. Then getting them flush or slightly proud (don't forget theres a head gasket to still give some piston/head clearance) would also increase the CR. Skim the top face of the block or changing the piston/conrod to bring the face up. Again, deeper cut-outs may be needed
@benmc
to get an image of the woessner pistons: https://www.xrallyparts.com/PBProduct.asp?ItmID=3675944
to get an image of the woessner pistons: https://www.xrallyparts.com/PBProduct.asp?ItmID=3675944
mazmaz":qg4r1pgf said:
That´s clear, but the shape is more or less the same.... :roll:
benmc":qg4r1pgf said:
For such a high CR you need also the other components to take full davantage. I think the Woessners have been initially designed for the ClioII S1600 rallye Kit-Car. It had 220hp @ 9000rpm.....
not really
https://ey95.com/forum/files/0078_755.jpg
this guy replace is k4m (110) pistons by forged one
so the wossner probably look more like that (I guess the picture are the wossner)
https://ey95.com/forum/files/0078_755.jpg
this guy replace is k4m (110) pistons by forged one
so the wossner probably look more like that (I guess the picture are the wossner)