port velocity

[transient]

I looked on howstuffworks.com but I couldn't find anything on it... I really would like to know how port velocity affects low end power. I know that faster port velocity gives better low end, but does anyone know why that is?

[yenpit]

give it a shot.....i asked my cohort-in-crime.....with improved intake ports (port & polish) there is theoretically an increase in flow....increase in flow means higher/faster port (intake) velocity. with higher port velocity more air flows into the combustion chamber. more air (oxygen) into combustion chamber the more combustion expansion. the more combustion expansion (explosion) the more power produced. that power translates into torque (low end).
how does that sound...??? uuuuuh huhuh.

[MingMing]

port velocity gives u mroe power all throughout ur powerband
just that port-n polish is more useful for low end, cuz thats when ur pistons hafta suck in the air
at high end, ur fuel mixture flows in with a lotta pressure, and so it can push itself in, and the smoothness of the intake isnt that important in high end

[transient]

So how does this relate to a smaller exhaust giving you more low end, or is that something alltogether different?

[allmotorKA]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from transient on 12:25 am on Nov. 20, 2001
So how does this relate to a smaller exhaust giving you more low end, or is that something alltogether different?</td></tr></table><span id='postcolor'>
The theory is that smaller exhaust pipes will have higher exhaust gas velocity at low rpm vs. larger exhaust pipes. The higher the exhaust gas velocity, the greater the vacuum that is created at the exhaust port... the result is that more exhaust gas is evacuated from the cylinder during the exhaust cycle which allows more fresh air to come in during the intake cycle. The most common problem is when the exhaust pipes are too small which causes a reduction or limit in the upper rpm and even mid-range rpm power.

[transient]

ok, that's what I thought, but I wanted to get some confirmation on it.

[zephyr]

did you know that apparently an e36 m3 engine is just an e36 328is engine bored and stroked and ported and polished? 50 hp difference...just interesting little rumours...

(Edited by zephyr at 7:18 pm on Nov. 20, 2001)

[MingMing]

<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=':p'> is the 328 engine is an inline 6
but the m3 engine
has 340 hp
the 328 ci has 193 hp
thats a lot more than 50
i'm sure its alot more than just port'n' polish

[konkman]

Before porting and polishing your engine there are alot of rough edges that slow the incoming are and causes turbulance. &nbsp;P&amp;P allow more air into the cylinders and creates a smother flow of air.