Intake Manifold Polishing Theory
 

Part I:

The way I understand it there are two things that are key to a good FE intake manifold. The first is long, narrow runners, and the second is air velocity.

The runners will be dealt with in part II, with my ideas, anyway:

Increasing the speed of the air charge increases turbulence in the combustion chamber, which allows for better mixing and combustion. Would it make sense then, not to port, but to polish our intake manifolds in order to facilitate high speed air flow?

I'm not real sure about
 

I'm not real sure about intake manifolds but the head on my car is being modified, as we type, to increase velocity. The opening on the outside of the head will probably look stock but by the time it gets to the combustion chamber it will be smaller. The intake ports will be completely filled in then material will be removed so that they will basically look a funnel. Since the piston will try to draw the same amount of air through a smaller hole the velocity will significantly increase. Along with these mods, the combustion chambers themselves will be polished so that there won't be anything for carbon to build up on and cause detonation. My compression ratio will go from stock 9.5:1 up to 10.5:1 or more but I should still be able to use 87 octane.

Polishing is good for
 

Polishing is good for combustion chambers and exhaust ports but should be avoided on the intake ports due to fuel puddling. ie: take some rubbing alcohol and put a drop on glass and it will cling to the glass as it rolls down. Then put a drop on sandpaper/emery cloth...it rolls right off. check out metricmechanic.com and look into his surface turbulance patent info. Flow actually increase with a rough texture on the ports as vortex's are generated as the air flows over the sides. Larry's head is getting numerous modifcations to increase velocity and aid vaporization and burn. One head was recently put onto a 2.2 Lebaron turbo and mileage went from 26 in town to 33 and its still running WAY too rich with these head mods. Power is also up noticeably. Due to owners request compression is lower than stock which is actually hurting mileage and low end torque/response. Larry's head is getting those mods along with some others that should result in better numbers across the board. The intake is undergoing mods that we hope do more yet. Once tested we'll be sharing the info.

in carburated cars you
 

in carburated cars you wanted the rough texure of the intake manifold to help cause turbulance to help mix the fuel/air, with fuel injection polishing seems like a good idea, another step that is not quite porting, I'm not sure what it's called exactly, is basicly matching the opening in part "A" to opening in part "B" an extream example of this would be if you had a round opening in your intake manifold, and a squar hole in your head, you would want to modifiy those to openings so the flow between them was as smooth as possible, of course without taking to much metal... I supose to a point that is what porting is, only in extream cases porting would be boring out the entire passage, mostly you don't want obstructions, or steps that cause turbulence... and on the flip side of that turbulence helps mix the fuel, so a smoother air flow befor the fuel injectors is going to be most helpful, or at least that is my oppinion as Click here
shows that turbulence inside the combustion chamber helps to improve combustion.

Ryland, I think what you are
 

Ryland, I think what you are refering to is port matching. My head has a very rough transition because the IM ports are so much smaller than the head's. I couldn't possibly pot match though because the difference is greater than the amount of metal in the manifold runners.

Oh, and to iburnh20, I see
 

Oh, and to iburnh20, I see no problem with puddling gas because there is no gas in my intake manifold at all, and I do believe the great majority of the people on this site are all fuel injected.

the best option to do is to
 

the best option to do is to make sure the exaust stuff is smooth, not the intake.

Like I said before try using lighter engine parts. Especially the valves.

Why though?
 

Why though?

if the parts are lighter
 

if the parts are lighter they will move more freely. Which means better fuel economy.

that is part of the reason
 

that is part of the reason that pushrod engines are not ideal, more weight moving back and forth, each part working agenst another part.
that is why I am thinking of looking in to titanum valve keepers, only thing keeping me is the price, titanum valves, and springs I'm still a little iffy on, as steal springs are going to last longer, but the keepers on top of the valves weigh something and are alwas moving.
the only part of the engine that I would hesitate about removing weight from, would be the fly wheel, as the more efficent the engine is, the more the fly wheel seems to weigh, the insight got around this by useing the motor as the fly wheel to dampen the engines variation in speed between the power stroke, and the compression stroke.

I was asking why just polish
 

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, :)

I guess I was wrong on
 

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...

longer coasts. The lighter
 

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

There really is no reason to
 

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

i use a fidanza 6lb
 

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...

https://www.mototuneusa.com/

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

yea thats what i was going
 

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....

