Fd
10-20-08, 02:03 AM
#2
well define "an stuff" is.
To begin with tho, to get more air/fuel into a rotary, you need to increase the port size. There are several types of porting, each with their own pro's and cons.
Starting from the smallest and heading to the largest we start with
Stock ports
how the car comes from the factory, depending on the generation, engine size (13B, 12A, 110B etc).
Streetporting
Streetports are the lowest end of the porting scale, enlarging the port size by a small amount. This type of port increases top end power marginally, and takes away some bottom end power, but overall retains the stock driveability of the car. This is by no means a "weak" port, as many FD's have seen 400 - 500 whp numbers on street ports.
Considering porting is refering to opening the actual port size, there are many types of streetports. Some are marginal, only slightly opening up the port, others extend down farther and create a bigger opening.
examples would be "Mild" "Large" "Agressive" and so on, all depends on the engine builder, really there is no set name for the actual port size, although, all ports that dont require a "bridge" are generally considered a streetport.
as a note, as ports get bigger idle begins to decrease and become "lumpy". Fuel consumption generally drops as power goes up, and the powerband begins to start higher up the rev scale. As well reliability begins to drop with larger ports, although "mild" and "small" streetports generally retain almost stock reliability without sacrificing the power increase.
Bridgeport
A Bridgeport opens an "eyebrow" above the port, which leaves a "bridge" for the apex seal and corner seals to run along and keep them from falling into the port. With a bridgeport, the size of the brow tends to be again ranging from a smaller to larger brow, depending on the power wanted and so on.
this is a larger bridgeport, as you can see the "eyebrow" is fairly large, extending the full length of the port.
With a bridgeport, low end power is sacrificed for a high end power, generally power bands start above 5k rpm, and when balanced can redline as high as 14k rpm. Low end power is poor, idle is very lumpy, generally idling at 1500 rpm or higher. Fuel consumption is very poor and reliability is virtually down the drain. Ive heard between 25k - and 40k miles for a Bridgeport to last effectively while being driven. This is really a race style port and many consider it to be a "non streetable" porting. Although many people DO drive bridgeports on the street.
J-ports
These ports extend the brow out as far as it can possibly go, letting in much more air and fuel into the engine. Like the bridgeport, idle is very lumpy, power is high end. Reliability and Fuel Consumption are poor.
Peripheral Porting
The Holy Grail of race porting, Peripheral Ports move the the port from the side plates of the engine to the rotor housings themselves, positioned above the Exhaust housings. These ports are generally VERY large, inleting much more air, but are VERY expensive. As well, fuel consumption, reliability and engine life take a nose dive from the Bridgeport which is already poor. These ports produce power over 8k rpm and typically wont idle under 2000 rpm. They will produce massive power in a forced induction engine, but because of the high RPM range, reliability is very very poor. Typically considered a totally unstreetable porting.
Peripheral port image from Mazdatrix's website, all other pictures from turborx7.com
To begin with tho, to get more air/fuel into a rotary, you need to increase the port size. There are several types of porting, each with their own pro's and cons.
Starting from the smallest and heading to the largest we start with
Stock ports
how the car comes from the factory, depending on the generation, engine size (13B, 12A, 110B etc).
Streetporting
Streetports are the lowest end of the porting scale, enlarging the port size by a small amount. This type of port increases top end power marginally, and takes away some bottom end power, but overall retains the stock driveability of the car. This is by no means a "weak" port, as many FD's have seen 400 - 500 whp numbers on street ports.
Considering porting is refering to opening the actual port size, there are many types of streetports. Some are marginal, only slightly opening up the port, others extend down farther and create a bigger opening.
examples would be "Mild" "Large" "Agressive" and so on, all depends on the engine builder, really there is no set name for the actual port size, although, all ports that dont require a "bridge" are generally considered a streetport.
as a note, as ports get bigger idle begins to decrease and become "lumpy". Fuel consumption generally drops as power goes up, and the powerband begins to start higher up the rev scale. As well reliability begins to drop with larger ports, although "mild" and "small" streetports generally retain almost stock reliability without sacrificing the power increase.
Bridgeport
A Bridgeport opens an "eyebrow" above the port, which leaves a "bridge" for the apex seal and corner seals to run along and keep them from falling into the port. With a bridgeport, the size of the brow tends to be again ranging from a smaller to larger brow, depending on the power wanted and so on.
this is a larger bridgeport, as you can see the "eyebrow" is fairly large, extending the full length of the port.
With a bridgeport, low end power is sacrificed for a high end power, generally power bands start above 5k rpm, and when balanced can redline as high as 14k rpm. Low end power is poor, idle is very lumpy, generally idling at 1500 rpm or higher. Fuel consumption is very poor and reliability is virtually down the drain. Ive heard between 25k - and 40k miles for a Bridgeport to last effectively while being driven. This is really a race style port and many consider it to be a "non streetable" porting. Although many people DO drive bridgeports on the street.
J-ports
These ports extend the brow out as far as it can possibly go, letting in much more air and fuel into the engine. Like the bridgeport, idle is very lumpy, power is high end. Reliability and Fuel Consumption are poor.
Peripheral Porting
The Holy Grail of race porting, Peripheral Ports move the the port from the side plates of the engine to the rotor housings themselves, positioned above the Exhaust housings. These ports are generally VERY large, inleting much more air, but are VERY expensive. As well, fuel consumption, reliability and engine life take a nose dive from the Bridgeport which is already poor. These ports produce power over 8k rpm and typically wont idle under 2000 rpm. They will produce massive power in a forced induction engine, but because of the high RPM range, reliability is very very poor. Typically considered a totally unstreetable porting.
Peripheral port image from Mazdatrix's website, all other pictures from turborx7.com
