nates7

I searched but all the pics dont work any more. I want to port my UIM at the dynamic chamber and at the LIM but I am not sure on what it should look like. I looked at the thread in the archive but the pics dont work. So if anyone has pics or liks to good sites with pics of a ported s4 intake manifold that would help alot.

Hyper4mance2k

iTrader: (40)

TTT
what he said!!!

rotarygod

iTrader: (1)

Regardless of what anyone says, there are no gains to be had by porting an S4 manifold. If anyone says otherwise, ask for a dyno sheet. You won't get one. Butt dyno opinions are unreliable.

KarmaWeasel

Enjoy. I have more if you want but this is the best one.

rotarygod

iTrader: (1)

The throttlebody mod is a good thing but porting the manifolds is worthless.

tweaked

iTrader: (4)

Untrue. I love mine in my 88. I did make them bigger, but not much. I mostly just smoothed out the flow. I have never had that car dynoed, but the butt told me I did a good job. I also did the TB mod at the same time. but the gain was too good to only be the TB.
That car pulled very hard until I threw an apex seal. I still have it and it is on the list for a new keg next summer. I miss that car.
Glad i have spares

Hyper4mance2k

iTrader: (40)

ttt
so are there any pics of manifold porting???

oakback

What's your opinion on port MATCHING?

rotarygod

iTrader: (1)

Matching is fine but there is a better way to do it. You don't want a lip in the airflow that catches the air so people like to match them. The biggest problem is that people enlarge these holes out to the larger size of the gasket. Don't do this. All you've done is to create an area in the manifold where the air slows down from the area increase and then it has to speed up again. You actually want the lower manifold hole to be larger than the manifold section feeding it. You really don't want them matched at all. Don't even touch the upper runner hole. Only enlarge the lower one to slightly larger. With a little increase in area at the joint, it combats reversion since the air flows better into the manifold than out of it. Anti reversion is useful. Larger port runner area isn't. Read on to see why.

I still find it funny how I say porting manifolds is worthless and anyone that claims they are faster is wrong becuase butt dyno's lie. Then someone posts right after saying they are faster because their butt dyno says so! Proven correct so fast! I love it. Here's the thing about porting manifolds. People say a restriction is a restriction so making it larger is better. Not necessarily. If the part you are making larger isn't the restriction, it will only hurt you by reducing velocity. Your intake ports and engine intake runners are a larger restriction than the manifold runners. What good is making the manifold runners larger if the engine can't flow this much? You did nothing! Also remember that the single biggest restriction in the entire system is the air flow meter. At only 5 sq. inches of area combined with a spring loaded flap door across the air path, flow is terrible. People are so concerned with airflow when in reality making larger intake runnes is only going to hurt you in the low to midrange and do nothing on top. The manifold already outflows the air flow meter. The manifolds aren't a problem. The most improvement you can even get on the manifolds is around 10% more flow. This however does not translate into 10% more power or even 10 hp. If the air flow meter can't flow this much anyways, that 10% increase in flow potential is wasted. Instead of porting manifolds and buying S-AFC's to go faster, people should be saving up for a standalone ecu so they can get the most performance potential out of their cars.

therotaryrocket

What about on FD's people get their manifolds extrude honed and gain a lot of dynoproven horsepower...and if you put nitrous on a car with 1.5" exhaust piping which is already restrictive you still get plenty more horsepower so just because the mass air flow sensor is plenty a problem doesn't mean porting the manifold won't help. I really don't know for sure I just hate when people acting like ******** are right.

rotarygod

iTrader: (1)

I don't know how I'm acting like an ******* when I'm just telling the truth. I have a bigger problem with people who spread wrong information around and miseducated others. This is a high percentage of the threads in this forum. Look at exhaust design as an example.

Nitrous gives you more power because it gives you more oxygen and cools the intake charge. I've never seen an RX-7 with 1.5" exhaust piping but you can be sure that the gains would be bigger if the exhaust pipe were bigger. A 1.5" pipe would be THE restriction in the exhaust. There is no afm choking the flow more than this in the exhaust. However we are talking about the intake manifold and you've actually proven my point. The smallest spot is the biggest restriction and it is the only thing critical to more power. On the 2nd gen, your restriction is the afm not the intake runners. Enlargening them won't help you.

