I'm going to be porting my throttle body, UIM, and LIM here pretty soon, and I was gonna see if anybody had any input. My plan was to smooth out the corners in the metal on the TB to make it flow better into the TB. For the UIM to LIM I was going to scribe out the lines for the gasket, and open the ports up the same size. I can't port far into the manifolds, as I only have a little die grinder, but I'm supposing that just matching the port openings makes a difference. Any advice is always welcome.

I want to do this too, I don't want to screw up as i don't have a backup.

the tbody part sounds good, but on the intakes i think you want to remove the imperfections, more than porting it. kinda like if you got a perfect casting



mike

If you matched the intake exactly to the engine would you not have more intake charge reversion? Thus cancelling any gains you make?



J

see thats one reason i would just remove casting imperfections. the factory guys know more than i do



mike

I heard that is a bad idea. Can't remember why tho. https://www.nopistons.com/forums/pub...IR#>/dunno.gif

I really don't know how it all works. I just thought that you wanted all the runners to line up perfectly.

Not always, and it's because of charge reversion - this is more important in the exhaust system, where you never want the header to flow continously out of the exhaust port, you want a step up in diameter to help keep the exhaust from "backing up" and contaminating your intake charge during the overlap period. On piston engines some people use the same principle in the intake manifold but since the rotary flow characteristics are rather different I'm not sure which approach would be better for the intake.



J

Where's the judge when you need him? https://www.nopistons.com/forums/pub...#>/biggrin.png

considering NA intake manifolds are easily found, it can't hurt to experiment if you're willing to waste the time, documenting the results would be useful for others.

i think that matching the ports on the uim and lim only about a 1/2 an inch down would not cause inlet charge reversion...porting the entire manifold on a N/A motor will have detremental effects..think of sucking a milkshake through a 2 inch wide straw...then suck it through a 1/2 inch straw :bigok:

I tried to pry this info from crispeed once. didn't work :( all I got was there is a lot of power in the intake manifold. I wanted to know what to port and how ect...

I just briefly spoke with Steve Kan on AIM, and he said that it is a good idea, but not to go overboard. I asked him what overboard meant, and then he logged off. I'll seek clarification next time he logs on.

I dunno, if you are running a ported motor it might be more like sucking a milk shake through a coffee stirrer.



I don't see any harm in matching the manifolds and smoothing out any imperfections in the castings (there are alot, my s4 manifolds were pretty nasty). One thing I noticed is when I got my housings back from mazdatrix the ports on the outside were larger than stock also, not just the ports on the faces. I port matched my LIM to these ports as it made no sense to me to have these ports larger if my LIM ports were significantly smaller than them, that difference is not good for flow or velocity... So I've tried my best to match them all up and smooth it out, the junctions should not have large abrupt differences in shape and/or size..

i agree 100% as well. i do not think that with your intent, your actions will be detrimental to your performance. the casting on these manifolds is soo sketchy, it cold not hurt....i mean, it is good to increase the flow charachteristics of anything, to a certain extent....but it is when you think too big that you get into the reversion affects, and you have the exhaust flow and backpressure travel issues....

Help me understand this reversion a little better. All I'm talking about is matching the runners at the UIM to LIM connection, and maybe the throttle body. The runners will taper back to their normal size long before the LIM to side housing connection.

Then you should be all good, thats what i plan on doing.

Oh yeah, I misunderstood - I thought you were talking about matching the intake to the housings. No risk whatever in doing what you were considering.



J

I have some 6" long carbide burr bits I use

I just saw this with my name mentioned :-D Here're the reason why you have to be very careful when porting your TB or LIM in a FD. The wall on the TB is very thin and is hollow inside. You don't want to go too far with it or you'll have to trash the TB. I had one done for experiment and went a little too far. As for the LIM, if you ported too much, you can crack the wall adjacent to the EGR which could leak air or suck dust into your motor. You just can't go too extreme with them or you'll end up trashing it.



Hope that helps