If you get a good exhaust on your engine, you'll notice a difference. Get a new intake system and ecu on there in addition to the exhaust and you'll be completely shocked at the difference over how it runs right now.

Start simple with the intake manifold. Try a weber style upper manifold with the stock lower and a fuel injection throttlebody. Remove the aux port sleeves and rods. They are a huge source of turbulence on the aux port runners and you don't need that with a bridge. This might actually work out better than you think and will certainly be easier than fabbing up a crazy intake with 6 runners. If you don't want to fab anything up but want something nice, I'd try the Weber IDA manifold that you can get from Mazdatrix. It's not hard to use fuel injection with them. This would also work well with a half or full bridge later on. Scroll down a little.

http://www.mazdatrix.com/r-idamanifolds.htm

 

Im holding out for 2 weeks or so to see what Fuji racings ITB setup looks like. They have a really nice complete kit for the Miata so I wanted to see what they can do for the 13B. The kit is supposed to be ready with details and pricing in two weeks, or so says Jimmy at Fuji. Granted he said the same thing in december.

Im looking at the link your provided right now

BC

 

I just don't see why an aux BP wouldn't be a gain (power), even if its only a little gain (power).
Also considering its (not sure of the wording here, but,) simple, conservative etc...

What I mean, for example...
Theres 3 choices in porting as far as street and bridge porting go. And adding the mix of technicalities (tuning) and cost($).

1. Street porting. hardly any tuning needed, so no need to add extra fuel or upgraded ecu etc...so low cost, no extra parts. My GTU has mild street porting, I haven't done any mods besides pre-silencer and an air filter. Although u can add extra fuel and etc... Maybe if the SP is large. Low end(power etc.) is still good as well as high end (of course).

2. Half to full bridge-porting. Tuning needed, along with extra fuel, ecu, etc...Cost gose up. Low end(power, etc.) is decreased. High end is good.

3. Aux bridge porting. Some tuning (extra fuel, ecu, etc...) needed but not as much as with a half or full BP. (thats what I think.) Since your aux. BP'ing and keeping the aux. actuation (the reason why its an aux BP), the low end is still good, high end is good.

So Street Porting and Aux Bridge Porting seem to be on the same page as far as low end, low cost, and not much tuning, compared with going half to full bridging.
But I believe, and its easy to think, that Aux BP'ing is (at least a little) better than Street Porting.

Don't forget that my plan is to Aux Bridge and Street Port the 5th & 6th ports.

Later.

 

The problem is flow. There isn't any. There is so much turbulence through that small port and it needs to turn sharply in a small runner with small area. Flow is practically nill. What you do get though are the downsides of a peripheral port. That's because although flow isn't really taking place, a pressure balance is. During port overlap you are getting some exhaust gasses back into the intake side. This is because the exhaust has more pressure than the intake side does at this point. This is exagerrated with a stock exhaust intake or exhaust manifold. When the engine is running though and you are trying to get extra air into the intake port through that small bridge, all the turbulence and poor flow characteristics are hindering this. You are not getting a gain.

Do it if you want to. It's your car. Keep in mind that you will not be getting anything beneficial from it. Bridgeports are really an all or nothing proposition.

 

I know what your saying about flow.
I know what you've said about "its better to go all the way with Bridge Porting" OR "just do a Street Port"
We both know that I don't want to go far with a Bridge Port.
So lets consider my setup with just a Street Port.

So I Street Port the aux.
And I still want to keep the aux. actuation. (I believe the whole debate that keeping the aux. actuation is good.)
So about flow, isn't there still turbulence in the 5th & 6th port runners? Isn't there still "poor flow"?
Or is there just poor-er flow with adding an aux bridge?
Would a good open exhaust header help flow? (even though I wouldn't do that with a bridge.)

 

There are some flow issues through the aux ports. The actuator rods really hurt this. They do so to the point that the 6 port inserts that add a radius at the end only add about 1 cfm to total airflow through those ports if the actuators are still in place. That's it. Turbulence is terrible. A bridge needs to be very free flowing on the intake and exhaust side. As little turbulence as possible. It is possible to make a small bridge like that work and they actually do work good at that size on 4 port housings. Flow is good through those runners.

