piratius

Before anyone pulls teh "search" card, I tried several.

I'm just curious what's involved in a Bridgeport, i've seen it discussed, and have a pretty good feeling of the pros and cons, but I still don't know wth it is.

Is it just a "bridge" across teh ports, like the name suggests, that allows a significantly larger amount of fuel/air to flow based on the offsets of the rotors...

Just talking this through makes it seem to make more sense. If I'm right, someone please confirm my dumb question....if I'm wrong, lemme know, I'm trying to figure out as much as I can (i'm researching a TII I'm considering buying, and trying to find out my options for performance, etc)

~Brad

karism

Well, you close!
A BP is when,another port is cut,above the original intake port.The result is a bigger area for intake : More port timing,+ additional size for gas to come in.

If you plan to run a Bp,there is some measures that needs to be taken,in order for it to be reliable ,and off course quick!

Oil pressure mods ,balancing ,clearancing,rotor pinning,3 window bearings,carbon seals and so on.

It all depends on the application ,and the size of the bridge. how high you want to rev,how long do you want it to last,and will it be a dail driver ?

Bridge Port need to have freeflowing exhaust to make HP,which results in high noise levels

Feel free to fire away ; if you have more questions.

Karis

piratius

I was just kinda curious what it was...

So here's another question, I'm going to sound like a n00b. I'm guessing a full bridgeport is having a second port of equal size to the original, and a half bridgeport is havinga second one half teh size?

*smiles* it does kinda make sense, when you think about it. Actually, I'm still confused, I just need to get back under the hood of the TII i'm thinking about buying, and do a closer look, I'm sure when I do, I'll see what you're talking about.

Thanks!
~Brad

Kenku

http://home.iprimus.com.au/bluey3/po...htm#Bridgeport quick google. Scroll up and compare that to the extend or street port; what you're seeing is the extra "eyebrow" cut. As you can see from that pic, the extra hole isn't anywhere near the size of the original port. It does change the timing a lot though.

Bridgeporting lets you have more port area than is possible with a street port; the "bridge" provides a place for the apex seal to ride on so it doesn't fall into the port. The extreme form, J-porting or mega bridgeports as they're sometimes called, involves having to cut away the rotor housing too, and plugging water passages; the port is extended past where the water seal o-rings are! Needless to say, this harms long-term durability.

1/2 bridges involve a combination of a bridge and street port... say, the end plates are bridgeported while the center plate has a street port. This provides a bit of a compromise between a street port and bridgeport.

karism

Well said Kenku!

Bp on primary and secondary makes it more difficult to drive,seeing that you loose low end ,or as some say ; off-idle torque

People are doing more Primary street ,and Secondary bridge ports these days,keeps it more driveable.

ps :piratius nothing wrong with asking questions!

gambone

iTrader: (3)

BP, back when there was a one peace apex made of carbin is when BP came out. The brige was to keep the apex from sliding over and out the port. So some peaple tryed it on the two peace apex motors guss what that little corner peace could and would fall out

piratius

Wow, that link rocks! It explained everything perfectly. Maybe the mods should make a locked forum, and people submit links with guides and FAQs for the most commonly asked confusing questions.

Either way, thanks guys, that totally answers my questions...about bridge, 1/2bp, and all the other ports to boot. *grin*

Was especially curious because the TII I'm thinking about buying has been streetported, and was wondering how extreme on the scales of porting that was.

Normal < Streetport < Extend Port < 1/2 BP < BP < PP



With a streetport, how hard would it be to pass emissions in Virginia, does anyone know? (I'm gonna ask the guy I'm buying it from to get it inspected & emissioned before I buy it, so i can see how close to the limit it is)

Thanks!
~Brad

piratius

Just found this, it's awesome...check it out!

~Brad

http://www.rotaryengineillustrated.c...-ports101.html

Swift_7

This will help alot with your questions. Click Here

gambone

iTrader: (3)

I'm back and I live in the sticks some where in Oregon and the only place close that has EPA is Portland, so as for the emissions I dont know, but I should becouse I do driveability and have all that good stuff like 5 gas, dyno so on so onbut being out in the sticks no one cares so there is ne real reson to know much.
When it comes to porting I've done a few and rite now my RX4 is huged out to the max and I have no problems driven it, OK so it wont idle below 2k rpm and I still can drive in slow trafic

piratius

Heh. Those are almost the same pictures as were listed above on a different site, but still cool. I get it, and it rocks

~Brad

Kenku

Well, the problem with buying a street ported engine is that "street port" covers a lot of ground. A lot of people (including me, actually) regard a street port as any port that doesn't need a bridge to work... IE, the "extend port" is still a street port. The problem is that the distinctions between various sizes of street port are... well, kind of arbitrary. In addition, the skill of the person carving the port can make a huge difference as well.

Irritating in a way, but oh well. What I'm saying though, is that there's not really much way to tell what you have in terms of a port without getting it tested. I will say that from what I can tell, street port engines *can* pass emissions, and most of the street ports out there are relatively mild.

Oh yeah, and gambone brought up a point with the bridgeports eating corner seals, one that I often forget. IIRC, that was another reason people started doing 1/2 bridge motors; you can turn the apex seals around so the corner seal is on the street port side, and thus still use the stock 2-piece apex seals. A full bridge means going to 1-piece seals, and IIRC the only ones available are carbons with their (comparatively) short lifespan and intolerance for boost, or ceramics with their... well, price tag.

Personally, I'm not much of a bridgeport fan. If you make them big enough you can actually get a little more peak HP than a peripheral port, but over a much narrower powerband... and with much reduced engine lifespan considering that monster bridges like that go *way* into the rotor housing. Peripheral ports are actually a *LOT* better than people think; even on the Mazda factory race ports the torque curve is pretty flat from 4k RPM on up, and they can last a really long time because they don't require cutting coolant o-rings or any such silliness. They do suck at low load / part throttle operation though... but so do bridgeports.

Oh yeah, I live far enough out in the sticks where I don't have to worry about emissions either.

piratius

Yeah, I think this is a fairly mild "street" port in the TII. sometime, after I get it, I'll try and get someone in the area to help me tear apart the intake manifold and see what the ports look like.

The car didn't idle with the "bridgeport" sound, so i'm pretty sure it's a fairly mild one. As far as I know, (and the Autometer boost gauge says), he's pushing 10-12psi on the stock turbo, and it idles right between 750 and 1000, no surging whatsoever.

The car will be mine by May 15th, so I'm quite excited

~Brad