I am practicing my porting techniques and trying to build up some skill before doing my real engine plates before an upcoming rebuild. Here is my progress so far, what used to be a six port primary port.



I would do a couple things differently next time around, mainly not getting into the oil control ring track. I would also not go down nearly as far because this port's area is more than the runner leading up to it, meaning that it would not help flow any more air than a port with an area matching the runner cross section. It might slow down the incoming air, which is not good. Everything in the intake system should be balanced so that the airflow slowly accelerates during its path from the throttle body to the combustion chamber, and a port that is too big for its intake manifold and runners would be pointless.

It is amazing what can be done to an intake system to improve it.

 

Just for reference, here is what the stock primary port looks like:



It is a little on the small side and not very smooth. This is a short duration port created with the intention of making a driveable car with decent low-end torque and good fuel economy. It is also designed to be quick to manufacture, hence no smooth bowl like the professional ports you might see from time to time. This type of port seems to limit the top end a great deal. I remember this car driving great until I expected it to take off above 4000 rpms like my Acura's 16 valve B16 engine likes to . . . hopefully a good street port will make it happen in the future.

 

I just did pretty much the same thing. If i can find a camera I'll get some pics up. I did go just about as low as you did , but as you said it doesn't really matter. I realized that as there was pretty much a 90 degree bend, so I did the best I could without going too depp and took out some metal as too make the turn a lot more gradual.

It doesn't look like your going to have the port open too soon, which is also what I did. I didn't even really touch that part, overlap is bad and I don't want more of it.

Also if you grab an end plate with the gear in it and lay a rotor on it in the right position you will be able to determine a lot. For example I noticed thaton the bottom of the port it cuts in quick towards the oil seal. If you put a rotor on there in the roght position, you will notice that the area at the bottom is covered by the rotor the whole time.

Not trying to tell you what you did right or wrong, because I really don't know what is right and wrong. Just rying to give you some more insight. Good luck.

 

Yeah I realized that no port area is gained by going into the oil track about a month after I started porting this plate. The real magic in S4 NAs is the aux port and sixth port. I am not yet ready to go after them.

Looks like 1% of us FC owners actually port our own engines. What a dying art.

 

Okay, with that porting experiment completed I decided to try a different style of port. Here it is so far:



I found some pics of ports done by Racing Beat and Mazdatrix and they both have an outward curve at the top which my first port did not have. So I tried to do that with this port.

 

Well I think this is the shape of port that I will settle on:



I looked at it while rotating an old rotor around inside an old housing and it opens nice and quick but closes gradually. When I sprayed some compressed air through the runner, the air flowed out the nose of the port toward the opposite end of the combustion chamber, which was what I was hoping to achieve. I am trying to angle the incoming airflow into the direction of the combustion chamber's movement as the engine runs.

Here is a shot of how it will still flow air even as the port is nearly closed:



Come on guys! No one here has ever thought of doing their own design street port?

 

I think about it every damn day.

I got a spare motor that's lost compression and I plan on toying with the side housings. Learning about the intake overlap and such.

Unfortunately the spare motor is still in an FC.

I would like to customize some type of design for any type of porting that may happen in the future on another car (or my GXL should she decide to cough up on me - seems unlikely to happen anytime soon. )

 

I thought about doing it, and then..... I DID. Did a couple practices on some POS irons and then did the final ones. Mine is a TII though, so I don't know much about the 5th/6th ports or anything. I tried to do it straight accross on top; its supposed to yield more high end hp but less midrange. I did this in conjunction with very mildly ported primaries to help keep some low end, then went wild on the secondaries. I'm finishing up the engine tomarrow so we'll see how she does...

 

Yea this stuff takes practice! I need more fuxored housings!

 

yea, a dying art indeed.

 

I'm trying to learn more about port design before I just go blindly cutting into a housing. Learning more about the internals of the motor itself will also help. Like for example in the first post I dont understand what he meant by not going into the oil control ring track.

 

It is the circle in the middle of the side housing. Not the hole cut in it but the circular shaped wear mark. This is where the oil control ring slides across when the engine is running.

 

ahh, I see. I cant really tell you got into it that much from the first pic (maybe its just my eyes or the pic). I see what you are saying about the area matching the cross sections though. From studing pics I've seen I too have decided that once I start my port job I'm going to "angle" the end of the port for better flow characteristics. This seems to be the norm in performance ports that I've seen If anyone has anymore info on porting and what not please post it. Even up to the types of porting tools and skills used. I'm trying to take in as much knowledge as possible first. (of course nothing teaches better than experience)

 

It looks like the subject of porting is not discussed much by those who have knowlege of it, or at least not on the second gen specific board. Well, I will join the rarified group of porting rotorheads and show some more pics.

