Torque South

What if I wanted my daily driver to idle and sound like a bridge or half bridgeport? They are less reliable because of the seal passing over the gap or something right? I know you can "make" a streetport idle fucked up, but I have always wanted a bridgeport and never had one. What is the best compromise of daily driving reliability and a nasty idle? (turbo 2nd or 3rd gen if that matters) I also learned by using SEARCH that too much overlap can cut into the power that's useable on the street. It's the overlap that makes the sound right? I really don't care, since gearing can be improved and huge turbos have bad lag anyway. Porting helps the turbo spool up too right? I feel like I am only half *** correct about all this, I would appreciate if someone could set me straight. I'm sick of watching bridgeport 3rd gens on YouTube and being jealous - sounds so much better than an LSX motor. Thanks

Torque South

http://www.mazdarotary.net/porting.htm

Looking at the pics on the above site, a bridgeport is about as far as I would want to go. So how reliable (on unreliable) is it? And is a half bridge just a smaller second port?

killahrx7

i drive a bridgeport to work sometimes and have no problems with it. it is true what you said about low end power the experts say that when you have too much overlap you tend to loose power cause the intake air goes out through the exhaust but it also helps spool the turbo that i have on the car(holset hx55 i like it). what you can also try is a secondary bridge instead of a full bridgeport. you will like it.

killahrx7

yeah half bridge=secondary bridge. secondary ports only.

Kim

I know this qoute is pistonpowered but here goes

"My experience tells me that once the cam with the lumpy idle is selected, the thinking mostly stops. Decisions then are based on lowest price, looks, ease of installation, coolness factor, the 'latest thing' syndrome, peer pressure, old wives tales, and bad advice. "

You can still get the brap brap idle with a streetport, let it open early and make the exhaustport close a few milimeters later

Torque South

Thanks for the info. Seems like half bridge and big turbo is the ticket for a street killer. What's the life expectancy? I was able to get almost 4 years of daily driving out of my street port with 400 hp worth of boost, and the engine was still as strong and healthy as day 1 when I sold the car. How many miles / years can a 500 hp / 20 psi nasty half bridge live if maintained meticulously but driven hard?
(Approximately of course - you never know when **** happens)

BDC

Mechanically, there's no reason why you can't get the same reliability out of a partial bridge or even a full bridgeport depending on the width of both the cuts and the bridges leftover. That yields one of the two reliability concerns. The other has to do with whether or not the o-ring land adjacent to the intake port is cut into, ala old school non-turbo bridgeporting, AKA J-Port.

http://bdc.cyberosity.com/v/EnginePo...Bridgeporting/

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gracer7-rx7

iTrader: (16)

A big street port will idle lumpy.

Bridge ported motors generally need a higher idle and will be a pita to drive on the street as low end is affected pretty strongly. It will also be much less fuel efficient and a lot louder.

I would hate to have to drive one on the street. It could be fun on a road course though.

Torque South

My mild street port used to idle really cool when it was cold. Especially when you scoot a little in 1st gear, then let off but stay in gear. And also right after a cold start-up. But it's nothing like a bridge, I must have that idle!!

BDC

PITA to drive on the street? Could've fooled me.

http://bdc.cyberosity.com/v/ProjectC...y2007_Rebuild/

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DelSlow

iTrader: (2)

It seems the only people who think that bridges are hard to drive on the street are the people who have never driven one before.

BDC

Love the avatar! Fallout!!!

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ericgrau

iTrader: (1)

I'd assume a bridgeport is as reliable as any other, but if more exhaust is going past the apex seals then I can see how that'd shorten their life. The issues most people talk about come from poor low end power (it's plenty enough to drive, but it's still low), emissions, mpg, noise, etc.

BDC

With respect, have those same people ever driven one? Even my friend's full bridgeport, which is more radical than the partial (half) bridge, is still sane to drive down low around town even though the car is much louder.

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Viking War Hammer

iTrader: (8)

BDC

Drillport!

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djseven

iTrader: (56)

BDC, How is your idle with your half bridge? What is it set at? Also, are you cutting into the rotor housing or are you still using your old template which doesnt really go that close to the coolant seal?