The only reason why a 6 port engine still makes good power even though flow is bad is because of intake velocity. As the rotor turns and closes the intake ports, it closes them from bottom to top. The secondary port closes first. The air traveling towards the engine in the intake manifold has inertia. The bottom port is now closed off and this air has to go somewhere. It all crams itself into the upper aux port runner, turbulence be damned! This gives a last little supercharging effect right before the port closes which forces more air into it. With a small bridge here, the advantage comes from early opening. However when the port first opens velocity in the runner is low. You get no ram charging effect at this point so no air can be helped into the engine. All you have done is to allow a pressure release during port overlap which dilutes the incoming air. You'll find that low end, idle, and mileage will suffer but the top end will not increase over a good streetport.

There is also no need to go crazy with porting on 6 port housings. We see many people go hog wild with the aux ports making all kinds of claims. You can get too much port timing and it already closes at 80 degrees which is pretty late. The chamber has actually started getting smaller by this point. The Mazdatrix/Racing Beat templates are fine for these engines. I know they don't look like they do much to the timing but they do all they need to. Most of the secret of good ports is not in the size of the port but rather in the shape underneath where the transition from runner to port is. A smaller port that has more attention paid to it in the transition area will make more power than a larger one where the transition area was ignored. It's not all about size. It's about velocity!

 

So how far up can you go (cm. or in.) with just Street Porting the aux. ports, so it makes decent power?

I had an idea just now how to figure all this out with actual results.
I take the engine apart and just Street Port it. Put it back together. Drive it for awhile, then tear the engine down again. This time adding the aux bridge. Put it back together. Drive it for awhile. And see if theres any difference. Might be a little expensive and take some time, but ill get actual results. Ill post the results next year. Depends on the time though.

Cause I just cant believe all this talk about how this whole aux bridge is bad and wont do much, I have to see it for myself. Im stubborn.

 

If you do that and post the results, regardless of what they are, that would be awesome! Don't think being stubborn is a bad thing. The stubborn people are usually the ones that eventually do great things. There is no better way to learn than to do. If you really want to be stubborn about things, dyno multiple combinations on the streetport and then when you do an aux bridge later, try all of these combos out again to see how they changed. You may actually stumble on a combination that does work good. You may find some do work good and some don't. You won't know until you test them all though.

 

Little change of subject... I fixed the idle and timing, and the bent tie-rod end. I took the tie rod off a slammed a hammer to it a couple times, and straitened it out. Put it back on, eye-balled the toe adjustment, an drove it for the second time. It drove a lot smoother and straiter. And doesn't stall anymore.
The only thing that still needs work is the charging problem and 2 new tires. It still has a flooding issue, but Im just shutting it off every time by unplugging the fuel pump connector, And plugging it back in when I want to start it. So it wont flood on me.

 

So as far as the port closing, I would think any porting done would be an advantage.

And of course you have allowed pressure release, but with an aux. bridge its "way up there" in the housing, as far as port timing goes. When the exhaust port starts to close, the bridge is 1/4 to 1/2 open(ing). By the time the bridge is fully open the exhaust is maybe 1/2 closed. That compared with a 1/2 bridge, where the bridge port is lower in the housing., and you have a lot more overlap exposure.
I don't think the overlap / dilution will be that bad.
Let me also add the whole fact of pressure release, (I learned a little about this in electrical class.) Where voltage is like pressure and wants to take the path of least resistance.
So this pressure, it has a big ol exhaust port to go out, or a way smaller bridge port, It will go out the exhaust port a lot more and easier.
Like I said before, the overlap etc. wont be that bad.

And Im keeping the aux. actuation / sleeves etc...

Can you explain the "too much port timing" and "80 degrees is pretty late" ?
I think that also goes along with my previous question:And I know what your saying about "secret of good ports" with "not in the size... but the shape"
Well, since I want to keep the aux. actuation / sleeves. Theres not much to do about that.

One other reason I have that this idea will work is, Im only going so far with each aspect. I'm adding together a lot of little things like, just an aux bridge port, and a mild street port, etc. Im not going so far with one thing that it will have any ill effect. Unlike a big *** bridge port or street port.