dumb question about porting
02-07-02, 04:46 AM
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dumb question about porting
hey everyone. my 13bt is in the mail and my friend is getting really excited about doing the swap. thing is, he is building a crx with a b16, completely built motor that will be putting down 220 horses at the front wheels. he is gonna have huge turbo in it by the end of the summer and looks to be putting 360+ horses to the front wheels. this has put me in a mind set of starting a horsepower race. i got the motor, ill soon have a nice big turbo, but even with that i wont be able to touch him (his crx weighs 1800 pounds). so i keep reading your guys post on porting. since my motor is gonna be out when i get it, i was thinking i would port it. i know i can really keep up with him. my goal is about 250 horses at the rear wheels. but the thing is, i know this makes me dumb, but ireally dont know what "porting" a rotary means. can someone please explain this to me. im sure the explanation isnt that complicated and i already feel dumb, so please go easy on me. thanx guys.
mike
mike
02-07-02, 05:34 AM
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this link tells about porting, http://mrmazda.members.atlantic.net/...t.html#NOSTART
02-07-02, 07:06 AM
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Really basic explanation. The fuel and air mixture is sucked into the motor though a hole, which is called a `'port'. As the rotor chamber goes round it passes two spark plugs in line called leading and trailing, the explosion keeps the rotor chamber going round intil the burnt gases can escape through another hole [port] on the same side but below the first.
To a large extent the power of the engine depends on the size of those ports. The longer they are, the more time the hole is in effect open as the rotor chamber passes over it during ithe input and exhaust period
However, the bigger the ports are the more power is developed at high revs and comparitively little power at the lower end. Thus, as a generalisation, the bigger the ports the more suitable the motor is for racing.
The art is making the port the right shape for the power you want [porting].
The stock size is what Mazda worked out would be a good compromise between performance with economy and minimal polution. In the late 1970s made the ports smaller to pass ever harder pollution controls with the result the same motor became less powerful.
If you make the ports a little bigger you get increased power but not to the extent you can not drive the car on the street, ie Street port. Consumption and pollution goes up but to a level acceptable to car enthusiasts. Sometimes this is called an extended port.
If you make them even bigger the seals on the ends of the rotor can fall into the hole. So you leave a thin strip of metal across the hole, a bridge so naturally called a bridge port. Fuel and exhaust gases have more time to enter/exit the motor resulting in far greater power, you use more fuel and pollution is greater.
As the ports are made bigger you have to have better carbs and exhausts to cope with the flow.
There are some good websights linked to the forum which have working diagrams. Much of the talk on the Forum is on methods and improvements to get the power, for example long disputes on the best carb to use.
A turbo in effect pushes more fuel and air into the motor in effect making it behalf like a bigger engine. Like porting it gives more power thus more stress resulting in engine damage. The major difference is that a motor must be stripped down to get at the ports and enlarge them, a turbo can be bolted on with the engine in the car.
The above is the simplest I can make an explanation. There are many experts who could write a book on the subject, porting is a critical part of a rotary engine and few piston people understand it. The nearest to it is the design of the cam to contrl the opening and shutting of the valves.
In summary, porting is increasing the size and shape of the ports to give you the power you want, in the rpm range you want, subject to whether the carb and exhaust system lets it happen, all subject to whether the level of noise and pollution is legal. To many it is magic, to some an art, and to a chosen few it is a science!
To a large extent the power of the engine depends on the size of those ports. The longer they are, the more time the hole is in effect open as the rotor chamber passes over it during ithe input and exhaust period
However, the bigger the ports are the more power is developed at high revs and comparitively little power at the lower end. Thus, as a generalisation, the bigger the ports the more suitable the motor is for racing.
The art is making the port the right shape for the power you want [porting].
The stock size is what Mazda worked out would be a good compromise between performance with economy and minimal polution. In the late 1970s made the ports smaller to pass ever harder pollution controls with the result the same motor became less powerful.
If you make the ports a little bigger you get increased power but not to the extent you can not drive the car on the street, ie Street port. Consumption and pollution goes up but to a level acceptable to car enthusiasts. Sometimes this is called an extended port.
If you make them even bigger the seals on the ends of the rotor can fall into the hole. So you leave a thin strip of metal across the hole, a bridge so naturally called a bridge port. Fuel and exhaust gases have more time to enter/exit the motor resulting in far greater power, you use more fuel and pollution is greater.
As the ports are made bigger you have to have better carbs and exhausts to cope with the flow.
There are some good websights linked to the forum which have working diagrams. Much of the talk on the Forum is on methods and improvements to get the power, for example long disputes on the best carb to use.
A turbo in effect pushes more fuel and air into the motor in effect making it behalf like a bigger engine. Like porting it gives more power thus more stress resulting in engine damage. The major difference is that a motor must be stripped down to get at the ports and enlarge them, a turbo can be bolted on with the engine in the car.
The above is the simplest I can make an explanation. There are many experts who could write a book on the subject, porting is a critical part of a rotary engine and few piston people understand it. The nearest to it is the design of the cam to contrl the opening and shutting of the valves.
In summary, porting is increasing the size and shape of the ports to give you the power you want, in the rpm range you want, subject to whether the carb and exhaust system lets it happen, all subject to whether the level of noise and pollution is legal. To many it is magic, to some an art, and to a chosen few it is a science!
02-07-02, 01:13 PM
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I just reread the first part of the thread. If you have a 13BT for an engine, you will be able to smack the ricer easily with the turbo. Another Aussie with some long tag like ACJ98162354854664,whatever...has gotten 406 REAR WHEEL horsepower on 15 psi boost from his 13B. That comes out to about 450 HP at the flywheel with the manual transmission. The 13B's are heavier but they're also able to take more abuse than a 12A. Hell, you could probably run a 50 shot of juice to break the 500 HP barrier.
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