6 Port vs 4 Port
 

What are the advantages and disadvantages of either? I own a 6 port but the PO blocked off both of these ports. Why would he do this?

What do you mean they are blocked off? Any chance you can post a picture?

The actuators are removed and the holes are sealed up. I can post a picture in the morning

The previous owner was an idiot that did not understand the car. This is unfortunately common. The aux. ports are supposed to stay closed under 3800 RPM to preserve low-end torque. Once that RPM is reached, they open to maximize top-end power. With your actuators and sleeves removed, you get to have the loss of low-end, but at least still have the top-end. You'd benefit from a LIM that hasn't been messed with, and actuators/sleeves.

but back to the topic im curious what the pro's and con's to 6 vs 4 port?
which has the potential to make more n/a power?

Isn't that last bit, reversed?

The ports being CLOSED under 3800 - providing ever-so-needed low-end torque, and open over, is the OEM setup, correct?

The only difference in that and how he's got it is the variable of the top-end, not the low-end.

His are ALWAYS closed, so he'll lack the air-flow, in the top end, not the bottom.

91RX7N/A: There's been a bit of a debate on this, for years... The answer varies, depending on the series, since compression is a variable, as well; NTM where you're looking to MAKE the most power.

TECHNICALLY the 6-port should make the most even (linear) power-band - given that the engine's revs are affecting the port's activity and once power is made they'll open.

With them closed, you'll notice that the lower end is a bit more responsive, but the top-end will feel like it's struggling, of sorts; it'll feel like there's more, but the engine can't put out.

With them fully OPEN, the above will be inverse.

Years ago, I played with mine, on my S4 GXL, to see if various things HUGELY affected power, since one was having problems actually actuating... There wasn't a HUGE difference. I ended up wiring the about 1/2-way and never thought about it, again. I wasn't looking for power-gains that would've been notable, but it was a difference, on the open road.

The ports actuating properly will give enough vac pressure below 3800 revs to help the engine make power, and help air-flow above 3800 to get in and out, efficiently.

Turbo guys, as well, are up in arms about this. Since some guys want them closed, all the time and others leave it be. Mine are blocked off via the LIM is a 4-port Tii, and the power-band is noticeable.

But, like I mentioned before, there are a few variables, involved, but all-in-all having them in place and functioning correctly is the best way to go - especially if you're looking to stay N/A.

Hope that helped give what you were looking for.

The advantage of the 6 port is basically to have both small and large ports depending on the rpm. A simpler 4 port could potentially make a little more peak power if it were enlarged to the right size. But a 6 port closes off some port area at low rpms for better power and mpg and gets almost the same area at high rpms by opening the auxillary ports. Basically a 6 port gives better acceleration and better power across the spectrum so it's usually better. A 4 port would be a simpler approach if all you want is to be a dino king, though I dunno how much it'd help. Blocking off the auxillary ports without enlarging the other ports OTOH only means less power.

No, you're assuming that someone actually sealed up the aux. ports on the block (lots of jb weld?). To me it sounds like the actuators, sleeves and the rods connecting them were removed, then the holes in the LIM were sealed up (where the rods were). Of course, maybe someone filled the block with jb weld, and it's a question of how long before pieces flake off and damage seals.

Think of the 6 port system as VTEC for rotary engines, except Mazda had it before VTEC ever existed. The ports stay closed under low rpm so you have a higher velocity of air entering the engine. Then at higher rpm the ports open and you are essentially increasing the "lift" and "duration" similar to what you would get from the VTEC cam profile on a Honda. On the s5 you have the VDI system which is similar to the two-stage intake manifold later used on the NSX, Integra GSR, and other models from the era.

Technically a 4 port engine with big ports and the right intake manifold design will have the best high-end powerband for racing type of applications, but won't have the broad useable power and torque that you want for a street car.

i complete understand how each works and i know stock for stock the 6 port will make more power. but after fully porting a 6 port so that the ports are combined and after bridge or j porting a 4 port which will make more n/a power?

My question is a bit off topic but when you are installing the sleeves for a 6 port N/A the Haynes manual it tells you to align the thick part of the shaft on the sleeves with the notch on the gasket. I realized that when you are installing them the opening on the sleeves do not match up with the port inside the block. I'm assuming this is because the ports stay closed until 3,800 rpms and then they will open??? I am just making sure before I install all of the other parts on the engine and put it back in the 7 just to find out I installed the sleeves wrong.

the real answer is... we dont know WTF has been done to the engine. maybe the actuators where removed? maybe left in place? maybe they where removed and the 5th and 6th ports are still there, and open, or they have been closed by some means. NO ONE KNOWS.

Maybe... take a picture.

2slow4stock, are you talking to me or 91rx7n/a?

so here is a question to deal with this thread.

what if the sleeves were removed and the actuator holes sealed?

open all the time. horsepower difference? mpg difference? if so, what numbers are we looking to gain/lose hp and fuel economy difference?

i think this is what answer the thread poster was looking for.

i think the only way to gain more power at the low end with the sleeves removed is to run bigger injectors and tune it to add a "little" more fuel to make the air/fuel ratio proper to the mod.

does this sound right to anybody else?

You need to find out weather the port valves have been removed or if they are still laying in there if they are gone you you are ok on the top end if they are still in there and closed you loose on the bottom .. if they are hooked up and working you are a winner they work good on the bottom and open for top end power I don't think it is a hard decision to make.. Get them working if you no longer have a air pump then you can do what trochoid suggests and run a 1/8 pipe from the exhaust pipe to the actuators so they will open with exhaust pressure .. not having the port valves working on a 6 port is the same as wiring the secondaries closed on a 4 barrel carburetor on race day :icon_tdow fix them ,make them work you will be amazed at how smooth they actually function when the ports , valves and actuators are all cleaned up and functioning properly to hell with gas mileage but it will probably be better with everything working like it should :)

^wut?



Peak hp difference? Probably not. But having the ports open all the time does kill the low end a bit(mine are always open). Its not bad, just got to get use to it. The best way to go is have the aux ports actuated some way or another(multiple writeups on this subject).
MPG's would get worse with the ports open, seeing as you are in the throttle more(more fuel getting dumped in) to get the same amount of acceleration as if the ports were closed.

No. Its about the velocity of the air coming in, not the afr's so much. At low RPM's with the aux ports closed, air is getting drawn in at a higher speed, thus providing more torque. With the ports open at low RPM's, there is less flow of the air, being there is more area it is coming into. The vacuum of the engine will be the same at a given RPM, but it will pull air in faster with less area on the intake(ports closed). But at higher RPM's with the ports closed, it will start to choke out, so then the aux ports open, providing more area in the intake to flow a greater amount of air, and being the engine speed is higher, it can flow the greater amount of air in at a fast speed.