what port for single
06-10-03, 02:24 PM
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what port for single
Ive ssearched and not really a exact answer to my question... im thinking ofdoing a bridgeport..on my new engine its either that or a large streetport im going to be running a t04s ( i think) my car is going to basically a street car but will ocassionaly goto the track so lag needs to be minimal as possible thats why i want to go with a t04s.. but with a brigeport would lag be even a issue with a t-78 or something. .. thanks for the input
06-10-03, 04:48 PM
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well, porting... it's a funny science. the guys at nopistons.com will undoubtedly tell you to go as big as you possibly can, advancing the port opening timing, delaying port closing timing, risking oil seal failure to the inside... whatever you can, just make it big.
well, i've read a few things (i don't want to seem like a know-it-all, 'cause i'm not... but the most recent book was Corky Bell's Maximum Boost) which have suggested to me that this may not be the best thing to do with a rotary in particular. as you know, it's a difficult situation between those side and intermediate housings: making the ports bigger to reduce resistance from high flow velocity (really only a problem at very very high rates of flow) and promote good fuel atomization, but this changes the timing in all sorts of directions...
if you're trying to flow 9000cfm (lol
) on stock ports, you're obviously going to run into some restriction problems from the reletively microscopic ports, but in an application where your target is something more resonable, like, say, 600cfm, then you might not be in such bad shape with the stock ports as you thought, but would probably still do well with a healthy, well thought out street port... as in everything: it's all about the comprimizes
advancing the intake timing to the point of significant overlap (bridgeport) means that you'll end up crushing a whole lot of air and raw fuel out the exhaust port before it closes completely, which won't win you any friends with the emissions testing machine, not to mention the even more dreadful fuel economy. delaying the port closure time more, which on all stock FI Mazda housings is 50 degrees ABDC, would only increase the reversion of intaken fuel and air as the compression cycle squashes it back out the intake port (trust me, the rotor will win out against the impeller)...
on the exhaust side, again, some will suggest that you just make it bigger in all directions, including advancing the port opening timing, and delaying port closure timing... this would be very beneficial if you're running something in the range of 500hp's worth of air in and out of the engine, but would only really hurt you if you're looking for a more streetable setup, even if at a lower power number. exhaust gas reversion (having it flow backwards) is probably the worst thing that can happen with a turbo motor, so it's to be avoided (although it's challenging to be stupid enough to port the exhaust enough that it could revert significantly into the intake cycle)... a longer combustion stroke will help your thermal efficiency, torque (at any rpm), and emissions, so i don't know if i'd touch it going down either... out to the sides a little can increase the area quite a bit, but i'd worry much more about everything BEHIND the port, rather than the port itself... not that you asked... sorry, i'm just rambling.
i have a headache, so i'm going to get back to work now.
well, i've read a few things (i don't want to seem like a know-it-all, 'cause i'm not... but the most recent book was Corky Bell's Maximum Boost) which have suggested to me that this may not be the best thing to do with a rotary in particular. as you know, it's a difficult situation between those side and intermediate housings: making the ports bigger to reduce resistance from high flow velocity (really only a problem at very very high rates of flow) and promote good fuel atomization, but this changes the timing in all sorts of directions...
if you're trying to flow 9000cfm (lol
) on stock ports, you're obviously going to run into some restriction problems from the reletively microscopic ports, but in an application where your target is something more resonable, like, say, 600cfm, then you might not be in such bad shape with the stock ports as you thought, but would probably still do well with a healthy, well thought out street port... as in everything: it's all about the comprimizesadvancing the intake timing to the point of significant overlap (bridgeport) means that you'll end up crushing a whole lot of air and raw fuel out the exhaust port before it closes completely, which won't win you any friends with the emissions testing machine, not to mention the even more dreadful fuel economy. delaying the port closure time more, which on all stock FI Mazda housings is 50 degrees ABDC, would only increase the reversion of intaken fuel and air as the compression cycle squashes it back out the intake port (trust me, the rotor will win out against the impeller)...
on the exhaust side, again, some will suggest that you just make it bigger in all directions, including advancing the port opening timing, and delaying port closure timing... this would be very beneficial if you're running something in the range of 500hp's worth of air in and out of the engine, but would only really hurt you if you're looking for a more streetable setup, even if at a lower power number. exhaust gas reversion (having it flow backwards) is probably the worst thing that can happen with a turbo motor, so it's to be avoided (although it's challenging to be stupid enough to port the exhaust enough that it could revert significantly into the intake cycle)... a longer combustion stroke will help your thermal efficiency, torque (at any rpm), and emissions, so i don't know if i'd touch it going down either... out to the sides a little can increase the area quite a bit, but i'd worry much more about everything BEHIND the port, rather than the port itself... not that you asked... sorry, i'm just rambling.
i have a headache, so i'm going to get back to work now.
06-11-03, 02:01 PM
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wow.. lotsa info i didnt know good stuff thanx for the input.. emissions is not a problem as i live in a rural area that doesnt smog me.. but fuel economy would be a big factor... but its also taken into consideration im going to be building a 400+ hp machine.. so should i really be cheap on a port just cuz i want the gas mileage i dont know.. but i keep looking into my options.. again thanks for the info
06-11-03, 02:35 PM
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any time you go for more power, that inherently means you have to burn more fuel at one time to get that level of energy... so, being that you have a rotary and want to go fast, fuel economy is right out the window... how far out is a matter of how clever you are.
learn lots before you even consider dreaming up a system/picking parts off the shelf.
learn lots before you even consider dreaming up a system/picking parts off the shelf.
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