I spent the last couple of days doing my secondary and sixth port on one of my real plates to go back into the engine. In other words, this was not practice; the pressure was on not to let the dremel jump out of the port and take a walk over the side housing! Here is what I came up with after about three hours of grinding:



This is a comparison shot between a stock housing and my ported housing. There is not much material to hog out on the secondary / sixth ports because their timing is already fairly large. I did open both of them a little eariler (ground toward the outside of the housing, toward the corner seal track) and took the nose of the secondary port way out as far as it could go while giving it that convex arc right before its exit into the combustion chamber that I did to my primary. I also ground up on the primary a little, taking care to leave enough metal in the side seal bridge to give support to the side seals as they pass over the partition while in motion. I also took the sixth port up and inward and did a lot of shaping under the port opening. I will install pineapple sleeve inserts and shape the sleeves to blend in with the port opening.




These shots show my final ports, center and end plate. I will trace templates of these before I assemble the engine just in case the ports turn out to give good performance. That way I will know what shape I had to make the engine the way it was, in case I ever port another rotary.

If anyone is wondering where I got my info on porting, it came from a few reliable and experienced sources. In other words, people who have ported a few engines themselves.

 

Looks good, real good.

Again somewhat like what I did. In your pic i circled red where we had the major changes. I had the 6th ports open earlier, I think. I didn't jut out as far as you did on the secondary. At least it doesn't seem like it because I followd with the bottom part of the port, not just the top.

Also on the secondaries I went just a little lower. All in all seems like a good job.

 

Ha ha, cool. I love how there are so many parameters to change when doing ports. I tried blowing through the ports when they had gotten some iron shavings in them to see how they sprayed out of the port. The primary ports seemed to direct the shavings out and up toward the top of the plate while the secondary port sprayed the filings straight out in kind of a mild fan shape. The sixth ports did not flow at all; the difference was dramatic. I need to get some Pineapple sleeve inserts, install them in the sleeves, and then port the inserts of the sleeves to form a bowl shape like the other ports. I was surprised at how poorly the sixth ports flowed; no filings ever made it out of the sixth port when I blew through the runner. It appears that bowl shape plays a big part in the flow characteristics of the port.

 

yea, I flushed the shavings out with a hose. Noticed that I really need those pineapple inserts. It just dead ends. The other ports pretty much just shot up and out. I was pleased with the results.

 

Has anyone every tried to do a bridge port of sorts? I'm still not in the "position" to port my own just yet (time is coming very soon). I want to take a look at a few more things before I take it apart and go to town. I'm studying 1/4, 1/2, and full bridge setups right now. I don't want a full bridge (it will remain my daily driver), but I do want to learn more about the advantages and disadvantages of the style of port itself. The 1/4 bridges really interest me (especially for something like the aux port...high velocity and more area). I'm glad that there are people who still have interest in porting their own stuff. You guys keep the flame kindled...can't wait to see what kinda results you guys get.

Good luck,
Kiyo

 

Oh yea...keep the pics coming! Talk is not very useful (but still GREAT) w/out showing pics if possible.

 

Personally i don't know much about dridge porting, I would like to try it but now is not the time.

As soon as i can get my hands on a camera i will post pics of my porting.

 

*starting to feel slightly post whorish right now*

Also 88IntegraLS I like the 2nd port style that you did on the primary port (the "ramp" effect), it's something that I've thought about quite a bit. Glad to see it actually on a housing .

On another note...I've always wondered what would the results be like if you did a rally port (large port) on the primary port only, AND just touched up (not really touching...mainly just polishing and giving the bowl effect) the 2ndary and aux ports. Or even doing the same and putting a small bridge (1/4) on the aux ports (maybe 2ndary). The 2ndary and aux ports are already of a very nice size so there's not really much you "want" do to to those, but the primary definately hurts the top end very much (but gives a very nice broad powerband which is what we all need anyway). If the primary was larger how much would the low end be affected (of course none of this takes into account the intake and exhaust mods you have done on the car...it's better to NOT think about those until after you find out what the ports will do...they just compliment/better what you've already got).

