Intake roughening or polishing??????

Nemesis

Member
Messages
9
Location
Estonia
Hi, this is my first topic in this forum :) (don`t count the introduction)
I am planing to resurface the engine ports on my new model.
So i was thinking about engine theory. There is no question about the exhaust, polish all the way to help the flow, but what about the intake. I`we looked at some of the aftermarket headkits and motors, they all have intake polished.
I know that in 1/1 world only very very high reving motors(blown) have their intake polished, but most of regular preformance engines have intakes roughned. You might ask why: thats because polishing of the ports causes the fuel to set out from the mixture and you only benefit from polishing in case of realy fast flow of mixture.
In 1/10 GP onroad the roughening is allowed but the maximum width of one grove is 0.5mm and those are really high reving motors!!!!????
So what roughneing does? As much as i understand it helps the gas and air to mix by creating small "twisters" in ports and creates more even burning. The small matter of lost flowspeed isnt that crucial than a goof mixture.

So guys whats your opinion, how it would work in large scale engines?? Which way should I go???
Maybe somebody has some experiances???

PS:Sry if i used some incorrect expresions and words, i`m no native english speaker.
 
Last edited:

Timmahh

Bajastafarian Madnes
PLUS member
Messages
3,376
Location
Michigan
Intake should be roughened to help atomize the fuel mix. but you can be too rough too. its a fine line between good and bad. 2strokes depend a good deal on the atomization of the fuel. the roughness of the intake helps to deterimine the amount.

Look for any information on Porting the intake. JimsBoatDocks has alot of this info on it. Look over at the sister site www.hpibajaforum.com and search for threads on Porting, and especially threads/posts by member ESP. Doug (ESP) is an outstanding 2 stroke motor builder and has Mucho knowledge and experience.
T
 

Nemesis

Member
Messages
9
Location
Estonia
Thanks for the answer i will look up those threads.
I did some more resrearch on this topic myself. It seems that polished ports start to work in case of realy high airflow (250-300cfm). For instance regular street 1/1 engine only produce around 60-80cfm. I think that our engines are about the same so roughening seems to be the way to go.
I was thinking of doing roughening with 400 grit.
So all the polished aftermarket headkits lose some of their preformance because of polished ports???
 
Last edited:

Timmahh

Bajastafarian Madnes
PLUS member
Messages
3,376
Location
Michigan
not sure. im not a builder so only know the basic stuff with these motors.

I do know there is a limit to how much porting (size/shape/material removed ect) before performance starts to drop. Port Times is Critical in these small motor, and the timing is determined when the piston start to close off the port during the revolution. take off too much material on the intake, and you could change the port timeing enough to much up the performance and even the way it runs.

but to just take something and roughen up the surface shouldt be a hard thing to do or mess anything up. but like i said, im not a builder and im only thiinking outloud!!!

T
 

bigmodman

Active Member
Messages
26
Location
mckinney tx
well to start what are you lookin for????torque or hp??????for torque you would need to leave it rough and for hp you would need to polish it.hope this helps
 
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