Ok, I've decided that my next engine is going to be a brideport. I've rebuilt rotary engines before but I've never done a bridgeport, does anyone have any sites with any info?

I know what is involved but I wanted to see if there was anything more detailed than the maxdatrix site. Something more than just a couple pictures

 

http://members.home.com/sofronov/Cars/Mazda/Rotary.html

Go all the way to the bottom. Porting pics and details. Very nice.

 

Wow... great history site.

But this bugs me... the site says NSU gave up on peripheral intake ports, and that side ports give better fuel economy under heavy load.

This is totally false. NSU production engines had peripheral intake ports. They were also sized equivalent to a 10A (in the Ro80) and made 125hp factory. They were designed for best fuel economy under heavy load, so they went to a peripheral port in a fairly small engine in a fairly heavy car, so it'd require heavy throttle to make a given HP, and the small size meant economyunder low load was acceptable too.

Side ports' advantage is that they have better fuel economy under LOW LOAD conditions.

For comparison... The NSU's 10A sized engine made 125hp at only 5500rpm. Mazda's 12A made only 100hp, at 7000rpm, at that time.

 

That sight got several things wrong. I noticed that much of the years stated were incorrect. It also didn't mention the Sundowner '77 REPU long cab (or I didn't notice it). It also stole almost word for word from Craig's rotary page about the 20B engine. The Cosmo (RX-5) page had a 10A pic for the engine pic. There were a few other things that I can't think of at the moment.

Now for the good stuff. It was pretty good over all if you don't mind a few spelling mistakes here and there. I bookmarked it for later perusal (sp? lol!).

 

Huh??? Where are you guys seeing this stuff? I wanna see.

 

Is a bridgeport even remotely streetable? what about durability?

 

It depends on what you want to call "streetable"

The port itself shouldn't hurt durability as long as the bridge isn't wafer-thin. The trick is, if you want to run over 8500 then you need carbon-aluminum seals which WILL hurt durability. Plus there's the usual wear-and-tear that comes from high revs, which will wear some things faster than normal, but IMO that's a lot better than babying an engine its whole life and then it carbons up and an apex seal sticks in the "out" position and it snaps.

Now... I've heard some of the bridge port masters in the Single Turbo section mention that with 2-piece seals you can't have the corner piece against a bridge... I infer from that that you can only do a half-bridge (only 2 ports bridged) unless you go with one piece seals. I've also inferred that the 3-piece seals as used in '86-up engines can easily withstand 10,500 or higher when properly clearanced. Still waiitng for answers on some questions about that though...

- PJ (I want a half-bridge T2... amassing parts and info)

 

I'm hoping to do the bridge on a spare 12A (perfect housings) I'm looking for more information on the basics of porting. What does the bridge do for intake timing? overlap? what about extending the port up? down? what do they all do?

As for partial bridging, what housings do you port? end or center?

 

First of all, I'm by no means an expert on porting so anyone feel free to correct me if I say something stupid. Opening the port up either way will give you longer port timing while opening it down also provides earlier port opening and more overlap. The additional "eye brow" on a bridgeport provides far earlier port opening which greatly increases overlap and gives you the cool brapping idle. Half bridgeports are always performed on the secondaries which means the end plates. Hope that helps.

 

What is more overlap going to do? performance wise? how far up can you go before port closing is too late?

Great info so far! thanks alot

 

Overlap is bad and good. Bad because it means the intake port is partially open before the exhaust cylce has gotten rid of the exhaust. So some of that exhaust is going to get mixed in with your air/fuel mixture. This gives you less power, and can even make you run lean, depending on how bad it is.
The good thing about overlap, is that means your intake is opening earlier, theoretically allowing it more time to take in air/fuel. If your exhaust ports are ported, and you have a very free flowing exhaust, you can actually have negative pressure in the exhaust chamber, that will help pull in air/fuel mixutre through the intake ports.
If I'm wrong about any of this, than I apologize, this is just stuff I've read from people like Paul Yaw, and other rotary Guru's around the net.

 

this has nothing to do with bridgeporting in particular, but in refrence to the 'great history site' thing, here's a better one. it hasnt been uptaded in like a year, but if anyone knows of a better one let me know. got to the racing section and look near the jim downing section and there should be some good porting info (bridge and perif). there is just soooo much good info on here:http://monito.com/
go to the bottom of this page and look at the 'other' rotary engines before the wankel http://www.monito.com/wankel/rce.html

 

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