Intake Manifold Polishing Theory

[SVOboy]

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?

[diamondlarry]

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.

[iburnh2o]

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.

[GasSavers_Ryland]

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.

[SVOboy]

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.

[SVOboy]

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.

[Compaq888]

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.

[SVOboy]

Why though?

[Compaq888]

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

[GasSavers_Ryland]

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.