Bridgeport Sizing and Positioning
02-13-21, 01:08 PM
#1
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Thread Starter
Bridgeport Sizing and Positioning
I’ve been doing a lot of research on porting lately and it seems one piece of info I can’t find is about the length and positioning of the bridge port, maybe I’m not searching hard enough or there’s a term for this that’s going right over my head.
Typical bridge port’s I’ve seen run down the whole side of the port, either secondary or primary. What would be the effect of the length of the bridge port? Like only bridging the top half of the port and leaving the rest of the port stock, or possibly streetport with a small bridge port? 😳 Because the bridge would start slightly later in the intake stroke I would assume the loping idle would be lessened, making for a slightly more pleasant down low, day to day drivable car with the trade off of overall high end power of a full length bridge.
I thought this term was called a half bridge but from what I read, a half bridge just means bridging the secondary ports and leaving the primaries either stock or street ported. Correct me if I’m wrong.
Does anyone have experience and input on both full length and shorter cut bridge ports? And has anyone messed with combining both street ports and shorter bridge ports? Or would that just absolutely kill low end air velocity and driveability?
Thanks
Typical bridge port’s I’ve seen run down the whole side of the port, either secondary or primary. What would be the effect of the length of the bridge port? Like only bridging the top half of the port and leaving the rest of the port stock, or possibly streetport with a small bridge port? 😳 Because the bridge would start slightly later in the intake stroke I would assume the loping idle would be lessened, making for a slightly more pleasant down low, day to day drivable car with the trade off of overall high end power of a full length bridge.
I thought this term was called a half bridge but from what I read, a half bridge just means bridging the secondary ports and leaving the primaries either stock or street ported. Correct me if I’m wrong.
Does anyone have experience and input on both full length and shorter cut bridge ports? And has anyone messed with combining both street ports and shorter bridge ports? Or would that just absolutely kill low end air velocity and driveability?
Thanks
02-15-21, 09:36 AM
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http://foxed.ca/rx7manual/manuals/Rx...%20(70-73).pdf
start here, you end up with a bridge port that just works. if you get a sheet of plexiglass (or some other clear stuff you can cut), you can make a template and mock up an engine and see what moving things around does.
some rules of thumb, reducing overlap, will help at part throttle. impact on full throttle should be minimal (if you're starting with FC housings, maybe leave the exhaust port alone?)
closing later, will help the high end power at the expense of low end. no impact on part throttle
adding port area (making it bigger), will help the top end power, and may help the bottom end too. the holy grail would be a larger port with less overlap, like the Rx8
start here, you end up with a bridge port that just works. if you get a sheet of plexiglass (or some other clear stuff you can cut), you can make a template and mock up an engine and see what moving things around does.
some rules of thumb, reducing overlap, will help at part throttle. impact on full throttle should be minimal (if you're starting with FC housings, maybe leave the exhaust port alone?)
closing later, will help the high end power at the expense of low end. no impact on part throttle
adding port area (making it bigger), will help the top end power, and may help the bottom end too. the holy grail would be a larger port with less overlap, like the Rx8
02-15-21, 12:19 PM
#3
Newbie
Thread Starter
http://foxed.ca/rx7manual/manuals/Rx...%20(70-73).pdf
start here, you end up with a bridge port that just works. if you get a sheet of plexiglass (or some other clear stuff you can cut), you can make a template and mock up an engine and see what moving things around does.
some rules of thumb, reducing overlap, will help at part throttle. impact on full throttle should be minimal (if you're starting with FC housings, maybe leave the exhaust port alone?)
closing later, will help the high end power at the expense of low end. no impact on part throttle
adding port area (making it bigger), will help the top end power, and may help the bottom end too. the holy grail would be a larger port with less overlap, like the Rx8
start here, you end up with a bridge port that just works. if you get a sheet of plexiglass (or some other clear stuff you can cut), you can make a template and mock up an engine and see what moving things around does.
some rules of thumb, reducing overlap, will help at part throttle. impact on full throttle should be minimal (if you're starting with FC housings, maybe leave the exhaust port alone?)
closing later, will help the high end power at the expense of low end. no impact on part throttle
adding port area (making it bigger), will help the top end power, and may help the bottom end too. the holy grail would be a larger port with less overlap, like the Rx8
How would overlap be reduced? Is it how I said and having the bridge start later in the intake stroke? Like cutting out a shorter bridge?
Thanks for the response
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