I still cant grasp the idea, anyone care to explain?

 

i dont know much about them my self so i cant help ya

but i would think it involves some sort of porting : D

 

thisll clear up a little

 

http://www.racingbeat.com/rotary2resultnav.asp

 

you can see the port that is cut closer to the water jacket, thus making the intake port open up earlier, and you can see the bridge in the middle of the port

 

The material left between the 2 ports is for the corner seal to have something to pass over so it doesn't fall out thus creating a bridge for the corner seal between the 2 ports, hense the name "Bridgeport". The advantage of this is from what i know mainly to be port timing. From what i just learned from a forum member who has more knoledge then me on the subject while comparing my large SP vs his Bridgeport, is that, even a large SP starts to open ATDC while a Bridgeport can open (i think it was) 115deg. BTDC.

Now i was really tired during that conversaion but if the it's not right it should still give you a better understanding of why it's called a bridgeport and why ppl use it.

If anyone has the actuall facts of where a BP starts to open (specifying Half BP or full BP would be nice) please do so. I'm mearly trying to give an example with what i at least remember having been said.

 

I hope you know your port timing theory...

Since you mentioned bridge porting, we'll keep the reply specifically to the intake port.

There are two ways to "open" the intake port.
Open the intake port EARLIER.
Close the intake port LATER.
Bridge ports will significantly open the intake ports EARLIER.

Opening a (Mazda) rotary engine port means the port opens up more from the "outer" edge (toward the water jacket).
BUT, if we start to open up the intake port toward the water jacket, we NEED to worry about the corner seal path.
If we just hog out the intake port without worrying about the corner seal, the corner seal (off the rotor itself) will fall inside the port!
This is where the BRIDGE port comes in - the bridge is there to help the corner seal travels over the intake port without falling in.
Thus, this is where the "bridge" in bridge port comes from.


-Ted

 

here's one i did for an fd.
if you notice only the upper half is done--as opposed to my avatar. this controls the amount of overlap and tweaks the powerband.

this one is a bit more street friendly and doesn't eat quite as much gas as a longer one. still produces decent low end too. this particular one actually produced a really REALLY punchy low end...but the 9.7:1 rotors might have had something to do with that

 

Very interesting^^^. So would that be considered a half bridge?

 

yep. i can't remember if we even took pics of the primaries on that motor. if i find any, i'll post them.

 

very good information here. Thanks for taking the time to educate us!

 

do most people b-port just the primaries, the secondaries, or both???

 

full bridge= primary and secondary
half bridge= just the secondaries

aux bridge= good to retain the low end in n/a's and give it an extra kick up top.

 

could anyone elaborate on the effects on the power band of Aux vs. Half vs. Full bridge? Which ones make more where, and which ones hurt power most/least where.

 

I dunno if you can compare them and give hard numbers...

Bridge ports open the INTAKE TIMING earlier.
This increases OVERLAP.
OVERLAP is bad for low end.
OVERLAP allows exhaust gases to mix with the fresh intake charge, supressing potential power.
But, the earlier opening intake timing makes for more intake charge (+ fuel) to enter the combustion per revolution of the engine - this means more power.
At a certain RPM point, the advantage of more intake charge overcomes the bad OVERLAP down low, and the power climbs.

Half bridge port is just a COMPROMISE porting design to get the advantages of the bridge port but tame the idle and low end with the stock port primaries.

Personally, I think a bridge is a waste of time for a daily driven street vehicle.
So what if your car now makes 450hp instead of 400; you just can't use that extra 50hp anywhere unless you're street racing, which is dangerous and illegal.
All the pro BP+turbo guys are now going to jump down my throat for those statements.


-Ted

 

I'm interested in doing an aux bridge port, and get it to close with the actuators as well as I can.

 

you shouldn't have a problem with that.

obviously, you'd see the best results with an engine management system...

i haven't done any testing on it, but i'd be really interested in seeing how the motor would react to opening the ports and vdi at various rpm settings to optimise. it might end up liking it exactly where it is stock, but then again, it might not.

 

come to think of it, the only people i've ever heard knock the turbo bp's are the people who have never done it.

 

I remember a time when you were scared of the BRAP BRAP BRAP Dave..."dude just do a big streetport" lol. Now we've both converted to the Dark Side...BTW the beast lives again and is running PERFECT...except for the imitation of the Exxon Valdez every time I park. Now if I can only get the MPG above 15 I'd be set...

 

ahhh yes...there was the time before we had done them.

dood, you were right. i admit it freely

 

i made this account to reply to this

 

Do you have something constructive to add to this topic? If not, the new member section is a good place to start.