so here's the deal. i finally am ready to start my rebuild and am now trying to make my final decision on what kind of porting. the engine is a S4 6 port na.

to get the best answers, this is my goal: make about 200rwhp or more if possible. i will be going to ITB's in the future and want to know what is best for that. i've been trying to find information on my own but mostly seem to find things for turbo.

can people help lay out the pros/cons of doing a half bridge vs a full bridge? and what to do with the aux ports? i will be getting a standalone, most likely megasquirt for its affordability. and once i get the ITBs i'm thinking of running larger primary only injectors (something between 800-1000cc)

any input from guys who have experience with setups like these is greatly appreciated...i seem to be finding a lot of conflicting information

 

I think Bridges and half bridges on a 6-port were covered in your other thread in the 2nd gen forum. Maybe PeeJay will chime in here. I think he had a half bridged 6 port at one time before his full bridged 4 port.

What to do with the aux ports depends on what intake manifold you run. Something like this Sidedraft Carburetor Upper Manifold Section for 86-92 13B 6-Port - Racing Beat from RB uses the stock lower so you may could keep them functional. Something like this 84-92 13B N/A Rx7 Wrap Over Manifold... from Atkinsrotary and you'll remove the sleeves as there is no provision for them. These TB's from Borla should bolt to either one according to their literature. https://www.borlainduction.com/2900-series.html

It is hard and not many achieve it but 200whp can be hit with a streetported 6-port. A 4-port block ( TII, 13B-RE, 13B-REW) is a better base to start with it seems.

Check this thread: https://www.rx7club.com/naturally-as...-gtus-1032737/ 230rwhp with a n/a 13B-RE. He doesn't say specifically but I'm pretty sure he's using n/a rotors of some kind.

 

yeah as far as what was in the other thread, that was more geared towards the debate between street and bridge and not using a standalone. at this point i'm fully committed to running a standalone ems and have been doing a lot of research. as far as the itb's go i was looking more at IDA style and found this 84-92 Rx7 45mm Throttle Body & Intake Kit.... might just buy the manifold on its own and opt for larger TB's (also looking into the EFIhardware stuff), i'm not sure what the optimal size would be. still trying to learn all that stuff, so any help here would be great. i realize i'll be losing the aux ports once i go ITB, but at that point it shouldn't matter, right? but i guess if i bridge the aux they are useless beofre i get to that part, so maybe don't bridge them, just the primary and secondary ports?

and i might be mistaken but isn't it the lower manifold that is the big restriction? so in that instance a UIM would really be no benefit other than to accommodate the itb setup? please correct me if i'm wrong here. and any more links to where i can find intake manifolds would be helpful. i've only been able to find a handful (racingbeat, atkins, rotaryshack)

i guess that brings up a new question for me. other than the looks, what are the major differences between an IDA and DCOE. what effect does it have on making power, seeing as the IDA has a much shorter runner. i don't understand it well but i know that getting the proper length and diameter is a big part of the process

and one more thing. i read aaroncake's writeup about running the megasquirt and he made it out to sound like you can't do it without the BAC, which i have already removed...but then i got to thinking and with an ITB setup, thats gone anyway so how can that be true?

 

Hopefully someone else will chime in as I don't know much about carbs. Seems the IDA is a downdraft and the DCOE is a sidedraft carb which doesn't matter on in this application as I don't think a TB cares what angle it sits at. What will matter is the manifold style and it's runner length. Someone please correct me if wrong but I am thinking the shorter runners you'd have with the IDA style manifold makes more peak power but the longer runners that wrap over the top of the engine give a broader powerband. Look at the dynos in this article https://www.borlainduction.com/media/carb_vs_fi.pdf in the Borla link. The Holley carb with the shorter runners made more peak power yet the power on the Dellorto was broader.

Not sure if the lower is where the restriction is( once you get the actuator rods and sleeves out of the way) as it is pretty short and could probably be opened up if needed. I think the benefit of that RB UIM is a cheaper ITB setup.

