Intake Manifold Polishing Theory

[SVOboy]

I was asking why just polish the exhaust.

Also, the vx flywheel, it has been confirmed to me, is 15 pounds, rather than a stock 18,

[GasSavers_Ryland]

I guess I was wrong on flywheel weight, altho, then why would you want a heavier fly wheel on your engine then? if a light fly wheel is good for proformance, and a light fly wheel is good for ecconomy... then a heavy fly wheel is good for...

[Compaq888]

longer coasts. The lighter the flywheel the faster the revs fall and go up.

[SVOboy]

There really is no reason to want a heavier flywheel except for ease of drivability because of the revving.

[molecule]

i use a fidanza 6lb flywheel...its pretty touchy at first
after 2 years...i'm used to it...
its less rotating mass...
belive it or not the civic cx has a unique stock lighter flywheel than other civics...the rest are the same in each gen...

the king of intake design as the OP of this thread i believe is doing
increasing port velocity...yeah this is motorcylces...but for all intents and purposes...it works for us mileage makers...

http://www.mototuneusa.com/

anyone have any pictures of the honda civic vx intake ports...?

[thisisntjared]

yea thats what i was going to suggest. more velocity is what are motors need with the intake ports when under low throttle positions. but i definitely wouldnt want to do that.... and yea the z1 ports are uber small.

as far as efficiency goes, more power can be taken from the amount of fuel burned if the exhaust side is tampered with. remember the design of the motor is to provide a flexible amount of power across an rpm band and throttle position range. if you modify it to be more efficient with a lower rpm range and a more 'gentle' throttle position you will see more fuel efficiency in weak sauce driving....

[SVOboy]

For us n00bs, you need to explain the modifications on the exhaust side of things. Preferably while the exhaust I'm going to swap is sitting in my garage.

[molecule]

i agree
though its a stab in my throat...
thats my entire career...
LOL !!!

brings up an good point though
each cars purpose will likely have numerous beneficial mods that wont be good for another...

of the head porting i have been schooled about
polishing the exhaust ports has only a 1-2 hp gain...
its usually done to just clean it up before her first run

exhaust backpressure is the turning/tuning point
how much scavenge is ideal for your motor
motors reburn fuel from backpressure...
backpressure is vital to any non-highoutput motor
F1 (F one) is a different story...there is no backpressure...
all the power comes from the injected fuel or however they get it in there...
one of the reasons you wont ever see flames coming out of tailpipe of an econo car...its reusing the fuel...

[thisisntjared]

haha and it has a cat

im a n00b, too, in such respects, all i know is a few things in theory.

heres a little bit more to chew on, the major of the power gains on the intake side are realized because more air(and fuel) are able to be crammed into the cylinder. thus for us mpg nuts the only things that really matter are how the air/fuel mixture enters the cylinder with the rich and lean areas etc.

with exhaust however, things become more complicated, as the exhaust gains velocity leaving the cylinder, it will actually suck the piston up if the head/header is designed properly, thus creating a little more power in a very different way. however techniques in maximizing this effect are beyond me. it has a lot to do with primary(and secondary) length, thickness and to a lesser extent, tappering. also some simple things anti-reversion tricks will help. but mostly, the key is maintaining the 'ideal' exhaust velocity, whatever that may be....

[molecule]

just one of my experiences along the way
i put a 4-1 dc header on my stock vx
i could barely accelerate to get into the higher rpms
i couldn't maintain highway speeds in 5th gear