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Bridgeport vs. 1/2 Bridge ?

Old 10-05-06, 05:34 PM
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Bridgeport vs. 1/2 Bridge ?

I have been doing some reading about different porting methods and would like to see the difference in a full bridge and a half-bridge. So, could someone post pics of half- bridge irons?

Does a half-bridge reduce the amount of overlap between intake and exhaust ports? Does it also bring the powerband down in comparison to a full bridge?


Some info gathered from here: http://www.rotaryengineillustrated.c...ts-intake.html


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Old 10-05-06, 05:55 PM
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a half bridge is only adding an "eyebrow" on the secondary ports. The primaries remain stock (or usually street ported)

A full bridge is adding an eye brow to both the primary and secondary ports.

A half bridge "technically" reduces the overlap a tad, but in reality not much. They still have a lopey idle that settles around 1000-1200rpm.
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Old 10-05-06, 06:02 PM
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IMO, half-bridged is half-assed. You still get the lopey idle and most of the disadvantages of a full bridge, but without as much performance potential. If you're gonna bridge, do it right.
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Old 10-05-06, 06:07 PM
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Does anyone have some comparison pics?
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Old 10-05-06, 08:04 PM
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PM the half bridge king BDC and get his opinion on this becuase 99% of this forum have ever had one of these exotic port jobs so he would give you the info you need.
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Old 10-05-06, 09:04 PM
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Originally Posted by Sideways7
IMO, half-bridged is half-assed. You still get the lopey idle and most of the disadvantages of a full bridge, but without as much performance potential. If you're gonna bridge, do it right.
Baloney.

B
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Old 10-05-06, 09:08 PM
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BDC, what are the attributes of the 1/2 bridge over a full bridge?
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Old 10-05-06, 09:09 PM
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if I did it again, I'd go fullbridge this time.
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Old 10-05-06, 10:03 PM
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Originally Posted by BDC
Baloney.

B
Could you elaborate? Most of what I've read on here says that a half-bridge exhibits many of the "bad" qualites of a bridge, but doesn't have as much power potential. That says to me that you should just go ahead and do a full bridge. I'm very interested in your opinion on this, since you have first hand experience with this. I am strongly considering bridge porting my engine and want as many opinions on it as possible.
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Old 10-06-06, 09:02 AM
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Well, from what I've seen, a half bridge can net damn near the same peak horsepower as a full. On an N/A engine...

I really don't know EXACTLY why, other than the fact that the largest percentage of flow at higher RPM is coming through the secondaries anyway - so as long as they're getting good flow you'll get good peak power. And generally speaking, in a half bridged engine, the primaries recieve a nasty street port also, so they'll get only marginally less then if they had eyebrows

Long and the short - on an N/A configuration - even though a half bridge is (technically speaking) half of a bridgeport, you don't get 50% less power then a full, probably in reality only 5-10% less.

NOW - on a turbo'd motor, from my experience, the absoulute BEST porting is simply a mild to wild street port. You lose negotiable reliability, and because its forced induction, the air flow isn't really going to care exactly how it enters the motor - because its being FORCED in there by the turbo. That being said though, I am trying a half bridged motor on my T04-S...but its mostyl just for my ego, so we'll see how I make out
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Old 10-06-06, 09:42 AM
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Full bridge has more port area, more duration and earlier opening. It will make a higher peak power higher in the rev range.

Half bridge still has most of the overlap of a full bridge but is easier to manage down low.

There's absolutely nothing "half assed" about a half bridge. Most people have no intention of making the power that even a street port can achieve so a half bridge is overkill for 99.9% of people.

My next engine will be full brige, but that's just because I'm crazy.
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Old 10-06-06, 11:44 AM
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Yeah, I guess I forgot about the whole "low-end driveability" thing.
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Old 10-06-06, 02:30 PM
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In my reading it says that a full bridgeports power comes at 5k and up. Where does the half bridge start making peak power.

This is good info, please keep it coming!
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Old 10-06-06, 03:18 PM
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If you are talking about turbo cars, both bridges will make adaquate power almost everywhere. I can drive mine easily (mild half-bridge) at ~2K. Both half and full bridges will go like hell over 5K when flow velocity and the exhaust scavanging effect really take hold. And of course, when you see boost.

NA bridges really need high RPM to get going but will still show a much better midrange then stock ports. It's just the low end (<3K) suffers a lot.