3rd gens aren't restricted by an afm. Extrude Honing doesn't necessarily make your runners larger. It can if you want but it is primarily used just to smoothen them. They don't have to be larger to do this. Show me a dyno of a 3rd gen that gained solely from Extrude Honing with no other mods. Since you can get different readings very easily on a dyno, the change had better be quite a bit for me to believe it.

Everlastingboost

so wouldnt it be smart then rotarygod to put a tII maf on for the the people that cant afford a stand alone? Just wondering because ive seen the insides of a t2 maf and its just a big ball looking thing in there that is pushed according to air flow right? Also if you can do this is there a write up on this, lol i know but ive wanted to this i just dont know how heeh. The throttle body mod is still a good mod though correct?

rs_1101

i do tentativley agree with rotarygod. making one part of the system larger wouldnt do anything, but i cant complain about port matching and actual smoothing of large burrs and solid areas. i dont know how far off our ports can be, but if theyre off.. no prob with smoothing it out. keep in mind however that the ever so popular knife edges actually dont flow too well. its the reason why airplane wings are rounded at the front and not.. knife edged. the edge creates a really strange series of vortices, and wont do much for flow, probably hurts flow by creating bad turbulence.
if you can imagine it, using a rounded edge, as air hits it, the air forms (itself) into a pressure knife edge and air then flows past that. using and actual knife edge, the air then creates two low pressure vortices on either side of the knife edge kinda like this --> O/\O and you can imagine how that flows..

Everlastingboost

so what do you think about the tII afm idea? I mean this should work right because the tII does flow better correct? Does anyone have any dynos of the car before and after porting of manifolds. Im trying to decide if I should do this i mean rotarygod makes a lot of sense and really seems to have a good graspe on this topic. Anyway let me know thanks.

rs_1101

when you consider how little restriction the afm poses, maybe you can see what rotarygod is trying to say here.

alwayssideways

what your talking about is the S5 Maf. which flows alot better than the s4. as fa as i know ( probobly wrong) but they are not compadable. Rotarygod is very right in this instance. the only way to really get any gain on the intake system of a 2nd gen rx7 is to eliminate or open the most restrictive part of the intake. which is the s4 Maf or AFM. the s5 is a little bit better but still restrictive compaired to the newer editions of mafs used on cars nowadays. Like Rotarygod said the only real way for a portmatch or porting the intake in any would be benificial would be to get a stand alone ecu and remove the AFM or Maf completly.

with that said and that situation in mind. and with the Maf gone . now look at what would be the most restrictive part. the TB and or the Ports. I would think mainly the TB in this case. but for the most part Rotarygod is correct.

rotarygod

iTrader: (1)

Don't think that I am against taking big burrs and casting marks out of runners. I'm not. Nothing wrong with that at all. Don't expect to be able to feel the gain though. There might in fact be a gain, but that wasn't big enough to make you noticably faster on it's own. My issue is with people who want to enlarge their intake runners to make them flow better but who still use the factory afm. The runners may have the ability to flow more air but it doesn't mean they will. It doesn't matter how little or much room you have in your bedroom if you can't fit the bed through the door! In this case it's the afm. Just by removing the afm with a standalone ecu, you can get over 10% more power. That's not even including tuning. I'm not necessarily saying that everyone needs to go out and buy a standalone (if you want full potential for your engine you do!). I am just showing how the afm is the restriction and how "every little bit" does not always help. It takes more than 10% more airflow to equal a 10% increase in power. If you have a 160 hp engine stock and you gain 10% more power, you're up to 176 hp. Alot of guys here kill for 5 more hp. People go insane by removing their a/c, power steering and air pump only to pick up a few horsepower. People add Pineapple sleeves to their engines when they don't do much. The rods in the airstream are too restrictive and turbulent for the sleeves to matter. At least an exhaust does give you good power. Porting the manifolds doesn't give you a 10% increase in flow though because of that damn afm. Making the runners larger only slows down the air velocity in the runners. This gives you LESS power. Remember, velocity over volume. Utilize what you have to it's fullest before you make it bigger.

The S5 afm supposedly has less total area than the S4 afm but flows better due to the conical design rather than the flat flapper door. I've never flowed both though so I don't know. There is a way to adapt the S5 afm onto the S4 cars with little effort. You'll have to run a search on that one but it was posted here at one time.

