Different types of porting.
11-25-08, 11:55 AM
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Different types of porting.
I was just wondering if someone would be willing to explain the differences in the types of porting I keep reading about on here. If you look you'll see that there a few different types like streetport, bridgeport, and peripheral port. thanks in advance.
Last edited by mar3; 11-25-08 at 02:16 PM. Reason: rlsd
11-25-08, 02:32 PM
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Streetport comes in two flavors...small or big. The "definition" of what is big or small is determined by the size of the grinding work done on the rotor housing's face that the rotor sees as it rotates by. Extending or enlarging that opening is like adding a cam to a V8....if the cam is a little bit big, you still have decent vacuum and idle and a little more torque and HP...if you go too far, the idle is compromised but you have HP on top. A 5 - 15% increase in HP is the normal range for this modification. Exhaust work is absolutely necessary to realize gains that hit potential on any of these porting regimens, BTW.
Bridgeport is referring to the practice of grinding even more away but now you have actual seals to worry about that ride with the rotor. A "bridge" of metal is left so that seal can cross the now hogged-out port. Now, you're in the "solid lifter 310 degree race cam" territory where the beast needs 1100 rpm just to idle...EFI can calm it a bit. I'm not sure where HP increase percentages fall for this category...anyone got some real numbers?
Peripheral Port is simply saying that the normal RX-7 housings with ports that make a 90 degree turn to empty into the rotor chamber are unacceptable. The exhaust port is peripheral...why not make the intake port dump right into the spinning rotor also, right? The iron housings with the side ports are filled in and the aluminum housing that the rotor itself actually spins in is machined for the fabricated intake ports and manifold...there's much more involved than that, but there's the basic definitions for you. 100% gains in HP plus increased breathing for revs to 10,000 rpm become possible but now that monster won't idle below 1800 rpm.
Mario III
Bridgeport is referring to the practice of grinding even more away but now you have actual seals to worry about that ride with the rotor. A "bridge" of metal is left so that seal can cross the now hogged-out port. Now, you're in the "solid lifter 310 degree race cam" territory where the beast needs 1100 rpm just to idle...EFI can calm it a bit. I'm not sure where HP increase percentages fall for this category...anyone got some real numbers?
Peripheral Port is simply saying that the normal RX-7 housings with ports that make a 90 degree turn to empty into the rotor chamber are unacceptable. The exhaust port is peripheral...why not make the intake port dump right into the spinning rotor also, right? The iron housings with the side ports are filled in and the aluminum housing that the rotor itself actually spins in is machined for the fabricated intake ports and manifold...there's much more involved than that, but there's the basic definitions for you. 100% gains in HP plus increased breathing for revs to 10,000 rpm become possible but now that monster won't idle below 1800 rpm.
Mario III
11-25-08, 07:06 PM
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awesome, thanks guys...i would say that i'm fairly profeicient with mechanics. but i'm pretty much a noob in general when it comes to rotorys. thanks again.
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