GoRacer

oh, ok. I thought it meant the bridge was 1/2 the size. Like bushy eyebrow to pencil eyebrow. What does 1/2 bridge do compared with full bridge? So what would be the differences with a mild street port and a 1/2 bridge compare to an extended race port? Noise is not a problem with my Buddy Club Spec IV exhaust.

dantheman

This sounds like such rice, but will it give you the brap sound?







while looking at the 6port in the garage I was thinking that might be a good way to get some hp out of it. Big street port on the engine with an aux bridge. This would give you a bridge port you could turn on and off if I think this through right.

Rotoraider

An extra large carefully done streetport can provide you with more than enough flow while still maintaining far better streetability than a bridgeport. You can port quite a ways, even about a 1/3 or 1/2 the way into the corner seal area, as long as it's still supported well.



With that turbo you plan on using, I'm sure you don't really need to bridgeport it to attain your desired powerlevel... unless you're looking at making 600+hp or something rediculous like that.

BDC

I don't believe that, Rotoraider. The bridgeport opens substantially earlier and will produce a potential for chamber flow well in excess of any street port. The advent of substantial overlap is what makes this possible.



B

Rotoraider

Well of course you can't make a streetport large enough to flow like a bridgeport, but you can make it large enough to allow a large turbo to power a 13b easily up to 500 whp.

Bridgeports are ultra cool and make great power, but uncessarily kill some driveability unless i guess you need to make X amount of power.

Maxt

I would rather open up the bridge then push the streetport wall back toward the water seal, or push the closing later on the streetport trying to stretch out power.. Pushing the opening to the max on a streetport is hard on the side seals, and pushing it later does nothing on a stock intake manifolded motor for the most part, late port closing shows up minimally in the very very top end, and reduces power everywhere else, hence why the 6 port is valved off..



One of the other advantges of the bridge port is you open up intake on the combustion side of the side seal instead of the crankcase side, the more you open up the standard port, the more time you expose the crankcase side of the rotor to boost pressure, more lost charge, more side push on the rotor, and more blow by..Some people think bp's wear faster than large streetports, if you compare the 2 from new state and then disassembly the bp will have less iron wear at the usual places...

heretic

IMO the overlap is just a byproduct of the port shape and not the reason why the port flows so well.



If you just sit the engine down and look at the thing, it's easy to see why a bridge or especially a peripheral port flows so well. Ignore the exhaust port completely for a minute, and start the rotor at TDC. With a side port engine, the port's not even open yet. When the rotor swings up and opens the port, the airflow must make a very short radiused, acute turn, from 90 to 180 degrees depending on if the air is going towards the ends of the rotor or towards the rotor housing. It isn't until the rotor has had any significant travel before the airflow doesn't have to make such a horrible turn into the chamberspace.



The bridge port doesn't have this kind of extreme limitation. At TDC and earlier the eyebrow is not only open, but it's aiming right into the chamber. There's never any period where the airflow has to make a direction change as extreme as the side port has to endure. Further, the port is always open.



Peripheral ports are even better when airflow early in the intake stroke is considered, although I'd suspect that a really extreme Monster bridge would best a peripheral port.



The overlap is, again IMO, more of something that has to be accepted and dealt with, rather than the means to greater intake flow.

pvillknight7

anyone have a picture of an aux bridge?