For us n00bs, you need to
 

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.

i agreethough its a stab in
 

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...

haha and it has a cat
 

haha and it has a cat :p

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....

just one of my experiences
 

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

Because it had too much high
 

Because it had too much high end bias?

What is your opinion on me using that cx/vx exhaust on my d15b2 in terms of mileage?

first thing i would do is
 

first thing i would do is measure with a micrometer the port width openings and MAKE ABSOLUTELY SURE that cx exhaust manifold is not a step-down in size...

that would be really bad...probably too much reversion...lack of escape...higher temps...etc...

i dont think it is...but i have never measured...
other than that...the cat is great for the environment...
and it seems to be a good design that has stuck with the economy civics thru 2000...

Did the hx have the same
 

Did the hx have the same design? Yeah, I figured that cat alone would be a good thing about it, also the o2 sensor would warm up a lot more quickly.

Right now I'm wondering about some cat insulation I saw a while back that keeps it warm for 24 hours to reduce start up emissions.

the dc 4-1 header on the z1
 

the dc 4-1 header on the z1 has too much highend/wot bias. remember, the section of the rpm band controls the frequency the gas is pushed ,which indirectly effects the amount of gas. while throttle position decides the amount of gas pushed. the z1 has super small ports and the header is just too large for while in the primary cam. do you follow?

GENERALLY the shorter the primaries and secondaries the lower the intended use in the rpm band. which is why your super expensive headers have adjustable primaries, so that you can tune it for the power band your aiming for and harmonize the lengths of all the primaries so the exhaust flows through the collector sequentially. also the thinner the pipes, the less gas is intended to flow.

google 'anti-reversion' for a little help in understanding some of the tricks with stepped primaries and things of that nature.

I just have trouble
 

I just have trouble following the differences in the frequency **** for intake and exhaust, *shrug*

When I get the superMID we'll see some good exhaust ****.

intake
 

With FI the smoother the better as it minimizes the surface area and keeps the air cooler - my xB has plastic intake manifolds that are extreemly smooth and thermally insulating from the engine block temps all adding to more power and MPG. Raising the compression is going to help the most.

The plasticness of the
 

The plasticness of the intake manifold could only hurt FE as I see it, since a warmer intake charge is generally better.

Hence the reason honda people cut off their coolant to the IM and use insulating IM gaskets in order to squeeze more HP.

weird
 

Not with this engine - seems a lot of people are adding cold air intakes and the engine doesn't run right. I get pretty poor mileage when very cold but too hot is bad too - this engine has high compression ratio. Better not to second guess the people that created the motor.

I'm not second guessing
 

I'm not second guessing them, but the fact nowadays is that most engines are designed for power.

I think they knew what they were doing, just that they were doing it not for MPG but for power.

ok
 

OK then I guess I should play with a warm air intake - as it is, it takes the air from the left fender under the hood next to the battery to the side of the radiator. I can monitor the intake air temp with the ScanGauge so adding a little ductwork to get some air from the rear of the engine near the header should give some different results. Might be cool to increase the MPG even more ha ha ha!

You should try it at least,
 

You should try it at least, you're car might doing timing **** but you never know until you try with different cars and all that business.

I don't have an easy way to
 

I don't have an easy way to check the temp on my civic VX, but the stock air intake is taking air from a little to the right of the top of the radiator, and then of course the throttle body has what looks like the hot side of the coolent line running thru it, I'm told to prevent it from icing up, the whole intake manifold seems to stay pretty warm.

if you really want warm air intake something to think about might be the warm air intake design that older carburated cars used, they have a little vaccum "motor", and a theromostat valve that sits in the air cleaner houseing, right on top of the carubrator, when the air is cold, the valve closes, and the "motor" opens a flap that lets the engine pull air from a cover that goes around the exaust manifold, it's one of those things that if you buy a carubrated car, and the owner says it has a hard time running in cold weather, look to see if they removed this "useless" piece of ductwork, I've seen countless cars on Ebay discribed as only likeing warm weather, and you can see this duct missing in the photo.

yea, the xb has that
 

yea, the xb has that composite intake manifold, and i want one!!

i think when the air/fuel mixture gets warmer or colder the motor adjusts the timing and you get different results and if its two warm the timing is thrown too much because of the cr, as previously mention, either way its pretty interesting...