Mira fräsning M20

Dragon · Post by **Dragon** » 02 Mar 2006, 10:33

Vilken vinkel på ventil/säte ska det vara?

stian329 · Post by **stian329** » 02 Mar 2006, 12:24

Søkte på "mira cut" på google:

If more horse power is your goal, then mira-cut and pocket porting might be one of your options. Mira-cut is a 3-step radius carbide cut system that machines a 90 degree cut down the side of the combustion chamber, radiused into a 15 degree angle, radiused into a 30 degree angle, radiused into a 45 degree (valve seat) angle, radiused into a 76 degree angle down into the valve pocket area. Then a pocket port is done with a carbide burr to hand shape the short side radius and bowl area to an exact shape. Then a sandpaper type cone is used to blend everything in. For every 1.4 CFM gain in cylinder head flow, there is a 1 horse power gain. Therefore, the more work that is done for better flow, the more horse power there is to be had

Dragon · Post by **Dragon** » 02 Mar 2006, 12:30

ska bara renovera toppen så endast en vinkel är det väl då?
De där kanske vore nåt för min turbo topp däremot.

bemmerfanatic · Post by **bemmerfanatic** » 03 Mar 2006, 22:01

stian329 wrote:Søkte på "mira cut" på google:

If more horse power is your goal, then mira-cut and pocket porting might be one of your options. Mira-cut is a 3-step radius carbide cut system that machines a 90 degree cut down the side of the combustion chamber, radiused into a 15 degree angle, radiused into a 30 degree angle, radiused into a 45 degree (valve seat) angle, radiused into a 76 degree angle down into the valve pocket area. Then a pocket port is done with a carbide burr to hand shape the short side radius and bowl area to an exact shape. Then a sandpaper type cone is used to blend everything in. For every 1.4 CFM gain in cylinder head flow, there is a 1 horse power gain. Therefore, the more work that is done for better flow, the more horse power there is to be had

hva betyr CFM??

Burn0ut · Post by **Burn0ut** » 04 Mar 2006, 02:01

bemmerfanatic wrote:
stian329 wrote:Søkte på "mira cut" på google:

If more horse power is your goal, then mira-cut and pocket porting might be one of your options. Mira-cut is a 3-step radius carbide cut system that machines a 90 degree cut down the side of the combustion chamber, radiused into a 15 degree angle, radiused into a 30 degree angle, radiused into a 45 degree (valve seat) angle, radiused into a 76 degree angle down into the valve pocket area. Then a pocket port is done with a carbide burr to hand shape the short side radius and bowl area to an exact shape. Then a sandpaper type cone is used to blend everything in. For every 1.4 CFM gain in cylinder head flow, there is a 1 horse power gain. Therefore, the more work that is done for better flow, the more horse power there is to be had

hva betyr CFM??

cubic feet per minute

Dragon · Post by **Dragon** » 06 Mar 2006, 16:27

Jajja får väl prova med 45grader eller nåt å se om de funkar.

Vipe · Post by **Vipe** » 07 Mar 2006, 19:53

stian329 wrote:Søkte på "mira cut" på google:

If more horse power is your goal, then mira-cut and pocket porting might be one of your options. Mira-cut is a 3-step radius carbide cut system that machines a 90 degree cut down the side of the combustion chamber, radiused into a 15 degree angle, radiused into a 30 degree angle, radiused into a 45 degree (valve seat) angle, radiused into a 76 degree angle down into the valve pocket area. Then a pocket port is done with a carbide burr to hand shape the short side radius and bowl area to an exact shape. Then a sandpaper type cone is used to blend everything in. For every 1.4 CFM gain in cylinder head flow, there is a 1 horse power gain. Therefore, the more work that is done for better flow, the more horse power there is to be had

Vel dette må man ta med en klype salt; bedre flow i en evt. testbenk betyr ikke nødvendigvis mer power.. :wink:

Som de fleste vet så er det ikke altid teori og praksis går hånd i hånd. Porting av topper er en hel vitenskap, og det finnes ingen 100% fasit på dette.
Skal man få mest mulig ut av en topp må det prøves, og feiles.
Men for all del, toppene til BMW, som jeg har sett, har som regel vært såpass "grove" at det skal godt gjøres at man ikke henter noen HK på en portjobb