The T-II and n/a afm's may look the same and use the same plugs, but they are not the same. If you plug a T-II afm into your n/a, you will be much slower. I did this to my old n/a once when my afm died and ran around for a month clueless to why my car was so slow. I even dyno'd it. The car had all the usual mods including a header, no cat and a catback system, MSD 6A, intake, etc. The car did 108 on the dyno! That sucks. The T-II afm flapper foor is no larger. They are the same size. Each unit has a different part number though because the spring tension on the flapper door is different. The T-II has more resistance. This is why my car ran like carp. The a/f ratio was all wrong. Even if it did work good, I couldn't get more power than the stock afm because the flapper is the same size. It does not flow more. Look at the inlet size of the T-II stock turbo. Compare it in size to the flapper door. A turbo can force more air into the engine. An n/a can't.

Carl Byck

So we are clear, this applies to stock AFM equiped cars. What about a stand alone controlled car. It seems quite a few guys are using RE motors for better flowing manifolds, right??? Anyway, port matching makes sense to me, enlarging the runners upper, and or lower without understanding fuid dynamics is potential more harm than good. Could someone who ghas done the porting on a system that can take advantage off the larger volume post pics of what they did? Thanks, Carl

rotarygod

iTrader: (1)

Yep Carl, that is my whole point. Not on a stock afm equipped car.

Everlastingboost

ok well thanks for clearing that up i really appreciate someone dropping knowledge, i know i neded it heeh. Im going to research the stand alone units a little more. What would be the best option for me(broke college student) with no real experience in tuning as far as stand alones go? What would be the best priced option. I probably wouldnt want to spend over a grand on this. I would also need a aftermarket igniton setup as well correct? I dont know if its even worth it, i mean for the money im putting into this i could just as easily turn around and sell my na, get a tII. Then put the money i get off selling my na towards a tII.....hmmm choices choices. Maybe ill just sell it and get dsm lol. later

pengarufoo

I recommend port matching the manifolds but all while keeping the cross sectional area the same of the mated runners. The stock manifolds that I have worked with all have an increase in area right at the mating surface, I presume this is to compensate for manufacturing variances. If you want to port match the manifolds it may require adding material near the mating surface inside the runner before you begin porting it out to a common size among the two manifolds. (best way to do this IMO is with a aluminum-capable welder)

you can use ID calipers to compare the sizes and come up with a plan to get a constant area across the junction.... the runners overall should however be tapering down in diameter progressively from the throttle body down to the engine ports so the charge gets accelerated on it's way down, so keep this in mind when modifying the manifolds. If you find the outlet side of a manifold has slightly smaller ports than the inlet side, DON'Twork towards making them the same size by porting the outlet side! There should be a smooth reduction in size, just try to make the regions where the manifolds meet up smooth without making them fatter than the area before and after where you are porting.

There is also another issue here, if you work towards matching the ports exactly together, without taking precautions you will likely have issues getting the matchup to be reproducable. There is some slop in the bolts/studs when they are inserted into the manifold mounting holes.
If you get perfectly matched ports, they will only all be matched in ONE orientation, this orientation cannot be reproduced consistently when your bolt holes have slop in them! The way around this, is to add one or more dowels to one of the manifolds' faces. As long as you make the receiving side of the dowel a tight fit, you now have a reliable reference point for making a pattern to match your ports to. You will have to reproduce the holes for the dowels on any gaskets you use, being careful to match the gasket to the ports also! I suspect the primary reason why the OEM manifolds have an increase in area near the faces is to compensate for the slop in the bolt holes, anti-reversion affects may also have been a reason but I'm not sure on that.

rotarygod

iTrader: (1)

Since it was briefly mentioned, for anyone interested in attempting an S5 to S4 afm swap, here's how to do it.

alexdimen

iTrader: (13)

this thread is officially hijacked... what happened to posting pictures?

nates7

holy **** I thought this thread was long gone! but anyway I port matched the manifolds and I dont want to say it but damn it was a waste of time. I dont know about the true gains dyno wise but my *** dosent feel anything. Im the kind of person that if I dont feel its not worth it. The main thing now is finding a cheap way to operate my 6 ports. O and if you do port the manifold dont use that drill bit it takes to long and it is to easy to make mistakes..

rotarygod

iTrader: (1)

That's the first truthful claim I've ever seen about manifold porting results on an essentially stock car!