IDK about the bridging. Maybe someone else will chime in.

 

well that graph made things easier to understand as far as power effects, but the reading was a bit hard to follow and the other graphs and info just confused me somewhat haha.

can anyone else offer up some helpful info? the car is probably going under the knife starting this week!

 

You don't need a bridgeport to hit 200 rwhp. Your S4 intake manifold can easily flow enough air to hit your power goal.

 

but if i were to do a half/full bridge, wouldn't that prove more beneficial when i do ITB's? i'm looking into the future here too. i've read its difficult to hit 200whp with a streetport. i'm really set on doing at least a half bridge at this point. so wouldn't all this amount to easily breaking the 200whp mark once ITB's are in the mix. and i've been told the s4 manifold is restrictive

i feel like i keep finding/getting mixed information all over the place. its making it very difficult to make informed decisions.

 

It's not difficult to hit 200 rwhp on a streetport. The difficult part is for people to do things properly or in a logical order. Porting is the very last thing I'd do. Get an ecu first and get it tuned. Then as you do other mods, you can take full advantage of them by tweaking the tune a little. Then get an exhaust. Then do the ITB's. You'll be shocked by how much power you get this way. I guarantee you'll get more than if you started with a port job and saved the rest for later. There are little things you can do in there as well to get faster such as a light flywheel, which is one of my personal favorite mods, and an ignition box to make sure you can light it off at higher rpms but porting isn't what you should be thinking about right now. Unfortunately it's what most people people start with. Then they wonder where 200 rwhp is.

 

Ditch the 6 port plates and find a good set of 4 port plates. Porting 6 ports has minimal effect compared to porting 4 ports.

 

I disagree. Hitting 200 rear wheel horse power on a n.a 13b without a semi or full P-port isnt the easiest. I really dont know why people bother to do so.

 

200 rwhp on a street port 6 port is pretty easy. You just have to know what you are doing. Most people start with porting and wonder why they didn't hit 200 rwhp. Porting is always, always, ALWAYS, the absolute last performance mod you should do for power because for a nonturbo street car, it's the least important. Racing is a different matter. The downside to trying to hit 200 rwhp on an na is that for the money spent to do it, you could have gotten far more power from forced induction. Being expensive doesn't change the fact that it's not hard at all to hit that number.

 

If 200rwhp N/A was easy, we'd see a lot more 12 second street tire N/As.

 

I am going to disagree but only because it is being torn down for a rebuild anyway. I don't see the harm in a street port while it is apart. I do agree he won't see the full benefit of it until he does the exhaust, and gets a standalone ecu and tunes it. I also agree that one shouldn't tear down a perfectly good engine to port it if they haven't already done everything you mentioned in your other post.

Some people just like a challenge I guess or just don't want or already have a turbo car. I personally would like to hit the 200whp mark to know I took a street ported engine about as far I could go with it. Then maybe defect to the other side.

 

i already have a full exhaust system. pacesetter headers, 2.5" test pipe, and 3" catback (i know thats a little big for n/a) i've already had a turbo car, and would like to have another, but i'd rather build this n/a since thats what it started as, i don't have time to source t2 components and to keep reliability up. if it turns out that my engine is overly worn, then i'll consider finding 4 port plates, but its not really in the budget. i most likely am getting a flywheel to help the car rev more freely, cut a few more pounds and i know i'll need a clutch with more bite for the type of driving i will be doing

 

Ditch the Pacesetters. They are a power drain compared to the OE manifold.

 

At least someone gets it.

 

I'm not making close to 200whp and my heavy-*** car (~2800lb with me in it) runs mid 13s with no traction...

So either I am one hell of an awesome driver or there are a lot of optimistic dynos out there!

 

how are those headers a power drain? i'm definitely not putting the heavy *** stock manifold back on, plus if i did the the rest of my exhaust wouldn't fit. i weighed everything out when i installed everything and the OE system weighed in at ~90lbs compared to my current setup at about 33lbs.