And much of this is dependant on tuning. With standalones, you can maximize the engine through the entire RPM range if you can tune...
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Old 10-06-06, 03:30 PM
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Yes, I am talking about a turbo motor. (Aaron) Are you running stock intake manis? I have read that they are restrictive with bridgeports due to the volume of air that they introduce to the motor.(but I don't know) Also, how does it affect reliability?
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Old 10-06-06, 03:59 PM
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I run a custom intake manifold.

Bridge porting should not effect reliability as long as the eyebrow port does not intrude onto the side seal path. But any ported engine will be less reliable then a stock one because the owner will run it harder.
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Old 10-06-06, 04:27 PM
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How restrictive is the stock mani? Would running the stock mani defeat the purpose of this style port job?

Who would be a trusted person to do a half brideport?

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Old 10-06-06, 05:44 PM
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Originally Posted by NMJ87T2
How restrictive is the stock mani? Would running the stock mani defeat the purpose of this style port job?

Who would be a trusted person to do a half brideport?

Thanks
Stock manifolds won't inhibit the flow...
BDC is THE man when it comes to Half-BP's.

Check out some of his work:
http://bdc.cyberosity.com/main.php

And here is my setup:
http://bdc.cyberosity.com/v/Tuning/Ohio_June06/

How much power do you intend on making? and how deep are your pockets? Those are some key factors when looking at taking on a project, as there are many ways in doing it.
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Old 10-07-06, 11:42 AM
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What he said. The stock TII manifolds are fine. The NA manifolds are a different story since they rely on the stock port timings to make their power.

Most builders can bridgeport an engine if they have a template to follow...

But as mentioned, how much power do you want? More then 400?
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Old 10-07-06, 04:34 PM
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i personally don't see the point of any bridge for a street car wanting under 600rwhp. alot the high hp guys you will see only have well done street ports

but if you like the lope, just go extreme on the exhaust ports and create an early opening for the gases to fly out better.

i have driven alot of half and full bridge cars. we build them on a regular basis and i just have not seen one that i would want for my own. a proper street port in a turbo car will do more than enough. it's all about the rest of the setup from there. just my opinion.

a good buddy of mine ,Neil , has a bdc built half bridge setup in his TII. the car hasn't really had a chance to show what it's capable of but we'll soon see for sure. we're finishing his new T70 turbo setup tonite and i'm gonna turn that **** up

maybe i'll change my mind, but i doubt it.
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Old 10-07-06, 07:01 PM
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I've had the Half BP Since around Jan 04 and drove that for over a year with a MP T70. I must admit it was quite beefy...If anyone knows the half-BP stuff its BDC. buut..people get older and since then I moved to a full-BP, BDCs only. I drive this car to work..and nearly everywhere. IF you are weak sauce and want full boost at 2.5k look else..its full drag or highway. Dont get me wrong it is very streetable. But where else does a LARGE single turbo BP car shine?
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Old 10-07-06, 08:23 PM
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Is it true that bridgeporting has the least effects on reliability and streetability (for an n/a)?
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Old 10-07-06, 09:12 PM
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So, I am curious, this means that you can't half-bridge a 4 port engine?
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Old 10-07-06, 09:20 PM
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highway definitely, that's the only place me and my friends really let our cars shine lets just put it this way... I am to bridge porting as BDC was to Alcohol Injection. he used to be against it but now see's the beauty of it. i currently don't see a point to a half-bridge, BUT i am open to seeing his in action which i will starting this week as i tune on one. but i'm not new to bridges as i said and the super high power band, even for a boosted car, just seems useless to me when you can make the same power and have even more powerband with a large street port. it's like having a cam in a turbo v8 that has too much over lap, it just doesn't work as efficiently as a more mild cam with a couple more lbs of boost

we just did 550rwhp with a slipping clutch on a large streetported t-66 fd. what more would you need that a bridge could offer? if he goes bigger turbo 600rwhp is completely attainable. that's just my view as of now. my personal engine is torn down and i'm about to start the porting on it.... but i am waiting to see how this bdc ported car does because i AM open about this. if i feel it's made a difference then hell, maybe i'll give it a shot on my own car for shitz and giggles
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Old 10-07-06, 11:36 PM
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The whole point was to half bridge to run the same turbo and have a wider powerband because the half bp "spooled" the turbo earlier and harder. It may not directly equal more power but it allows more air flow in higher rpms
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