i have heard a lot of problems regarding the use of this type of exhaust port like the failure of the piston ring due to the overheating of the bridge. i just would like to know if i would remove this bridge (port it) will it weaken the structure of the cylinder? how about the performance?
butterfly type exhaust problems
- Thread starter makikulit
- Start date
makikulit said:
If you remove the bridge the continuous /exhaust/ port width will be too big, and the piston ring will foul to the port edge, and everything will damage.
There is no problem with the butterfly port, if the bridge is grinded a little bit, so it will be 0,05 mm deeper than the cylinder wall!
Hey Browni, how do you relieve the exhaust port bridge? On most sites I saw that they grind all the bridge wear surface for a bigger clearance.
Instead over here tuners make it rounded, so actually only 1/3 of the bridge wear surface gets in touch with the piston and ring.
Instead over here tuners make it rounded, so actually only 1/3 of the bridge wear surface gets in touch with the piston and ring.
roost said:
Sorry my mistake the 0,05 mm is an usual value (but I don't think much more bigger clearance is necessary), maybe some case it is bigger! And you are right this is rounded a little bit , not everywell, so it can help cleaning the ring groove!
I mean this:
Last edited:
No I didn't mean this. Here you go, this is a photo of my MHR;
http://fpp.hamradio.si/roost/pictures/bridge_relief.jpg
Sorry its a gsm photo.
See only the darker part of the bridge touches the piston and ring.
http://fpp.hamradio.si/roost/pictures/bridge_relief.jpg
Sorry its a gsm photo.
See only the darker part of the bridge touches the piston and ring.
roost said:
Oh yes I understand now!
Maybe this is good, cause the less friction! It's my tommyrot but I think this mean more surface stress in a concentrated point to the ring, so it will wear out sooner in that point!
Don't forget this bridge is for support the ring, if you make it sharp it will cut like a knife! And that thin coating is weaker too if you have a little failure it will fall off! Finally, I use little cooling bores on the piston where the bridge is, so I need a little gasket surface on this bridge (less pressure loss).
But as I said my therory is maybe wrong!
On the other hand the standard Polini EVO has a very wide bridge, so it need a little modification, but the other side is the Hebo Manston with a very thin bridge!
tiba_karotsu
OVERREV TUNING
i relieved mine as well, with the untouched bridge wear is more apparent on my ring & piston but i never tried drilling holes on the skirt to lubricate the bridge does it really work?