Oh, how the hell are you getting that finish on the port work??? I dont expect you to answer, but figured I would ask anyway

ericgrau

iTrader: (1)

Some of them, yeah. Their point is that, yeah, you don't have any problem whatsoever driving them. But you get more low end power out of a street port (or maybe even a stock port?). That plus the other issues (mpg, emissions, noise) make it impractical for normal driving on public streets. While the low end performance is still ok, there's nothing to be gained at the lower rpms and you pay money for the port job plus those problems. And as for noise, I know someone with a red TII w/ stock ports that gets pulled over all the time for his loud exhaust even though it doesn't exceed the legal noise limit. He's been thinking of selling it.

They also say that a half bridge is just halfway in between. The issues aren't as bad but the power isn't as great either. But I'd have to understand a half bridge better before I'd agree or disagree. If it's really half a bridgeport, then I can see their argument. But I'm getting the idea here that it might be something else.

BDC

Interesting points and they're well-reasoned. I've been through some of that before and admittedly things like the very low-end power and gas mileage MPG factors are ones I've worked on quite a bit. Even 5 years later, I still look for ways to try and yield better gas mileage for daily driving and highway type stuff on my own car. I did it on the way back from a 2hr drive from Oklahoma just last week as a matter of fact. The part bridge is slightly radical and I would personally have a hard time putting one into, say, a convertible FC. It's too elegant of a car IMO to have a loud, "brap brap brap" noise with a drop in fuel mileage. The Turbo II, N/A body FC, or FD3S, I'd definitely do it.

But really, the perceived negatives here, which are fairly unsubstantial and marginally worse at best, pale in comparison to what the overlap yields torque and power-wise. The main benefit is a much more ferocious boost thresshold with higher power and torque per lb of boost compared to a stock/street port. Everyone (that I can recall, atleast) that's ever paid for one of my HBP's, someone else's, or one they've built themselves, all seem to claim the same thing with adamancy.

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ericgrau

iTrader: (1)

Yeah I can see how if you have the wallet, drive the car up high and like the sound then the bridgeport is the way to go. And I just realized I was responding to a professional engine builder who probably makes some serious(ly awesome) RX-7's for some serious drivers (for whom a bridgeport is ideal). I OTOH am the kind that might not even port my engine at all, or I may wait until it needs a rebuild.

diabolical1

iTrader: (3)

i just want to throw this out there ...

for street driving, i'm sure that a bridge with a turbo ready to spoonfeed air to it at any given loaded RPM, is a totally different animal from a normally aspirated bridge - so yes, the negatives that have been mentioned are definitely a factor when considering a bridge on the street. a turbo sort of softens or decreases those negatives, so when Brian (and many other respected guys) says it's close to being a non-issue he is sort right and wrong at the same time. i haven't driven a turbo bridge yet ... i suppose i'll have to build one first at this point, but i have driven an N/A bridgey - and yes, aside from the cool-factor at the time, i wouldn't trade any of my streetports for daily driving duties.

now to move on to my comments on the original question as i understood it. you can have great low end with a bridge - as has clearly been established. however, reliability can be great, too provided you not get greedy with the size of the bridge. basically, if you (or your engine builder) can avoid the "if-big-is-good-then-huge-must-be-better" type of thinking, then i don't see why you'd have less reliability than a large street given the same driver/uses. obviously, turbo sizing is key, and in addition to the usual reliability mods (oil system, clearancing, etc.) i would probably look a bit closer at rotational balance.

BlastinSideways12A

I second that! One of my favorite games! Ever beat it with only fists, melee weapons, and throwing knives? Ninja Style!!!!

Rx7_Nut13B

iTrader: (1)

Half Bridge-port with a turbo = No problem on the street

I drive mine on the street alot with no problems even near 500hp

BDC

I idle my HBP's around 1300-1400. It idles great. The AFR's bounce around at that RPM, of course, but I target for mid-high 12's:1 if I can get away with it. The negative effects of overlap are pretty apparent down at that RPM.

I don't go into the land where the rotor housing rests. When I cut the ports, I try my best to use it as an edge. I've cut into the rotor housings some when I'd made larger bridgeport cuts (closer to 5/32" - 3/16" wide) but I rarely do it.

How do I get the finish? Carefully and painstakingly. Seriously, I don't polish the intake ports even though sometimes the pictures suggest it. They're only sanded to 120 grit with the exception of the centre ports which I leave rougher. If you look closely, you'll see fine scratch marks still.

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BDC

I agree. And certainly bigger isn't always better. And IMO sometimes it's worse.

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