Hell...another thing is what would happen if you just touched up (not enlarged) the primary ports, but added a 1/4 or 1/2 bridge (which would in turn be better for the street since it's really the EXTEND port AND bridge port that kill the streetability of the engine). Since you still have the flow of the stock port (good velocity) and you've added the bridge (also good velocity since it's small) how would that effect the engine. I've heard of a few people doing this over in the aussie forums (you can learn much from reading over there...of course be wary of what you read/take to heart ) with very good results. Okay...I think I'm done for now

 

I dunno what it would do in terms of driveability, but you are going to have a hell of a lot of overlap. That is why I considered doing only the auxs.

 

Going big on the primary is said to hurt the low end and gas mileage. That is why I did my primary small but with the ramp to create late closing without making a large opening. Remember the runners leading up to the primary if you do a large port there; the runners are small and would need to be enlarged if you did any kind of radical enlarging on the primary. You are right, there is not much enlarging possible with the secondaries and sixth port. It is mostly bowl work with some timing work to open them earlier and create the bevel (ramp) on their closing sides to help flow air while the rotor is about to close the ports.

I basically did my second port all up and outward toward the corner seal track and didn't go down at all; I just kept the stock round bottom of the tiny stock primary. I was hoping to create more duration but to direct the airflow up toward the top of the housing so it wouldn't flow directly into the airflow from the secondary port, which would be across from it in an assembled engine. This way when the engine is at large throttle openings, both ports flow into different areas of the combustion chamber (primary up towards the top and secondary straight across into the bottom). Theoretically, this would prevent the port flow from colliding in the combustion chamber, reducing the chance of creating slight backpressure in the ports and reducing their flow.

I am not (yet) an engineer but put some thought into the ports. I also mirrored the philosophy of my mentors who helped me (and have quick NAs themselves).

 

Amen on the port flow ideas (don't think that too many people think about the collision in the ports). I agree that the larger primary port would definately hurt the low end also (just and idea or a thought just to see what the trade off would be). The biggest problem with the full bridge ports is not the bridge itself it's the larger primary port that goes with it. Lots of the people on the aussie forums have done bridges w/out making the primary port larger so that you don't have the huge low end loss (of course there's still a bit of one, but not that bad). It'll give you a nice broad powerband since you have high velocity in the little port as well as the primary port. Can't wait til I have more than one engine to work on and try some things.

Question though on your porting theory...do you port to match what you have intake and exhaust wise...OR do you port and then tailor your intake and exhaust to what you've ported (you yourself not in general). I would prefer to tailor things to what I've ported instead of the former...better results I would think.

 

I would say neither. I port to make the ports flow and then do the same with anything else related to fluid dynamics in the engine. I will port my exhaust soon and completely remove the sleeve and diffuser. Then I will coat it with a ceramic coating. I don't really worry about the limits of the intake manifold or exhaust because that will be able to be fixed later if they prove to be too restrictive. Noise is one concern I have and headers make a rotary loud. So I will be using my stock main cat and mufflers, perhaps even with some glass packs welded in between the two on the Y pipe segments.

Intake and exhaust are complex due to pressure wave tuning and velocity scavenging. Dirt bikes with high power two stroke engines have "tuned pipes" that bounce the exhaust waves off the exhaust port at just the right time to push air / fuel that would have flown out the exhaust back into the combustion chamber. Though this is not possible with a rotary it is possible to set the pressure waves (by the distance of the first restriction and header collector) to be at their minimum when the exhaust port is open and at their maximum when closed. You can only tune for one frequency, however.

The intake manifold is tuned this way but also takes into account the pulsing nature of the engine's ability to ingest air. When one intake port closes it causes a pressure wave to form and reflect back up the intake runner through the manifold. This is harnessed by the "u" shaped paths in the stock intake manifolds to allow this reverse wave to arrive at the other housing's intake port at the right time, forcing in more air / fuel. Velocity and runner size are important due to inertial scavenging, otherwise known as inertial supercharging. Simply stated, as intake gas flows toward the intake port, the faster it is moving, the more of it will get shoved into the combustion chamber before the port closes, unless the port closes too late or the RPM is too low for this effect to take place. Length of the "u" shaped runners and length of the tubes connecting the ports to the throttle body play a part in tuning these waves for a certain RPM range. With my S4 NA manifold the runners are a little long which means it is tuned for midrange power. VDI is two "u" shaped paths, one tuned for midrange and the other tuned for top end power (hence the VDI valve opens at 5400rpm or some such engine speed).

Ports are a very small patch of the overall picture of engine flow efficiency, especially when you consider that the engine is a pulsing system and flow is not continuous.

I can't wait to start engineering classes this fall and learn all about fluid and thermodynamics! But I will need to learn a lot of math first.